This PDF file contains the front matter associated with SPIE Proceedings Volume 6582, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We investigate numerically the self-focusing dynamics of femtosecond pulses in the frame of new non-paraxial amplitude equations. We find that the nonlinear regime strongly depends on the initial form of the pulses. In the case of pulse with small transverse and large longitudinal size (long pulse), the dynamics is closer to the nonlinear paraxial dynamics of a laser beam, and the difference is in the large spectral and longitudinal spatial modulation of the long pulse. We show also that non-paraxiality plays an important role on the evolution of light bullets and light disks. In regime of light bullets we observe weak self-focusing without pedestals for input power P valued from the critical power for collapse P_cr up to 16 P_cr. We find also nonlinear non-collapsed regime of propagation of light disks (pulses with small longitudinal and large transverse size), when the input power exceeds the critical power for collapse P_cr. Our results are in good agreement with the recent experiments on nonlinear propagation of femtosecond pulses. We have demonstrated for the first time that a non-paraxial model can explain such effects as spectral broadening, collapse arrest and nonlinear wave guide behavior of ultrashort optical pulses in nonlinear regime near to critical power for self-focusing.

The evolution of short optical pulses towards a self-similar parabolic intensity profile in normally dispersive nonlinear fiber optic amplifiers can be described with good accuracy by means of a simple analytical model. This approach enables the evaluation of the optimal input pulse time duration and chirp for decreasing the distance of convergence towards the asymptotic regime. We show that pulse spectral broadening in dispersive nonlinear fiber amplifiers may be enhanced by introducing a suitable dispersion tapering. We obtain an analytical dispersion profile which permits to reduce pulse propagation in a varying dispersion fiber to the case of an equivalent fiber with constant parameters.

The existence and robustness of dark vortices in bi-dispersive and/or normally dispersive self-defocusing nonlinear media is demonstrated. The underlying equation is the bi-dispersive three-dimensional nonlinear Schrdinger equation. The dark vortices are investigated numerically as well as variationally. These vortices can be considered as extensions of two-dimensional dark vortex solitons which, along the third dimension, remain localized due to the interplay between diffraction and nonlinearity. Linear stability analysis predicts that for fairly long propagation distances these objects are subject to a very weak transverse instability (in the temporal domain). On this basis the maximum growth rate of the instability is estimated. However, numerical simulations depict that 3D vortices are robust objects. Instability is observed only in the case where the vortex is subjected to relatively strong transverse perturbation. Furthermore, in our simulation is observed that a dark vortex does not break into vortices of a lower vorticity. The variational approach predicts that the synenergy content (the finite ambient energy that remains when the infinite energy of the dark object is excluded) of a vortex of high vorticity is lower than the sum of the synenergies of unitary vortices with the same pedestal. Such vortex solitary objects can be observed in optical media with normal dispersion, normal diffraction, and defocusing nonlinearity such as specific AlGaAs alloys.

In this paper we study second harmonic generation in Lithium Niobate in presence of photorefractive and photovoltaic effect. Our investigation reveals that the application of a strong external bias causes a self focusing effect that efficiently traps both the generated second harmonic and the fundamental beam, resulting in an improved conversion efficiency. The variation of the second harmonic output power during the build up of the space charge field also testifies that the phase relation between the interacting waves is affected by the photorefractive effect, and that the phase matching condition is modified in the part of the crystal shined by the light. Finally, we introduce a numerical model in order to explain the complex dynamic between the photorefractive effect and parametric process. The developed theory is in qualitative agreement with the performed experiments.

We describe the waveguiding principles of optical slow-wave structures that lead to the tight-binding form of the dispersion relation. In the presence of the optical Kerr effect, we show that soliton-like non-propagating envelopes ("frozen light") can be expected, but the presence of disorder e.g., in the coupling coefficients between neighboring unit cells, creates a band-tail at the edges of the dispersion relation and causes non-zero propagation velocity of such pulses.

Electromagnetic surface waves in magnetic superlattices (LANS) film bounded by a nonlinear dielectric cover are discussed as a function of the film parameters. Magnetic superlattices (antiferromagnetic-non magnetic) which are linear frequency-dependent gyromagnetic media are described with an effective - medium theory, we found that, surface waves are reciprocal for H_o= 0 and non reciprocal for H_o≠ 0. We also calculate and illustrate the variation of the wave index with the power flow for various values of the thickness of (LANS) t and the magnetic fraction f₁ where f₁ is the fraction of the superlattice occupied by the magnetic material.

A photonic band-gap structure (a small periodic corrugation at the surface) present in a planar nonlinear waveguide can enhance the nonlinear process of second-subharmonic generation provided that all interactions are phase matched. Compared with a perfectly quasi-phase matched waveguide, better values of squeezing and higher intensities of the output fields are reached under these conditions.

We demonstrate an integrated semiconductor source of counterpropagating twin photons in the telecom range. A pump beam impinging on top of an AlGaAs waveguide generates parametrically two counterpropagating, orthogonally polarized signal/idler guided modes. A 2 mm long waveguide emits at room temperature one average photon pair per pump pulse, with a spectral linewidth of 0.15 nm. The twin nature of the emitted photons is tested through a time-correlation measurement.

We review results we obtained by nonlinear time-resolved laser spectroscopy of silicon nanocrystals. The results of photoluminescence measurements on the femtosecond to microsecond time scales and of the picosecond pump and probe absorption measurements indicate the important role of carrier trapping into nanocrystals surface states and of Auger process in photoexcited carrier relaxation and recombination. The optical response of assemblies of silicon nanocrystals was found to be strongly dependent on the wavelength of the excitation light. The relation between microscopic carrier processes and optical nonlinear properties of the material as well as the impact on possible development of silicon laser are discussed.

Silica glass with SnO₂ nanocrystals, obtained from sol-gel synthesis and thermal densification at 1100 °C, was poled by means of a two-step process consisting of infrared 1064 nm laser irradiation followed by 532 nm laser exposure in high-voltage static electric field. Maker fringe experiments were then carried out at 1064 nm. The results show the formation of second-order nonlinearity with macroscopic nonlinear thickness (about 1 mm) and nonlinear susceptibility comparable with thermally poled silica (about 0.1 pm/V). Photoluminescence measurements suggest that mechanisms for this process should involve the activation and anisotropic ionization of defects at the interface between nanocrystals and glass.

Second harmonic generation via periodically-poled nonlinear materials offers an efficient means of generating high-quality visible light at wavelengths that would be otherwise unattainable with traditional laser sources. While this technology has the potential for implementation in many mass-industrial applications, temperature stability requirements, often as restrictive as 0.1°C, can make packaging with a pump source problematic. In this work we are investigating the use of synthesised response PPLN gratings to create crystals that are better suited to visible SHG. Our route towards addressing this issue is to convert the standard sinc-shaped temperature-tuning response of a uniform grating to a flat-top temperature tuning function with widths of up to several degrees. We have achieved a computationally efficient means of designing such gratings with a required temperature tuning profile based on a simulated annealing algorithm using repeated local changes of grating layout and subsequent Bloembergen-style analysis of the second harmonic, successive iterations of which quickly lead to the desired temperature tuning profile. Using our high fidelity poling technique we have fabricated synthesised response PPLN with precise placement of poled domains in Lithium Niobate based on the designs from our mathematical models. Measurements on these initial devices provide more than 4°C flat-top temperature stability, albeit with a corresponding loss in operational efficiency. Our aim is to implement improved designs in magnesium-doped Lithium Niobate for packaging with near-room temperature diode-based pump sources, as could be applied towards RGB TV and projector applications.

The motivation of this work is the development of a laser sensor and gyroscope based on short pulse solid state ring laser. In comparison with regular ring laser containing the gain medium and saturable absorber where counterpropagating pulses overlap, a ring synchronously pumped optical parametric oscillator (OPO) where the pulse crossing point is controlled externally by the arrival time of the pump pulses is the ideal source for short pulse laser sensor. The optimum configuration is OPO synchronously pumped inside the resonator of mode-locked solid state laser. The operation of a picosecond synchronously intracavity pumped optical parametric oscillator (OPO) is reported. A magnesium doped lithium niobate crystal (MgO:PPLN), periodically poled, is used as the optical parametric oscillator crystal coupling the pump and the resonant signal cavities. The active medium of the passively mode-locked pump cavity is a diode pumped Nd:YVO₄ crystal. Continuous mode-locked operation was achieved, tunable from 1531 to 1554nm by adjusting the OPO crystal temperature from 31 to 56 °C. The spectral width of the generated radiation was 2 nm.

We report the demonstration of a wavelength-agile coherent tunable mid-infrared (IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO). The mid-IR wavelength was tuned by varying the KTiOPO4 (KTP) OPO pumping wavelength, while the ZGP crystal angle remained fixed. The wavelength of pump OPO was controlled by changing the KTP crystals angle using a Galvano-optical beam scanner. Our mid-IR source can jump to a arbitrary wavelength without scanning through the intermediate wavelengths. A nonlinear optical crystal ZGP is suitable for OPOs in the mid-IR region. In most cases of mid-IR light generation using an OPO, the wavelength tuning is achieved by controlling the phase-matching angle or temperature of the nonlinear optical crystal. However, there are several disadvantages of this method including the walk-off angle, beam pass instability, refraction losses due to the high refractive index of ZGP (n~3.1), slow tuning rate, and so forth. Therefore, we developed a 2-&mgr;m-band pump-wavelength tunable mid-IR ZGP-OPO source. The mid-IR wavelength from the ZGP-OPO could be tuned from 5 to 9.8 &mgr;m, when the pump wavelength was controlled from 1.95 to 2.3 &mgr;m. The output pulse energy at 8&mgr;m was 1.3mJ/pulse at repetition rate of 30Hz. As an application of random wavelength accessibility, we could achieve the real-time measurement of phase change (solidification) of candle wax by measuring the change of absorption at two arbitrary wavelengths. We selected two wavelengths on the spectrum where significant changes of absorption upon solidification were detected and performed two-wavelength absorption measurements as the sample is allowed to cool from melted state.

We show that the novel heat mitigation technique called "Coherent Anti-Stokes Raman Scattering (CARS)-based heat mitigation" is able to substantially reduce the quantum-defect heating in hydrogen-based Raman lasers. This CARS-based heat mitigation technique causes the amount of phonons created in the hydrogen Raman medium to decrease by establishing an increase of the ratio of the number of anti-Stokes photons to the number of Stokes photons coupled out of the laser. To illustrate the effectiveness of this heat mitigation approach for a concrete hydrogen-based Raman laser setup, we numerically demonstrate for a Raman laser based on a hydrogen-filled hollow core photonic crystal fiber that the heat dissipation can be reduced with at least 30%.

We present different methods to enhance the effectiveness of CARS-based heat mitigation, a novel approach for reducing the quantum-defect heating in Raman lasers. More specifically, we discuss the influence of the CARS-related phase mismatch and of backward Raman scattering on our CARS-based heat mitigation technique and explain how these heat-mitigation-affecting factors should be managed to enhance the effectiveness of our technique. To illustrate the feasibility of obtaining efficient CARS-based heat mitigation, we discuss to what extent the described effectiveness-enhancing methods can be applied to near- and mid-infrared silicon-based Raman lasers. Finally, we numerically demonstrate that for near-infrared silicon-based Raman lasers a heat mitigation efficiency of 15% can be obtained, whereas the corresponding efficiency for their mid-infrared counterparts can be as high as 35%.

We have demonstrated a quasi-monolithic THz-wave parametric oscillator (TPO) to confer more stability, a lower threshold, and more compact size on THz-wave generating devices. In this report, we describe narrow linewidth generation in a quasi-monolithic TPO. The cavity configuration was designed so that the noncollinear phase-matching condition was satisfied in the crystal. A 5 mol% MgO:LiNbO₃ crystal within dimensions of 15 mm × 20 mm with three surfaces for total reflection was used as a nonlinear optical crystal. The quasi-monolithic TPO in a ring-cavity configuration consisted of a nonlinear optical crystal and a super-mirror that reflected the idler beam (&lgr; > ca. 1067 nm) and transmitted the pump beam (1064 nm). We obtained narrow oscillation linewidth of < 760 MHz at 1.6 THz of THz-wave radiation. The low threshold of the oscillation was around 5.4 mJ/pulse.

We report the experimental results of generation and coherent detection of narrow linewidth tunable terahertz radiation at room temperature utilizing a difference frequency generation as a result of stimulated scattering in the nonlinear crystal of MgO:LiNbO₃. The terahertz radiation was generated from an all-solid-state tunable injection-seeded THz-wave parametric generator (is-TPG), which emits the monochromatic THz-wave over a wide tunable frequency range from 0.6 THz to 2.4 THz with the linewidth of narrower than 100 MHz. Mixing of terahertz radiation (frequency &ohgr;_T ) with a near-infrared intense pump pulse (frequency &ohgr;_P ) results in the excitation and amplification of the difference frequency component with frequency &ohgr;_i =&ohgr;_P -&ohgr;_T, which is detected with a InGaAsbased photodiode. We demonstrate this method a fast response and very sensitive THz-wave detection running at room temperature, which is at least three of magnitude faster and two of magnitude more sensitive than a typical Liquid-He cooling Si bolometer for detecting the quasi-cw THz-wave beam. This detection technique is possible for coherent detection, it can measure the THz electric field, not only the intensity. As a result, the phase information is preserved, the real and imaginary parts of a sample's dielectric function may be determined simultaneously with this detection.

We present a comparative study of nonlinear optical materials for terahertz pulse generation by optical rectification and detection by electro-optic sampling, with the aim to find a material the is best suited for the use together with femtosecond lasers operating at a wavelength of 1.5 μm. Three crystals are identified that fulfill the condition that the optical group velocity matches the terahertz phase velocity: the organic salt DAST and the inorganic semiconductors GaAs and ZnTe, the latter showing velocity-matching with the second harmonic of 1.5 μm. A combined figure of merit for optical rectification and electro-optic sampling is derived. For the three materials under consideration, we find numerical values of 4300 (DAST):110 (GaAs):370 (ZnTe), in units of (pm/V)². We also present experimental evidence that the performance of DAST is an order of magnitude better than those of the inorganic semiconductors, and we present spectroscopic data in the terahertz range of DSMOS, a chemical derivative of DAST that may in the future also be used for terahertz applications.

A variational approach with an arbitrary ansatz is used to derive the governing equations for the characteristic parameters of dispersion-managed solitons. The Gaussian pulses are considered as a particular case. Moreover, the adiabatic evolution equations of the dispersion-managed pulse parameters under perturbations are derived, considering an arbitrary pulse profile. The theory is applied to the case of Gaussian pulses under different types of perturbations, such as the amplifier noise, nonlinear interaction between pulses, and polarization-mode dispersion.

We investigate the suitability of silica graded index multimode fibers (MMF) for distributed Brillouin sensing in structural health monitoring, where the measurement range is limited by small bendings that appear during the integration process of the sensing fibers into the structures. For the investigation of stimulated Brillouin scattering (SBS) in MMF, we use an MMF connected on both ends to the SMF measurement setup by fusion splices to ensure that only the fundamental mode is transmitted. The SBS spectra in MMF are recorded using a 1319 nm single frequency (line width 5 kHz) laser. Results found for standard singlemode fibers and the fundamental mode in multimode silica optical fibers are compared. We present the gain spectra showing the dependence of frequency shift, attenuation and modal noise to both temperature and strain. The dependence of the attenuation due to bending is shown. Finally, the perspective of the excitation of SBS in polymer optical fibers is discussed against the background of our research on SBS in MMF.

We designed, built, and demonstrated a highly scalable incoherent Optical CDMA testbed under DARPA contract as a novel platform for testing different avionics applications which will be characterized by Lockheed Martin. It enables users to communicate with each other at the OC-24 rate of ~1.25 Gbit/sec per user with raw BER of less than 10^-12. The system architecture uses (3,11) fast wavelength-hopping, time-spreading prime codes with a chip size of 73 ps utilizing standard on-off-keyed picosecond optical pulses allocated in the time and wavelength domains. A novel design of optical encoders and decoders enables the realization of a secure connectivity approaching a so called "one-time-pad" security. The testbed is also designed to conduct eavesdropping studies among testbed users.

In this work nonlinear light propagation in a photonic crystal fiber (PCF) infiltrated with a nematic liquid crystal (NLC) is presented. Such a photonic structure, called the photonic liquid crystal fiber (PLCF), combines the passive PCF and the active NLC guest mixture. The analyzed configuration with a periodic modulation of spatial refractive index distribution corresponds to the matrix of waveguides. This kind of structure can be controlled by optical power and additionally by temperature and it allows for studying variety of discrete optical phenomena. For properly chosen parameters of the analyzed fiber, discrete diffraction in the linear case and generation of the discrete spatial soliton in nonlinear regime can be obtained. In this paper a possibility of the transverse light localization and delocalization due to both focusing and defocusing Kerr-type nonlinearity was analyzed. In the case of the positive nonlinearity the refractive index increases as a function of light intensity in such a way that the stronger guiding of the light within NLC cores is obtained. Light modifies the refractive index distribution inducing a defect in the periodic structure. That can lead to the situation in which light becomes self-localized and its diffractive broadening is eliminated. Eventually the discrete soliton can be created. In the case of negative nonlinearity, the difference between NLC waveguides and glass refractive indices decreases and the beam guidance becomes weaker for higher light intensities. In such a case the generation of the bright soliton is possible only in the regime of negative discrete diffraction. However, in the case of defocusing nonlinearity a decrease of refractive index with the optical power can lead to the bandgap shifting. The incident beam with a frequency initially within a bandgap is then turned outside the bandgap resulting in changing of the propagation mechanism to the modified total internal reflection.

Photonic crystal fibers (PCF) have enlarging application potential in information technology and spectroscopy enabling different photonic operations in fast and effective manner. The present work was performed on index guiding double core PCF with square lattice, in which the cores are separated by a single air hole. Femtosecond laser pulses with wavelengths 1.1-1.5 &mgr;m were utilized to excite the PCF samples and the nonlinear spectral transformations were registered in the visible-near infrared region. During the manufacturing process the same PCF structure were prepared in four different sizes allowing to study the influence of the fiber diameter on the spectral transformation. Employing several nJ femtosecond pulses, polarization tunable narrow spectral features and broadband supercontinuum generation was observed and tailored by changing the excitation wavelength and polarization, coupling geometry and fiber diameter. In the case of excitation in anomalous dispersion area the effect of dispersive wave generation is evaluated.

The dynamics of dark spatial soliton beams and their interactions under the presence of a continuous wave (CW), which dynamically induces a photonic lattice, are investigated. It is shown that appropriate selections of the characteristic parameters of the CW result in different soliton propagation and interaction scenarios, suggesting a reconfigurable soliton control mechanism. Our analytical approach, based on the variational perturbation method, provides a dynamical system for the dark soliton evolution parameters. Analytical results are shown in good agreement with direct numerical simulations.

We present a white-light spectral interferometric technique which is used for measuring the absolute spectral optical path difference (OPD) between the beams in a slightly dispersive Michelson interferometer with a thin- film structure as a mirror. Two spectral interferograms are recorded to obtain the spectral interference signal from which the spectral phase is retrieved that includes the effect of both a cube beam splitter and the phase change on reflection from the thin-film structure. Knowing the effective thickness and dispersion of the beam splitter made of BK7 optical glass, a simple procedure is used to determine both the absolute spectral phase difference and OPD. The spectral OPD is measured for a SiO₂ thin film on a silicon substrate and is fitted to the theoretical spectral OPD to obtain the thin-film thickness. The theoretical spectral OPD is determined provided that the optical constants of the thin-film structure are known. We measured also the nonlinear-like spectral phase and fitted it to the theoretical values in order to obtain the thin-film thickness.

We study the dynamics of beams propagating in a planar waveguide with Kerr-type nonlinearity where a Bragg grating is written and diffraction is taken under consideration. The interaction of the forward field with the backscattered one due to the presence of the grating is considered both in the case of planar waves, and in the case of pulse propagation. Our results are demonstrated via numerical simulation of the governing propagation equations.

In the current work we study beam interaction in media with normal dispersion and self focusing nonlinearity, ruled by the two dimensional NLSE. The circular or elliptical Gaussian beams propagate over a continuous wave background (CW) which raises the X-like gain profile of Modulational Instability. That, along with self-focusing nonlinearity, can lead the beams to collision along the spatial dimension, then to fusion and finally to splitting and creation of two major filaments that move along the temporal dimension. Thus, the energy and momentum of the beams are effectively "reallocated" from one dimension to the other. By conducting primarily a numerical study, we reveal the relation of the resulting filaments to the interacting beams and the characteristics of the CW. Analytical description of this relation is also attempted and a new mechanism of beam-control is proposed. Explanation of the physical phenomena involved is also offered.

We carried out real-time measurement of gas density using monochromatic terahertz waves. The THz-wave absorbance is useful to measure the density of a gas having a characteristic spectrum in the THz region. We used the ring cavity THz-wave parametric oscillator (ring-TPO) as a monochromatic tunable THz-wave source. One can change the oscillation frequency of ring-TPO with a rotating galvano mirror forming the ring cavity. The frequency can be changed by synchronization with a repeating pump-pulse of 500 Hz. We demonstrated real-time measurement of the gas density in R-22, which had some spectral structure in THz frequency region. The gas density in the sample cell was changed by controlling the pressure to lower than 1 atm. When the gas density in the cell was the most tenuous, the maximum sensitivity was about 5%, which was limited by the fluctuation of THz-wave intensity.

ZnS/ZnSe Bragg reflectors under condition of ZnSe interband excitation by a femtosecond laser pulse exhibit strong narrow-band modification of absorption and wide-band modification of reflection. Mean decay time for nonlinear reflection in heterostructures ranges from 2 to 3 ps whereas in bare ZnSe monolayer it exceeds 5 ps. Possible underlying physical processes responsible for nonlinear refraction in the transparency region include interplay of absorption driven nonlinear refraction via Kramers-Kronig relations and intrinsic dielectric properties of dense electron-hole plasma. For nonlinear absorption at ZnSe band edge, interplay of plasma screening effects and states filling effects are relevant.

Pump-probe femtosecond transmission measurements in the vicinity of the first excitonic resonance are performed in a silicate glass embedded with Cd-S-Se semiconductor nanoparticles. In the experiment, the pump at 400 nm (duration 50 fs, energy up to 0.1 mJ) excites the sample, while the change of the optical absorption is probed by femtosecond continuum. The time-resolved spectrum of the absorption change in the wavelength range 450-650 nm is visualized using a two-channel imaging spectrometer. A strong optical nonlinearity of the glass containing Cd-S-Se nanoparticles results in the up to 50% bleaching of the first excitonic resonance via the depopulating of the ground state. The temporal evolution of the bleaching consists of fast (with relaxation time as small as 3 ps) and slow (>15 ps) components. The dependence of the nonlinear absorption on the detuning of the pump and probe wavelengths with respect to the exciton resonance is evaluated.

Photoluminescence (PL) characteristics of CdTe nanocrystals (NCs) adsorbed into polymer films are presented compared to the PL of bulk CdTe. Using the dependence of PL on excitation power we determined the carrier lifetime at 80K which indicates that carrier trapping in surface and polymer states was the main decay mechanism of excitation. The occurrence of at least two deep defect induced luminescence bands in CdTe NCs was demonstrated for the first time. Our investigation also revealed changes in PL properties induced by the visible light irradiation or by the preparation conditions. These results were explained by an increase of nonradiative recombination in the surface states of NCs and in the polymer.

An all-optical and ultra-fast combinatorial network based on semiconductor optical amplifiers and able to detect packet contention in a 2x2 photonic node is demonstrated. The signal at the output of the combinatorial network has a contrast ratio higher than 8.4 dB. The combinatorial network is used for demonstrating the feasibility of a 2x2 photonic node at 160 Gb/s.

We study theoretically the phenomenon of four-wave mixing in intersubband transitions of a symmetric double quantum well structure. In the theoretical model we consider two quantum well subbands that are coupled by a strong pump electromagnetic field and a weak probe electromagnetic field, taking into account the effects of electron-electron interactions. For the description of the system dynamics we use the density matrix equations obtained from the effective nonlinear Bloch equations. These equations are solved numerically for a realistic semiconductor quantum well structure GaAs/AlGaAs. We show that the four-wave mixing spectrum can be significantly dependent on the frequency and the intensity of the pump field and on electron sheet density.

We generated dark photovoltaic spatial solitons in the iron doped lithium niobate, and we studied the generation process with a numerical model. The Schrodinger nonlinear equation was simulated with BPM (beam propagation method). This numerical method is also called symmetrical split-step Fourier method. For the generation of dark solitons, we used both the amplitude mask and the phase mask. The amplitude mask generated the even number of solitons, and the phase mask created the odd number of solitons. Every result from our experiment can be verified with BPM. The numerical program was programmed in Matlab. We created dark photovoltaic solitons in a bulk crystal with the optical intensity 1 - 10 mW/cm², and the soliton's FWHM about 5-18 μm. We observed the temporal evolution of the one-dimensional dark photovoltaic solitons under open-circuit condition and the self-defocusing effect of the laser beam. The steady-state measurement (stable soliton) was obtained after a 6-15 min exposure. For the generation the argon ion laser beam at the wavelength of 514nm was used. It was polarized along the optical axis and collimated to a diameter of about 2mm on the input face. The resulting index perturbation forms a planar waveguide.

In this paper, we propose a tunable optical filter using a photorefractive planar waveguide. The index grating generated by the control beam drops off a part of wavelength components in the wavelength division multiplexed signal beam. It make possible to select the wavelength components of the signal beam by optically adjusting the wave vector of the grating. The photorefractive effect is one of the most efficient nonlinear effects, and therefore the signal beam can be controlled by the relative low beam power. The proposed optical filter can be applied to an active add-drop module when the signal beam is fed back to the module as a control beam. Therefore, it contribute to development of the all-optical network systems. It is also able to apply to photonic label processing technology by multiplexing the index gratings. We investigated the signal beam propagation and the permittivity distribution in the photorefractive waveguide by using a finite dimensional beam propagation method (FD-BPM) and analyzed the filtering property. Considering the two optical setups using the transmission and reflection grating, we compared these performances.

We propose a new LD-fiber-coupling-method for bidirectionally-pumped erbium-doped fiber amplifier (EDFA) using two mutually-pumped phase-conjugate mirrors (MPPCMs). MPPCM is formed by two mutually incoherent beams in photorefractive crystal (PRC) and can convert each incident beam into each phase-conjugate beam of them. Owing to mode conversion by phase-conjugate characteristics, the coupling loss due to mode mismatching between a pump beam and a fiber is improved. Therefore, precision lens and lensed fiber for mode matching are not required. Additionally, because photorefractive index gratings that compose a MPPCM are rewritable in real time, MPPCM can dynamically adapt to a variety of system error factors, such as misalignment of components, mode conversion generated by LDs or fibers with defects. In our system, the overall coupling efficiency of pump beams is mainly determined by diffraction efficiency of MPPCMs that depends on the photorefractive coupling strength and the intensity ratio of two incident beams. However, achievable diffraction efficiency in this system is restricted by optical loss between two MPPCMs. This is because the transmitted pump beams passing through the EDF are reused for forming the opposite MPPCM. To achieve a high signal amplification gain, absorption loss of pump beam powers in the EDF is unavoidable. Therefore, we analytically and experimentally evaluate the acceptable loss between two PRCs to form both MPPCMs.