Many of the applications of photonic crystals and photonic crystal fibers require the periodic structure to have some type of defect. In photonic crystal fibers a point defect defines the fiber core, whereas in photonic crystals a line defect acts as a waveguide, and point defects act as cavities. The modeling of these defects usually either makes use of periodic boundary conditions, by which the defect is replicated periodically, or models a photonic crystal of finite extent. However, some applications, for example the cut-off behavior of a defect mode where the field extends very widely, require methods that can model a defect in an otherwise infinite and perfectly periodic structure. Here we present such a method. It combines the method of fictitious sources with averaging over the Brillouin zone, and we apply it to study the long-wavelength behavior of the fundamental mode of photonic crystal fibers.

Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.

We present the fundamental concept and experimental results of a new optical sensor structure based on a 1D photonic crystal consisting of a polymer light waveguide, a cladding layer and a nanostructured gold layer. The polysiloxane layers are deposited by spin-coating and dip-coating, respectively. The gold nanostructure is deposited by DCmagnetron sputtering and structured by UV-laser lithography. The gold nanowires have a period of about 400 nm and cover an area of 5×5 mm². This thin flexible structure shows high sensitivity to inclination and strain. Our method enables the fabrication of a new sensor for non-conducting measurement of strain, force, torque and angle.

Theoretical analysis of the magnetic photonic crystals optical properties has been performed. Original theoretical approach similar to the adiabatic approximation in the solid state physics is described. Effect of the light polarization rotation is described for the case of three-dimensional photonic crystal with the relation of recent experiments. Magnetooptical Faraday and Voigt effects have been studied near extremum points of photonic bands where their significant enhancement takes place. Several possible applications of the magnetic photonic crystals for the modern optical devices are discussed.

A description of spontaneous parametric down conversion in finite length 1-D nonlinear photonic crystals is developed using semiclassical and quantum approaches.

Optical properties of photonic crystal heterostructures with embedded n-i-p-i superlattices are studied. Nonlinear behavior of the transmission and reflection spectra near the defect mode is investigated. Self-consistent calculations of the output performance characteristics are performed using the transfer-matrix method and taking into account the gain saturation. Features and characteristic parameters of the nonlinear gain in active n-i-p-i layers are determined. Detail analysis of the gain saturation and accompanying nonlinear refraction effects is carried out for one-dimensional photonic crystal heterostructure amplifiers in the GaAs-GaInP system having at the central part an active "defect" from the doubled GaAs n-i-p-i crystal. The gain saturation in the active layers in the vicinity of the defect changes the index contrast of the photonic structure and makes worse the emission at the defect mode. Spectral bistability effect which can be exhibited in photonic crystal heterostructure amplifiers is predicted and the hysteresis loop and other attending phenomena are described. The bistability behavior and modulation response efficiency demonstrate the potential possibilities of the photonic crystal heterostructures with n-i-p-i layers as high-speed optical amplifiers and switches.

We predict theoretically and observe experimentally tunable refraction of beams in optically-induced lattices. By selective excitation of diferent Bloch modes in a tilted lattice, we observe positive and negative refraction for beams associated with the first and the second spectral band, respectively. We demonstrate tunability of the output beam position by dynamically adjusting the lattice depth. At higher laser intensities, the beam broadening due to difraction can be suppressed through nonlinear self-focusing while preserving the general steering properties.

The spatio-temporal dynamics of the broad-area photonic crystal surface-emitting laser is investigated numerically. Excitation of the high-order transverse modes can result in transition from one type of a transverse field distribution to another. Such process is similar to spontaneous symmetry breaking and mode competition in broad-area lasers. Formation of a complex transverse field distribution in photonic crystal surface-emitting laser depends on transverse distribution of pump and on initial conditions. Photonic crystal surface-emitting laser generates the fundamental mode independently on initial conditions only for a small area of a pump region. The modification of the pump region allows to control the transverse structure of an output laser beam.

One of the most distinctive features of photonic crystals (PhCs) is their unique wavelength dispersion allowing novel device concepts for enhancement of photonic functionality and performance. Here, we present examples of our design and demonstrations utilizing dispersion properties of 1D and 2D photonic crystals. This includes the demonstration of negative refraction in 2D PhC at optical wavelengths, filters based on 1D and 2D PhC waveguides, and the design of a widely tunable filter involving 1D PhC.

We report on direct numerical calculations and experimental measurements of the group-index dispersion in a photonic crystal waveguide fabricated in silicon-on-insulator material. The photonic crystal is defined by a triangular arrangement of holes and the waveguide is carved out by introducing a one-row line defect. Both the numerical and experimental methods are based on the time of flight approach for an optical pulse. An increase of the group index by approximately 45 times (from 4 to 155) has been observed when approaching the cutoff of the fundamental photonic bandgap mode. Numerical 2D and 3D simulations of pulse dynamics in the waveguide made by the time-domain method shows excellent agreement with measured data in most of the band. These group index values in a photonic crystal waveguide are to the best of our knowledge the largest numbers reported so far by direct tracking of pulse propagation.

In this paper we analyze theoretically how introduction of the third component into the two-dimensional photonic crystal influences on the photonic band structure and the density of states of the system. We consider the periodic array of cylindrical air rods in a dielectric and the third medium is introduced as an intermediate layer of the thickness d and the dielectric constant εi between the air pores and the dielectric background. Various combinations of the parameters R (pores radius), d, and εi which allow the band gap to appear were considered. Using the plane wave method we have obtained the band structures and density of states for the triangular lattice 2D photonic crystals. The dependencies of the band gaps width and gaps edges position on the interlayer dielectric constant and interlayer thickness were analyzed. In the framework of this approach we have estimated the influence of the surface oxide layer on the band structure of macroporous silicon. We observed the shift of the gap edges to the higher or lower frequencies depending on the interlayer thickness and dielectric constant. We have shown that the existence of a native oxide surface layer should be taken into consideration to understand the optical properties of 2D photonic crystals, particularly in macroporous silicon structures.

Out-of-plane optical transmission spectra of 2D photonic macroporous silicon structures are investigated. By the plane wave expansion method all possible 2D lattice symmetries are considered and analyzed both in general case and for p-, s-polarizations. Sharp increase of absorption and formation of photonic band gaps is measured for wavelengths between one and two optical periods of macroporous silicon structure. Thus, for periodic structures one photonic band gap is formed, and some narrow peaks of density of states are formed for structure with the arbitrary macropore distribution. Theoretically unpredicted reduction in the transmittance of electromagnetic radiation and the step formation are observed for wavelengths less than optical period of macropores. Transmission spectra of macroporous silicon as well as steps were explained by a model of directed and decay optical modes formed by macroporous silicon as a short wave-guide structure. Prevalence of absorption over reflection of light, dependence of photoconductivity on incidence angle of the electromagnetic radiation testify to formation of the polaritonic type band formation.

Photonic Crystal Fibres (PCFs) have appeared as a new class of optical waveguides, which have attracted large scientific and commercial interest during the last years. PCFs are typically microstructured silica waveguides with a large number of air holes located in the cladding region of the fibre. The size and location of these air holes allows for a large degree of design freedom within optical waveguide design, and PCFs with properties tailored for fibre lasers, airguiding fibres, nonlinear fibres, hybrid fibres etc. have been demonstrated. Further, the existence of air holes in the PCF gives the possibility of propagating light through air, or alternatively allows access close to the fibre core for interactions with new materials placed in the air holes. This makes a well controlled interaction between light and material possible.

Recently left-handed materials (LHM) attracted great attention since these materials exhibit negative effective index, which is due to simultaneously negative permeability and permittivity. Negative refraction is also achievable in a dielectric photonic crystal (PC) that has a periodically modulated positive permittivity and a permeability of unity. In this paper, we report our experimental and theoretical investigation of negative refraction and subwavelength focusing of electromagnetic waves in a 2D PC. Our structure consists of a square array of dielectric rods in air. Transmission measurements are performed for experimentally verifying the predicted negative refraction behavior in our structure. Since we know the optimum frequency for a broad angle negative refraction, we can use our crystal to test the superlensing effect that was predicted for negative refractive materials. We achieved a subwavelength resolution for the image of two incoherent point sources, which are separated by a distance of lamda/3. We also measured the spectral refraction analysis and focusing properties of a two-dimensional, dielectric photonic crystal (PC) slab in free space. We demonstrate experimentally and numerically the focusing of the field emitted from an omnidirectional source placed in front of the crystal. Both the source and the focus pattern are away from the PC interfaces of the order of several wavelengths. The focus pattern mimics the arbitrary lateral and longitudinal shifts of the source, which is a manifestation of true flat lens behavior.

Photonic Crystal Fibers (PCFs) are optical fibers with unique guiding characteristics as well as unusual nonlinear and dispersion properties. Since PCFs offer the possibility to engineer the zero-dispersion wavelength, the dispersion curve and the nonlinear coefficient value, they are very interesting for optical parametric amplification. In the present paper the phase-matching condition has been deeply analyzed in different triangular PCFs configurations. In particular, highly nonlinear PCFs have been designed to achieve flattened dispersion curves around the zero-dispersion wavelength in the C band. Very flat parametric gain, around 16 dB, on a bandwidth up to 35nm can be obtained with short PCF and low pump power level.

We discuss the formation of a tunable one-dimensional photonic band gap structure through the modulation of the resonance frequency of an optical microcavity by a surface acoustic wave (SAW). The microcavity consists of a λ/2 GaAs layer bounded by AlAs/GaAs Bragg mirrors. The SAW periodically modulates the optical thickness of the cavity layer, leading to a light dispersion relation folded within a mini-Brillouin zone (MBZ) defined by |k_x|≤ π/λ_SAW (k_x denotes the photon wave vector component along the SAW propagation direction x-with-caret). In reflection and diffraction experiments, we observe photon modes bounding the gaps in the center and at the boundary of the MBZ as well as a renormalization of the optical energies. Furthermore, the width of the energy gaps can be tuned by changing the acoustic power densities. The experimental results are in good agreement with a simple model for the dispersion in the presence of SAWs. We show the application of acoustically tunable microcavities in efficient optical on/off switches and modulators as well as a tunable cavity operating at 1.3μm.

We study the interplay between parametric and Raman gain in photonic crystal fibers by taking into account the vector nature of the electric field, the fiber frequency dependent birefringence, the Kerr nonlinear coefficient, the Raman gain profile and chromatic dispersion. In particular, we show that an accurate representation of the frequency dependence of the nonlinear and dispersive properties of a photonic crystal fiber is essential for correctly describing the overall gain profile for a probe signal at large frequency detuning from a continuous wave or pulsed pump. For example, we found that fourth and higher order dispersion have a striking influence on the spectrum of modulation polarization instability gain in both the high and low birefringence regime, in that the vector parametric gain is suppressed above a critical level of linear birefringence. We validated the theory by experimental observations of vector parametric amplification in high birefringence holey fiber with triple defects.

Using group theory arguments and numerical simulations we demonstrate the existence of spatial solitons in non linear photonic systems with discrete point-symmetry. This new approach permits a systematic classification of all non-linear solitonic solutions. New spatial effects can be derived and numerically tested in the context of two-dimensional photonic crystal fibers, optical lattices or, equivalently, in that of Bose-Einstein condensates in periodic potentials.

Supercontinuum generation using picosecond pulses pumped into cobweb photonic crystal fibres is investigated. Dispersion profiles are calculated for several fibre designs. The influence of the fibre structural parameters on the location of the Stokes/anti-Stokes peaks and gain bandwidth is investigated. We find that four-wave mixing is the dominant physical mechanism for the pumping scheme considered here, and that there is a tradeoff between the spectral width and the spectral flatness. The balance of this tradeoff is determined by nanometer-scale design of the fibre structural parameters.

Microstructured fibres (MOF), also called photonic crystal fibres (PCF), constitute a class of optical fibres, 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 fibres with a doped core. We have made a preliminary exploration of MOF with doped regions and possibly inscribed Bragg gratings. The extensive study of the fibre cross-section structure in respect to possibilities of writing the Bragg gratings was our main concern.

The recently invented photonic crystal fibers have brought about new possibilities for novel photonics applications. We describe light sources based on supercontinuum generation in microstructured fibers and use of bandgap fibers for sensor applications.

Triangular photonic crystal fibers with different core geometries have been investigated, in order to design single-mode large mode area fibers. In particular, 7-rod core fibers, obtained by removing the central air-hole and the first six surrounding ones in the transverse section, have been considered. By taking into account the leakage losses of the second-order mode, a phase diagram, which describes the boundary between the single-mode and multi-mode operation regimes, as well as the endlessly single-mode region, has been evaluated. Moreover, starting from this analysis, the cutoff normalized frequency has been calculated according to a formulation of the V parameter previously adopted for traditional 1-rod core triangular fibers. Simulation results have shown that, for a fixed air-filling fraction, 7-rod core triangular photonic crystal fibers are single-mode in a smaller wavelength range than 1-rod core ones. However, it is possible to obtain high effective area values, as well as single-mode operation, with 7-rod core fibers by considering low air-filling fractions and relatively small hole-to-hole distances.

We perform numerical computations of photonic band structures of core-shell opal-based photonic crystals to explore the influence of structural parameters on the optical properties. In particular we consider variations of the refractive indices of the shell. Based on our results we propose a way of controlling the photonic band gap in this type of photonic crystal.

Defect modes and related transmission peaks arising in photonic crystals (PC) due to deterioration of the periodicity have extensively been studied since about ten years in connection to various applications related to optical and microwave engineering. In this paper, we study plane wave scattering by thin slabs of dielectric PC with air and metallic defects. The aim is to consider some effects exerted by single and multiple line defects on transmittance within and beyond structural gaps and on the corresponding field patterns. Calculations have been performed using the recently developed fast coupled-integral-equations technique, for both frequency-independent and frequency-dependent descriptions of the permittivity of regular rods and defects. The emphasis in the numerical study is on the effect of the angle of incidence on the transmission behaviour related to the presence of defects within and beyond structural gaps, on variation of the field pattern in the vicinity of defect-mode-originated transmission peaks, on poorly known regimes of the field localization arising due to defects, and on superposition of structural and polariton, and structural and plasmonic gaps. Several numerical examples are presented, which illustrate some interesting manifestations of the defect-related regimes.

The concepts of microstructured and photonic crystal fibers have greatly enhanced flexibility in achieving specific propagation and guiding properties in optical fiber waveguides. Additionally, they have enabled alternative principles in light guiding and wave field shaping compared to conventional optical fibers. Besides applications in communication technology and for fiber light sources, these properties meet with increasing interest in sensing applications. The specific properties of microstructured and photonic crystal fibers are discussed in view of such applications in optical fiber sensing systems.

The results of numerical modeling and experimental investigations of manufactured diamond-shaped and large area hollow core photonic crystal fibers with periodical cladding (kagome-lattice and closely packed tubes) are presented. The use of soft glasses allows to fabricate high-quality structures with moderate losses. Numerical methods, designing strategies and fabrication issues of these promising fiber structures are discussed.

Intermodally phase-matched third harmonic generation (THG) in a multimode microstructured fiber (PCF) accompanied by nonlinear spectral shifts both for fundamental and for third harmonic (TH) was observed. Femtosecond pulses of a Cr:Forsterite laser oscillator with the central wavelength of 1240 nm were used to excite several PCF samples. This wavelength plays important role for actual optical communication systems being in close proximity to the 1.3 μm window. Depending on the coupling geometry, two different high-order third harmonic fiber modes were observed accompanied by spectral shifts in IR. Instead of broadband radiation as in the IR, isolated peaks were generated in the TH region of the spectrum. By the rotation of input polarization, changes in the THG mode patterns were observed and a detailed analysis revealed the intensity and a polarization effects on the sampled spectra. Observed phenomena are interpreted by numerical calculations of modal dispersion properties for the examined PCF. Simulation results confirm the narrow band multi-peak character of the THG radiation and a good agreement was found between experimental and theoretical peak positions. This work is aimed to extend the knowledge about the spectral control of third harmonic signal by tailoring parameters of the fiber.

We report on research towards application of birefringent photonic crystal fibers as active and passive elements of fiber optic sensors for measurements of different physical parameters. Using experimental and theoretical methods, the sensing characteristics of different photonic structures are studied, including spectral behavior of phase and group modal birefringence, polarization dependent losses, sensitivity to temperature and hydrostatic pressure.

Most works on photonic crystal fibers with a photonic bandgap are concerned with structures made of silica glass with a hexagonal lattice. However, there are many other possible choices for the crystal structure of the fiber. In this paper, we study the optical properties of photonic bandgaps in a hollow-core photonic crystal fiber with a square lattice fabricated from multi-component glass. A composition of oxides was chosen to obtain a refractive index contrast higher than in fused silica fibers. The core size of the fiber is 11 microns and the cladding is made of an array of 17 x 17 air capillaries. A full-vector mode solver using the biorthonormal basis method is employed to analyze the modal properties of the fiber. We verify the guiding properties of the fiber by FDTD simulations. The transmission properties for several lengths of the fiber were measured by using broadband light from a nanosecond-pulse supercontinuum source and an optical spectrum analyzer. Preliminary results show that light is guided around 1650 nm. Possible modifications of the structure and potential applications will be discussed.

A pure silica microstructured optical fiber(MOF) with seven dual cores is designed for chromatic dispersion compensation by a finite difference frequency domain(FDFD) method with a perfect matched layer(PML) boundary condition. The multi-core structure fiber is presented for the first time. The negative chromatic dispersion peak value of the designed microstructured fiber is -4500ps/nm.km and the full width at half maximum (FWHM) is evaluated at 12nm. Furthermore the effective area of the inner core fundamental mode can reach 65mm² at 1550nm wavelength, which is three times that of a conventional dispersion compensating fiber (DCF).

An analysis of nonlinear operation in phased array laser based on two dimensional photonic crystal is presented. We develop semi-analytical model of supermodes propagation in a structure consists of N-coupled photonic crystal waveguides. We obtain relations between the signal gain saturation and geometry of the structures that provide maximal power efficient.

The opal-GaN-ZnS:Mn composites with various GaN:ZnS ratios were synthesized by chemical bath deposition. These materials are perfect three-dimensional photonic crystals, which produce effective photo- and electroluminescence at room temperature. The emission spectra are considerably modified by the photonic crystal structure to become anisotropic in accordance with the photonic band gap angular dispersion.

In this paper, we present a semi analytical, approximate model of relaxation oscillation of Nd³⁺:YAG DBR (Distributed Bragg Reflector) laser with one dimensional photonic crystals (1D PC). In our theoretical model, we take into account the gain saturation effect, transversal and longitudinal field distribution. With the help of time dependent laser rate equations, we obtain an approximate formulas relating the damping rate and frequency of relaxation oscillations to the output power and laser parameters such as photonic crystal geometry, losses, and reflectivity coefficient of laser mirror. With this approximate formulas, we obtain the laser characteristics, which reveal an optimal feedback strength for DBR cavity laser structure.

In this paper, we present a simple, yet versatile, analytical model of one-dimensional photonic crystal (1D PC). In our theoretical model, we take into account direction of propagation and therefore do not neglect anisotropic nature of photonic crystals. We derive analytical expressions for mode spectrum and density of states in 1D photonic crystal. With those formulas, we obtain mode spectrum characteristics, which depict formation of photonic band gap and reveal properties of photonic crystals.

The increasing demand of wide band internet services has led the research to improve optical networks also outside the conventional C-band. In this frame, Raman amplifiers play a critical role being able to provide amplification at any wavelength. This paper investigates the properties of Photonic Crystal Fiber based Raman Amplifiers. An accurate Raman amplifier model, suitable for any kind of germano-silicate photonic crystal fibers, has been implemented. Starting from the photonic crystal fiber design, by using a full vectorial solver based on the finite element method, it is possible to calculate the Raman gain coefficient and the Rayleigh backscattering coefficient of the fiber. Therefore, by solving the coupled equation system that describes the Raman amplification in optical fibers, it is possible to evaluate the gain spectrum at the end of the fibre. The mathematical model includes stimulated Raman scattering and its amplification, the spontaneous Raman emission and its temperature dependance, the Rayleigh backscattering, the fiber loss, and the arbitrary interaction within pumps signal and noise from either propagation directions. The fundamental role of background losses is highlighted. The study is focused on multi-pump configuration to obtain a flat gain spectrum. Considering a practical photonic crystal fiber, with d/Λ = 0.625 and Λ = 4 μm and varying the number of pumps, their wavelength and power, the shape of the gain spectrum has been adjusted to provide a flatness of 0.5 dB from 1540 nm to 1572 nm.

Microstructured optical fibers have ability to change their optical properties through inserting different materials into their holes. Filling the microstructured fibers with liquid crystals opens up a possibility of dynamic switching between different guiding mechanisms. In this paper we present the influence of electrical field on propagation properties of microstructured photonic crystal fibers filled with either low or highly birefringent nematic liquid crystals. Depending on the liquid crystal material introduced into the micro holes different propagation mechanism controlled by external electric field have been observed. This creates great potential in fiber optic sensing and optical processing application.

A variant of scalar approach is applied for modeling of the spectral broadening of femtosecond pulses in few-mode microstructure fiber. The excitation of new spectral components in a high-order mode is possible due-to the nonlinear coupling between modes. The energy transfer between modes appears even without resonant coupling between modes.

This letter deals with the guidance mechanism in Photonic Crystal Fibers. Setting the band condition in a microstructure is described. The Mode Profile dependent on the band condition is presented. Cross-section patterns presenting the propagation of elecrtomagnetic field are shown. The comparison of a guidance mechanism in various types of PCF's is discussed. Cross-sections shots of Photonic Crystal Fibers set to suitable input parameters are presented, value of losses, normalized frequency of second mode cut-off are calculated. The choice of input parameters such as lattice constant or Refractive Index profile is discussed. Simulations of Single Mode propagation in a wide operating range are done.

We present the results of calculations of the transmission/reflection characteristics of finite length 1D PC with air-glass-doped layers. For these calculations we used the transfer matrix formalism. We present also the results of calculation accounting nonlinear deformation of the field distribution along the structure due to gain and refraction index saturation. The results of calculations of laser power are presented on the dependence from gain.

Photonic crystal fibers (PCFs) constitute a new class of optical sensors because of its diverse advantages. Large possibilities of tailoring different parameters and sensing properties of PCFs by means of geometry design are very promising and are extensively investigated. One of research fields of the PCF are interferometer sensors, where demodulation (processing) of an output signals needs a phase sensitivity to a measurand. We present our theoretical research of phase sensitivity of the Photonic Crystal Fibers with different geometry. In our computations, we make use of the Multipole Method for calculation of an effective refractive index of the fiber. On this basis we determined the phase changes caused by the mechanical disturbances (elongation, bending) as well as temperature changes.

Intermodal interference in a photonic crystal fibre is measured in fibre samples of different lengths. The measurement was performed for attenuation of the first higher order mode determination. Also, the mode field distributions at the end of short and longer samples were measured. This measurement allows finding field distribution of the second mode.

We present experimental realization of elliptical-hole rectangular lattice photonic crystal fibres fabricated from multi-component glass. The photonic cladding has a lattice constant 2.17 μ and 3.72 μ for main axis, respectively and elliptical holes with ellipticity 2.14. The rectangular lattice is chosen to obtain two-fold geometry and to increase the global asymmetry of photonic structure, which enhance birefringence of fibre. Rectangular lattice allows also a better control of elliptical air holes uniformity during fabricating process. Fabricated fibres have a cladding with a rectangular cross-section. It allows for easy identification of the fibre's principal axes and orientation of the fibre with respect to directional measured perturbation like axial stress, bending force in sensor applications. Using a 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 fibres are studied. Potential applications of the fibres are discussed.

The full vectorial finite difference beam propagation method is used for modelling light propagation in photonic crystal fibre. We have simulated light propagation in 10 mm long fibre with the structure consisting of an air-filled silica and characterised by triangular lattice of air holes with a pitch Λ = 2μm and with the central high refractive index defect acting as a core. Both the index guiding and photonic band gap effect guiding are considered. The computed wave field is discussed and compared with the results of other authors.

The new designing of Bragg reflectors as generalized Fibonaccian AlAs-GaAs semiconductor optical superlattices is presented. We found aperiodic superlattices which, with 1μm thickness, have reflectances exceeding 99% in the 1.31 μm wavelength range. These aperiodic Bragg reflectors can be used in fabrication of vertical-cavity surface-emitting lasers (VCSELs).

We calculate, using finite difference method, the dispersion relation of photons transmitting through a one-dimensional photonic quasicrystal arranged in a generalized Fibonacci, generalized Thue-Morse and double periodic sequence. The structure of dispersion curves clearly shows their self-similar structure. With this method of calculation, we can obtain distribution of the electric field and energy density, group velocity and effective refraction index for the structure. We discuss taking into consideration the dispersion in layer materials and negative index materials.

The analysis of the transmission of system "dielectric grating- thin metal film-dielectric grating-substrate" is conducted by method of coupled waves. The 53 diffraction orders are used at the analysis that ensures the suitable precision of numerical calculations. It is reveal, that at the certain parameters the system has the anomalously high transmission for the reflection of about zero. For example, the silver film with thickness of 0.0385 μm, which is placed between a two grating with the certain parameters, transmits more than 0.86 and 0.83 for TE and TM polarizations, respectively, at wave-length of 1.5 μm. Under vacuum the silver film of the same thickness has the reflection more than 0.98 and transmits less than 0.004. The analogical results are obtained for other metals: cold and potassium. The transmittance value sharply decreases at deviation of wavelength from optimum magnitude. Basing on such structures it is possible to build the narrow-banded filters. The effect of great transmission can be explained in the following way. The gratings serve as matched elements of impedance for the thin metal film and of impedance for homogeneous mediums. The field distribution inside structure meets standing wave, node of which placed on thin metal film that leads to low absorption.

Two-dimensional (planar) photonic crystal waveguides give a possibility to propagate a light beam at narrow angles with small or no energy losses. Line and point defects introduced into the lattice modify the photonic structure of the crystal, which further leads to the possibility of designing more advanced integrated optical structures, such as strip waveguides, splitters or emitters. In our research we adopted Electron Beam Induced Deposition technique to produce the point and the line defects in a photolithographic pattern of a photonic crystal. First, we produced a pattern of holes in a positive photoresist film by two-beam interference lithography¹. Then we utilised EBID technique to fill the selected holes, by adopting SEM Hitachi S 570 device. As a process precursor we used diluted vapour of trimethylpentaphenyltrisiloxane, which is the dominant constituent of diffusion pump oil². Focused electron beam locally decomposes precursor molecules, which leads to solid material deposition. Composition of deposited structure is a mixture of amorphous carbon and some polymers. By the beam scanning in a line mode, the line of carbon can be deposited. Such a line defect in photoresist can act as a protecting mask during the further etching process. This controllable and high-resolution method can be used to fabricate W1, W2 and W3 types of channel waveguides. The best EBID resolution obtained in the selected setup gives lines with width of 15-25 nm.

We numerically analyzed the polarization properties of two birefringent photonic bandgap holey fibers with different geometries. Our calculation method is fully vectorial and uses a hybrid edge/nodal finite element approach with PML absorbing boundary conditions. In both structures, we determined the spectral dependence of the phase modal birefringence and the spectral dependence of the losses for the fundamental modes of orthogonal polarizations. Our results show that the dependence of losses upon mode polarization is so high that both structures can be used as fiber polarizers.

In this communicate, we present a numerical approach allowing to model propagation characteristics of the large core birefringent holey fibers with stress applying elements. The main advantage of the proposed method is that it takes into account simultaneously both geometry of the holey region as well as material birefringence induced by stress applying elements. Using this approach, we calculated the spectral dependence of phase and group modal birefringence for different geometry of the analyzed fiber. Furthermore, the spectral dependence of polarimetric sensitivity to temperature was determined. The calculation results were compared with experimental data published earlier.

We proposed and theoretically analyzed birefringent holey fibers of new construction. The birefringence in these fibers is induced by a highly asymmetrical cladding, which is composed of only two rows of large holes separated by one row of small holes The fiber cores have the form of single defects made of pure silica or containing GeO₂ doped circular inclusion The geometries of both fibers were preliminarily optimized in order to assure minimum number of structural elements, while keeping the confinement losses of the fundamental mode below 1 dB/km. We used an edge finite element method to calculate the spectral dependence of the confinement losses and the phase birefringence. Due to small number of the cladding holes, the proposed fiber construction with GeO₂ doped inclusion in the core region may be especially useful for inscription the Bragg gratings.