This PDF file contains the front matter associated with SPIE Proceedings Volume 8425, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

In this paper, we consider the propagation of slow light optical pulses inside photonic crystal slab waveguides (PCSW) both from a theoretical and an application point-of-view. The numerical model used relies on a nonlinear envelope propagation equation that includes the effects of second and third order dispersion, optical losses and self phase modulation. Pulse propagation is examined both in the linear and nonlinear regime. It is numerically shown that for rates of 10Gb/s, the order of nanosecond delays can be achieved through the PCSW defect modes without excessive pulse broadening in the nonlinear regime. In the nonlinear case, it is shown that soliton pulses exhibit less broadening than pulses in the linear case. In comparing the linear and the non-linear case we consider launching pulses with the same initial full width at half maximum or the same RMS width. The influence of optical losses on the soliton pulse broadening factor is also incorporated and discussed providing a more practical perspective. The results demonstrate the potential of implementing a variety of linear and nonlinear signal processing applications in PCSWs, such as optical buffering.

We introduce a novel design of wide Slot Photonic Crystal Waveguides (SPCW) by structuring the slot as a comb. This allows performing dispersion engineering in order to achieve very low group velocities over a few nanometers bandwidth. This kind of SPCW offers opportunities to realize devices requiring strong interactions between light and an optically non-linear low index material by providing an ultra-high optical density while easing the filling of the slot due to its width. We will present dispersion engineering results by Plane Wave Expansion method and Finite Difference Time Domain analysis.

We demonstrate that the lifetime of a nanocavity can be enhanced by inserting a medium with a strong index dispersion in the cavity. The strong dispersion is achieved through coherent population oscillations effect in the quantum wells of a two-dimensional photonic crystal nanocavity. The initial cavity lifetime of ~3-6ps has been extended to a maximum value of about 336 ps.

We discuss the properties and potential of slotted photonic crystals devices as small optical, label-free biosensors. This approach combines slot waveguides, which guide light in a narrow air slot, with photonic crystals in which cavities and slow light behaviour can be engineered. We use cavities based upon the heterostructure approach, demonstrating experimental quality factors of up to 50,000 in air and 4,000 in water. As the peak of the cavity mode interacts with the contents of the slot, small changes in refractive index can be inferred from the cavity resonant wavelength with high sensitivity (~500 nm/RIU). We also integrate microfluidic channels, which when combined with the small footprint of each sensor, allows potential for dense multiplexing with only micro-litres of analyte. As the dispersive properties of the fundamental mode of a standard and slotted photonic crystal differ greatly, a suitable interface for coupling into the device must be found. We here utilise a resonant defect approach, which preferentially couples into the slot mode. Functionalising the surface of the device with antibodies allows us to detect specific binding of a target protein on the sensor surface. As a proof of principle demonstration we show detection of dissolved avidin concentrations as low as 15 nM using biotin functionalised devices.

Photonic crystal (PhC) cavities made in broadband luminescent material offer attractive possibilities for flexible active devices. The luminescence enables the cavity to operate as an autonomous entity. New applications of this property are demonstrated for cavities made in the InGaAsP underetched semiconductor membrane with embedded InAs Quantum Dots that emit in the range of 1400-1600 nm. Planar photonic crystal membrane nanocavities were released from the parent chip by mechanical nanomanipulation. The released cavity particle could be bonded on an arbitrary surface, which was exploited to make a novel fiber-optic tip sensor with a PhC cavity attached to the tip. A single mode from a short cavity is shown to couple simultaneously to at least three cavity modes of a long cavity, as concluded from level anticrossing data when the small cavity was photothermally tuned. Reconfigurable and movable cavities were created by locally varying the infiltration status by liquid oil near a PhC waveguide or defect cavity. Liquid was displaced locally on a micron scale using capillary force effects or laser-induced evaporation and condensation phenomena.

Based on recent experimental and theoretical results obtained with gold-glass nanocomposite films, we propose a plasmonic device which uses the backscattering of light in order to make a highly sensitive gas/vapour sensor. The backscattered reflectance is used as the sensing signal since it has been shown, under certain conditions, that this component of the diffracted light is much more sensitive to a change of refractive index in the surrounding medium than the specular component. In addition, the backscattering presents an azimuthal angular dependency which is viewed as an advantage for practical implementation. The device consists of three planar layers. First, a glass substrate acting as incidence medium. Then a dielectric layer with a reduced refractive index with respect to the substrate is added which acts as a leaky-waveguide in order to maximize light coupling into the third sensing layer. The third layer is composed of gold nanopillars embedded in a dielectric matrix. Through numerical simulations, 2D periodic square and hexagonal arrays of gold nanopillars are compared in order to point out the influence of the nanocomposite arrangement in the photonic response. Moreover, disorder is introduced into these arrays in order to highlight the robustness of the sensing principle with respect to defects in the particle arrangement and size. For the purpose of gas/vapour sensing, we study the backscattered reflectance as it changes according to modifications in the dielectric environment at the external surface due to adsorption from gas or vapour. We determine the optimized device parameters and incidence angles.

The performance of quantum well infrared photodetectors (QWIP) can be significantly enhanced combining it with a photonic crystal slab (PCS) resonator. In such a system the chosen PCS mode is designed to coincide with the absorption maximum of the photodetector by adjusting the lattice parameters. However there is a multitude of parameter sets that exhibit the same resonance frequency of the chosen PCS mode. We have investigated how the choice of the PC design can be exploited for a further enhancement of QWIPs. Several sets of lattice parameters that exhibit the chosen PCS mode at the same resonance frequency have been obtained and the finite difference time domain method was used to simulate the absorption spectra of the different PCS. A photonic crystal slab quantum well infrared photodetector with three different photonic crystal lattice designs that exhibit the same resonance frequency of the chosen PCS mode were designed, fabricated and measured. This work shows that the quality factor of a PCS-QWIP and therefore the absorption enhancement can be increased by an optimized PCS design. The improvement is a combined effect of a changed lattice constant, PC normalized radius and normalized slab thickness. An enhancement of the measured photocurrent of more than a factor of two was measured.

Here we discuss the experimental characterization of the spatial far-field profiles for the confined modes in a photonic crystal cavity of the L3 type, finding a good agreement with FDTD simulations. We then link the far-field profiles to relevant features of the cavity mode near-fields, using a simple Fabry-Perot resonator model. Finally, we describe a technique for independent all-electrical control of the wavelength of quantum dots in separated L3 cavities, coupled by a waveguide, by electrical isolation via proton implantation

We present the design and the fabrication of a dual-wavelength micro-photonic resonator combining a photonic crystal membrane (PCM) and a vertical Fabry Perot (FP) cavity where the former is embedded in the latter. A strong optical coupling between a PCM Γ-point Bloch mode and a FP mode at the same frequency can be used to provide a dual-wavelength device with a frequency difference which is analysed in terms of modes overlapping. We propose and demonstrate a process flow that can be used to provide such a device. Optical reflectivity characterisation is presented for a monolithic device and photoluminescence dual-wavelength spontaneous emission is demonstrated in an extended vertical cavity. Finally the dual-mode laser emission stability is examined with numerical Monte Carlo simulation.

We propose and for the first time realize a concept for dynamic frequency conversion in silicon photonic crystal cavities using an in-plane pumping configuration. The required fast index change of silicon is performed by generating free carriers through two-photon absorption of a pump pulse. We perform a theoretical analysis of the time dependence of the energy in a cavity coupled to two identical ports that is excited by a Gaussian signal. We find that the maximum energy that can be stored in the cavity is always lower than the energy of the excitation pulse and that it depends on the ratio of the cavity lifetime to signal duration. At the optimum of this ratio, a maximum of 40% of the input pulse energy can be stored in the cavity and thus submitted to the dynamic frequency conversion process. We show experimentally a dynamic frequency shift of 7.5•10^-2 THz .

We consider phoxonic crystals in relation with their application to photon-phonon interaction. The main interests of such structures are the possibility to confine simultaneously optical and elastic waves in cavities and waveguides and to engineer the photonic and phononic dispersion relations of waveguides. A variety of coupling mechanisms are discussed for exaltation or quenching, including classical photo-elastic coupling as a volume interaction effect, and couplings introduced by moving boundaries or resonator dimensions.

Light control through elastic waves is a well established and mature technology. The underlying mechanism is the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately designed structures that simultaneously localize light and elastic waves in the same region of space and operate as dual optical-elastic cavities, often called phoxonic or optomechanical cavities. Typical examples of phoxonic cavities are multilayer films with a dielectric sandwiched between two Bragg mirrors or, in general, defects in macroscopically periodic structures that exhibit dual band gaps for light and elastic waves. In the present work we consider dielectric particles as phoxonic cavities and study the influence of elastic eigenmode vibrations on the optical Mie resonances. An important issue is the excitation of elastic waves in such submicron particles and, in this respect, we analyze the excitation of high-frequency vibrations following thermal expansion induced by the absorption of a femtosecond laser pulse. For spherical particles, homogeneous thermalization leads to excitation of the particle breathing modes. We report a thorough study of the acousto-optic interaction, correct to all orders in the acousto-optic coupling parameter, by means of rigorous full electrodynamic and elastodynamic calculations, in both time and frequency domains. Our results show that, under double elastic-optical resonance conditions, strong acousto-optic interaction takes place and results in large dynamical shifts of the high-Q optical Mie resonances, manifested through multiphonon exchange mechanisms.

The concept of photonic and phononic crystal sensors is based on the measurement of changes in the transmission properties of the devices caused by changes of material properties of one of the materials building the crystal. It has been demonstrated that in the optical case the key parameter is the refractive index, i.e. speed of light, in the acoustic case it is sound velocity. Both parameters can be measured with accuracy competitive with other optical and acoustic sensor principles. A phoxonic crystal sensor combines both concepts in one device, therefore allowing for a dual parallel determination of two independent material properties. Such a sensor is especially attractive for complex analytes as common in chemistry and biochemistry. We have designed and modeled a phoxonic crystal consisting of a solid matrix and holes where the central cavity acts as analyte container. We especially concentrate on the generation of a characteristic feature within the transmission spectrum like a transmission peak within the phoxonic band gap where the respective wavelength or frequency of maximum transmission is sensitive to material properties of the analyte. We could show theoretically that a (geometric) defect is required in photonics whereas in phononics separation of the sensitive peak is the challenge. The respective wavelength/frequency of maximum transmission moves in accordance to the resonance conditions. We further analyze the transmission of light and sound through a phoxonic crystal plate at normal incidence.

We study theoretically the potentiality of phononic and dual phononic-photonic (the so-called phoxonic) crystals for liquid sensing applications. We investigate the existence of well-defined features (peaks or dips) in the transmission spectra of acoustic and optical waves and evaluate their sensitivity to the sound velocity or refractive index of the liquid environment. Several geometries are considered that can be divided into two sets depending on the direction of propagation of the incident waves with respect to the phononic/photonic crystal, namely in-plane and out-of-plane propagation configurations. In the first configuration, we study the in-plane transmission through a two-dimensional (2D) crystal made of cylindrical holes in a Si substrate where one row of holes is filled with a liquid; possibly, the infiltrated holes may have a different radius than the normal holes. Another geometry we have studied consists of a periodic array of ridges on top of a thin Si membrane with incident waves parallel to the slab. In the out-of-plane configuration, we calculate the transmission between two solid substrates connected by a periodic array of pillars as well as the normally incident transmission upon a phoxonic crystal constituted by a periodic array of holes in a slab.

In order to achieve high efficiency photovoltaic devices and sensors, we propose to implement photonic crystals on thin absorbing layers in such a way to generate two Bloch mode resonances with opposite symmetries. Through FDTD and RCWA simulations, we track and adjust the characteristics of these modes so as to reach their degeneracy. Design and simulations were carried out considering a hydrogenated amorphous silicon layer. We demonstrate that up to 92% absorption can be achieved, far above the 50% limit corresponding to the critical coupling condition between an incident wave and an optical resonance. Moreover, the robustness of the absorption peak was tested by varying both the topographical parameters of the PhC membrane and the angle of incidence. Finally, some guidelines are provided to generalize our approach for the design of broadband absorbers.

In this paper, we present the integration of an absorbing photonic crystal within a monocrystalline silicon thin film solar cell stack. Optical simulations performed on a complete solar cell revealed that patterning the epitaxial monocrystalline silicon active layer as a 1D and 2D photonic crystal enabled to increase its integrated absorption by 38%_rel and 50%_rel in the whole 300-1100 nm range, compared to a similar but unpatterned stack. In order to fabricate such promising cells, a specific fabrication process based on holographic lithography, inductively coupled plasma etching and reactive ion etching has been developed and implemented to obtain such photonic crystal patterned solar cells. Optical measurements performed on the patterned stacks highlight the significant absorption enhancement, as expected by simulation. A more advanced structuration combining a front and a rear 1D binary photonic patterning with different periods is designed, enabling a 60%_abs larger absorption in silicon.

We report on experimental and theoretical investigations of light diffraction from opal films of different thickness. A special attention was paid to the transformation of diffraction patterns upon building up the opal structure from two-dimensional (2D) film structure towards bulk three-dimensional (3D) structure. In our setup the diffraction patterns are displayed on a narrow cylindrical screen with a specimen fixed in its center. The diffraction patterns have been studied visually and recorded in different scattering geometries with the films illuminated with white unpolarized light. With increasing number of layers, certain regions of 2D diffraction patterns fade out and finally form diffraction spots characteristic for 3D diffraction. We also found that stacking faults in bulk opals lead to formation of a 2D-like diffraction pattern, i.e. such structure demonstrate 3D to quasi-2D transition in optical properties.

The transformation of 2-dimensional slab photonic crystal into 2-dimensional photonic glass was achieved by gradually increasing the sphere spacing and by randomising the lattice. The materials were prepared by assembling colloidal particles at the air/water interface using a Langmuir-Blodgett trough and the subsequent deposition on glass substrates. Highly ordered monolayers were obtained by using colloids of one size, while use particles of two different sizes and different partial concentrations allows to increase the spacing of the larger spheres and to randomize the lattice. Changes in the spheres arrangements result in a change of in-plane light propagation from band-like to hopping photon transport.

Sub-micron waveguides and cavities have been shown to produce the confinement of elastic and optical waves in the same devices in order to benefit from their interaction. It has been shown that square and honeycomb lattices are the most suitable to produce simultaneous photonic and phononic band gaps on suspended silicon slabs. The introduction of line defects on such "phoxonic" (or optomechanical) crystals should lead to an enhanced interaction between confined light and sound. In this work we report on the experimental measurements of light guiding through waveguides created in these kinds of two-dimensional photonic crystal membranes. The dimensions of the fabricated structures are chosen to provide a "phoxonic" bandgap with a photonic gap around 1550 nm. For both kinds of lattice, we observe a high-transmission band when introducing a linear defect, although it is observed for TM polarization in the honeycomb lattice and for TE in the square. Using the plane-wave expansion and the finite element methods we demonstrate that the guided modes are below the light line and, therefore, without additional losses beside fabrication imperfections. Our results lead us to conclude that waveguides implemented in honeycomb and square lattice "phoxonic" crystals are a very suitable platform to observe an enhanced interaction between propagating photons and phonons.

Experimental results on light bending effect in a non-homogenizable graded photonic crystals operating at optical wavelengths are presented. A square lattice photonic crystal made with a two-dimensional chirp of the air-hole filling factor is exploited to produce this bending effect in a near bandgap frequency range. Experimental results are in good agreement with the prediction that had been performed using the equations of Hamiltonian optics and Finite-Difference Time-Domain simulations. This experimental demonstration performed in one particular configuration opens opportunities for light manipulation using a combination of unusual dispersive phenomena in PhCs and additional degrees of freedom brought by a generalized two-dimensional chirp of PhCs lattice parameters. This approach is also an alternative solution to the use of photonic metamaterials combining dielectric and metallic materials with sub-wavelength unit cells.

The marriage of photonics and microfluidics ("optofluidics") uses the inherent mobility of fluids to reversibly tune photonic structures beyond traditional fabrication methods by infiltrating voids in said structures. Photonic crystals (PhCs) strongly control light on the wavelength scale and are well suited to optofluidic tuning because their periodic airhole microstructure is a natural candidate for housing liquids. The infiltration of a single row of holes in the PhC matrix modifies the effective refractive index allowing optical modes to be guided by the PhC bandgap. In this work we present the first experimental demonstration of a reconfigurable single mode W1 photonic crystal defect waveguide created by selective liquid infiltration. We modified a hexagonal silicon planar photonic crystal membrane by selectively filling a single row of air holes with ~300nm resolution, using high refractive index ionic liquid. The modification creates optical confinement in the infiltrated region and allows propagation of a single optical waveguide mode. We describe the challenges arising from the infiltration process and the liquid/solid surface interaction in the photonic crystal. We include a detailed comparison between analytic and numerical modeling and experimental results, and introduce a new approach to create an offset photonic crystal cavity by varying the nature of the selective infiltration process.

Zero-average index metamaterials and photonic crystal superlattices are well known for presenting uncommon properties such as a new forbidden band for photons and self-collimation effect. In this work, we show how these two approaches can be combined to finely control beam propagation and we develop a theory that provides a comprehensive understanding of these phenomenon. We show that the curvature of the dispersion relation plays a crucial role to cancel light diffraction. This concept leads to the design of PhC superlattices with a very low filling factor in air and presenting a slow light regime. The frequency selectivity of the self-collimation effect is in addition shown to be increased by 10 or 50 compared to common 2D photonic crystal devices.

We report and analyze experimental observation of the formation of a narrow, well collimated laser beam at optical frequency behind the woodpile photonic crystal fabricated using a femtosecond laser multi-photon polymerization technique. We show that the collimation depends on the input laser beam focusing conditions. We discuss the experimental results and give theoretical interpretation.

We discuss resonant photonic crystals and quasicrystals focusing on the quantum well (QW)-based structures. Formation of exciton-polaritons in the light-coupled Fibonacci QWs is demonstrated. Analytical two-wave approximation, allowing to obtain optical spectra and polaritonic band structure and to interpret experimental results, is presented.

In this paper we discuss the elaboration, optical properties and possible applications of thin films and nano-patterns of molecular spin crossover complexes. These bistable nanostructures can respond reversibly with fast response times to various external stimuli, such as temperature changes, application of an external pressure, light irradiation or exposure to gas/vapor molecules. The response can be either transient (gating) or non-volatile (switching) depending on the experimental conditions. We show that these assets provide a very appealing scope for a variety of applications including tunable photonic devices, thermal imaging and chemical sensors. In particular, we discuss three photonic application principles based on fluorescence energy transfer, grating diffraction and guided plasmon-polariton waves.

In order to realize the regime of strong coupling between Bloch modes of periodically structured dielectric and surface plasmon polariton modes of corrugated metal film we prepared 2-dimensional slab hybrid plasmonicphotonic crystals. Angle-resolved transmission/reflectance spectroscopy was used to assess the composition of guided modes in such hybrid crystals. In the case of a monolayer photonic crystal encapsulated in a plasmonic waveguide we achieved the splitting of major resonances, which was interpreted in terms of mode hybridization and controlling the spatial localization of modes.

We have fabricated a Ge_11.5As₂₄Se_64.5 2-D photonic crystal containing a hetero-structure cavity fully embedded in a cladding with index of 1.44. Because of the low index contrast of this structure (≈1.2) we had to use a W0.54 defect waveguide to inhibit losses to continuum modes above the light line. By has allowed optical cavities with very high Q (>750,000) to be obtained.

We demonstrate a novel concept for the fabrication of high Q photonic crystal heterostructure cavities. First, photonic crystal waveguides without cavities are fabricated. The cavities are defined in a later fabrication step by spatially resolved bleaching of a chromophore doped polymer cladding. Bleaching of polymer films either by UV light or by electron beam illumination is well known to reduce the refractive index of the film. The reduction of the cladding refractive index leads to a reduction of the effective lattice constant of the photonic crystal waveguide. The maximum refractive index change was found to be 6•10^-2 which corresponds to the effective lattice constant change of 12.2 nm. With this approach it is also possible to achieve very small effective lattice constant shifts of 0.02 nm which is not possible with state of the art lithography. Being able to precisely define the effective lattice constant at every point of the photonic crystal waveguide we are able to impose cavity mode profiles which closely resemble a Gaussian envelope. This leads to a dramatic increase of the Q-factor. In simulations we have obtained Q-factors as high as 3.0•10⁶ for a vertically symmetric polymer cladding. First results for non-vertically symmetric structures are presented.

We propose a new approach for the 3D control of light in real 3D optical micro-resonators that can be assimilated to 'cages', where photons are efficiently trapped. The main attractive feature of this photon cages lies in their ability to result in a considerable enhancement of the electromagnetic field in the central part of the cage, that is in the air region, opening the way to new sensing or trapping of nanoparticles in fluidic (gas or liquid) ambiances. Fabrication of three dimensional structures consists in exploiting the process of elastic relaxation of patterns formed in pre-stressed multi-layer structures. The final shape of these objects can be predetermined by the distribution of the deformations in the various semiconductor layers, imposed during their epitaxial growth, before their freestanding from the substrate by selective etching. We will present the basic concepts and fabrication we exploit to confine photons in air using spherical structures based on progressive relaxation of pre-stressed InGaP/InAsP bilayer films. It is worthwhile to notice that the formed microstructures exhibit patterns with dimensions compatible with optical operation in the visible/NIR wavelength range.

A random laser is formed by a haphazard assembly of nondescript optical scatters with optical gain. Multiple light scattering replaces the optical cavity of traditional lasers and the interplay between gain, scattering and size determines its unique properties. Random lasers studied till recently, consisted of irregularly shaped or polydisperse scatters, with some average scattering strength constant across the gain frequency band. Photonic glasses can sustain scattering resonances that can be placed in the gain window, since they are formed by monodisperse spheres [1]. The unique resonant scattering of this novel material allows controlling the lasing color via the diameter of the particles and their refractive index. Thus a random laser with a priori set lasing peak can be designed [2]. A special pumping scheme that enables to select the number of activated modes in a random laser permits to prepare RLs in two distinct regimes by controlling directionality through the shape of the pump [3]. When pumping is essentially unidirectional, few (barely interacting) modes are turned on that show as sharp, uncorrelated peaks in the spectrum. By increasing angular span of the pump beams, many resonances intervene generating a smooth emission spectrum with a high degree of correlation, and shorter lifetime. These are signs of a phaselocking transition, in which phases are clamped together so that modes oscillate synchronously.

The second harmonic light generated in crystals with a random distribution of nonlinear domains is usually emitted in a broad range of directions. When the fundamental light has good coherence, the intensity of the second harmonic shows a speckle pattern even when the crystal is transparent. We explain that with the interference at the detection point of the second harmonic generated by the different domains. Using a phase-only spatial light modulator in the fundamental beam, it is possible to concentrate the second harmonic intensity in one direction at the same time that the intensity is reduced in the other directions. In our experiments we measured enhancements in the selected direction up of 700 times over the average intensity in other directions.

Herein, we report two different dual-periodic Photonic Crystals (PCs) in dichromated gelatin emulsion which are fabricated by four-beam holography and double-exposure holography. The minibands with high Q-factors have been evidently located in both two structures. By taking into account the non-uniform distribution of material, the numerical results agree quite well with the experimental results. We also compared the band-edge lasing in single-periodic PC and miniband lasing in Moiré dual-periodic PC. Due to extremely flat dispersion and large mode volume of the miniband, high optical conversion efficiency in miniband lasing is achieved as compared with that of band-edge lasing. Such effect may provide potential applications in low-threshold lasers and ultra-sensitive fluorescent probes in biological assays.

The nonlinear properties of quasi-periodic photonic crystals based on the Thue-Morse and Fibonacci sequence are investigated. We address the transmission properties of waves through one dimensional symmetric Fibonacci, and Thue-Morse system i.e., a quasiperiodic structure made up of two different dielectric materials (Rogers and air), in quarter wavelength condition, presenting in the one directions. The microwave spectra are calculated by using transfer matrix method in normal incidence geometry. In our results we present the self-similar features of the spectra and we also present the microwave properties through a return map of the transmission coefficients. We extract powerfully the band gaps of quasi-periodic multilayered structures, called `pseudo band gaps' often contain resonant states, which can be considered as a manifestation of numerous defects distributed along the structure. Taken together, the above two properties provide favorable conditions for the design of an all-microwave reflector.

In this report we present the results of optical induction of 1D and 2D micrometric and sub-micrometric scale annular symmetry photonic lattices in singly and doubly doped photorefractive lithium niobate crystals by Bessel beam technique. The non-diffracting Bessel beam was formed by axicon and the counter-propagating Bessel beam (CPBB) geometry was used to build-up the Bessel standing wave. The cw single mode 532 nm, 17 mW laser beam and 2mm thick lithium niobate (LN) crystals doped by Fe and doubly doped by Fe and Cu with 0,05 w% of impurity ions were used for lattices recording. The crystals with optical C-axes oriented along and perpendicular to the crystal surface (Y-cut and Z-cut LN crystals) were used for photonic lattices recording. The duration of recording was 60 min. 2D photonic lattices formed by CPBB method is a combination of annular and planar gratings and have the periods of 9.0 μm in radial and 266 nm in axial directions. The recorded lattices were tested by diffraction of probe laser beam at 633nm on the lattices. The direct observation of recorded lattices by phase microscope was also performed. The pronounced azimuthal dependence of recorded annular lattices was observed for Y-cut LN crystals. The photonic lattices recorded in LN:Fe:Cu crystals showed high stability against erasure during readout by weak probe beam at the recording wavelength. Under illumination by 2 mW probe green beam the total erasure of the photonic lattice occurred after 8000 sec, which was controlled by measuring the diffracted beam power during readout. The readout destruction of lattices recorded in LN:Fe crystal takes several minutes.

In this paper we present a preliminary study to realize an integrated photonic crystal double cavities refractive index sensor calibrated in temperature. The studied conguration allows to realize a very compact device with only one interrogation channel, since the monitored signals are the cavities re ected signals. The sensitive elements used are the modulation of the cavities linewidth due to temperature and refractive index change, measured by means of the cavities detuning. The appeal of such type of devices, respect to the corresponding ones in optical bers, is the possibility to expand the conguration to create on the same chip the detector and the requested signal processing devices. The reliability of the proposed conguration is related to the interrogation technique, based on the radio-frequency phase modulation of the impinging laser light. This techniques was widely demonstrated in the last years^1-4 and initially borrowed by the cavity frequency stabilization and locking Pound-Drever-Hall methods.⁵ Here we demonstrate as it is possible to use it for simultaneously detection of the detuning of two cavities with only one interrogation channel.

The combination of two planar photonic crystal areas is proposed to circumvent some limitations frequently encountered when using the so-called superprism effect, and especially the beam broadening phenomenon that accompanies strong prism spatial dispersion. The basic idea that is pursued is to choose two strongly dispersive photonic crystals but arrange their properties to make their diffraction effects cancel out as a whole. In-depth investigation of a possible global configuration is performed by using Plane Wave Expansion simulation and post-processing calculations to estimate second order dispersion parameters that govern both dispersion and diffraction. A two photonic crystal structure is chosen and the predicted dispersion-accumulation and diffraction-compensation mechanism is verified using Finite Difference Time Domain simulation.

In this work, we explore the generation of slow and fast light (SFL) in a linear and passive three-beam interferometer for center pulse frequency close to the transmission minima. We show that the group delay can be tuned from subluminal to superluminal values by simply changing the length of one of the interferometer's arms. Some figures of merit of this three-beam interferometer as an SFL system are discussed, namely fractional delay and pulse distortion. We build our interferometers using 50-Ω coaxial cables and 1x3 power splitters in order to perform the experiments in the radiofrequency range, where a full frequency-domain characterization of them can be performed with a vector network analyzer. Together with the frequency domain results, we present direct measurement of the group delay in time domain. Fractional delays of ±25% were measured for a train of sinusoidally modulated wavepacket with 300 kHz repetition rate. Additionally, a Lithium Niobate interferometer operative in the optical range (1.55 μm) was simulated and discussed. This system is proposed as an alternative to active systems and photonic band-gap structures for sustaining both slow and fast light, with special emphasis in sensing purposes.

We demonstrate a possibility of oscillating soliton formation near the interface between nonlinear photonic crystal (PC) and ambient medium. This soliton is being formed from the initial distribution of intensity distribution under the perturbation of transverse component of wave vector of optical beam. The main feature of considered soliton is that only its part localizes in the PC and spreads over a few layers with regular intensity profile of beam. Its other part localizes near the boundary outside the PC. Hence, one can tell about the light energy localization at the lateral surface of the PC. Intensity profile of soliton and maximum intensity of soliton localized near the interface of the PC depends on initial intensity distribution of optical beam in PC. However, the initial intensity distribution does not influence essentially on the appearance of interface soliton. To proof this we consider three different kinds of initial beam profile which belongs to the central area of the nonlinear PC and spreads over a number of layers. The soliton can propagate across the layers many times without leaving the PC. After its achievement of PC boundary the soliton leaves partly the PC and then comes back in PC. Then, soliton propagates to other PC boundary. This process can be repeated many times. We also investigate the influence of initial beam profile on the laser light propagation.

We report first experimental evidences of spatial filtering of light beams in three-dimensional photonic crystals. The photonic crystals were fabricated in a glass bulk, where refractive index was modified by applying femtosecond laser pulses. We observe the modification of the angular spectra (the far field) in the central diffraction maximum of the transmitted radiation in accordance with the theory of spatial filtering.

The performance of magnetic-field sensors and optical isolators is largely determined by the efficiency of the active materials. This efficiency could be dramatically increased by integrating Faraday materials in photonic crystals. For this purpose, monodisperse nanospheres were self-assembled into a colloidal photonic crystal and magnetic functionality was introduced by dipping the photonic crystal in a suspension containing superparamagnetic nanoparticles. Reflection and absorbance measurements of these magneto-photonic crystals revealed clear relationships between the time spent in suspension and the position and strength of the photonic band gap. When additional magnetic material was introduced, the band gap was red shifted and the strength of the band gap was decreased. Using Bragg's law and the Maxwell-Garnet approximation for effective media, the filling fraction of the magneto-photonic crystals was calculated from the observed red shift. While superparamagnetic nanoparticles did confer magneto-optical properties to the photonic crystal, they also increased the absorption, which can be detrimental as the Faraday effect is measured in transmission. Therefore a trade-off exists in the optical regime between the amount of Faraday rotation and the absorption. By carefully controlling the filling fraction, this trade-off was investigated and optimized for photonic crystals with different band gaps. Both polystyrene and silica photonic crystals were filled with superparamagnetic nanoparticles. In case of the polystyrene photonic crystals, it was found that the maximum achievable filling fraction was influenced by the size of the polystyrene nanospheres. Smaller polystyrene nanospheres gave rise to smaller pore diameters and a faster onset of pore blocking when filled with superparamagnetic nanoparticles. As a result, the maximum achievable filling fraction was also lower. Pore blocking was found to be negligible in silica photonic crystals. Together with a higher mechanical strength, this makes silica photonic crystals more suited for the fabrication of colloidal magneto-photonic crystals. In this paper, a nanoscale engineering approach is described to carefully control the filling fraction of magneto-photonic crystals. This allows fine-tuning the absorption and the position and strength of the photonic band gap. By tailoring the properties of magneto-photonic crystals, the means for application-specific designs and a better description of Faraday effects in 3D magneto-photonic crystals are provided.

In this work, we show group delay tuning from superluminal/tunneling to subluminal pulse reflection on asymmetric Fabry-Perot filters with quarter-wavelength Bragg reflectors. As opposed to other photonic band-gap systems, reflected pulse delay control occurs in an entirely linear and passive asymmetric structure where the tuning mechanism consists in adjusting the mirrors spacing or the attenuation. Our results are obtained in the radiofrequency (RF) range through frequency- and time-domain characterization of Fabry-Perot filters based on high and low impedance coaxial cables. Group delay predictions within the phase-time approach were supported by pulse delay measurements of a modulated RF wave-packet tuned at the mirrors Bragg frequency. Superluminal, subluminal and tunnelling pulse reflection was detected, respectively, for mirror spacing adjusted to λ/4, λ/2 and 3λ/2 (where λ is the mirrors design wavelength). Fractional delays similar to those predicted in active asymmetric fiber Bragg gratings were obtained. These RF operating devices could be scaled to their analogous structures in the optical range and are proposed as an alternative to active or non-linear media for group velocity control.

Photonic quasi-crystal structures have been prepared and investigated. Symmetrical patterns were fabricated by interference lithography in negative tone photoresist and transferred to silicon by reactive ion etching. Theoretical influences of pattern detail (radius of hole) on the photonic band gap have been studied. Three types of 2D photonic quasi-crystals have been prepared: 8-fold, 10-fold and 12-fold pattern. Finally, finite-difference time-domain method was used for theoretically prediction of transmission spectrum for fabricated 12-fold quasi-crystal.

Photonic crystal structures have become increasingly popular due to their unique optical properties. In particular, photonic crystal band edge lasers have shown continually improving performance. In this paper, the development of an erbium doped two dimensional dielectric photonic crystal band-edge laser is reported. A computational study using the plane wave expansion method is performed to optimise the structural properties of square and triangular arrays of air holes in an erbium doped rutile titanium dioxide matrix for optical performance. Complete photonic band gaps adjacent to the third orthogonal band for both the square and triangular lattice patterns were achieved for r=0.46a and r=0.51a respectively. The monopole electric field distribution and narrow saddle point in the Γ direction for the third orthogonal band of the triangular lattice suggest that highly directional emission of TM polarization can be achieved. The preliminary experiments for fabrication of the 2D photonic crystals using a two beam interference lithography technique provides time efficient patterning over many square centimeters.

A design of a point-defect cavity in two-dimensional photonic crystal slab with both high Q factor and high transmission intensity has been achieved by adjusting the radii and position of lattice points in both parallel and perpendicular directions. Analysis shows that discrete resonant modes have been found in the 1550 wavelength range with Q factors up to 40,000. Moreover, the cavity was verified to subject to minor intensity decrease of 1.2 dB due to the introducing of external waveguide access. All these features make the cavity a very promising candidate for light transmission and detection in practical application. We also demonstrate the potential application of such a cavity being used as a sensitive index sensor with a high sensitivity of 400nm/refractive index unit.

We propose a tunable resonant narrow-band optical filter based on a two-dimensional grating on the top of a stack of dielectric layers including a layer of electro-optic (E-O) material, and demonstrate numerical results of the tunability. The structure is periodic in two orthogonal directions and the basic pattern is designed in order to increase the angular tolerance of the filter. The LiNbO₃ and BaTiO₃ were chosen due to their strong electro-optical properties. When an external electric field is applied on the E-O material layer, a displacement of the resonant peak in the spectra is observed. We have chosen the orientation of each E-O crystal so that the external electric field is applied in the direction corresponding to the greatest E-O coefficient.

Confinement Loss of microstructured fibers whose cladding is composed by a triangular arrangement of tubes of various shapes is theoretically and numerically investigated. Kagome Fibers belong from this family of fibers with cladding tubes with hexagonal shape. The shape of the cladding tubes is proved to strongly affect the performance of the microstructured fiber. In order to understand the reasons for this behavior, the spectral properties of the tubes that constitute the cladding are investigated first. It is proved that also these tubes suffer from additional Fano Resonances when they are given a polygonal shape. It is proved that, by using the analytical model developed for the stand alone polygonal tubes, it is possible to predict the spectral position of Fano Resonances also in microstructured fibers. This is extremely important since it suggest new ways to reduce confinement loss in kagome fibers and microstructured fibers in general.

Dispersion and loss properties of hollow core tube fibers with elliptical cross section are numerically investigated. Results show unusual characteristics. For example, the birefringence always goes to zero in the middle of the low loss region irrespectively of the ellipticity and it always assume opposite sign approaching the two edges of the low loss region.

We demonstrate that the acoustic phonons involved in stimulated Brillouin scattering (both forward and backward) in phoxonic waveguide can be completely described by using electrostrictive forces. Numerical calculation for bridge waveguide in silicon and silica illustrate the model.

We report on theoretical and experimental studies of multiple Bragg diffraction of light in three-dimensional photonic crystals possessing high dielectric contrast. Self-assembled opaline photonic crystals made up of monodisperse polystyrene microspheres are used as an example in our measurements. A new approach is considered to analyze and quantitatively describe the Bragg reflection and transmission complex-shaped contours. Our method is based on the dynamical diffraction theory generalized to the case of a three-dimensional spatially periodic medium characterized by high dielectric contrast and allows one to calculate in a simple analytical way the reflection and transmission spectra. The spatial Fourier components of the dielectric function are calculated taking into account a sintering of the spheres forming the opaline structure. Numerical calculations of the angle-resolved Bragg reflection and transmission spectra are performed, and those are compared with the dispersion curves of the electromagnetic eigenmodes for the opaline photonic crystals spatially confined along the [111] direction. The peculiarities in the optical spectra are found to correspond to singular points in the eigenmode dispersion curves. It is shown also that under the multiple Bragg diffraction conditions the reflection and transmission contours are shaped due to conventional photonic stop-band states as well as additional low-group-velocity modes ("slow light" modes). The contours calculated show a good agreement with our experimental data if a uniaxial strain along the sedimentation direction [111] and the particle sintering are accounted for.

Using Finite-difference time-domain (FDTD) method, the excitation of surface plasmon polaritons (SPP) at the sinusoidally corrugated metal-dielectric interface was simulated. The sample structure was made by creating onedimension sinusoidally corrugated dielectric layer on top of metal thin film deposited on dielectric substrate. The thickness of metal film was simulated in range from 10 to 200 nm. Sinusoidally corrugated grating was modelled with different pitch and height. Additionally influence of a dielectric layer between grating and metal layer was simulated. The optical response of the structure was obtained in the regime of wavelength and angle. All simulations were performed for gold (Au) thin films deposited on glass substrate. Then selected structures were fabricated and measured. The gold film was thermally evaporated on glass substrate then the one-dimension sinusoidally corrugated dielectric layer was made in a photoresist using interference lithography.

A hybrid structure of the type Bragg mirror-(Fibonacci)^S is proposed to enhance the zero transmission band through the one dimensional photonic crystal in microwave domain and in the infrared. The efficiency of the configuration is proved in microwave domain for angles below 57°. In the infrared, the use of the configuration exhibits a large photonic band gap at any angle of incidence and for both polarizations. The proposed structure is a quarter wavelength omnidirectional mirror of 37 layers with a bandwidth larger than that of the periodic structure with an increasing ratio 3.7 and it covers all the optical telecommunication wavelengths 0.85, 1.3 and 1.55 μm. Unlike the previous devices, the structure is simple to fabricate and it shows interesting optical properties. The configuration Bragg mirror-(Fibonacci)^S-Bragg mirror is also investigated to more extend the photonic band gap. Since different physical phenomena have their own appropriate physical scales, we exploited the physical properties of the proposed hybrid structure in different wavelength domains.

We report on the fabrication of inverted Yablonovite-like three-dimensional photonic crystals by nonlinear optical nanolithography based on two-photon polymerization of a zirconium propoxide hybrid organic-inorganic material with Irgacure 369 as photo-initiator. Advantage of this material is ultra-low shrinkage that guaranty high fabrication fidelity. Images of the fabricated structure are obtained with a scanning electron microscope. The photonic crystal consists of three sets of nearly cylindrical structural elements directed along the three lattice vectors of the fcc lattice and cross each other at certain angles to produce inverted Yablonovite geometry. To investigate photonic properties of the inverted Yablonovite structures, we calculate the photonic band structure for ten lowest-frequency electromagnetic modes. In contrast to the direct Yablonovite structure that has a complete photonic band gap between the second and third bands, we find no complete photonic band gaps in the inverted Yablonovite lattice. This situation is opposite to the case of fcc lattice of close-packed dielectric spheres in air that has a complete photonic band gap only for the inverted geometry.