In this work, we report the spectral and modulation characteristics, as well as bit-error-rate performances of stabilized hybrid distributed Bragg reflector lasers including a chirped fiber grating. An original analysis of such lasers based on a modified second order rate equation will also be presented to explain the observed stability behavior.

Uncooled DFB lasers directly modulated at 10 Gbit/s are a key devices for Optical communication systems operating at 10 Gbit/s, such as 10 Gbit Ethernet, since their effective use in optical transceivers to reduce cost, size and power consumption. The paper describe the current status of these sources (including well assessed InGaAsP MQW and recent progress for AlGaInAs MQW active layers), as well as the Agilent's very recent results. Combining an optimized active region based on InGaAsP strained MQW (Multi Quantum Well) and a low parasitic lateral confinement region, we have fabricated 10 Gb directly modulated uncooled DFB lasers which represent, we believe, the state of art. Our DFB lasers work up to 100 degree(s)C (chip temperature), with eye diagram perfectly open (showing an extinction ratio > 5 dB), and with Bit Error Rate over 10 km without error floor. Up to 90 degree(s)C our DFBs show threshold current as low as 29 mA, optical power as high as 13 mW and meet perfectly 10 Gb scaled Ethernet mask with extinction ratio > 6 dB.

Above-threshold analysis of various distributed feedback laser structures using the transfer matrix method is presented. Special attention is given to the possibility of obtaining single mode stability, regarding their applications in the field of coherent optical communication systems. A summary of the main laser figures of merit in modified DFB laser diodes and their variation with the injected current will be referred.

Nonlinear dynamical effects of a multi-section DFB semiconductor laser such as self-pulsations or hysteresis can be described by the traveling wave model. The present paper demonstrates that such a model can be effectively approximated by a low dimensional system of ordinary differential equations where only few dynamically varying longitudinal modes of optical field are taken into account. A bifurcation analysis of the reduced models allow us to identify the mechanisms of switching on and switching off of the self-pulsations by tuning model parameters. An explanation of hysteresis is given as well.

The development of 1.3 micron VCSELs is currently considered to give a strong impulse for a wide use of ultra-fast local area networks. In the present work we discuss MBE growth and characteristics of InAs/GaAs quantum dot (QD) lasers, we also give characteristics of 1.3 micron QD VCSELs grown on GaAs and compare them with those of 1.3 micron InGaAsN/GaAs QW VCSELs. Overgrowing the InAs quantum dot array with thin InGaAs layer allows us to achieve 1.3 micron emission. Long stripe lasers showed low threshold current density (<100 A/cm²), high differential efficiency (>50%), and low internal loss (1-2 cm^-1). Maximum continuous wave (CW) output power for wide stripe lasers was as high as 2.7 W and 110 mW for single mode devices. Uncoated broad area lasers showed no visible degradation of characteristics during 450 hours (60C, ambient environment). 1.3 micron InGaAsN/GaAs QW VCSELs are characterized by higher optical loss and lower differential efficiency than QD VCSELs. Due to high gain in the active region QW VCSELS demonstrate high output power (1 mW). QW VCSELs show extremely low internal round-trip optical loss (<0.05%), low threshold currents (<2 mA), high differential efficiency (40%) and output power (600 microW).

LO-phonons in the active region of interband cascade lasers based on type-II multi-quantum well are investigated in detail. The dispersion relation and phonon potential for interface LO-phonon modes are calculated by the macroscopic dielectric continuum model. The expression of electron- phonon overlap with multiband k*p approximation is obtained and energy separations of hole subbands for fast LO-phonon assisted depopulations of the lower lasing state are proposed.

The development of type-II Sb-based interband cascade lasers has attracted a considerable interest. For modeling of type-II quantum-well lasers in the mid-IR regime, the coupling of the conduction and valence bands, as well as the screened potential due to electron and hole distributions in separate layers, should be take into account. In this paper, a self-consistent model that solves simultaneously the effective-mass equation for the coupled conduction and valence bands and the Poisson's equation is applied to obtain the band structure. We reduce an eight-by-eight Hamiltonian based on the k*p method to two block-diagonalized four-by-four Hamiltonians under the axial approximation. The carrier accumulation in different layers and its screening effects are considered. The optical gain spectrum for type-II quantum-cascade lasers is then calculated. We compare our theoretical results based on the self-consistent model with those of the flat-band model (which ignores the carrier screening effects). Our model is applied to study temperature dependence of type-II quantum-well lasers. The self-consistent model is shown to be important to give a better agreement with experimental data. Our model is useful for designing high-power, high-efficiency, and high-temperature type-II interband cascade lasers.

Electroluminescence is reported for the first time from InAs_0.75Sb_0.25 quantum dot light emitting diodes. The quantum dots were grown from the liquid phase at 590 degree(s)C on an InAs (100) substrate and embedded within the undoped active region of an InAs homojunction pin diode. At 4K and 250 mA injection current, three transitions were identified, centered at 4.01, 3.80 and 3.63micrometers , associated with the sp, p and d states of the confined holes inside the quantum dot. Each of the transitions exhibits a blue shift with increasing injection current, but the electroluminescence results indicate the presence of a phonon bottleneck in these devices. The quantum dot electroluminescence was observed to persist up to room temperature.

Quantum well infrared technology has been progressing rapidly in the last several years. There are a number of focal plane array development projects conducted in earnest around the world. Different applications areas are also being explored. In this article, I will give a brief overview of the current technology, and discuss some of our recent progresses. They include the more accurate prediction on the material optical properties, the better understanding of the light coupling mechanisms and the demonstration of the corrugated-QWIP FPAs. Despite the current achievements, there are still problems in QWIPs in reaching out to both low and high temperature operation. I will discuss the prospects of using quantum dots and quantum grids in improving this technology.

This paper discusses issues related to the quantum dot infrared photodetector (QDIP). We attempt to address the following questions of what is its potential, what is lacking, and what is needed to make the device interesting for practical applications.

Mid- and far-infrared detectors operating at elevated temperatures (T>150K) are critical for imaging applications. In(Ga)As/GaAs quantum dots, grown by self-organized epitaxy, are an important material for the design and fabrication of high-temperature infrared photodetectors. Quantum dot infrared photodetectors (QDIPs) allow normal-incidence operation, in addition to low dark currents and multispectral response. The long intersubband relaxation time of electrons in quantum dots improves the responsivity of the detectors, contributing to better high-temperature performance. These devices also exhibit photoconductive gain. The characteristics of state-of-the-art lateral and vertical QDIPs will be described. We have achieved peak responsivity for wavelengths ranging from 3.7-18micrometers . We have also obtained extremely low dark currents (I_dark=27pA,T=100K,V_bias=0.5V), high detectivities (D*=2.9x10⁸ cmHz^½/W, T=100K, V_bias=0.2V), and high operating temperatures (T=150K) for these quantum-dot detectors. The excellent performance of these devices at low bias voltages indicates the compatibility of high temperature QDIPs with commercially available silicon read- out circuits for imaging focal plane arrays. These results, as well as infrared imaging with QDIP arrays, will be described and discussed.

A separated-absorption-and-multiplication (SAM) AlInAs/GaInAs waveguide avalanche photodiode (APD) has been developed for 40-Gbps receivers. It has the widest bandwidth of 30-35 GHz and a gain-bandwidth product of 140-180 GHz, as a result of its small waveguide mesa structure and a thin 0.1micrometers thick avalanche layer. Preliminary results show the highest 10-Gbps sensitivity ever reported: -28.8 dBm at a bit-error-rate of 10^-9. This waveguide APD is a candidate for 40-Gbps applications as a cost-effective super-efficient photodetector.

We present an optically-detected time-of-flight technique with femtosecond resolution that monitors the change in the electroabsorption due to charge transport in a p-i-n diode, and show how it may be used to determine the electron transit time, velocity-field characteristic, and transient electron velocity overshoot in GaN at room temperature. In a GaN homojunction p-i-n diode, the peak electron velocity of 1.9x10⁷ cm/s , corresponding to a transit time of ~2.5 ps across the 0.53 micrometers depletion region, is attained at ~ 225 kV/cm. The steady-state velocity-field characteristic is in qualitative agreement with theoretical calculations. A measurement of the high field transient electron velocity overshoot was also performed using a semi-transparent p-contact AlGaN/GaN heterojunction p-i-n diode. Transient electron velocity overshoot is observed at fields as low as ~100 kV/cm, with the peak transient electron velocity becoming larger with increasing electric field until a maximum of 7.25x10⁷ cm/s is observed within the first 200 fs after photoexcitation at a field of 320 kV/cm. At higher fields, the measurement of the peak velocity is limited by the 80 fs duration of the pulses, but the increase in transit time with increasing field suggests the onset of negative differential resistance. Theoretical Monte Carlo calculations incorporating a GaN full-zone band structure show that although the peak steady-state velocity occurs at ~200 kV/cm, the ensuing negative differential resistance region of the velocity-field curve is not initially associated with intervalley transfer, as the majority of electrons do not attain sufficient energy to effect this transfer until they are subjected to much higher fields (>325kV/cm). Insight into this behavior can be gleaned from the band nonparabolicity deduced from the constant energy surfaces in the (Gamma) valley, which shows that the effective mass in the c-direction can be viewed as becoming larger at high k-values. This larger effective mass may play a role in velocity overshoot by reducing the velocity and momentum relaxation time at high k-values in the (Gamma) valley. Theoretical calculations employing a semiclassical transport model in the collisionless regime confirm the importance of this nonparabolicity for the determination of the temporal shape of the transient velocity overshoot curves.

The optoelectronic mixing effect in metal-semiconductor-metal photodetectors (MSM-PDs) is studied. Numerical results, using the Scharfetter-Gummel scheme, are presented for gallium-arsenide (GaAs) MSM-PDs with different donor concentrations and analytical results are presented for devices with high background donor concentration operating below the flat-band condition and for low background donor concentration operating above the flat-band condition. MSM-PDs with unequal Schottky barrier heights at the electrodes (asymmetric MSM-PDs) are also studied. We find that asymmetric detectors exhibit asymmetric dc characteristics with the photocurrent asymmetry opposite to the dark-current asymmetry. We also find that the mixing efficiency of the MSM-PD increases with increase in applied ac voltage and decreases with increase in ac frequency. For asymmetric detectors, a rectification current exists even under zero mean ac bias that varies not only with ac voltage and optical power but also with ac-bias frequency. The theoretical results agree with observed experimental results.

Improvements in the performance of InGaAsN quantum well VCSELs operating near 1300 nm are reported. The effects of alloy composition on the photoluminescence intensity, linewidth, and anneal-induced wavelength blueshift of molecular beam epitaxial InGaAsN quantum wells are detailed. VCSELs employing a conventional p-n diode structure are demonstrated and compared to devices using two n-type DBR mirrors and an internal tunnel diode. Room-temperature differential efficiencies as high as 0.24 W/A, output powers of 2.1 mW, and a maximum CW operating temperature as high as 105 degree(s)C have all been demonstrated in these devices.

We study 1.55micrometers filter and VCSEL devices capable of wide and continuous tuning based on a single control parameter. Ultra-high reflective DBR mirrors are realized with a low number of DBR periods using high refractive index contrast: (I) (Delta) n=2.17 for InP/airgap DBR's (3.5 periods) and (II) (Delta) n=0.5 for Si₃N₄/SiO₂ DBR's (12 periods) with a polymer sacrificial layer to implement the air-cavity. Corresponding fabrication technologies are presented in detail. In both cases spectral tuning (>100nm, theoretically) is obtained by micomachined actuation of the included air-cavity. Large stopband widths and very large tuning efficiencies are obtained by model calculations. For VCSEL's a trade-off between lasing efficiency and tuning efficiency is obtained. Experimental results show very good optical properties: high mirror reflectance and clear single-line filter transmission. The first tunable dielectric filter based on polymer sacrificial layers is presented: (Delta) (lambda) /(Delta) U= -7nm/V at 1mA. The potential of the airgap concept: the filter transmission or the laser emission wavelength can be continuously tuned over more than 100nm, thus, the whole spectral gain profile can be addressed by a single control parameter.

In the literature, theoretical studies have indicated the quantisation of optical modes by cavity confinement may lead to enhancement of spontaneous emission factor (beta) . Placement of a radiating system within a cavity with a dimension the order of one wavelength alters the number of allowed optical modes to which photons couple. However, this does not guarantee enhancement. A typical semiconductor laser will be required to operate over a temperature range of at least 80 degree(s)C. Here we model the confinement of a radiating source between two DBR mirrors forming a planar microcavity and consider (beta) as a function of temperature where we use a calculated temperature dependent emission line, which the authors believe to be the first investigation including cavity effects. The results show that at threshold (beta) has a broad maximum with increasing temperature.

We propose a novel treatment that enhances the accuracy of the Effective Index Method (EIM) when used for gain-guided oxide-confined VCSELs. If a thin oxide is placed at or near a z-field null position, the diffraction caused by the oxide becomes negligible. Gain-guiding subsequently dominates and causes the EIM to break down. To circumvent this problem, we propose to use an artificial index-guided diffraction effect to simulate the gain-guided diffraction effect. This is achieved by increasing the oxide thickness and making a correction to the oxide index by taking a weighted sum between the original oxide index and the center region index at the oxide layer position. The weight is specifically chosen to be the mean z-field (normalized to its local z-field variation) at the position of the oxide. We show that this simple correction to the EIM successfully simulates the gain-guided diffraction effect and produces the correct transverse phase variation for oxide-apertured VCSELs when gain-guiding becomes the dominant mechanism. Therefore, the improved EIM is able to produce resonant wavelengths which are in excellent agreement to those of the vector Green's function method for the COST-268 VCSEL model, both in the gain-guided and index-guided regimes. Comparisons with an experimental model have also been made and excellent agreement is shown.

As quality and power of light emitted by GaAs-based vertical cavity surface emitting laser (VCSEL) devices are rather sensitive concerning temperature a dynamic description of the multi-mode field dynamics require the incorporation of temperature effects in the Maxwell-Bloch laser equations. In our approach we extend the equations of motion for the carrier density and the light field by dynamic equations for the spatially resolved lattice and plasma temperatures, which reflect the exchange of energy between the different subsystems in thermal quasi-equilibrium. The gain and refractive index spectra of the active quantum-well structure will be derived from temperature dependent microscopic scattering rates. Calculations are performed for both, carrier-carrier and carrier-phonon scattering processes, starting from Boltzmann's equation which then is approximated by a relaxation rate approach. The resulting scattering rates enter the band-resolved Semiconductor-Bloch equations which are directly coupled to the macroscopic field equations for the electric field and the carrier density. Based on that nonlinear system of equations, time resolved simulations are carried out and recorded over the transverse spatial coordinates for the vertically emitting laser structure. Numerical investigations of the dynamic behavior reveal the strong influence of temperature on the resulting near-field polarization mode patterns.

This work focuses on the effects of spatial hole-burning (SHB) on the modulation response of oxide-confined vertical-cavity surface-emitting lasers. The comprehensive laser diode simulator, Minilase, as well as a simple 1-D rate equation models are used as simulation tools in the studies. We demonstrate that, due to the non-uniform transverse optical intensity, carriers at different locations of the quantum well (QW) have different stimulated recombination rates, and therefore exhibit different dynamic responses under direct modulation. This non-uniformity is revealed to be responsible for an over-damping of the relaxation oscillation and the reduction of the modulation bandwidth. Due to the limit of this nonlinear effect, VCSELs with small oxide apertures show lower intrinsic maximum bandwidth compared with that of large aperture structures. Further simulations demonstrate that this damping effect can be greatly reduced by making the electrical aperture smaller than the optical aperture, thereby significantly improving the modulation response.

A new micro-cavity design is proposed and structures are realized using a 2D photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q-value of 816+/- 30 is achieved at (lambda) =1.55micrometers . This high-Q cavity will enable realistic realization of spontaneous emission modification and on-off optical switches.

We develop a model that describes the polarization dynamics of VCSELs with an absorbing region surrounding the active zone. We find that the dynamical behavior of the optical field is organized in four regions: stable linearly-polarized operation, intensity pulsations of a linearly-polarized component, pulsations of both total intensity and polarization, and polarization self-pulsations with constant total intensity. We characterize the four regions by computing the polarization resolved optical and power spectra. The predicted scenario agrees with recent experimental results.

An analysis of the nonlinear dynamics of current modulated weakly index-guided VCSELs in a multi--transverse mode regime is performed by using a model that takes into account all the transverse modes supported by the waveguide. Nonlinear dynamical behavior is studied when applying current modulation of high frequency and large modulation depth. Chaotic behavior is obtained in the multitransverse mode regime due to transverse mode competition. Chaotic operation is such that multistability of the chaos-chaos type is observed. Injection of appropriate optical pulses can switch between different stable chaotic solutions. The case of a VCSEL in which the fundamental mode is selected is also analyzed. Nonlinear dynamics of the single mode VCSEL is such that the chaotic behavior is not present for the considered range of current modulation amplitudes and frequencies. Only periodic behaviors are observed, in such a way that multistability of different periodic solutions also appears. Switching between different stable periodic solutions also appears when appropriate external optical pulses are injected. Finally, we show that spontaneous emission noise increases the number of available channels in chaotic optical communication systems in which frequency division multiplexing with multi-transverse mode VCSELs is used.

In this contribution, we analyze the synchronization properties of two chaotic optical field generated by two VCSELs in presence of a saturable absorber. The vectorial nature of the chaotic field requires a continuous control scheme to achieve a high-quality synchronization between the two sources. We proposed a novel encoding scheme, exploiting a two contact VCSEL structure, which allows an easy and direct modulation of the transmitter. The added degree of freedom constituted by the chaos in polarization allows a reduction of the probability error (or enhancement of the transmission capacity) at the receiver.

Two-transverse-mode vertical cavity surface emitting lasers (VCSELs) subject to external optical injection is experimentally investigated. The spectra of the VCSEL with two parallel-polarized modes, under optical injection, demonstrate significantly different behaviors, compared to the VCSEL with two orthogonally-polarized transverse modes. In a VCSEL with two orthogonally-polarized transverse modes, the experimental results are good qualitative agreement with the theoretical prediction that the external optical injection can be used to achieve single-mode operation. However, in the case of a two parallel-polarized transverse modes VCSEL, single-mode operation cannot be obtained via optical injection. When the injection frequency is close to one of the modes, the coexistence of the injected beam and the mode gives rise to very rich dynamical behavior, however, the other mode is unperturbed by the optical injection.

Two different approaches are commonly used for Fabry-Perot Semiconductor Optical Amplifiers (FP SOAs) performance analysis: the Fabry-Perot resonator approach and rate equation approach. Compared with the Fabry-Perot resonator approach, the rate equation approach is more powerful because noise and mode-related performance analysis can be included. However, it has been shown that the results based on Fabry-perot approach contains multiplicative factor which arise from an explicit consideration of the resonator and those factors are missing in the rate equation approach. As a result, the existing rate equations provide a poor description of FP SOAs. Our analysis shows that this is due to the fact that the interference between the injected optical field and the intracavity optical field has not been taken into account properly. In this paper, a new photon density rate equation for Fabry-Perot semiconductor optical amplifiers is derived based on the electric field rate equation. By taking this interference into account, our derivation shows that the input coupling term in the photon density rate equation is a function of the top and bottom mirror reflectivity, as well as the bias condition. Optical gain predictions from this new photon density rate equation match well with experimental measurements.

A general scheme for the determination of vital operating characteristics of semiconductor lasers from low intensity photo-luminescence spectra is outlined and demonstrated. A fully microscopic model for the calculation of optical properties is coupled to a drift diffusion model for the mesoscopic charge and electric field distributions to calculate photo-luminescence and gain spectra in barrier-doped semiconductor laser material. Analyzing experiments on an optically pumped multi quantum-well structure it is demonstrated that the electric fields arising from the space charges of ionized dopants contribute to strongly excitation dependent optical properties, such as significant shifts of the luminescence versus peak gain wavelengths.

The position-dependent effective mass Hamiltonian H=- (h/2)[m(z)]^(alpha )(Delta) [m(z)]^(beta )(Delta) [m(z)]^(alpha )+V(z) with 2(alpha) + (beta) =-1 is applied to the problem of periodic heterostructure with abrupt interfaces and discontinuous mass distribution. In order to determine the most suitable operator ordering, numerical results for interband and intersubband transition energies are compared with experimental data for various GaAs/Al_xGa_1-xAs superlattices and quantum wells. The ordering- related energy shift as a function of structural parameters (well thickness, barrier thickness and height) is investigated. We find that variation of kinetic energy operator ordering can cause transition energy shift exceeding 40 meV. The model with (alpha) = 0 and (beta) = -1 consistently produces the best fit to experimental results.

The material physics of digitally grown InAlGaAs quaternary alloy systems are investigated using Molecular Beam Epitaxy (MBE) grown layers. With MBE, arbitrary epitaxial alloy compositions can be achieved, without changing the group III elemental constituents flux rates, by simple sequential shuttering of the relevant fluxes. Monolayer fluctuations create inhomogeneities that lead to a broadening of the photoluminescence (PL) spectra. Multiple PL peaks are also seen in select alloy compositions.

Determining the electron and hole subband energy levels in a quantum-well (QW) laser itself is a key issue for the device design to improve laser characteristics such as temperature insensitive performance and so on. The resonant electron Raman scattering (ERS) spectra has been observed at room temperature above threshold by self-photo-excitation in InGaAs/GaAsP single 7nm QW lasers and InGaAs double 8nm QW lasers both grown on GaAs with different Indium contents. The first and the second subband energies of the electrons and holes in the QW are determined from the ERS spectra. The efficiencies of some ERS peaks exceed ~10^-3. The confined self-photo-excitation occurs along the laser active waveguide and induces the efficient intersubband transitions in the QW. These indicate that the efficiency of the ERS is possible to increase by lengthening laser photon lifetime in the cavity with a high reflective coating for the laser light, and by enhancing the TM polarized intersubband transitions with TM polarized laser light, which is generated between electron and light hole transition by introducing tensile strained QW. We propose a new type semiconductor with coherent wave generation and amplification by the self-induced ERS in Qws and quantum wires and quantum dots.

A fully microscopic model is used to calculate the carrier capture times in quantum-well lasers operating at wavelengths in the 1.3 micrometers regime. The capture times are shown to be crucially dependent on the carrier confinement and therefore on the well and barrier materials. For a common well width of 6nm the capture times in InP/InGaAlAs and InP/InGaAsP structures are found to be in the 5ps range, whereas about a factor of ten longer times are predicted in GaInNAs/GaAs. By lowering the barriers using GaInNAs instead of pure GaAs or widening the well capture times similar to those in the InP-based structures can be obtained in the GaInNAs-based structures.

Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. It is well known that the value of diffusion coefficients affects the threshold pumping current of a semiconductor laser. At the same time, the strength of carrier diffusion process is expected to affect the modulation bandwidth of an AC-modulated laser. It is important not only to investigate the combined DC and AC effects due to carrier diffusion, but also to separate the AC effects from that of the combined effects in order to provide design insights for high speed modulation. In this presentation, we apply a hydrodynamic model developed by the present authors recently from the semiconductor Bloch equations. The model allows microscopic calculation of the lateral carrier diffusion coefficient, which is a nonlinear function of the carrier density and plasma temperature. We first studied combined AC and DC effects of lateral carrier diffusion by studying the bandwidth dependence on diffusion coefficient at a given DC current under small signal modulation. The results show an increase of modulation bandwidth with decrease in the diffusion coefficient. We simultaneously studied the effects of nonlinearity in the diffusion coefficient. To clearly identify how much of the bandwidth increase is a result of decrease in the threshold pumping current for smaller diffusion coefficient, thus an effective increase of DC pumping, we study the bandwidth dependence on diffusion coefficient at a given relative pumping. A detailed comparison of the two cases will be presented.

Characteristic temperature coefficients of the threshold current (T₀) and the external quantum efficiency (T₁), on highly-strained In_0.35Ga_0.65As- ((lambda) =1.17micrometers ) and In_0.4Ga_0.6As- ((lambda) =1.19micrometers ) QW lasers, are studied as simple functions of the temperature dependent of the physical parameters of the semiconductor lasers. Simple expressions of characteristics temperature coefficients of the threshold current (T₀) and the external differential quantum efficiency (T₁) are expressed as functions as physical parameters and their temperature dependencies. The parameters studied here include the threshold (J_th) and transparency (J_tr) current density, the carrier injection efficiency (N_inj) and external (N_d) differential quantum efficiency, the internal loss ((alpha) _i), and the material gain parameter (G₀). Simple expressions for T₀ and T₁ are derived in terms of the fundamental device parameters, indicating that the observed cavity length dependence is due to the length dependence of the modal threshold gain. The influence of monomolecular, radiative, and Auger recombination on the characteristic temperature of the transparency current density, T_tr, are analyzed. A measurement of T_tr, then allows one to determine the dominant recombination mechanisms in the QW. The characteristic temperature of the internal loss, T_(alpha i), can be used to determine the influence of intervalence band absorption on the value of T₀. The analysis done on the InGaAs QW lasers show that the simple expressions for T₀ and T₁ values gives consistent results between experiments and theory.

The modulation response of a diode laser for telecommunications applications is a critical performance metric for high speed operation. In particular, for uncooled laser applications, the temperature sensitivity can by quite important. We have done microscopic calculations for 1.3 micrometers InGaAsP and InGaAlAs based quantum well laser designs using an integrated laser simulator. The simulator includes the normal carrier transport, the bound carrier populations in each well, the gain from the quantum wells, the optical fields and the stimulated emission self consistently for each bias condition of the device. In particular, the quantum wells are explicitly treated, including the quantum mechanical calculation of the bound levels, the density of states and the gain. With the inclusion of temperature dependent Auger recombination the details of the temperature sensitivity of the laser characteristics is well modeled. The final modulation response of the laser diodes depends both on the intrinsic quantum well gain characteristics and on the transport of carriers through the multi-quantum well active region of the diode. A compact model of the dynamic laser response must account for the impact of the transport.

We present a quantized version of the Maxwell-Bloch equations keeping spatial dependency. The equations of motion for a semiconductor laser are derived in density matrix theory. The underlying approximations in various limits are discussed carefully. The derived equations of motion allow a comparison to the Langevin approach and a discussion of its validity. An analytic solution for the stationary problem that includes phase sensitivity will be given. A natural consequence of the phase sensitivity is an enhancement of the laser linewidth (beyond the Schawlow-Townes limit) in addition to the one that is commonly attributed to non-orthogonality of modes in longitudinal or transverse direction.

We describe the different mechanisms to generate waves in the transverse section of lasers. Our analysis, based on the Maxwell-Bloch equations, is compared to recent experimental results.

Measurements of the optical gain, differential refractive index and linewidth enhancement factor ((alpha) parameter) in 980 nm InGaAs/InGaAsP broad area lasers diodes are presented. Two different experimental configurations for the measurement of the Amplified Spontaneous Emission spectra, both using a spatial filtering technique, are compared. A new procedure for extracting the modal index change in the case of low optical confinement factor laser structures is proposed. We present and discuss the influence of the experimental technique, and of the data processing on the extracted value of the gain and ß parameter as a function of injection level.

A quasi-3D model has been developed with the aim of studying the different factors limiting the performance of high-brightness high-power tapered lasers. The model solves the complete semiconductor and thermal equations, neglecting the flow of carriers and heat along the cavity ax is, together with a 2D Wide-Angle Beam Propagation method solving the optical propagation. The coupling between electrical, thermal and optical equations yields a stable solution which incorporates carrier and temperature induced perturbations of the refractive index. Although tapered lasers have already demonstrated superior beam quality performance in comparison with broad area devices, they still suffer of beam filamentation at high power levels. We analyze the influence of the different competing factors in the self-focusing process for 980 nm lasers with a gain guided taper section. The simulation results indicate that the lasers with the longest taper section provide the highest output power before the filamentation process is triggered, and that the backward propagating field plays a crucial role in the stability of the output beam.

Twin stripes laser diodes emitting at 1.3 micrometers are presented. The InP based devices were fabricated using a GaInAsP based quantum well structure. The technological processes included wet etching and photolithography that allowed a good control of the heights of the laser. The top electrodes were obtained by e-beam lithography giving sufficient resolution to allow the fabrication of twin stripe lasers with an inter ridge space from 1 to 10 microns. The wet etch solutions were H₃PO₄/H₂O₂/H₂O for the top GaInAs layer and H₃PO₄/HCL for the InP layer, the first has the advantage of being selective on InP. The final top electrodes were deposited also by e-beam lithography over a BCB insulating layer. The final laser chips showed to be effective in power (8 mW per stripe) and had a typical threshold of 40 mA. Optical and electrical coupling were investigated and showed that both were present in the lasers. The electrical coupling phenomena results in the modification of the slope and the threshold of the P(I) function when the second laser is biased while the optical coupling is demonstrated by a coupling of light in the waveguide of the second laser (shorted) while the first one is biased.

The effects of inter-ridge coupling on both the static and high frequency properties of twin stripe laterally coupled lasers emitting at a wavelength of 1.3 micrometers are investigated. It is found that when both ridges are lasing, the emission spectrum is multi longitudinal mode, with each peak being single valued close to threshold, or split in two at higher biases. Spectrally resolved near and far field measurements are made which clearly distinguish that the system lases predominantly in the out-of-phase mode close to threshold, whereas it lases in both in-phase and out-of-phase modes at higher biases. The out-of-phase mode is found to emit at higher frequencies than the in-phase mode.

Theoretical studies of twin stripe laser arrays have shown an enhanced modulation bandwidth over that achieved with single stripe devices. However, experimental data from the devices has concentrated mainly on the device spatio-temporal dynamics, by observation of the near- and far- fields. To our knowledge, only few experiments have been conducted to extract modeling parameters to feed the simulation with approximate values of its parameters. In this paper, based on our own experimental data from a twin stripe array, we clarify the role of the real and imaginary parts of the coupling constant. In the present paper we present procedures to evaluate their sign and modulus.

Our report focuses on the strong kink found in the P-I output of an asymmetric twin stripe semiconductor laser. A multi longitudinal mode model is used to describe the system. The model allows for asymmetric coupling of the two lasers and also accounts for multi longitudinal effects within and in-between the lasers.

A theoretical study of the control of the high-speed modulation of Two Laterally-Coupled Lasers (TLCL) is presented. The analysis is centered on the spatio-temporal dynamics of the TLCL when strength coupling between emitters is varied, depending of the distance between emitters and the carrier diffusion level. We have controlled the high-speed chaotic dynamics through the injection current, studying the temporal evolution of the relative phase between the fields of the two stripes. After controlling the high-speed dynamics, we have obtained a modulation scheme by asymmetric switching of the injected current in both stripes, which gives an output pulse modulation with a high repetition rate.

We report on the combined theoretical and experimental observation of an increase of the small signal modulation response of a Laterally Coupled Diode Laser (LCDL) system beyond its relaxation oscillation frequency. The increase is achieved by means of lateral coupling. Theoretical approaches are presented to explain the experimental observations obtained with these LCDL devices. Our results shed light on the principle of diode laser coupling an open up new perspectives for LCDL for high-speed optical communications.

Semiconductor lasers with optical feedback are prone to exhibit unstable behavior. When working near threshold with moderate to low optical feedback, intensity dropouts are observed. These intensity drops, also called low-frequency fluctuations, occur both in single-mode and multimode semiconductor lasers. In this paper, the dynamics of the power distribution between the longitudinal modes of a multimode semiconductor laser is experimentally and numerically analyzed in the low-frequency fluctuation regime. It is observed that power dropouts of the total intensity, corresponding to drops in the dominant modes of the laser, are invariably accompanied by sudden activations of several longitudinal side modes. These activations are seen not to be simultaneous to the dropouts of the main modes, but to occur after them. The phenomenon is statistically analyzed in a systematic way, and the corresponding delay is estimated, leading to the conclusion that the side mode activation is a consequence of the dropouts of the dominant modes. A multimode extension of the Lang-Kobayashi equations is used to model the experimental setup. Numerical simulations also exhibit a time delay between the side-mode activation and the power dropout of the total intensity.

We discuss some aspects of the excitability in a semiconductor laser with short external cavity. It is demonstrated both theoretically and experimentally how a two-section semiconductor laser consisting of a DFB section and an integrated passive phase tuning section performs an excitable response to optical injection. A mode analysis of the model equations allows to understand and explain the origin of the excitability.

We demonstrate analytically and numerically that multiple mixed external cavity mode solutions are possible for a laser subject to optical feedback from two external cavities. Such solutions exhibit a series of bifurcations and can be easily identified from optical spectra and their frequency content. Similar states have been proposed and analyzed within the framework of the usual Lang-Kobayashi equations describing a semiconductor laser subject to a single optical feedback in short cavities and with moderate pumping. We will present experimental results demonstrating the existence of mixed-mode states in a two-cavity system. We also find that the bifurcation sequence can terminate in low frequency fluctuation states before restabilization on a new maximum power external cavity mode.

We present and analyze a new concept for a semiconductor laser with a Fourier-transform external cavity that allows for purely electronically operated wavelength tuning, simultaneous control of multiple gain media within one shared external cavity, and simultaneous multi-wavelength emission from one laser diode only. We investigate the new setup with particular focus on simultaneous two or even multi-wavelength operation from the same diode. The simultaneity of the two modes is unambiguously proven by sum-frequency generation. In addition, we discuss applications of the simultaneous two-wavelength operation with a particular focus on Terahertz difference frequency generation in combination with a photomixer.

Through simulations based on the rate equations for diode lasers with filtered optical feedback, we show that in the Coherence Collapse regime a large variety of dynamics is predicted such as periodic and quasiperiodic oscillations and chaos. The control of the transition through these dynamical regimes is achieved through the filter parameters : the filter's spectral width and its central frequency.

A semiconductor laser subject to phase-conjugate optical feedback can be described by rate equations, which are mathematically delay differential equations (DDEs) with an infinite dimensional phase space. This is why, from the theoretical point of view, this system was only studied by numerical simulation up to now. We employ new numerical techniques for DDEs, namely the continuation of periodic orbits and the computation of unstable manifolds, to study bifurcations and routes to chaos in the system. Specifically we compute 1D unstable manifolds of a saddle-type periodic orbit as intersection curves in a suitable Poincare section. We are able to explain in detail a transition to chaos as the feedback strength is increased, namely the break-up of a torus and a sudden transition to chaos via a boundary crisis. This allows us to make statements on properties of the ensuing chaotic attractor, such as its dimensionality. Information of this sort is important for applications of chaotic laser signals, for example, in communication schemes.

A directly modulated semiconductor laser when subject to optical injection locking is experimentally investigated. The modulation bandwidth is observed to increase when the laser is injection-locked to an external optical signal. It enhances with increasing injection strength and positively increasing detuning frequency. A more than three fold of bandwidth enhancement is observed experimentally. The frequency chirping is observed to reduce in the injection-locked laser system. It reduces significantly at low modulation frequency and increases with modulation frequency, approaching to that of the laser in free-running condition at high modulation frequency. More importantly, simultaneous bandwidth enhancement and chirp reduction is experimentally achieved.

In this paper unprecedented agreement is reported between a theoretical two-dimensional bifurcation diagram and the corresponding experimental stability map of an optically injected semiconductor laser over a large range of relevant injection parameter values. The bifurcation diagram encompasses both local and global bifurcations mapping out regions of regular, chaotic and multistable behavior in considerable detail.

We numerically study the entrainment of two unidirectional coupled single-mode semiconductor lasers in a master-slave configuration. The emitter laser is an external-cavity laser subject to optical feedback that operates in a chaotic regime while the receiver has no optical feedback and consequently operates under CW when it is uncoupled (open loop scheme). We compare the performance of this scheme with the close loop one in which both emitter and receiver are subjected to optical feedback and operate in a chaotic state. We compute the degree of entrainment or synchronization of the two lasers as a function of the detuning, the emitter-receiver coupling constant and the feedback rate of the receiver. We find that the close loop scheme has, in general, a larger region of synchronization when compared with the open loop. We also study the possibility of message encoding and decoding in the both open and close loops and their robustness against parameters mismatch. Finally we compute the time it takes the system to recover the synchronization or entrainment state when the coupling between the two subsystems is lost. We find that this time is much larger in the close loop than in the open one.

Synchronization of chaotic semiconductor lasers has now been demonstrated experimentally using a variety of coupling schemes. Coupling methods include situations where the transmitter laser system is itself chaotic and drives a passive receiver system, both lasers are individually chaotic and, both lasers induce the chaos through mutual self-coupling. The qualitative dynamics for each of these scenarios is adequately captured by an appropriate set of coupled Lang-Kobayashi lumped rate equation models. Such lumped models however cannot distinguish between the possible coupling geometries realizable in real experimental systems and ignore multiple feedback from external reflecting surfaces. For example, real lasers may have AR/HR coated facets and there are several choices of placement of external reflectors and coupling paths relative to these facets. Moreover, nominally single mode FP lasers may exhibit pronounced multi-longitudinal mode dynamics in the presence of weak external reflection and DFB lasers may exhibit dual-wavelength operation or strongly asymmetric spatial hole-burning due to the presence of finite facet reflectivity.

We study numerically the synchronization regimes of optical-feedback-induced chaos in unidirectionally coupled semiconductor lasers. Depending on the operating conditions, the receiver laser intensity, I_R(t), synchronizes with the intensity of the optically injected field, I_T(t-t_c), where t_c is the flight time from the transmitter laser to the receiver laser, or synchronizes with I_T(t-t_c+t), where t is the is the external-cavity round-trip time. In the latter case, the intensity produced by the receiver anticipates the injected intensity I_T(t-t_c) by an anticipation time equal to t. We find that synchronization with a lag time t_c-t is much more sensitive to frequency detuning and noise than synchronization with a lag time t_c. Moreover, we also find that though synchronization with a lag time t_c can be obtained using either an external-cavity or an open-loop receiver, the synchronization quality is always better when an external-cavity receiver is used.

Chaotic dynamics in a self-pulsating laser diode has been shown theoretically to occur by modulation of the laser current. It has been also shown that synchronization of two chaotic self-pulsating lasers can be achieved by small amounts of optical coupling. This result has been obtained with a deterministic model for the laser intensity. We study coherent synchronization of single mode self-pulsating laser diodes by means of a field-equation model that takes into account phase-effects and spontaneous emission noise. It is shown that the size of the coupling required to achieved synchronization is influenced by spontaneous emission noise and by the linewidth enhancement factor. Numerical simulations are then used to identify the optimum regime for efficient synchronization. It is found that good synchronization can be obtained for large values of the bias current, such that the spontaneous emission plays a minor role. The degree of synchronization is studied as a function of the differences between the master and slave laser parameters. Finally, a sinusoidal signal is used to analyze a chaotic communication system based on self-pulsating laser diodes.

An experimental demonstration of the chaotic synchronization between two injection-locked semiconductor lasers is reported in this paper. Optical injection on the semiconductor laser not only generates optical chaotic output, but also broadens the bandwidth up to two fold of the laser intrinsic bandwidth. Since the chaotic synchronization based on this system is very sensitive to optical phase, the synchronization quality subject to both phase match and phase mismatch is measured in both time and frequency domains. The synchronization quality of each case is quantitatively expressed by the correlation coefficient.

Encoding information in temporal chaotic signals and decoding it via chaotic synchronization between transmitter and receiver constitute nowadays a well-established technique. The method has been successfully implemented in electronic and optical systems. The latter, besides offering high speed of information transfer, provide a natural way of spatiotemporal communication through the use of broad chaotic optical wavefronts. An optical setup for spatiotemporal chaotic communications was recently proposed based on nonlinear ring cavities. In this article, we examine further in detail such a proposal, comparing two different encoding methods, namely injection and modulation. In the two cases, the correlation between input, transmitted, and output signals is estimated by means of measures taken from information theory. The influence of the message amplitude and parameter mismatch is analyzed.

A semiconductor laser system with delayed optoelectronic feedback has very interesting nonlinear phenomena and important applications in optical communications. By controlling the operating conditions like bias current, feedback strength, and feedback delay time, the system is found to generate different states such as periodic pulsing, quasiperiodic pulsing and chaotic pulsing. With the system operating in periodic pulsing, a stable repetitive pulse stream is generated. The pulsing frequency can be tuned from hundreds of megahertz to a few gigahertz by simply adjusting the operating conditions. Therefore, we can make a new device which generates short optical pulses with a tunable pulsing frequency. Making use of the chaotic pulsing state, the system can be implemented in chaotic optical communications. Chaotic optical communications are of great current interests because of the advantages in improved communication security and bandwidth efficiency. In our chaotic communication experiment, the chaotic pulsing from a transmitter laser is used to encode messages, while at the receiver an identical semiconductor laser is used to reproduce the chaotic pulsing carrier for decoding. High quality of chaos synchronization between the transmitter and the receiver lasers is achieved in our experiment. Successful encoding and decoding of 2.5~Gbit/s NRZ signal is demonstrated.

Chaotic synchronization is investigated using two diode lasers as transmitter and receiver. The transmitter laser is rendered chaotic by application of an optical feedback in an external-cavity configuration. Changes in the spectrum of the synchronized system are shown to be associated with the transition between anticipating and lag synchronization.

Three diode lasers are used as message, transmitter and receive lasers. The message laser is amplitude modulated by a simple message and its output is optically coupled to the transmitter laser ensuring optical modulation of message. The transmitter laser is rendered chaotic by application of appropriate optical feedback. The receiver laser is used to decode the message. Effective signal masking is enhanced by the selection of an appropriate external cavity length, which could be a possible key for chaotic optical communication security.

We have demonstrated hole injection through a tunnel junction embedded in the GaN-based light emitting diode structure. The tunnel junction consists of 30 nm GaN:Si⁺⁺ and 15 nm InGaN:Mg⁺⁺ grown on a GaN-InGaN quantum well heterostructure. The forward voltage of the light emitting diode, included the voltage drop across the reverse-biased tunnel junction, is 4.1 V at 50 Z/cm$_2), while that of a standard light emitting diode with a conventional contact structure is 3.5 V. The light output of the diode with the tunnel junction is comparable to that of the standard device. We then employed the tunnel junction in vertical cavity surface emitting laser structures and dual-wavelength light emitters. In the vertical cavity structure, a good lateral current spreading was accomplished, resulting in uniform emission pattern. The dual-wavelength light emitter has been operated as a three- terminal device with independent electrical control of each LEDs to a nsec time scale.

The phenomenon of resonant mode coupling is modeled and numerically investigated in InGaN-based multiple-quantum- well laser structures. It is shown that under resonant conditions the internal mode coupling can lead to severe distortions of both near- and far-field characteristics. Taking into account the carrier-induced change of the modal effective index for the lasing mode, we show that the resonant internal mode coupling can result in a strongly nonlinear dependence of the modal gain on injection current, with possible region of negative differential modal gain.

A drift-diffusion device simulation model that includes energy balance equations is used for studying hot electron effect in Negative Electron Affinity (NEA) GaN pn junction diodes. Our modeling is focused on the temperature distribution of electrons prior to being emitted into vacuum where electrons have either thermalized to the lattice temperature in the band-bending region of the p-type electrode; or it is possible that some of these electrons emitted are hot. SimWindows, is used as a device modeling program for this study. We calculate electron temperature distributions and hot/cold electron density profiles in a GaN pn junction diode. Hot electron effect is modeled by Stratton's energy balance equations. A constant carrier energy lifetime is used for the electron energy loss mechanism in the interaction of electrons with lattice phonons. Our simulation results show that energy relaxation lifetime is the deciding parameter for electrons losing their energy to the lattice in the band bending region of the p-type GaN.

Semiconductor and fiber amplifiers and lasers are amongst the most complex and critically important components in most modern optical telecommunications systems. The ever increasing demand for bandwidth places severe constraints on component design. Active materials need to be accurately characterized in terms of their optical properties. In addition, realistic simulation tools must be capable of resolving the multi-THz bandwidths while providing a rapid turn around to the system designer. We will report on the implementation of an extremely efficient algorithm running within an object-oriented simulation environment. As an illustration, we will present results showing how a WDM-based semiconductor optical amplifier and a TDM Mach-Zehnder interferometer gate can be optimized using rigorously computed and experimentally validated semiconductor optical material properties.

Telecommunication systems using 200 fs optical pulses for ultrahigh bit-rate optical transmission require new concepts to be developed for ultrafast all-optical switching. On the basis of numerical experiments, we discuss how a semiconductor optical amplifier in a Sagnac interferometric arrangement can be used for switching these short pulses. The switching principle is based on gain and index saturation dynamics on a sub-picosecond timescale. The model accounts for bi-directional propagation of ultrashort optical pulses through the amplifier as well as free-carrier absorption and two-photon absorption.

A major advantage of the Four Wave Mixing technique for wavelength conversion is its transparency to modulation format. This advantage becomes important for some IP over WDM network realizations where part of the signaling information is an analog or subcarrier modulation approach. In such applications the phase noise characteristics of the conversion process are very important. In this work, a detailed theoretical and experimental study of the additional phase noise induced by the FWM process is presented. The nonlinear elements used in the experiments are semiconductor optical amplifiers as well as dispersion shifted fibers. Two linewidth measuring techniques have been used, the self-homodyne and the beating with a laser source with already known linewidth. The measurements are carried out for different operating conditions (wavelength, pumping level of the nonlinear elements, input power, input signals with different phase noise characteristics, etc). The theoretical interpretation of the above results is based on a modification (inclusion of the influence of the amplified spontaneous emission noise) of an already presented approach which has focused on the mixing process in a resonant optical cavity.

Electroabsorption modulators (EAMs) based on the quantum confined Stark effect have advantages in applications that require high speed, low drive voltage, and high extinction ratio. They are promising devices for external signal modulation in high-bandwidth optical communication systems. EAMs can be integrated with other devices like laser diodes, semiconductor optical amplifiers, and mode transformers. We have previously fabricated InGaAsP/InP multi-quantum well EAMs with a bandwidth of 25 GHz and a drive voltage of 1.2 V and 20 dB extinction ratio. Further optimization of our devices requires a detailed analysis of internal physical processes and their interaction. In this paper, we employ a two-dimensional electro-optic device model to analyze our EAMs. The model self-consistently combines kp bandstructure and absorption calculations with a carrier drift-diffusion model and optical waveguiding. The required low polarization sensitivity of EAMs leads to strong valence band mixing so that usual effective mass models cannot be applied. Optical transmission characteristics are calculated which are in good agreement with measurements. Modulation efficiency and linearity are analyzed in detail. Optimum operation voltages are identified.

Using the semiclassical approach the gain and noise powers, associated to signal and, generated in optical Raman amplifiers, are estimated for forward and backward configurations. Because it combines a corpuscular approach to a phase-amplitude description of the optical field and of the associated noise, this classical formalism allows to identify, to distinguish and to evaluate the respective noise contributions linked, first, to incident fields, such as input zero-point fluctuations, and relative intensity noise associated to the pump, and to the amplifier itself due to the electron momentum fluctuations at the optical frequency. The contribution of Rayleigh backscattering and pump depletion effects are taken into account. For both configurations, the effects of gain and pump power distribution on noise generation are underlined. The determination of the origin and of the amount of intensity noise at the output constitutes a first step toward the amplification of signal with reduced noise amount in Raman amplifiers.

The effective permittivities at dielectric interfaces for the 4th-order finite-difference time-domain (FDTD) method using a symplectic integrator propagator are proposed for the two-dimensional (2-D) TM polarization case. For a given accuracy level, the memory resources required by the 4th-order FDTD method with the effective permittivities are reduced by more than an order of magnitude with comparison to the standard FDTD method. The CPU time is also reduced. The permittivities are derived by matching the numerical reflection and transmission at the interface to the exact ones in 3rd-order accuracy. The accurate performance of the proposed method is demonstrated by various numerical examples.

We have experimentally demonstrated that the stability of CW and mode-locked erbium doped fiber ring laser can be significantly improved with a semiconductor optical amplifier (SOA) inside the cavity. The fast saturable gain of the SOA suppresses significantly the self-pulsing due to ion pairs in the erbium-doped fiber, which acts as a saturable absorber. A linear stabilization analysis of the laser system agrees with out experiment results.

We report the growth by molecular beam epitaxy (MBE) of InAlSb/InSb superlattice structures to investigate their potential for reducing the Auger recombination and intervalence absorption effects, which currently limit the maximum operating temperature. The devices were all grown onto InSb(001) substrates and are not lattice matched. They are a psuedo double heterostructure, comprising an active region 3micrometers thick, consisting of 10 repeats of In_0.904Al_0.096Sb/InSb (10nm/6.5nm), surrounded by undoped layers of In_0.944Al_0.056Sb. Electrical confinement in the active region is by means of a 20nm thick wide gap In_0.794Al_0.206Sb barrier layer onto which a p type In_0.944Al_0.056Sb tunnel contact and highly doped n type In_0.944Al_0.056Sb region is grown, which together with a substrate highly doped n type In_0.944Al_0.056Sb region gives optical confinement, due to a Moss-Burstein shift of the refractive index. We have demonstrated laser operation up to 160K for devices ~1000micrometers long by 15micrometers wide. FTIR spectroscopy measurements revealed a lasing wavelength of 3.65micrometers at 80K. Under pulse bias conditions, the threshold current density was 320Acm^-2 at 80K. The peak output power was in excess of 800mW. Detailed modeling of the structures shows that greater strain is required in the system in order to quench Auger losses at higher temperatures.

Using an Ikeda model, which was introduced to describe the dynamics of an optical bistable resonator it is demonstrated analytically that anticipating synchronization can be obtained in chaotic time-delay systems governed by two characteristic delay times. We derive existence and stability conditions for the dual-time anticipating synchronization manifold. We also show that increased anticipation times for chaotic time-delay systems with two characteristic delay times can be obtained by the use of cascaded systems. The theory is in excellent agreement with numerical simulations. We also derive existence conditions for cascaded anticipating synchronization in external cavity semiconductor lasers.

The coupling length of the dielectric optical waveguide is inversely proportional to the difference of the even- and odd-mode propagation constants. It is important to accurately determine these values, since their difference is in a fraction of 10^-3. To resolve this small difference, simulation using 2-dimensional finite-difference in time-domain method requires long computation time. Moreover, the time-domain method is not efficient to determine the modal functions. Frequency-domain method is cast as an eigenvalue solver, and the modal functions can be directly solved with the corresponding propagation constant. However, this method requires an initial knowledge of the eigenvalue to efficiently determine the modes of interest. This initial knowledge can be provided from the time-domain method. In this study, we conduct analysis of an AlGaN/GaN dielectric optical waveguide coupler combining time- and frequency-domain methods. Taking advantage from both methods, the propagation constants and the modal functions were obtained with a reasonable computation time.

In this article, a new variational approach for extraction of guided and leaky modes in layered waveguides is proposed. To verify the method, results of analysis of a typical test case is compared to the other references, being in agreement with them. The efficiency of the proposed approach is compared to other reported methods.