This PDF file contains the front matter associated with SPIE Proceedings Volume 6588, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

An all-solid photonic crystal fiber can be developed using two thermally matched glasses with one glass forming the background, and the other the lattice of inclusions. Optical properties of all-solid holey fibers (SOHO) are sensitive to the photonic cladding configuration, much the same as PCFs with air holes, and strongly depend on dispersion properties of the materials used. When a high index contrast between the glasses is assured photonic crystal fiber can effectively guide light with photonic band gap mechanism. This can be easily achieved when multicomponent soft glass is used for fiber fabrication. We report on new developments of F2/NC-21 silicate all-glass PCFs. F2 is a commercially available glass (Schott Inc.) with a high concentration of lead-oxide (PbO=45.5%) and the refractive index n_D=1.619. It can be used both as the background material and as a material for micro-rods (inclusions). A borosilicate glass (B₂O₃=26.0%) NC-21 glass has been synthesized in-house at IEMT. NC21 has the index n_D=1.533 and was used as the material for micro-rods (inclusions) or as a background glass in the structures. The two selected glasses have a high index contrast equal to 0,084 at 1,55μm wavelength. In this report we present new results on optimization of the filling factor d/Λ and reduction of the lattice pitch Λ necessary to obtain efficient guidance at 1.55 μm. The numerical analysis of SOHO F2/NC21 fibers has been carried out using a full-vector mode solver based on the plane-wave expansion method. In our paper we report on photonic crystal fibers with two guiding mechanisms: an effective index with a high index core (low index inclusions made of NC21 glass and F2 used as a background glass) and a photonic band gap with a low index core (high index inclusions made of F2 glass and NC21 used as a background glass).

Chalcogenide glasses present several original properties when being compared to the reference silica glass. They are very non linear, hundred to thousand times more non linear than the standard silica, they are very transparent in the infrared, until 10 μm to 20 μm depending on their composition, and they can be drawn into optical fibers. Thus, the case of chalcogenide photonic crystal fibers (PCF) is of particular interest. Indeed, the effective modal area is adjustable in PCF thanks to geometrical parameters. Then chalcogenide microstructured fibers with small mode area could lead to huge non linear photonic devices in the infrared by the combination of the intrinsic non linearity of these glasses with the non linearity induced by the PCF. Chalcogenide photonic crystal fibers offer therefore a great potential for applications in the fields of Raman amplification or Raman lasers and supercontinuum generation in the mid infrared until at least 5 μm. The possibility to design PCF exhibiting a working range in the mid infrared and more specifically in the 1-6 μm wavelength range opens also perspectives in the optical detection of chemical or biochemical species. This contribution presents the advances in the elaboration of such chalcogenide photonic crystal fibers.

The doping of silica yields additional degrees of freedom to vary the optical parameters of index guided and band gap controlled microstructured optical fibers (MOFs). Aside from the widely investigated rare earth doped microstructured fibers for lasers also the integration of conventionally doped structural elements with passive functions into MOFs allows to enhance effectively the optical performance of such fibers. We report on progress in preparation of microstructured fibers with air holes and solid structural elements composed of germanium and fluorine doped silica materials. The microstructured fibers were prepared by stack-and-draw technology. The starting materials are preform rods and tubes with graded dopant concentration prepared by MCVD and sintering technology. They were elongated to millimeter dimensions before packaging to final MOF preforms. We prepared MOFs with both holey core and holey cladding. The microstructuring of the holey cladding is achieved with fluorine doped capillaries. Several applications have been investigated. The high photosensitivity of germanium-silica MOFs makes possible the inscription of Bragg gratings with high efficiency. In fiber evanescent field sensors, such microstructured fibers improve the overlap between the propagating light field and the analyte and allow therefore an increased sensitivity e.g. for gas sensing with optical fibers. Solid MOFs with multiple cores in a highly precise array arrangement can been investigated as a model system for the study of nonlinear dynamics in discrete optics.

The delivery or generation of high power in optical fibre requires the increase of the core size to increase the threshold of nonlinear effects and the damage threshold. However the bend loss strongly limits the increase of the effective area (A_eff). All-solid photonic bandgap fibres are attractive for the delivery of power since they can be made singlemode whatever the core diameter is. Moreover the silica core can be doped with rare-earth ions. A Bragg fibre is a bandgap fibre composed of a low index core surrounded by N concentric layers of high and low index. We have fabricated Large Mode Area Bragg fibres by the MCVD process. These Bragg fibres present a ratio A_eff/λ² close to 500. A first Bragg fibre, defined by N = 3 and an index contrast between the cladding layers Δn = 0.01, exhibits a measured critical bend radius R_c close to 16 cm (bend loss equal to 3 dB/m). Increasing the index contrast Δn leads to a tighter field confinement. The field distribution of the guided mode strongly decays in the periodic cladding and is thus less sensitive to bending. We propose here the design of an improved Bragg fibre with a very large index contrast Δn = 0.035 which leads to a dramatic reduction of the bend loss. The critical bend radius was measured to be lower than 3 cm. This fibre is less bend sensitive than an equivalent solid core fibre, either a step-index fibre or a photonic crystal fibre.

A couple of multicomponent glasses was used to produce solid hole-free photonic crystal fiber (PCF) with high contrast of index. These glasses were a high index barium-lanthanum flint-glass (n~1.8) and a low index cron-glass (n~1.5). The compositions of selected glasses provided the coincidence of their viscosities in the temperature range of drawing, close thermal expansion coefficients, and chemical compatibility. To produce the PCF densely packed bundles of glass rods (elements) of 1 mm diameter assembled in a given structures were multiply co-drawn down to 0.2-2.0 microns diameter of a single element. This procedure allowed scaling of initial structures and resulted in two PCF structures: axially symmetrical eight-period structure and five-period "birefringent" structure. Optical transmission of the resultant PCF demonstrates the existence of photonic band-gaps, and intensity distribution of propagating mode corresponds to the results of numerical simulation performed.

Some recent developments made at XLIM laboratory in the field of supercontinuum generation in air-silica microstructured optical fibres are presented in this paper. These results concern the use of non usual nonlinear schemes in specially designed and home-made holey fibres for the improvement of white light sources. The design of three different guides and the specific nonlinear processes involved in the spectrum build-up are described. In a first microstructured fibre, dual-wavelength pumping (532/1064 nm) allows to generate both visible and infrared broadenings, with possible tunability of the visible spectral range according to the input polarisation. Moreover, a highly birefringent fibre is pumped at a single wavelength (1064 nm), located in large anomalous dispersion regime. In this case, a polarisation-controlled FWM process is initiated and permits to obtain very wide spectral broadening (350- 1750 nm) by avoiding the usual critical matching between the zero dispersion wavelength of the fibre and the pump wavelength. Non conventional second order nonlinearity is also analysed in this pure silica holey fibre. Finally, a specific air-clad Yb-doped microstructured fibre is used to combine laser amplification and nonlinear gain, resulting in an increase of the power spectral density level of the generated supercontinuum.

We demonstrate the generation of a low repetition rate picosecond, polarized, visible supercontinuum in a highly birefringent fibre. The polarization dependence of the supercontinuum spectrum is investigated, and the mechanisms responsible for the generation of visible light in these pumping conditions are described.

Optofluidics is the combination of photonic and microfluidic technologies to achieve enhanced functionality and compactness in devices with applications in sensing, chemistry, biomedical engineering, photonic devices and fundamental microfluidics research. Such a broad definition of the field lends itself many embodiments. Fiber optics provides a unique and versatile platform for building optofluidic devices. Optical fibers can be used not only in their traditional role, acting as a high quality waveguide for delivering light to an optofluidic device. Microstructured optical fibers and the voids that constitute them can provide a home for the fluid phase. Photonic crystal fibers, for example, can be filled with fluids to change the band gap properties of the fiber. The use of the fluid phase to tune photonic structures has several benefits. The fluid phase is inherently mobile allowing the tuning medium to be dynamically reconfigured through any connected aperture of the device. The nature of the fluid can also be adjusted through its chemistry, allowing for a very broad range of optical properties thus further enhancing tunability. Very high refractive index contrasts can be obtained between the fluid phase and the surrounding air, which can lead to great compactness in interferometric devices and novel, tunable, interferometric structures such as the single beam interferometer presented here. One of the great utilities of optofluidic devices is that where a photonic structure is tuned using microfluidics, the same structure can be used in reverse, where a photonic structure is exposed to an unknown fluid and can act as a sensor. A fiber Fabry-Perot is utilized here to measure the concentration of saline.

We present measurements on the non-linear temperature response of fibre Bragg gratings recorded in pure and trans-4-stilbenemethanol-doped polymethyl methacrylate (PMMA) holey fibres.

A numerical model of the sensitivity of long period gratings fabricated by electric-arc in photonic crystal fibres to strain, temperature and refractive index is proposed and evaluated by comparison to the experimental results. It is shown to be superior to the commonly used semi-analytical method. The generalized modelling procedure is thoroughly explained in order to facilitate its application to a wide range of long period gratings in different types of fibres.

Measurements of polarization properties (polarization dependent loss and differential group delay) of a long-period grating inscribed by means of high-intensity femtosecond 264 nm pulses in an endlessly single mode photonic crystal fibre are reported. Strong modulation in the spectra of polarization dependent loss and differential group delay with periods of 2.6 nm and 1.3 nm, respectively, were found. As such an effect has not been observed in standard optical fibres, it is believed that this is due to the specific mode structure of the holey fibre used for grating fabrication.

Microstructured fibers (MOF), also called photonic crystal fibers (PCF), constitute a class of optical fibers, which has a large potential for number of novel applications either in the telecom or in the sensing domain. However, some of the applications require the use of specialty fibers with a doped core. We have made a preliminary exploration of PCF with doped regions and with inscribed Bragg gratings. The extensive study of the fiber cross-section structure in respect to possibilities of writing the Bragg gratings and the sensitivities of PCF Bragg gratings was our main concern. Selective measurement of strain without temperature compensation is achieved with fiber Bragg grating (FBG) in highly birefringent (HB) PCF, since such grating is characterized by two reflection bands corresponding to the two polarization modes generated due to the fiber birefringence. The measurement range of such FBG in HB fiber sensor depends on how strong is the separation of the polarization modes, which is expressed as phase birefringence. In next step, we have modeled, designed and fabricated specialty PCF with Ge doped core in such way that after writing the Bragg grating into the fiber we have obtained a sensors exhibiting low sensitivity to any temperature drifts. Traditional optical fiber sensors are not able to make such a distinction between stress and temperatures and require complex temperature compensation mechanisms.

In this paper we report on progress in optimization of the material and structure of photonic crystal fibers for use as an element of fiber sensor of strain and temperature. The fabricated photonic structures consist of elliptical-like holes ordered in rectangular lattice. The rectangular lattice is applied to obtain global asymmetry of photonic structure with two-fold geometry and to create birefringence of fiber. Elliptical air holes allows to increase birefringence in the structure up to the order of 10 ^-2 for wavelength of 1.55 μm, theoretically. Additionally, rectangular lattice gives a better control of elliptical air holes uniformity during fabricating process. For fabrication of the fibers we use NC21 borosilicate glass. Use of high quality glass allows omitting problems with very high attenuation of the previously fabricated highly birefringent photonic crystal fibers made of SK222 glass. With full vector plane-wave expansion method an influence of structure parameters such as ellipticity of air holes and aspect ratio of rectangular lattice on birefringence and modal properties of the fiber is studied. In this paper we present optimization of the fiber structure design, which takes into account technological limits of fabrication of elliptical holes in fibers. Theoretical birefringence is compared with experimental measurements. Experimental results already obtained allows to predict birefringence at the order of 10 -3 for wavelength of 1.55 μm for optimized photonic cladding of the fibers.

We present the results of theoretical and experimental analysis of waveguiding in a two-mode birefringent holey fiber in which the birefringence is induced by two large holes adjacent to the fiber core. First, using a full-vector finite-element method we modeled the wavelength dependence of the phase and group effective indices for the fundamental and higher-order linearly polarized (LP) modes in two orthogonal polarizations. Then we evaluated the wavelength dependence of the phase and group modal birefringences for both LP modes and the intermodal dispersion in two orthogonal polarizations as well. Second, we used different interferometric techniques, including time-domain and spectral-domain ones and a lateral force method, to measure in a broad spectral range the wavelength dependence of the phase and group modal birefringences for the fundamental and higher-order LP modes. Employing a white-light spectral interferometric method, we also measured the wavelength dependence of the intermodal dispersion for two orthogonal polarizations of the two LP modes. Furthermore, using an unbalanced Mach-Zehnder interferometer we measured the wavelength dependence of the relative group effective index for the fundamental mode.

We present the structure of photonic crystal fibers and give a characterization results in birefringence and chromatic dispersion using scanning near field optical microscopy and low coherence interferometry.

We report our experimental investigation on characterization of Index-Guiding Photonic Crystal Fibers (PCF) from their far field intensity distribution. The below presented algorithm makes it possible to determine the geometrical parameters of the PCF (core diameter, air hole spacing and air hole diameter) from its far field pattern. We obtained good agreement with the manufacture data for all used fibers.

One of the most interesting features of photonic crystal fibres (PCFs) is their unique dispersion. Therefore knowledge of chromatic dispersion is very important for better utilisation and optimisation of PCF potential. A modified low coherence Michelson interferometer is described in the contribution. The modified interferometer consists of an arm with a reference fibre, which has a sputtered mirror at its end face and the other arm contains the fibre under test and the air line with variable length. The advantage of such setting is that the investigated fibre needs no manipulation (mirror creating) and that only one arm should be changed when an other fibre is to be measured. A monochromator and halogen lamp are used as the source that allow measrument of dispersion over a wide spectral range. The optical path difference between the investigated and the reference fibre is about 15 μm (delay 0.05 ps) and can be readily distinguished. Besides describing the interferometer set-up also some results of dispersion measurement in samples of PCF are presented in the contribution.

The nonlinearity in optical fibres can be enhanced significantly by reducing the effective mode area or by using materials with higher nonlinear-index coefficient (n₂). In this paper we combine these two concepts and experimentally demonstrate enhanced Kerr nonlinear effects in tapered highly nonlinear As₂Se₃ chalcogenide fibre. We taper the fibre to sub-wavelength waist diameter of 1.2 μm and observe enhanced nonlinearity of 63,600 W^-1km^-1. This is 40,000 times larger than in silica single-mode fibre, owing to the 400 times larger n₂ and almost 100 times smaller effective mode area. We also discuss the role of group velocity dispersion in these highly nonlinear fibre tapers.

We investigate the possibility of using poled silica photonic crystal fibers for self-defocusing soliton compression with cascaded quadratic nonlinearities. Such a configuration has promise due to the desirable possibility of reducing the group-velocity mismatch. However, this unfortunately leads to increased phase mismatch, and the dispersion is often anomalous. All this reduces the design parameter space where soliton compression is possible, and poses strong requirements on the poling efficiency. We propose to use quasi-phase matching in order to reach realistic requirements on the quadratic nonlinearity, and show that compression of nJ pulses to few-cycle duration is possible in such a fiber. A small amount of group-velocity mismatch optimizes the compression.

Photonic crystal fibers technology provides us with new way to obtain fibers with much higher non-linearity than conventional techniques. Upper limits of non-linear coefficients obtainable in silica-based photonic crystal fibers have been already investigated. Unique dispersion characteristic and enhanced non-linearity make this kind of fibers an ideal candidate for non-linear optical devices in telecommunication applications, for measurement and sensing and for supercontinuum generation. However, there are limitations given by material properties, which obstruct us from achieving theoretical limits of these fibers. Extremely small core and high air-filling fraction are here needed for reach higher non-linearity, so when material properties of conventional silica restrict us, there is a requirement on a novel matter. This could be poly-methyl metacrylate (PMMA), a common material for plastic optical fibers manufacturing. These microstructured polymer optical fibers are a recent technology, which gives us with new possibilities in core size, fiber geometry and related air-filling fraction. By this kind of fiber, we could be closer to ideal non-linear fiber, which is core strain surrounded by air, than even before. But new kind of fiber brings new issues, like which effect in fiber will be dominant or how will be coupled light affected by outer influences - and what difference will be between predicted and real values in general. This is a large task and hopefully, there will be answer at least for a small part in this paper.

New hollow-core geometries in modified honeycomb photonic bandgap fibers have been investigated in order to obtain high birefringence and, at the same time, to avoid the presence of surface modes. Birefringence values up to 10^-3 have been obtained in fibers which are effectively single-mode in both C and L bands, with confinement loss lower than 1 dB/km in the same wide wavelength range.

Finite element-based rigorous full-vectorial modal solution approach has been developed to calculate the effective index of the fundamental space filling mode, cutoff condition of the fundamental and the second guided modes to identify the single mode operation ranges for the photonic crystal fiber. The single mode operation regime for a Terahertz photonic crystal fiber has also been discussed.

The guiding properties of fabricated air-silica Bragg fibers with different geometric characteristics have been numerically investigated through a modal solver based on the finite element method. The method has been used to compute the dispersion curves, the loss spectra and the field distribution of the modes sustained by the Bragg fibers under investigation. In particular, the silica bridge influence on the fundamental mode has been analyzed, by considering structures with different cross sections, that is an ideal Bragg fiber, without the silica nonosupports, a squared air-hole one and, finally, a rounded air-hole one, which better describes the real fiber transverse section. Results have shown the presence of anti-crossing points in the effective index curves associated with the transition of the guided mode to a surface mode. Moreover, it has been verified that these surface modes are responsible of the loss peaks in the fiber transmission spectra, also experimentally measured. Surface modes are mainly localized in the regions of the cladding where the bridge supports join the cladding rings, forming silica islands where the field can focuses.

This paper deals with a new method of generation negative dispersion by introducing curvature into the fiber. The aim is to make a proposal of a photonic structure that could be an optical dispersion compensator. Strong deformation of fundamental mode for a certain bend radius results with negative dispersion of thousands of ps/nm/km at required wavelength. The structure mustn't be symmetrical because introducing a curvature strictly defines direction of deformation of the fundamental mode and splitting light into external holes making the mode highly dispersive. The dispersion is the same for a symmetrical lattice and for a lattice with holes only in regions with strong confinement. There is also a proposal of a unique detection method to precise the bend radius for which negative dispersion occurs. Only for certain value of bend radius, for which cladding mode can appear at propagated wavelength, it is possible to confine the mode and cause optical nonlinearities. Negative dispersion peak is accompanied by bending loss. Bending loss is interesting because of the possibility of detection of this unique combination with negative dispersion. There are local maxima of losses in loss wavelength dependency coming from the cladding modes. These cladding modes appear only for certain values of bending and the fundamental mode is highly dispersive.

Polaritonic resonancies are investigated in 2D silicon photonic crystals. Theoretically unpredicted reduction in the transmittance of electromagnetic radiation and the step formation are observed for wavelengths less than optical period of structures due to directed and decay optical modes formed by macroporous silicon as a short waveguide structure. Prevalence of absorption over reflection of light testify to the polaritonic type band formation. Surface polaritons are formed on decay modes in a silicon matrix or macropore at formation of directed optical modes relatively on macropore or silicon matrix. Absorption, photoconductivity and Raman scattering maxima are determined by a corresponding maximum of a longitudinal component of electromagnetic waves in macroporous silicon structure as short waveguide with a specific surface. Longitudinal component of electromagnetic waves in investigated structure interacts effectively with surface oscillators, and polaritonic resonances in 2D silicon photonic crystals are observed.

We investigated theoretically and experimentally the wavelength dependences of phase and group modal birefringence for the fundamental (E₁₁) and the higher order mode (E₃₁) supported by index guiding highly birefringent photonic crystal fiber. The birefringence in the investigated structure was induced by asymmetrical cladding consisting of one row of cladding holes with a diameter lower than the other cladding holes. The numerical simulations carried out with use of the full-vector finite elements method show that the birefringence of the E₃₁ mode can be about 30% higher than of the fundamental mode. Additionally, we measured the modal birefringence of the both modes using scanning wavelength method. A comparatively good agreement between the calculation and experimental results was obtained confirming the validity of the theoretical analysis.

In this paper, different interferometric techniques were used for measuring dispersion characteristics of specialty optical fibers, including Corning PMF-38 highly birefringent fiber. We measured the wavelength dependence of both the phase and group modal birefringences for two lowest-order linearly polarized (LP) modes. The phase modal birefringence was measured by a lateral force method. The group modal birefringence was measured by a method of spectral-domain tandem interferometry. The latter method was also used to measure the intermodal group dispersion for two orthogonal polarizations of the LP modes. The experiment revealed a distinct dispersion splitting between X-polarized and Y-polarized LP modes.

The LiNbO₃ crystals are well known for their great piezoelectric, electrooptic and photorefractive properties. The letter properties mentioned can be essential for many applications in photonics. This contribution deals with the generation of the records of specially structured optical fields which can, under appropriate conditions, behave as the photonic structures. We present the results of the investigation of the light-induced structures and discuss the possibilities of their utilization as the Bragg gratings, wave-guiding structures as well as the data records.

We present a novel splicing method for photonic crystal fibres (PCFs) with a double phase-conjugate mirror (DPCM). The DPCM is an optical device with photorefractive crystal (PRC) which generates phase-conjugate beams easily. In this report, we experimentally measure the splice losses of the DPCM for transverse PCF offset. We numerically estimate the splice losses in the case that butt coupled PCFs without DPCM. Comparing the experimental and numerical values of the splice loss of PCFs, we discuss the tolerance of the DPCM for the PCF displacement. Also, we discuss the causes of loss inside the DPCM module.

We numerically analyzed the polarization effects in birefringent all-solid photonic bandgap fiber with different index contrast between matrix and circular inclusions. The birefringence in the analyzed fibers is induced by elliptical shape of the core composed of double defect in the hexagonal lattice of high index inclusions. Our simulations were fully vectorial and based on a plane wave method and finite element method. We determined location of photonic bandgaps, spectral dependence of phase and group modal birefringence, and confinement loss characteristics for different polarization modes in three analyzed structures.

The possibilities of controlling and changing the state of polarization (SOP) as well as the degree of polarization (DOP) in an optical fiber taper are described in this paper. The in-line polarization analyzer POD-101A and Pola ViewTM software have been used for above polarization parameters investigation. In ours analyze we used a few kinds of optical fiber like: singlemode, multimode and photonic crystal ones. All of them were tapered in two different method to obtain different diameter and length of a waist. Diameter of taper waist was changing from 125 um to about 50 um for total taper length up to 100 mm. Polarization parameters was measured for wavelength 1310 nm. Set-up for manufacturing taper and software for measuring polarization also allows to produce optical fiber couplers and measured changes on their outputs.