Showing papers in "Journal of Nonlinear Optical Physics & Materials in 2002"
TL;DR: In this paper, the plasmon polariton modes in wires are numerically simulated and found to be dependent on the incident light wavelength and direction of propagation, and the existence of localized plasm modes and strong local eld enhancement in percolation nanowire composites is demonstrated.
Abstract: The electromagnetic eld distribution for thin metal nanowires is found, by using the discrete dipole approximation. The plasmon polariton modes in wires are numerically simulated. These modes are found to be dependent on the incident light wavelength and direction of propagation. The existence of localized plasmon modes and strong local eld enhancement in percolation nanowire composites is demonstrated. Novel left-handed materials in the near-infrared and visible are proposed based on nanowire composites.
230 citations
TL;DR: In this paper, the authors used electron-beam lithography to prepare arrays of noncentrosymmetric gold particles and study their linear and second-order nonlinear optical properties.
Abstract: The optical properties of nanoscopic arrays of metal particles are dominated by plasmon resonances and electromagnetic interaction between the particles. We use electron-beam lithography to prepare arrays of noncentrosymmetric gold particles and study their linear and second-order nonlinear optical properties. By varying the orientation of the particles in a fixed lattice, we observe shifts in the polarized linear extinction spectra. The second-harmonic generation efficiencies of the two types of samples differ by up to 60%. The results show that the properties of the samples are sensitive to the smallest details of their structure.
79 citations
TL;DR: In this article, the issues that arise in the extension of cascade nonlinearities to the femtosecond regime are outlined, and initial applications of the cascade phase shifts to femto-cond pulse generation and propagation are reviewed.
Abstract: Useful nonlinear phase shifts can be produced in cascaded quadratic processes The issues that arise in the extension of cascade nonlinearities to the femtosecond regime are outlined in this paper, and initial applications of the cascade phase shifts to femtosecond pulse generation and propagation are reviewed The results demonstrate that the cascade phase shifts offer unique properties, and in some cases pulse-shaping techniques based on cascade nonlinearities have potential to offer substantial performance improvements over existing approaches
46 citations
TL;DR: In this paper, the authors present a brief review of the use of nonlinear optics for broadband terahertz (THz) time-domain spectroscopy with femtosecond laser pulses.
Abstract: We present a brief review of the use of nonlinear optics for broadband terahertz (THz) time-domain spectroscopy with femtosecond laser pulses. The generation of THz pulses is accomplished by optical rectification and coherent detection by electro-optic sampling or field-induced second-harmonic generation. The approach permits exceptional time response, as well as the possibility for multichannel detection schemes.
37 citations
TL;DR: In this article, the beam cleanup properties of stimulated Raman scattering (SRS) in a multi-mode fiber have been characterized, and it is shown that a fiber which supports propagation of a highly aberrated pump beam, can generate a Gaussian-like Stokes beam consisting of one or more orders of Stokes components.
Abstract: Laser beam cleanup properties of stimulated Raman scattering (SRS) in a multi-mode fiber have been characterized. It is shown that a fiber, which supports propagation of a highly aberrated pump beam, can generate a Gaussian-like Stokes beam consisting of one or more orders of Stokes components. The beam cleanup properties are found to be similar to those of stimulated Brillouin scattering, which are briefly reviewed herein. The dramatic enhancement in beam quality achievable through SRS clearly demonstrates the potential utility of fiber-based Raman beam cleanup/combining devices for laser brightness scaling.
31 citations
TL;DR: In this paper, the authors present an overview of the physics of self-written waveguides created in photosen-sitive optical materials, including the experimental observations and correspondingtheoretical models for describing the growth of both bright and dark selfwritten beams.
Abstract: Department of Applied Physics, Osaka University, Yamadaoka 2-1,Suita, Osaka 565-0871, JapanNanophotonics Laboratory, RIKEN, Wako, 351-0198, Japanhttp://lasie.ap.eng.osaka-u.ac.jp/Received 3 August 2002We present an overview of the physics of self-written waveguides created in photosen-sitive optical materials, including the experimental observations and the correspondingtheoretical models for describing the growth of both bright and dark self-written beams.We discuss in more details the properties of self-written waveguides created in photosen-sitive polymers, which have been discovered in the recent experimental and theoreticalstudies. The self-writing process is essentially a nonlinear phenomenon, since the tempo-ral dynamics depends on the optical exposure. Under appropriate conditions, permanentlarge changes in the refractive index are induced along the propagation direction of anoptical beam, so that optical channels, or \ laments", appear as waveguides becoming\frozen" in a photosensitive material. We describe the growth of individual lamentsas well as the interaction of several laments, also making a comparison between thephysics of self-written waveguides and the concept of spatial optical solitons in self-focusing nonlinear media.Keywords: Self-written waveguide; spatial soliton; nonlinear response; photosensitivematerial; photopolymers; self-action of light.
31 citations
TL;DR: A detailed study of light-induced gratings in Methyl-Red-doped 4n-pentyl-4′-cyanobiphenyl (5CB) homeotropically aligned is reported in this paper.
Abstract: A detailed study of the light-induced gratings in Methyl-Red-doped 4-n-pentyl-4′-cyanobiphenyl (5CB) homeotropically aligned is reported. In particular, the dependence of diffraction efficiency upon the pump and probe polarizations has been investigated both for transient and permanent gratings. Our results confirm the earlier observations on the role of light-induced adsorption of MR molecules on the cell boundaries and demonstrate the common origin of the supranonlinear response and the permanent recording effect.
30 citations
TL;DR: In this paper, the authors considered feasibilities of using optical parametric oscillation and amplification, and difference-frequency generation for efficiently generating and amplifying terahertz waves in several second-order nonlinear optical materials.
Abstract: We have considered feasibilities of using optical parametric oscillation and amplification, and difference-frequency generation for efficiently generating and amplifying terahertz waves in several second-order nonlinear optical materials. They include GaAs, GaP, GaSe, CdSe, LiNbO3 and LiTaO3. The advantage of using birefringence in CdSe and GaSe is tunability of the output terahertz frequency. Furthermore, both CdSe and GaSe can be used to achieve the backward parametric oscillation without any cavity. On the other hand, in periodically-poled LiNbO3 and LiTaO3, one can take advantage of large diagonal elements of second-order nonlinear susceptibility tensor. In the diffusion-bonded-stacked GaAs and GaP plates, quasi-phase matching can be achieved by alternatively rotating the plates. It is also feasible to achieve phase matching in a single GaAs or GaP plate due to the presence of the absorption tail of polariton modes. In this case, tuning can be achieved by changing the pump wavelength. The advantages of using coherent parametric processes are possibilities of efficiently generating and amplifying temporally-coherent and narrow-linewidth tunable terahertz waves at room temperature. However, all other schemes do not possess these advantages. Compared with a noncollinear configuration, by using the parallel wave propagation configurations, the conversion efficiency can be higher because of longer effective interaction length among all the waves.
17 citations
TL;DR: In this paper, the authors showed that electrical pulsations generate highvoltage signals that may be used as a driving voltage for the conventional electro-optical modulator, and also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal.
Abstract: We review our results on conversion of CW laser Ar-ion beam power into pulsating multi-channel outputs: optical, electric and piezoelectric with simultaneous dynamic pattern formation. We show, that electrical pulsations generate high-voltage signals that may be used as a driving voltage for the conventional electro-optical modulator. We have also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal. Spatial distribution of scattered light is self-organized in different patterns (hexagonal and cross-type).
17 citations
TL;DR: In this article, nonlinear processes in quantum well infrared photodetectors (QWIPs) are reviewed and some intrinsic nonlinear QWIP properties are useful in applications, such as in autocorrelation of short pulses by two-photon absorption.
Abstract: Nonlinear processes in quantum well infrared photodetectors (QWIP) are reviewed. Being an intersubband dipole transition based photoconductor, the nonlinear behaviors in QWIPs are caused by both the (extrinsic) photoconductive transport mechanism and (intrinsic) nonlinear optical processes. Extrinsic nonlinearity leads to a degradation of QWIP performance at high incident power or low operating temperatures. Some intrinsic nonlinear QWIP properties are useful in applications, such as in autocorrelation of short pulses by two-photon absorption. The general area of QWIP nonlinear properties has not been extensively investigated. We point out some directions for further studies and hope to stimulate more research activities.
14 citations
TL;DR: In this paper, the authors considered soliton pulse compression in a dispersion decreasing ideal elliptical birefringent fiber with phase modulation and showed that there is exact balancing between the effective gain and the effective phase modulation, and as a result arrive at the fundamental soliton solution.
Abstract: We have considered soliton pulse compression in a dispersion decreasing ideal elliptical birefringent fiber with phase modulation. We have shown that there is exact balancing between the effective gain and the effective phase modulation and as a result arrive at the fundamental soliton solution. For the various dispersion decreasing profiles we have considered, we have shown that the hyperbolic profile is the best suitable choice for the dispersion decreasing profile as it provides fairly good compression even after compensating for the fiber loss.
TL;DR: In this article, the basic concepts and model equations for gap solitons in Kerr and quadratic nonlinear media encompassing a one-dimensional Bragg resonance are reviewed.
Abstract: Optical nonlinearity and feedback through Bragg periodicity are the basic ingredients for light localization into gap solitons. We review the basic concepts and model equations for gap solitons in Kerr and quadratic nonlinear media encompassing a one-dimensional Bragg resonance. With specific regard to frequency doubling media, we generalize the concept of a photonic crystal to band-gaps of a nonlinear origin, and finally address the slow character of quadratic gap-solitons with reference to their excitation.
TL;DR: In this paper, a novel optical fiber sensing technique for length and temperature measurement with accuracy of sub-nanometer and 10-4°C, respectively, is proposed, which is accomplished by counting the number of electrical pulses, provided by switching on and switching off of the optical bistability periodically.
Abstract: A novel optical fiber sensing technique for length and temperature measurement with accuracy of sub-nanometer and 10-4°C, respectively, is proposed. The new kind of sensor is a combination of a conventional interferometric sensor and a hybrid optical bistable device. The measurement is accomplished by counting the number of electrical pulses, provided by switching on and switching off of the optical bistability periodically. An optical bistable fiber sensor with a March–Zehnder interferometer is analyzed in this paper. The main advantages of this technique lie in the adjustable high accuracy and ability to distinguish the variation direction of quantities to be measured.
TL;DR: In this article, tetrasubstituted indium or gallium phthalocyanines and their dimers bridged with various ligands were dispersed in a polymer thin film, which was spin-coated on silver thin film vacuum-evaporated on a glass slide.
Abstract: Tetrasubstituted indium or gallium phthalocyanines and their dimers bridged with various ligands were dispersed in a polymer thin film, which was spin-coated on silver thin film vacuum-evaporated on a glass slide. All-optical reflectance control was achieved by complex refractive index changes upon photoexcitation of phthalocyanines by nanosecond laser in such a guided mode geometry. They gave rise in less than ns pulse width, and a few to a few tens of microseconds decay characteristic to the lifetime of the excited triplet state. Repeated and reversible reflectance changes were achieved. Axially bridged phthalocyanine dimers showed almost the same photoresponses as monomers.
TL;DR: In this article, a recording of a holographic grating on a homeotropically aligned dye-doped liquid crystal (DDLC) cell was described, where photo-excited azo dyes, methyl red (MR), diffuse and adsorb onto the substrates, thereby forming a ripple structure.
Abstract: This paper describes a recording of a holographic grating on a homeotropically aligned dye-doped liquid crystal (DDLC) cell. The photo-excited azo dyes, methyl red (MR), diffuse and adsorb onto the substrates, thereby forming a ripple structure. The adsorbed dye and the laser-induced ripple structure then reorientate the liquid crystal molecules, and induce a holographic grating.
TL;DR: In this article, a detailed quantitative experimental and theoretical study of laser induced refractive index changes in nematic liquid crystals doped with methyl-red, disperse red and azobenzene liquid crystal is presented.
Abstract: We present a detailed quantitative experimental and theoretical study of laser induced refractive index changes in nematic liquid crystals doped with methyl-red, disperse red and azobenzene liquid crystal. These refractive index changes, originating from molecular reorientations and order parameter modification, are measured by means of intensity and polarization grating methods. The reorientation of the director axis is calculated from polarization dependence of the probe beam diffraction efficiency. The contribution of each effect to the total diffraction efficiency is quantitatively evaluated. In general, we found that the reorientational direction of the NLC molecules depends on the dopants as well as the nature of the pump beam polarization state. In methyl-red doped samples, the laser induced reorientation mechanism dominates, whereas order parameter modification plays a major role in the others.
TL;DR: In this paper, the output face of a self-defocusing nonlinear medium was observed with a smooth cross-sectional intensity profile, but was elongated to an aspect ratio of 2:1.
Abstract: Vortex quadrupoles and a nonlinear optical cusp diffraction catastrophe were observed at the output face of a self-defocusing nonlinear medium. The initial beam had a smooth cross-sectional intensity profile, but was elongated to an aspect ratio of 2:1. The power-dependent evolution of the beam is described.
TL;DR: In this paper, various poly(amic acid)s with azobenzene-chromophore sidegroups have been synthesized and structurally and functionally characterized, and their amphiphilic properties allowed them to prepare stable monomolecular layers at the water/air interface of a Langmuir trough.
Abstract: Various poly(amic acid)s with azobenzene-chromophore sidegroups have been synthesized and structurally and functionally characterized. Their amphiphilic properties allowed us to prepare stable monomolecular layers at the water/air interface of a Langmuir trough, and to transfer these highly organized monolayers to solid supports via the Langmuir–Blodgett–Kuhn deposition protocol. The resulting multilayer assemblies were investigated by surface plasmon- and waveguide-optical techniques, by X-ray reflectometry, and by UV-vis and IR spectroscopies. Thermal imidization of the assemblies resulted in functional poly(imide) multilayers that still could undergo photoisomerization reactions in their azobenzene sidegroups. The kinetic parameters of this trans-cis and cis-trans isomerization, respectively, as well as, the resulting control of the alignment of a liquid crystal in contact to these "command layers" were evaluated.
TL;DR: In this paper, an irradiation geometry with the incident polarization parallel to the nematic director was used for laser-induced birefringence effects with a buildup time of several seconds to minutes and two different modes of spatial pattern formation with different patterns for parallel and perpendicular polarization.
Abstract: New cumulative effects in laser-induced birefringence have been observed under 10-Hz-pulse-repetition-rate, nanosecond-duration laser irradiation of azo-dye-doped planar-nematic liquid crystal layers at incident intensities I ~ 1–10 MW/cm2. An irradiation geometry with the incident polarization parallel to the nematic director was used. his geometry does not permit a first-order electric field induced reorientation of the nematic molecules, allowing us to exclude its contribution to the nonlinear response. New laser-induced birefringence effects with a buildup time of several seconds to minutes manifest themselves in: • the appearance of a polarization component perpendicular to the nematic director; • two different modes of spatial pattern formation with different patterns for parallel and perpendicular polarization: (1) At I ~ 1–5 MW/cm2, the perpendicular polarization component forms a four-leaf-clover (a Maltese-like cross) spatial pattern in the far-field from the initial Gaussian spatial intensity distribution. The incident, parallel polarization component forms a round spot with a single ring spatial pattern. (2) At higher incident intensities (I ~ 5–10 MW/cm2), a second regime of pattern formation is observed in the form of high definition patterns and only for the polarization component parallel to the nematic director.
TL;DR: In this paper, an electromagnetic propagator formalism with polychromatic photons is constructed to follow the space-time dynamics in the atomic near-field zone and a first-quantized description based on the photon energy wave function is extended in such a manner that the birth process of the photon can be followed.
Abstract: Elements of a new quantum electrodynamic theory which might enable one to obtain a better understanding of the linear and nonlinear interaction between atomic systems in near-field contact is presented. To follow the space-time dynamics in the atomic near-field zone an electromagnetic propagator formalism with polychromatic photons is constructed. A first-quantized description based on the photon energy wave function for free polychromatic photons is extended in such a manner that the birth process of the photon, which takes place in the near-field zone of the source, can be followed. In order to be able to describe harmonic generation processes in near-field optics polychromatic photons of the simple wave-train type are used. The wave mechanical (first-quantized) description based on wave-train photons is upgraded to a field-theoretic (second-quantized) formalism using a new so-called propagator gauge which is closely related to the Poincare gauge underlying the multipole description of quantum electrodynamics.
TL;DR: In this paper, an alternative experimental technique for the determination of weak localization of light in partially ordered nanostructured materials is proposed based on the criterion that the transport mean free path length of multiply scattered photons is reduced down to shorter than the wavelength of the light.
Abstract: An alternative experimental technique for the determination of weak localization of light in partially ordered nanostructured materials is proposed. The technique is based on the criterion for weak localization of light that the transport mean free path length of multiply scattered photons is reduced down to shorter than the wavelength of the light. This mean free path is calculated from the experimental dwell time of the photons in the scattering structure and by applying the photon random walk model using the diffusion approximation. The dwell time is experimentally determined by multifrequency phasefluorimetry. This technique is capable of providing corroborative intensity demodulation data that can be linked to the wavelength dependent transmission (optical bandgap) of colloidal crystals.
TL;DR: In this paper, the propagation of ultrashort laser pulses into a microstructured fiber having a large nonlinear coefficient is found to give rise to various nonlinear phenomena, such as supercontinuum generation, sharp lines due to third-harmonic generation and four-wave mixing.
Abstract: The propagation of ultrashort laser pulses into a microstructured fiber having a large nonlinear coefficient is found to give rise to various nonlinear phenomena. By using an input wavelength in the range 1300–1550 nm, the observed output spectrum presents, besides supercontinuum generation, sharp lines due to third-harmonic generation and four-wave mixing. When the input wavelength is around 800 nm, close to the zero-dispersion wavelength, the solitonic propagation is accompanied by a very intense and narrow-band emission in the blue spectral region.
TL;DR: In this article, the authors report on distinct dynamic regimes of optically induced redistribution of molecules in a reacting material, which are governed by spatially inhomogeneous photogeneration of radicals, their diffusion, and the photopolymerization-induced change in the diffusion constant.
Abstract: We report on distinct dynamic regimes of optically induced redistribution of molecules in a reacting material. The physical system is a mixture of photopolymerizable monomer and nematic liquid crystal with space-time modulated diffusivity. An empirical model is developed which provides an excellent description of all the stages of the experimentally observed highly intricate dynamics. This dynamics is governed by spatially inhomogeneous photogeneration of radicals, their diffusion, and the photopolymerization-induced change in the diffusion constant.
TL;DR: In this paper, an isotropic-layered liquid crystal with the extended Jones 4 × 4 matrix formalism is implemented to solve the problem of optical transmittance after the turnoff of the applied electric field of liquid crystals.
Abstract: Relaxation oscillations of optical transmittance after the turn-off of the applied electric field of liquid crystals are observed when the detected light transmits through a proper adjustment of the alignment of the polarizer and analyzer. Monte Carlo simulation of the equilibrium tilting and twisting angles of molecules at each layer that yield relevant polarization of the transmitted light can satisfactorily portrait this phenomenon. Optics of an isotropic-layered liquid crystal with the extended Jones 4 × 4 matrix formalism is implemented to solve this problem. The transmittance under linear changes of temperatures also reveals similar nonlinear relaxation oscillations.
TL;DR: In this paper, the photothermal mechanism was dominant in the laser-induced refractive index change in guest-host liquid crystal cells and it is expected that the analytical technique described here will be useful for characterizing the extent to which photothermal refractive-index change affects the laser induced refractive indices change in other kinds of guest-home liquid crystals in the future.
Abstract: Detailed characteristics have been performed for optical nonlinearity originating in photothermal effects in guest-host liquid crystals The effects of liquid crystal cell parameters and irradiation conditions on photothermal self-phase modulation and the resulting self-diffracted beam characteristics were quantitatively investigated by heat-conduction analysis and Kirchhoff's diffraction theory We successfully explained all optical phenomena and our experimental and theoretical technique described here was useful for characterizing the photothermal self-phase modulation This means that the photothermal mechanism was dominant in the laser-induced refractive index change in our guest-host liquid crystal cells and it is expected that our analytical technique described here will be useful for characterizing the extent to which the photothermal refractive-index change affects the laser-induced refractive index change in other kinds of guest-host liquid crystal cells in the future
TL;DR: In this article, the authors considered the higher order nonlinear Schrodinger (HNLS) equation, which governs the nonlinear wave propagation in optical fibers with higher order effects, and constructed the Lax pair associated with the integrable HNLS equation for the pulse propagation in normal dispersion regime of the fiber media.
Abstract: We consider the higher order nonlinear Schrodinger (HNLS) equation, which governs the nonlinear wave propagation in optical fibers with higher order effects. Lax pair associated with the integrable HNLS equation for the pulse propagation in normal dispersion regime of the fiber media is constructed with the help of Ablowitz–Kaup–Newell–Segur method. Using Hirota bilinear method, dark soliton solution is explicitly derived. Similar study is also carried out for simultaneous propagation of N nonlinear pulses in the normal dispersion regime of the fiber system with higher order effects.
TL;DR: In this article, a detailed study of fabrication and characterization of polyaniline (PA) and polystyrene (PS) prepared by vacuum deposition and dip coating method thin film optical waveguides is presented.
Abstract: We report on our systematic and detailed study of fabrication and characterization of polyaniline (PA) prepared by vacuum deposition and polystyrene (PS) prepared by dip coating method thin film optical waveguides The four-layer consisting of substrate (glass)/PA/PS/air has been used for demonstrating polarization filter action
TL;DR: In this paper, the photostabilities of nonlinear optical organic dyes doped as guests into poly(methyl mathacrylate), (PMMA), waveguide films have been investigated using measurements of planner waveguide transmission over time.
Abstract: The photostabilities of nonlinear optical organic dyes doped as guests into Poly(methyl mathacrylate), (PMMA), waveguide films have been investigated using measurements of planner waveguide transmission over time. Direct photodecomposition of the dyes is observed when the doped films are exposed to wavelengths lying within the main absorption bands. The dyes exhibit a rapid photochemical degradation that is enhanced when the experiments are repeated in an air environment at the irradiation between 450 nm and 515 nm. Excitation of the zeroth-order transverse magnetic mode (TM0) by prism couplers produced complete degradation within 30 minutes. The dye photostabilities are compared to that of a commonly studied laser dye, 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran, DCM, which exhibits a photo-oxidation mechanism. The experiments in air lead to comparable degradation after 3 to 4 hours but the dye proves to be exceptionally photostable in vacuum. Further interesting results are reported on the formation of crystallites in the films when irradiated at 632.8 nm where linear absorption in the films is low. Microscopic examination of the waveguide films at the input coupling position confirms the formation of crystallites for all the films studied. Cross coupling to higher order modes from the light scattering of crystallites is revealed by scanning m-line images of the waveguides. This is associated with a marked refractive index decrease in the films. An air and humidity environment is found to favor the crystallite formation in the dye-doped waveguides.
TL;DR: In this article, the dispersive and nonlinear phase components on the optical pulses of a nonlinear Schrodinger equation in the presence of fourth order dispersion and a parabolic refractive index profile is explicitly demonstrated when hyperbolic function pulses are injected.
Abstract: The cancellation of the dispersive and nonlinear phase components on the optical pulses of a nonlinear Schrodinger equation in the presence of fourth order dispersion and a parabolic refractive index profile is explicitly demonstrated when hyperbolic function pulses are injected. With the help of the split step Fourier method we obtain the frequency chirp associated with GVD and SPM phenomena. Its mutual compensation leads to the analytical exact soliton solutions of the high dispersive cubic and cubic quintic nonlinear Schrodinger equations.