We derive a CW theory for optical-fiber photon-pair sources, including the effect of non-zero response time of the fiber's Kerr nonlinearity. We also include the effects of realistic transmission and detection losses. This theory predicts stronger photon-number correlations than seen experimentally with a pulsed pump, showing the need for development of a pulsed pump theory.

A third-order-mode-emitting laser diode is demonstrated. The AlGaAs/GaAs hetero-structure is engineered to emit a photon pair through intra-cavity modal phase-matched parametric down-conversion. Device operations and twin photon generation experimental issues are discussed.

We present results on the state of the art in optoelectronic devices for chaos generation and message encryption/extraction. We concentrate on two kind of chaos based emitters and receivers: a semiconductor laser subject to all optical feedback and operating in a non linear regime and a semiconductor laser subject to nonlinear electro optical feedback and operating in a linear regime. We show that both configuration give very good synchronization properties and are suitable for message enconding/decoding at bit rates as high as Gbit/s.

A high efficiency, triggered single photon source with applications to quantum communications is discussed. The sources is formed from an InAs-based quantum dot located in the center of a micropost cavity formed from GaAs, with top and bottom GaAs/AlAs distributive Bragg reflector pairs, and lateral processing. When pumped above band into the semiconductor host, correlation measurements show a reduction in the two-photon probability to 0.14, compared to unity for a Poisson source. The external efficiency of this structure is 0.24.

This paper describes the current status of Coarse Wavelength Division Multiplexing (CWDM), and then progresses to discuss how it may evolve in networking applications in the future. As WDM can enhance not only transmission but also networking systems, the paper reports a potentially low cost WDM based access node architecture, particularly suited for routing optical data packets on nanosecond timescales. The scheme is cascadable and involves the use of a simple semiconductor optical amplifier (SAO) based add-drop switch. Preliminary results concerning the operation of the add-drop switches under multi-wavelength operation are reported.

Optical communication systems operating at 10 Gbit/s such as 10 Gigabit Ethernet (GbE) are becoming more and more important, even in Local Area Networks (LAN) and Metropolitan Area Networks (MAN). This market requires optical transceivers of low cost, size and power consumption, driving a need for "hot" transmitter: uncooled DFB lasers directly modulated at 10 Gbit/s for short link (up to 10 km) and high operating temperature integrated (hybrid or monolithic) solution, like laser and electro absorption modulator at 10 Gbit/s, for longer distance (40 - 80 km). The paper describes the current status of these devices for different applications. We will report results on uncooled high speed 1300 nm DFB laser which is capable of being manufactured in high volume at the low cost demanded by the GbE market. Combining an optimized active region based on InGaAsP strained MQW (Multi Quantum Well) and a low parasitic lateral confinement region, we have fabricated 10 Gbit/s directly modulated uncooled DFB lasers which work up to 100°C (chip temperature), with eye diagram perfectly open (showing an extinction ratio > 5 dB @ 100°C), and with Bit Error Rate over 10 km without error floor up to 10^-12. We will report the optimization and the results of an electro-abosorption modulator (EAM) based on quantum confined Stark effect in strained multiple quantum wells (MQWs), suitable for 40 - 80 km propagation of 10Gb/s optical signals on standard single-mode fiber at 1550 nm. The MQW structure has been designed and fabricated to obtain high extinction ratio, low insertion loss and negative chirp at 1550 nm, 60°C. Devices demonstrated a contrast ratio of above 10 dB, insertion loss of 5 dB and a negative chirp at 10 Gb/s, 60°C with a voltage swing of 2 V.

AlGaAs/InGaAs based high power pump laser diodes with wavelength of around 980 nm are key products within erbium doped fiber amplifiers (EDFA) for today's long haul and metro-communication networks, whereas InGaAsP/InP based laser diodes with 14xx nm emission wavelength are relevant for advanced, but not yet widely-used Raman amplifiers. Due to the changing industrial environment cost reduction becomes a crucial factor in the development of new, pump modules. Therefore, pump laser chips were aggressively optimized in terms of power conversion and thermal stability, which allows operation without active cooling at temperatures exceeding 70°C. In addition our submarine-reliable single mode technology was extended to high power multi-mode laser diodes. These light sources can be used in the field of optical amplifiers as well as for medical, printing and industrial applications. Improvements of pump laser diodes in terms of power conversion efficiency, fiber Bragg grating (FBG) locking performance of single mode devices, noise reduction and reliability will be presented.

Today's telecommunication market is characterized by conservative business practices: tight management of costs, low risk investing and incremental upgrades, rather than the more freewheeling approach taken a few years ago. Optimizing optical components for the current and near term market involves substantial integration, but within particular bounds. The emphasis on evolution, in particular, has led to increased standardization of functions and so created extensive opportunities for integrated product offerings. The same standardization that enables commercially successful integrated functions also changes the competitive environment, and changes the emphasis for component development; shifting the innovation priority from raw performance to delivering the most effective integrated products. This paper will discuss, with specific examples from our transmitter, receiver and passives product families, our understanding of the issues based on extensive experience in delivering high end integrated products to the market, and the direction it drives optical components.

Tunable semiconductor lasers have been listed in numerous critical technology lists for future optical communication systems. Lasers with full band tuning ranges (C or L) allow reduction of the inventory cost and simplify deployment and operation of existing systems in addition to enabling wavelength agile networking concepts in future systems. Furthermore, monolithic integration of full band tunable lasers with modulators to form complete transmitters offers the most potential for reducing system size, weight, power consumption, and cost. This paper summarizes design, fabrication technology, and performance characteristics of widely tunable CW sources and transmitters based on chip scale integration of a Sampled Grating Distributed Bragg Reflector (SG DBR) laser with a Semiconductor Optical Amplifier (SOA) and Electroabsorption (EA) or Mach Zehnder (MZ) modulator. Widely tunable CW sources based on SG-DBR lasers exhibit high fiber coupled output power (20 mW CW) and side mode suppression ratio (>40 dB), low relative intensity noise (below -140 dB/Hz) and line width (<5 MHz) across a 40 nm C-band tuning range. Characteristics of EA-modulated optical transmitters include fiber-coupled time-averaged powers in excess of 5 dBm, RF extinction ratios > 10 dB, and error-free transmission over 350 km of standard fiber at 2.5 Gb/s across a 40 nm tuning range. Monolithic integration of widely tunable lasers with MZ modulators allow for further extension of bit rate (10 Gb/s and beyond) and transmission distances through precise control of the transient chirp of the transmitter. Systematic investigations of accelerated aging confirm that reliability of these widely-tunable transmitters is sufficient for system deployment.

A summary of current work involving the development of high performance, wavelength-tunable integrated optical transmitters for analog applications is given. The performance of sampled-grating DBR lasers integrated with an SOA and an electroabsorption or Mach-Zehnder modulator is evaluated in terms of E/O conversion efficiency, noise performance and dynamic range. Optimization options to maximize either gain, noise figure or spurious-free dynamic range in analog link applications are discussed. It is shown how the combination of chip-scale integration and the use of bulk waveguide Franz-Keldysh absorption allows coupling of a large optical power level into the electroabsorption modulator, and its effects on the modulation response and analog link performance. Link results on an integrated SGDBR-SOA-EAM device includes a sub-octave SFDR in the 125 to 127 dB/Hz^4/5 range and a broadband SFDR of 103-107 dB/Hz^2/3 limited by third order intermodulation products or 95-98 dB/Hz^1/2, limited by second order intermodulation products, over a 1528 to 1573 nm wavelength range.

We report on recent progress in the design and application of vertical-cavity surface-emitting lasers (VCSELs) for optical interconnect applications in the 850 nm emission wavelength regime. Ongoing work toward parallel optical interconnect modules with channel data rates of 10 Gbit/s is reviewed and performance results of flip-chip integrated two-dimensional VCSEL arrays are presented. 10 Gbit/s speed as well as low thermal resistance of the lasers has been achieved. As a possible alternative to graded-index multimode fibers, we show 10 Gbit/s data transmission over 100 m length of a novel, entirely undoped multimode photonic crystal fiber. The use of VCSELs with output powers in the 10 mW range is demonstrated in a 16-channel free-space optical (FSO) module and VCSELs with even higher output power are shown to provide possible FSO connectivity up to data rates of 2.5 Gbit/s.

Vertical cavity surface emitting lasers (VCSEL) in the GaInP/AlGaInP material system have experienced a rapid development in their short history. In general lasers from that material system are suitable for a huge number of applications beginning with TV lasers and high power lasers for edge emitters, continuing with optical data storage, medical applications as well as data communication in cars, air planes, offices and between computers as application field for VCSELs. Especially automotive applications show the highest requirements on a laser with respect to operation temperature and power. In this talk we draw out the problems of the material system AlGaInP and its implications for laser applications. We discuss the epitaxial and technological solutions to overcome at least a part of these inherent problems. We will discuss the possible power that we can expect from VCSELs emitting in the range between 650 nm to 670 nm. We got from our lasers 5 mW, CW @ RT, 670nm and 2.5mW, CW@RT, 650 nm. We emphasize the role of doping, Bragg mirror grading, suitable detuning of cavity mode and gain, and optimisation of the contact layer and control of the oxide aperture in the VCSEL structure to get improved operation characteristics at higher temperatures. From the analysis of high frequency measurements, we could evaluate modulation bandwidths between 4 GHz and 10 GHz. The application of polyimide as a dielectric isolation material shows the potential to obtain modulation bandwidths beyond 10 GHz. For the intrinsic modulation bandwidth we get a value of 25 GHz, which is near the value edge emitters show. A more detailed discussion on photon lifetimes and carrier transport times will be given in the talk. Red light emitting VCSELS driven with short current pulses showed laser emission up to + 160°C case temperature. Thus, a CW operation up to +120°C can be expected after further improvement of power generation (decrease of series resistance) and heat spreading (optimized contacts and mounting). From these characteristics we can conclude that AlGaInP-surface emitting lasers have a real potential as low cost lasers for automotive applications as we all as data communication applications up to 10 GHz.

In this paper the realization, development and production of 1.3μm vertical cavity surface emitting lasers (VCSEL) with datacom suitable performance are presented. These low cost laser diodes are well suited for optical interconnect applications for LAN and MAN with transmission distances up to 15 km. The possibilities as well as the advantages and limits of shifting the wavelength from commercially available VCSEL emitting at 850nm to 1300nm are discussed. 1300nm VCSELs in a low cost SMD plastic package assembled into an intelligent SFP-module developed by Infineon Technologies are demonstrated.

Room-temperature continuous wave operation of Antimonide-based long wavelength VCSELs has been demonstrated, with 1.2mW power output at 1266nm, the highest figure reported so far using this material system. Single mode powers of 0.3mW at 10°C and 0.1mW at 70°C and side-mode suppression ratios up to 42dB have also been achieved. Preliminary reliability test results have shown so far that the devices can work normally without obvious degradation after stress testing at up to 125°C for thousands of hours.

We introduce a scheme incorporating wafer bonding and tunnel junctions to improve the performance long-wavelength Vertical Cavity Surface Emitting Lasers (VCSELs). Through careful design of PL-mode offset, mirror reflectivity, and aperture definition, we achieve lasing to 134°C, output power above 2 mW, single-mode output power at 80°C above 1 mW, and differential efficiencies of 46%. We achieve lasing at wavelengths as high as 1336 nm and show a versatile design that can be applied to any VCSEL functioning at long wavelengths.

A novel integrated cavity surface emitting laser (ICSEL) is proposed in this paper. An ICSEL integrates two different laser structures. One is an in-plane laser with a short lasing wavelength, and the other is a vertical cavity laser structure with a long lasing wavelength. The in-plane laser is used as the light source for optical pumping the VCSEL. By monolithic integration of both the laser structures, some problems related to electrically pumped VCSELs, especially long wavelength VCSELs, and externally optically pumped VCSELs can be solved.

A 1310 nm single-frequency grating-outcoupled surface-emitting (GSE) semiconductor laser with output slope efficiency exceeding 0.05 mW/mA into a multimode fiber, threshold current below 20mA and > 30dB side-mode suppression ratio is reported. The GSE laser consists of a 500μm long active ridge that excites one end of a surface emitting second-order (outcoupler) grating with a broadband reflector terminating the laser cavity at the end of the outcoupler. At the opposite end of the outcoupler is a 200μm long first order distributed Bragg reflector (DBR). The emitting output aperture is approximately 10μm in length. Higher output power is possible for outcoupler lengths greater than 10 um. The GSE laser has an open eye pattern for a nonreturn-to-zero signal at 2.5 Gb/s into a single mode fiber. The far-field beam divergence measured at full-width half-maximum (FWHM) is 5 x 8 degrees.

In this work we study the role of free carriers and excitons on the characteristics of 1.3 μm InAs/InGaAs quantum dot lasers. The study is carried out theoretically by building a mathematical model to calculate the threshold current in the laser and the charateristic temperature, T₀. In order to determine the role of free carrier and excitons on the laser characteristics the model allows for different carrier distribution assumptions to be used, and we look at three cases; all free carriers, all excitons, and both free carriers and excitons in the dots. Our model results show that if we allow either free carriers or excitons to exist but not both, the calculated threshold current and T₀ do not match with the experimental values. Thus we conclude that both free and bound carriers must exist and develop a method for modeling this case. We use a modified form of the Saha equation to calculate the ratio of free carriers to excitons and modify the material gain to account for this ratio. This model results in a threshold current density of approximately 39 A/cm² and a T₀ of 83 K, both of which are in excellent agreement with experimental results.

Experimental and analytical results for semiconductor electro-refractive modulators will be presented. Modulation structures investigated include quantum wells, coupled quantum wells and quantum dots.

Electro optic modulators are key components for fiber optic transmission at data rates exceeding 10Gbit/s. The monolithic integration of an electroabsorption (EA) modulator applying the quantum confined stark effect with a distributed feedback (DFB) laser diode was demonstrated using a novel approach based on a double-stack multiple quantum well (MQW) structure. This novel approach using an identical MQW layer structure for both devices, the DFB laser diode and the EA modulator, will be described and discussed. Recently, a maximum 3dB-cutoff frequency of 25 GHz was measured. Further experimental results obtained from devices operating at 1.3 µm and 1.55 µm, respectively, exhibit the potential of these devices for high-speed data rate transmission.

We reported the nonlinear properties of transfer curves of multiple quantum well (MQW) traveling-wave electroabsorption modulators (TW-EAMs) in analog optical link applications. A new method to extract the optical absorption coefficient of TW-EAMs was developed. By using the method, we investigated the dependence of the transfer curvs on both the input optical power and the bias voltage. The relationships between the RF output power and bias voltage as well as RF input power were studied experimentally and theoretically. A SFDR as high as 128 dB-Hz^4/5 was successfully obtained by adjusting the bias level as well as optical input power at 10.0 GHz.

Nonidentical multiple quantum wells (MQWs) had been widely used for broadening the emission or gain bandwidth of semiconductor optical amplifiers (SOAs). However, the carrier distribution among the MQWs is not uniform, leading to nonuniform gain contributed from different QWs. Thus using nonidentical MQWs for broadband purpose is not intuitively straightforward. Several factors need to be carefully considered. Those factors include the QW sequence, electron/hole transport time across the separate confinement hetero-structure, as well as carrier capture time. In this work, we will discuss the design of MQWs for broadband SOAs. With properly designed nonidentical MQWs, the emission bandwidth could be nearly 400 nm. Also, the tuning range of semiconductor lasers could be extended to be over 200 nm.

The Linear Optical Amplifier (LOA) is a chip-based amplifier that addresses many of the requirements of emerging optical networks: operation under diverse bit rates, channel counts, and switching protocols, as well as reduced cost and size. In this work, we review the operating principles of the LOA, and describe two versions of the LOA technology. The first is a polarization-independent amplifier that operates over the entire C-band. We present several examples of this technology's system performance, and also highlight its value in coarse wavelength-division multiplexing (CWDM) applications. We also demonstrate a new, single polarization LOA technology, which is designed to deliver high linear gain over an extended range of output powers. We measure typical chip gains in excess of 20dB, and demonstrate linear gain performance for an (average) chip power approaching 15dBm. These results indicate that this technology is well-suited for long-reach, 10Gbps transmitter boost applications.

Unlike semiconductor lasers that always operate within a narrow band in frequency domain, semiconductor optical amplifiers (SOAs) normally operate in a much broader area. The noise characteristic is also crucial for amplifier design. The study of the dynamic interaction among the signal channels and noise in SOAs is therefore highly demanded. In this work, a time-domain model is implemented based on the combination of the traveling wave equation, the effective Bloch equation and the modified carrier rate equation. The optical field propagation is described by the traveling wave equation. The interaction between the optical field and the polarization is treated by the effective Bloch equation hence both homogeneous and inhomogeneous gain broadenings over the entire operating frequency range is naturally considered. Finally, the carrier rate equation is modified to make the model self-sustaining. This model has the spontaneous emission noise incorporated hence effects such as noise introduced gain saturation, beatings among different signal channels and the noise are all captured. The key feature of this model is its capability of handling the signal-signal and the signal-noise indirect and direct interactions, generated by the mutual power saturation and the spectral hole burning (SHB), respectively. This model is implemented and validated through comparisons, and is also applied for the simulation of a typical SOA with an assumed operating condition that can hardly be treated accurately by other existing models.

We evaluate the performance of a wavelength conversion technique based on the modulation of the amplified spontaneous emission of semiconductor optical amplifiers through simulation software. Unlike conventional conversion technique the ASE-XGM does not require a CW probe signal. The converted wavelength is determined by an optical filter, which slices the modulated ASE spectrum. We focus on bit error rate (BER)conversion performance of a 2.5 Gbit/s non-return to zero, pseudo-random sequence of order 11. BER values better than 10^-9 are achieved for signal input power ranging from -6 dBm to 0 dBm, and for a slicing filter centered around 0.4 nm red shifted from signal wavelength.

Avalanche Photodiodes (APDs) are key components in modern lightwave communications systems. When compared to p-i-n diodes, APDs provide internal gain via impact ionization which leads to higher sensitivity. In addition, with proper device design, high gain bandwidth products can also be achieved. In this paper, we describe our work in making high speed, low noise APDs - operating at 1300 - using GaAs based multiplication regions. Our results to date have lead to a resonant cavity enhanced (RCE) APD, operating at 1310 nm, with an external quantum efficiency of 36% and an effective k factor of 0.1.

Morphology dependent resonances of dielectric microspheres are used for polarization insensitive optical channel dropping from an optical fiber half coupler to a silicon photodetector in the M-band. The dropped channels are observed in the elastic scattering and the transmission spectra. The highest quality factor morphology dependent resonances have a repetitive channel separation of 0.14 nm and a linewidth of 0.06 nm. The filter drops approximately 10% (0.5 dB) of the power at the resonance wavelength. The power detected by the photodiode is estimated to be approximately 3.5% of the power in the fiber.

We report on novel InP based traveling wave amplification photodetectors exhibiting an external quantum efficiency of more than 100%. Our detectors vertically combine a bulk InGaAs photodetector ridge region with laterally confined InGaAsP quantum wells for amplification. In addition to ultra high responsivities, such detectors have the potential to also achieve high saturation power and high speed. The device physics is discussed using advanced numerical simulation.

Waveguide based Bragg grating devices have the potential of integration with passive or active optical components. A narrow bandwidth Bragg reflection filter or Fabry-Perot resonant structures can be realised using the approach of periodic refractive index modulation in waveguide gratings to form reflective structures. Most authors have considered 1st order Bragg gratings with periods of the order of 228nm operating at 1550nm but at the expense of complexity and high cost of fabrication. This paper describes the design of Silicon-On-Insulator (SOI) rib waveguides operating in the single mode regime that exhibit low polarisation dependence. A rigorous leaky mode propagation method (LMP) has been used to investigate the influence of etch depth in 3^rd order Bragg gratings on the reflectance and bandwidth in the waveguides.

Optical chaos communications is becoming a hot topic since it is considered as a possible way to improve privacy and security in information transmission. To this end, a message can be encoded within a chaotic carrier generated by an emitter operating in a non-linear regime and decoded by an appropriate receiver. Consequently, the design and implementation of emitters and receivers that operate in a chaotic regime is a very important issue. To this end, two different architectures have been mainly followed: semiconductor lasers subject to all optical feedback and semiconductor lasers subject to electro-optical feedback. In the former, chaos is obtained from the light re-injected into the device that induces the laser to operate in a nonlinear regime. In the latter, the laser acts as a linear device that transforms a chaotic electrical input, generated in a combined electro-optical loop, into chaotic light. Encrypted information within the chaotic carrier can be recovered at a receiver that has to synchronize and match with the emitter. In this talk, both approaches to design the optoelectronic devices will be reviewed.