bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlin Jar Optical Phenomena in Ferromagnetic Semiconductor with Superlattices on Nonequilibrium Electrons and Magnons
Authors: Semchuk Alexander Yu. , Grechko Leonid G.
Published: February 2023

A wide gap ferromagnetic semiconductor (FMSC) of the EuO type with an average concentration n0 in external constt ut electric field F
o
along OZ in spin-wave temperature range is considered.
Nonlinear Schiieren System
Authors: Siahmakoun Azad , Harrer Thomas
Published: February 2023

In this paper we will present a dynamic phase filter system using optical phase conjugation in a photorefractive crystal. The theoretical description of the system reveals that the square of phase changes in an objec field can be mapped as the intensity modulation in the system output. This has been demonstrated experimentally using a single beam from HeCd laser and a BaTiO3crystal arranged in the self-pumped phase-conjugator (SPPC) configuration.
Multiple Image Storage Using Phase Encoding Latest Results
Authors: Lembcke J. , Denz C. , Barnes T.H. , Tschudi T.
Published: February 2023

1 Introduction In the context of optical information processing great interest is focused on the development of systems for optical data storage. Photorefractive materials are widely used in the schemes which have been proposed in this domain. They offer the possibility to easily obtain thick phase holograms with great diffraction efficiency. Volume holography allows the multiplexing of a great number of holograms within the medium by using the Bragg selectivity of the gratings to independently address the images. Several methods to realize multiplexing have been widely discussed during the last years: In the angular multiplexing technique the angle of the reference beam is varied from one image to the next, while in wavelength multiplexing the wavelength of the laser is the variable parameter to obtain independently addressable holographic gratings. The phase encoding method has been pro posed as a third possibility (Ref. 1): Here a set of reference beams are incident on the medium under a discrete angular spec trum as in the case of angular multiplexing, but the beams are not switched in suc cession but illuminate the medium conti- nouslV. The variable parameters which make up the address of a single image are the phase relations between the reference beams as we will describe in Chap. 2. Hence a phase modulator is needed which allows to adjust the relative phases of the set of ref erence waves. A sketch of a possible setup is shown in Fig. 1. An expanded beam is used in the signal arm of the holographic configuration Fig. 1 to create the respective image wave by illumination of a spatial light modulator or simply a series of diapositives. In the reference arm it is incident on a computer generated hologram to create a focus array in the Fourier plane. Here the p' ase modulator is placed which is a special purpose liquid crystal display, capable of independently inducing a phase shift.at each of the spots of the focus array. The beams are recombined in the medium where they interfere with the signal wave. In the our case the medium is a photorefractive BaTiO 3 crystal oriented for optimum holographic efficiency. With this setup alignmeit problems and speed limitations due to mechanical adjustment as occuring in the case of conventional angular multiplexing are overcome as well as technological complications associated with wavelength multiplexing.
Impurity Enhanced Photorefractive Processes at Near Infrared Wavelengths Using 'Blue’ BaTiO3
Authors: Ross Graeme W. , Hribek Petr , Eason Robert W. , Garrett Mark H. , Rytz Daniel
Published: February 2023

The wide availability of laser diodes operating at near infrared wavelengths has recently drawn attention to the possibility of extending the response of photorefractive crystals from the visible region of the spectrum out to longer wavelengths.
Photorefractive materiais, effects and devices topical meeting Kiev - 1993 : Optical Properties of Doped Sillenites Matching as Unique Multilevel Intrinsic Absorption Center Model
Authors: Marquet H. , Ennouri A. , Zielinger J.P. , Tapiero M. , Chevrier V. , Launay J.C.
Published: February 2023

Sillenites have attracted considerable interest because of their photorefractive properties.
Enhancement of Large-Modulation Recording In BSO by the Moving Grating Technique
Authors: Gillespie W. A. , Wang Z. Q. , Cartwright C. M.
Published: February 2023

Bismuth silicon oxide (BSO) has been widely used as a dynamic holographic medium for optical correlation [1], novelty filtering [2,3] and incoherent correlation [4] because of its relatively fast response, reliability and good optical quality over a reasonable surface area.
Photorefractive Beam Fanning and Spatial Coherence
Authors: Rehn Henning , Kowarschik Richard
Published: February 2023

The photorefractive beam fanning effect in barium titanate has been investigated for a long time [1].
Noise-free, high-gain signal beam amplification using beam fanning in a photorefractive KNbO3:Fe crystal
Authors: Jingjun Xu , Junmin Liu , Guangym Zhang , Simin Liu
Published: February 2023

A low-noise, high-gain optical image amplifier is the ultimate goal of two-wave coupling in the photorefractive crystal with large values of two-wave coupling coefficients. However, the beam fanning is also very strong in the photorefractive crystal with high two-wave coupling coefficient, which corrupts greatly the optical quality of the amplified image. Recently many techniques were demonstrated to get a high-gain, low-noise amplifier, in all of which people were making an effort to get rid of the beam fanning. On contrary, here we reported a new scheme utilizing the beam fanning effect to get a noise-free, high-gain amplified image by two-wave coupling.
The photorefractive planar gratings erasure in LiNbO3 gradient waveguides
Authors: Savtchenkov E. , Shandarov S. , Shandarov V.
Published: February 2023

Different analitical models are used for description of the photorefractive holografic grating relaxation in planar optical waveguides on LiNbO3.
Photorefractive properties of ion-implanted waveguides in BaTiO3
Authors: James Stephen W. , Youden Katharine E. , Jeifrey Philip M. , Eason Robert W. , Chandler Peter J. , Zhang Lin , Townsend Peter D.
Published: February 2023

Photorefractive materials have been used to demonstrate a wide range of potential applications in optical phase conjugation, image amplification and optical processing schemes.
The Formation of Nonlinear Optical Materials by Ion Implantation
Authors: Magruder Robert H.
Published: February 2023

There are several potential candidate systems for nonlinear optical materials including resonant and non-resonant semiconductor quantum dots, organic materials and glass systems. Two of the glass systems are based on glasses containing transition metal ions. The first system exploits the polarization of the transition metal ions (Ti, V, Nb) incorporated in the glass matrix, while the second is based on glasses with metallic nanoclusters of the transition ions (Cu, Ag, Au). While both systems have been shown to have desirable properties for nonlinear media each systems has different nonlinear properties.
Direct Correlation Between UV-Excited Photo-Luminescence and Refrative Index Change in Photosensitive Ge-Doped and Hydrogenated Optical Fibre
Authors: Martin Jean , Atkins Graham , Ouellette François , Têtu Michel , Deslauriers Jean , Duguay Michel A.
Published: February 2023

Many studies have been devoted to the origin of photosensitivity since its discovery in the 70's [1]. The time dependence of the UV-excited blue photoluminescence (PL) has been related to photosensitivity, but up to now the only correlation reported [2] is the relation between the decrease of the blue PL and the refractive index change. In this paper we intend to show a direct correlation between the increase of the blue PL and the refractive index change.
Characterization of photosensitivity in germanosilicate
Authors: Poulsen Christian V. , Haugbølle Søren , Hübner Jörg
Published: February 2023

Permanent UV-induced refractive index changes in germanium doped silica glasses have been a subject of intense investigation for the last decade [1]. In optical fibers UV-induced Bragg-gratings have many possible applications. In planar waveguides less work has been carried out, partly because the technology is not yet developed to the same maturity as for optical fibers. UV-induced refractive index changes in planar structures offer great possibilities as a new way of producing diffractive elements such as Bragg-gratings in existing waveguides [2] and writing buried channel waveguides directly [3,4]. The performance of the technique highly depends on the photosensitivity of the glasses used, making an investigation of the different glass types important. In this work we describe a characterization of the photosensitivity of germania doped silica glasses deposited by plasma enhanced chemical vapor deposition (PECVD). The degree of refractive index change is measured after UV-exposures at 193 nm and 244 nm.
Laser Applications of Fibre Gratings
Authors: Reekie Laurence
Published: February 2023

In recent years, rare-earth doped fibre lasers have matured from a fledgling laboratory curiosity into a device capable of taking on other lasers at their own game, due in no small part to the invention of the photorefractive fibre grating. Single-handedly, this component has changed the way in which these lasers are perceived and used. It is no longer necessary to use bulk dielectric coated mirrors or fibre ring resonators to provide the optical feedback required for laser operation. Instead, by writing a grating into each end of a length of doped fibre, it is possible to make a robust device that can be readily spliced to other fibre components such as couplers and pigtailed diode lasers.
A Hamiltonian Approach to Propagation in Chirped and Non-Uniform Bragg Grating Structures
Authors: Russell P. St. J. , Birks T.A.
Published: February 2023

One current and evolving use of fibre gratings is for chirped grating dispersion compensation[1]. Another is in the formation of effective λ/4 lasing cavities for DFB fibre lasers by imposing a slow local perturbation on the grating parameters[2], In both cases the essential analytical problem is the same: How to treat the behaviour of light in spatially heterogeneous Bragg gratings? In this paper an approach is developed based on the Hamiltonian optics elegantly summarised by a number of authors, including notably Arnaud in his 1976 book Beam and Fibre Optics[3]. The Hamiltonian approach can be applied where the dispersion relation in the homogeneous structure is known, and where, in the heterogeneous real structure, parameters like average index vary slowly in space. It is essentially an analytical method for stepping through a non-uniform structure, matching phase velocities normal to the gradient of the heterogeneity at each step, and propagating along the local group velocity to the next point.
Photodarkening in Upconversion Pumped Thulium Doped Fluorozirconate Fibre Lasers
Authors: Booth I. J. , Archambault J.-L. , Ventrudo B. F.
Published: February 2023

Upconversion pumped lasing in rare earth doped fluorozirconate optical fibre offers the potential for compact blue green laser sources pumped by commercially available infrared laser diodes. A promising candidate for such a source is the thulium system first demonstrated by Steve Grubb and co-workers [1], which lases in the blue at 482 nm with a single pump source at about 1130 nm. Figure 1 illustrates the relevant energy levels of the trivalent thulium ion, and the upconversion mechanism. Ions excited to the short lived H5 and F23 levels decay rapidly by phonon emission to the metastable H4 and F4 levels from which further upconversion transitions occur. The centre wavelengths of the three transitions are respectively 1220 nm (H6 to Hs), 1130 nm (H4 to F2), and 1150 nm (F4 to G4), but because of the broadening of the transitions in glass it is possible to excite all three with a single wavelength pump in the range 1110 nm to 1160 nm. The next energy level above G4 in thulium is D2 with a transition of 1480 nm separating the two, so that further upconversion above G4 should not occur, or only very weakly. A low phonon energy host material such as ZBLAN fluorozirconate glass is necessary so that the metastable levels do not decay rapidly by phonon emission.
Gain Spectrum Flattening of Erbium-Doped Fiber Amplifier Using Long-Period Fiber Grating
Authors: Dianov E.M. , Karpov V.I. , Kurkov A.S. , Medvedkov O.I. , Prokhorov A.M. , Protopopov V.N. , Vasil'ev S.A.
Published: February 2023

The gain spectrum nonuniformity is one of the most important problems in using erbium-doped fiber amplifiers (EDFA) in wavelength-division-multiplexing transmission systems. Several techniques for the gain spectrum flattening with the use of passive filters have been proposed: mechanical deformation of the fiber to couple fundamental and leaky modes [1], etching of the grating at the surface of a D-fiber [2], utilization of a twin-core fiber filter [3], application of photoinduced fiber Bragg grating [4], application of a Fourier filter based on the incorporation of the glass plate [5] or a tapered fiber filter [6].
Modal and Polarization Properties of SHG in Doped-Silica Waveguides: Transverse Modulation Effects
Authors: Kester John J. , Dajani Iyad , Ranon Peter , Alley Thomas
Published: February 2023

The generation of second harmonic light in optically modified fibers1 and thin films2 has been shown to arise from a periodic modulation of the second-order susceptibility, χ(2), along the direction of propagation.3 This longitudinal modulation allows the phase matching of the generated second harmonic light with the fundamental wave. The efficiency of the second harmonic for different waveguiding modes and different polarizations is governed by an additional modulation in the transverse direction. The overlap of χ(2) with the transverse profiles of the optical electric fields across the waveguide, as described by the overlap integral, governs the modal response of the waveguide generated light.4 Unlike the traditional second harmonic generation (SHG) processes, the overlap integrals describing higher order modal combinations may be on the same order as the overlap integral describing the combination of the lowest order modes. In planar waveguides the difference in the transverse charge density governs the polarization dependence.
A large second-order nonlinearity in poled phosphate glass containing mobile protons
Authors: Watanabe Yuichi , Takeshita Naoyuki , Tsuchiya Toshio , Hosono Hideo , Kawazoe Hiroshi
Published: February 2023

Recently, Myers et al. reported that a large second-order nonlinearity [χ(2)~1pm/V] was induced in the near surface region (~4μm) of commercial fused silica by electric-field (5× 104V/cm) poling process at 300°C1. Since the large nonlinearity that they observed were remarkable in the glass containing a small amount of alkali (Na+) impurity, they proposed a model, based on the formation of space-charge layer due to drift of Na+ during poling process, that could explain the nonlinearity. Here we report second-order nonlinearity in poled phosphate glass. The observed nonlinearity is explained tentatively by considering the drift of protons in the poled glasses.
Characterisation of UV-induced Birefringence in Optical Fibre Rocking Filters
Authors: Psaila D.C. , de Sterke C.M. , Ouellette F.
Published: February 2023

In single-mode birefringent fibre, a mode launched along a principal polarisation axis maintains that polarisation state. Optical fibre rocking filters (or polarisation mode converters) are structures that rotate the polarisation state of the optical field. To achieve this, the fibre’s principal axes are periodically rocked through a small angle θ by either oscillating the preform during the draw process [1] or by using UV light to externally irradiate the fibre periodically [2]. Since the birefringence beat length is wavelength dependent, there is a resonant wavelength at which the beat length is equal to the rocking filter twisting period. At this wavelength there is complete coupling from one polarisation mode to the other, while at other wavelengths, there is only partial coupling. At resonance, the state of polarisation is rotated by an angle 2θ per period and thus for complete power transfer, π/(4θ) coupling steps are required.
In-Fiber Transmission Filters with Broad Stopbands using Chirped Bragg Gratings
Authors: Zhang L. , Sugden K. , Williams J. A. R. , Bennion I. , Reid D. C. J. , Ragdale C. M.
Published: February 2023

Many optical fiber applications, such as wavelength division multiplexing/demultiplexing, frequency-guiding in soliton systems, and the filtering out of spontaneous emission noise from fiber amplifiers require transmission band-pass filters with a wide range of finesses and free spectral ranges. Bragg gratings written directly into the optical fiber by direct UV exposure [1] show particular promise in this area and there have been many reported techniques to date proposed for fabricating fiber grating transmission filters (e.g. [2–7]) Most of these techniques however do not allow independent arbitrary selection of the pass and stop band characteristics thus limiting their usefulness for many applications. While the recently reported wide stop band transmission filters based on resonant chirped grating Moiré and Fabry-Perot designs [2,3] do allow a large degree of control of the pass and stop band characteristics, in practice the parameters of the filter including transmissivity, transmission wavelength and linewidth are difficult to tailor during fabrication. Where multiple pass bands are required the number of passbands and the free spectral range are inherently fixed by the phase shift between the two interacting gratings.
Dissimilar wavefront technique for linear and quadratic chirps
Authors: Sugden Kate , Zhang Lin , Williams John , Bennion Ian
Published: February 2023

In this paper, we discuss and characterise two variations on the dissimilar wavefront technique1 that give near-linearly and quadratically chirped gratings. This technique is advantageous over others that have been proposed for the fabrication of chirped gratings because of its simplicity and flexibility. A high level of bandwidth control is demonstrated for gratings of bandwidths in the range of 0.5-23nm.
Novel Actively-Modelocked Dual-Wavelength Fibre Laser Using Chirped In-Fibre Bragg Gratings and its Application to All-Optical Memory
Authors: Pattison D.A. , Kean P.N. , Gray J.W.D. , Bennion I. , Doran N.J.
Published: February 2023

Ultrafast switching devices and high level processing architectures place two fundamental constraints on picosecond-regime data sources. The narrow spectral ranges of all-optical components for WDM [1] require multi-wavelength sources with output characteristics which are both arbitarily and accurately definable over a wide wavelength range. In addition, use of the nonlinear-optical loop mirror (NOLM) in higher level functional systems [2], in which pulse-streams symmetrically straddle the zero-dispersion wavelength, necessitates low levels of inter-pulse-stream jitter [3, 4].
A New Sensitive Method for Measuring Induced Refractive Index Change in Optical Fiber Core
Authors: Dianov E.M. , Kurkov A.S. , Medvedkov O.I. , Vasil'ev S.A.
Published: February 2023

It is well known that germanium-doped silica and a number of other fiber materials exhibit photorefractivity; that is, their refractive index changes in the process of exposure to ultraviolet or blue light. This phenomenon gives an opportunity to produce different types of in-fiber gratings, which are successfully used in many optical devices [1-3].
U. V. induced densification during Bragg grating writing
Authors: Poumellec B. , Niay P. , Douay M. , Bayon J. F.
Published: February 2023

It was expected that the bleaching of the 240-260 nm absorption band and creation of others were sufficient to explain all part of the index change through Kramers-Kronig conjugation. However, Williams et al. [1] taking into account the UV absorption change showed that at most 20% of the index change can be accounted for by this effect. This statement was confirmed also by Eric Fertein [2] in various type of fibers and in taking into account the VUV absorption change. In addition, some recent experiments by Albert et al. [3] using 193 nm light indicates that the bleaching of absorption bands near 242 nm is not essential to induce refractive index changes. A second phase of the process may be that transformed defects lead to a change in the microstructure of the silica. The first idea is a change of volume and so we can expect to see corrugations at the surface of irradiated flat substrate close as the ones of preform slices.
All Optically Written Planar Germanosilicate Waveguide Gratings
Authors: Moss D. , Ouellette F. , Faith M. , Leech P. , Kemeny P. , Ibsen M. , Leistiko O. , Poulsen C.V. , Love J.D. , Ladouceur F. J.
Published: February 2023

Photo-induced index changes in germanosilicate glass is a well known effect and has provided the basis for much recent activity on photoinduced refractive index gratings in fibres1. Since then, very large (>10-3) index changes in hydrogen loaded waveguide structures have been observed and used as the basis for patterning channel waveguides2 and directional couplers3. Recently, we have demonstrated waveguide structures patterned in PECVD grown material without the aid of hydrogen loading4,5, and in this paper we report the fabrication of all optically patterned buried waveguide grating structures, again without the aid of hydrogen loading. This demonstrates that the achievable index changes (without hydrogen loading) in this material is large enough to simultaneously support both waveguide and grating structures. The elimination of hydrogen loading is an important practical issue because, unlike fibres, planar waveguides need anomalously large overcladding layers to prevent rapid out diffusion of hydrogen during writing.
Glass Fibre Poling and Applications
Authors: Kazansky P.G. , Pruneri V. , Smith A.R , Sugihara O. , Dong L. , Russell P.St.J.
Published: February 2023

Glass is a dominant material in fibre-optics technology. Recently, the discovery that dopants such as Ge and Ce render silica glass photosensitive has made possible the routine fabrication of important passive components such as fibre Bragg gratings. The absence of a second-order nonlinearity in glass however makes impossible the fabrication of active components such as modulators, switches, parametric frequency converters and frequency doublers. Thus, when efficient photoinduced second-harmonic generation was first discovered in fused silica fibres, wide-ranging studies ensued into the mechanism and properties of this unexpected phenomenon. Nonetheless, until fairly recently second harmonic generation in specially treated glasses and glass fibres has been of more scientific than practical interest, owing to levels of nonlinearity that were typically 3-4 orders of magnitude less than in the best nonlinear crystals1-3.
Frequency Doubling in Thin Film Waveguides of Borate Glasses
Authors: Sasaki Keisuke , Horinouchi Suguru
Published: February 2023

Rf sputtered multi-component glass films on pyrex substrates exhibited novel quadratic optical nonlinearity by corona poling which was applied for the second harmonic generation in blue-green range1)2). Maker fringe method proved that d33 values of the films was up to 0.6 pm/V at appropriate sample preparation condition. Resistivities of substrate glasses remakably related to efficient poling. Borate component of multi-component glasses gave some effects to establish the quadratic nonlinearity coming from macroscopically noncentrosymmetric structure of the films. Also boudary situations and combinations of each layers gave influences to decay of the nonlinearity.
Photorefractive spatial light modulation by anisotropic self-diffraction In KNbO3 - crystals
Authors: Voit E. , Günter P.
Published: February 2023

In this contribution we analyze the configuration for anisotropic self-diffraction in KNbO3. First applications of this effect in spatial light modulators and incoherent- to-coherent converters are described.

Anisotropic Bragg diffraction can occur if off-diagonal elements of the electro optic tensor are involved in the grating formation. In KNbO3 this is the case for r42=380pm/V and r51 =105pm/V (for λ=633nm) [1,2].
Photorefractive Time Integrating Correlator and Adaptive Processor
Authors: Yu Jeffrey , Hong John , Psaltis Demetri
Published: February 2023

One major limitation of photorefractive crystals is their relatively slow response time at reasonable light intensities [1]. In this paper we present a time integrating correlator using a photorefractive crystal which uses the slow response time of the crystal to its advantage. Specifically, we show that the response time is equivalent to the integration period of the correlator. An increase in the response time of the crystal will thus correspond to a longer integration time and consequently a larger processing gain for the system. Hence, inputs with very low signal to noise ratios can still be detected. In addition to the temporal aspect, the correlator uses the high recording bandwidth of the photorefractive effect to allow processing of signals of high time-bandwidth products, as well as to give the system the ability of presenting correlation outputs without bias. Experimental results for the photorefractive time integrating correlator are presented.
Image Transfer in Photorefractive Gaas Using Counter-Propagation Beam Coupling Configuration*
Authors: Gheen Gregory , Cheng Li-Jen , Rau Mann-Fu
Published: February 2023

It has been demonstrated1-4 that GaAs is a sensitive photorefractive material with the potential to be used for optical processing in the infrared region. The advantages of using GaAs crystals for optical processing include: high sensitivity1, low power consumption5, fast response2,6, infrared operation, tunable information storage time, and compatibility with semiconductor lasers4, sensors, and VLSI circuits. The compatibility provides an excellent potential to integrate optical processing devices with advanced technologies of VLSI, lasers, and sensors for the development of future sophisticated information and image processing systems. One of the potential applications of such integrated systems is the optical interconnects for VLSI circuits8.
Raman-Nath Diffraction from Laser Induced Gratings in Barium Titanate
Authors: Ditman L.S.
Published: February 2023

We experimentally determined materials parameters in photorefractive barium titanate using a Raman-Nath probe technique of laser induced dynamic gratings. In this technique, shown in Fig.1, coherent co-planar writing beams (wavelength λw) propagating in the X-Y plane intersect inside the crystal and form an interference pattern, inducing refractive index grating planes via the photorefractive effect. A probe beam (wavelength λp) propagating in the Z-direction passes through and parallel to the grating planes and is diffracted. The resulting diffraction pattern on a screen which is parallel to the X-Y plane and located beyond the crystal consists of a set of discrete intensity maxima (modes) which are symmetrically located about the m=0 (undiffracted) order. The angle of diffraction, θDm, of a particular mode, m, (where m=0, 1, 2, 3,…, integer) is a function of the ratio of the probe beam wavelength to the grating spacing in the crystal. The grating spacing, ΛG, in the crystal is a function of the ratio of writing beam wavelength to intersection angle of the write beams in the crystal.
Two-Beam Coupling in Cerium-Doped Ba0.5 Sr1.5 K0.25 Na.75 Nb5 O15
Authors: Carson S.D. , Block K.L. , Hennessy C.J. , Gorbett P. , Bendow B. , Neurgaonkar R.R.
Published: February 2023

The electrooptic properties of photorefractive materials are currently under intensive investigation because of their potential applications in real-time holography, optical data storage and phase-conjugate wavefront generation. Recently, increasing attention has been focused on two-beam coupling in photorefractive crystals to achieve coherent signal beam amplification. Applications for this technique include image amplification, vibrational analysis, nonreciprocal transmission, laser-gyro biasing and optical computing. Critical issues for practical application of the photorefractive effect include the material's response time and coupling coefficient. If photoferroelectric crystals are to be used for device applications, their response time must be reduced to the order of 1 msec. or better, and a large photorefractive coupling coefficient is required for the construction of efficient devices. The ideal photorefractive crystal has yet to be discovered; hence a large number of ferroelectric crystal compositions have been grown and characterized. As part of this effort, two-beam coupling has been studied in single crystals (0.5 cm. diameter) of cerium-doped Ba0.5 Sr1.5 K0.5 Na0.75 Nb5 O15 (BSKNN-3) grown at Rockwell International Science Center.
Anisotropic Selfdiffraction in KNbO3
Authors: Külich H.- C. , Rupp R. A. , Hesse H. , Krätzig E.
Published: February 2023

Holographic recording of information in electrooptic crystals is based on a light- induced modulation of the elements of the dielectric tensor. For readout of these volume phase holograms the Bragg condition must be satisfied[1]. In birefringent crystals this may be achieved not only for waves with equal polarization (isotropic diffraction) but also for orthogonally polarized waves (anisotropic diffraction) [2].
Higher-Order Finite Element Method To Solve The Nonlinear Coupled-Wave Equations For Degenerate Two-Wave And Four-Wave Mixing
Authors: Ja Y. H.
Published: February 2023

In this paper we employ the one-dimensional (1-D) quadratic finite element method (FEM) to obtain the numerical solution of the nonlinear coupled-wave equations for degenerate two-wave mixing (DTWM) and four-wave mixing (DFWM) in photorefractive media. A comparison is made between the computed results obtained from the quadratic element FEM, the first-order element FEM [1] and the exact method.
Fast Hologram Erasure in Photorefractive Materials
Authors: Kavounas Gregory , Steier William H.
Published: February 2023

Real time holography in photorefractive materials has been considered for many applications, most recently to provide the reconfigurable interconnections in optical neural net computing.1 In these applications the existing holographic grating pattern must be erased and a new pattern written within the cycle time of the computer. The usual procedure for erasure is to flood the crystal with a separate erase beam or to use one of the write beams alone as the erase beam. We present a simple technique for rapid erasure by shifting the phase of one of the write beams by λ/2. This technique gives an almost complete erasure and is at least 8 times faster than using one of the write beams alone to erase.
Photorefractivity in Lithium Niobate Waveguides at 1.3 μm
Authors: Harvey G. T. , Astfalk G. , Feldblum A. Y. , Kassahun B.
Published: February 2023

Lithium niobate guided wave devices are currently being investigated for use in fiber optic systems operating at 1.3 to 1.5 um. At these wavelengths, little information exists on susceptibility of the devices to photorefractive damage. In this paper, we present clear evidence of the photorefractive effect in titanium indiffused Lithium Niobate directional couplers at a wavelength of 1.3 um. Using coupled mode theory, the index changes due to the effect can be inferred and used to calculate the crosstalk due to the effect in a coupler of known length and input power.
Amplification of High Bandwidth Signals Through two Wave Mixing in Photorefractive Bi12SiO20 Crystals
Authors: De Montchenault G. Hamel , Loiseaux B. , Huignard J.P.
Published: February 2023

We report a new two wave mixing interaction in photorefractive (P.R.) crystals Bi12SiO20 (B.S.O.) where the signal beam is time modulated at high frequency. It will be shown that the transmitted signal exhibits a differential gain γdiff at the same frequency and this even if the modulating frequency fm is much greater than the inverse of the material response time τ.
Signal Transmission Characteristics of a Photonic FDM Multichannel Selector
Authors: Habara Keishi , Sasayama Koji , Okuno Masayuki
Published: February 2023

This paper describes a photonic multi-frequency-channel selector using a coherent optical transversal filter. Arbitrary channel selection and signal transmission characteristics are confirmed.
Optically-Processed Self-Routing for 1D and 2D Photonic Switching Architectures
Authors: Prucnal Paul R.
Published: February 2023

The architecture of a 2×2 photonic packet switching node using optically-processed fixed-directory routing, contention resolution (using deflection routing), and synchronization is presented.
Lossless and Low Crosstalk InP Based 2 × 2 Optical Switch With Integrated Optical Amplifier
Authors: Kirihara Toshio , Ogawa Mari , Inoue Hiroaki , Nishimura Shinji , Ishida Koji
Published: February 2023

Photonic space division switching networks are one of the most promising switching systems. In designing such a network on a large scale, C. Burke et al. proposed and demonstrated that use of semiconductor optical amplifiers could reduce optical switch loss[1]. A lossless optical switch unit is most desirable for large scale photonic networks because it enables us to enlarge the network without being concerned about optical loss.
High-Contrast Modulation of Asymmetric Fabry-Perot Modulators at 20 GHz
Authors: Barron C. C. , Thibeault B. J. , Mahon C. J. , Coldren L. A.
Published: February 2023

Since their introduction in 1989 [1,2], asymmetric Fabry-Perot modulators (AFPMs) have attracted a great deal of attention because of their high efficiency (high contrast, low insertion loss, and low voltage) and the fact that their surface-normal configuration is particularly compatible with fiber optics and with proposed architectures for parallel optical free-space image processors and interconnection systems. In addition to their other virtues, AFPMs also have the potential for extremely high speed operation. Last year we demonstrated small-signal modulation of AFPMs to 21 GHz [3], and recently we have predicted that speeds in excess of 40 GHz may well be possible. [4] This capacity for high speed operation makes AFPMs suitable for high-speed photonic switching applications in which the optical switches are "smart" — that is, they perform functions on the data stream at the data rate, rather than simply switching packets at some slower rate.
A complexity analysis of optically implemented shuffle equivalent interconnection topologies based on computer generated binary phase gratings
Authors: Cloonan Thomas J. , Richards Gaylord W. , Morrison Rick L. , McCormick Frederick B. , Sasian Jose M. , Lentine Anthony L. , Hinterlong Steve J. , Hinton H. Scott
Published: February 2023

Free-space digital optics (FSDO) is an evolving interconnection technology that may permit signals to be routed between digital integrated circuit chips as beams of light propagating orthogonal to the plane of the device substrates. In switching systems, FSDO can be used to provide high-density, high-bandwidth, low-energy, low-noise connections between the nodes in multi-stage interconnection networks (MINs).[1] In this paper, various MIN architectures are examined and compared to determine the complexity and feasibility of their associated optical implementations. In particular, the paper explores efficient means of implementing two well-known interconnection topologies (the 2-banyan and the 4-shuffle ) and two novel interconnection topologies (the segmented-2-shuffle and the 4-banyan) using computer generated, space-invariant binary phase gratings. The paper also studies the effects of node-type and interconnection topology on the laser power requirements and the optical component requirements within the system. The general class of networks known as Extended Generalized Shuffle (EGS) networks will be used as a baseline for the analysis. The results should help identify optimum architectural parameters (node-type and interconnection topology) given the constraints of FSDO technologies.
Holographic Perfect shuffle interconnections for planar optics
Authors: Song S. H. , Lee E. H. , Carey C. D. , Selviah D. R. , Midwinter J. E.
Published: February 2023

The perfect shuffle network is one of the regular multiple-stage interconnection networks with wide applications for telecommunications and parallel computing processors.[1] Optical implementation of the perfect shuffle interconnects has been mainly achieved by the use of free-space optical components, such as lenses, prisms, or holograms.[2,3] In order to implement the interconnects in a compact, robust, and alignment-free manner, technologies of planar integration of the free-space optical components[4] are required. In this summary, we propose a planar optical configuration which can carry out the perfect shuffle interconnects, and it is suitable to link areas of a wafer scale integrated circuit together by means of computer-generated holograms(CGH). Two double-imaging diffractive-reflective CGH’s are used as key components acting as a set of four lenses in the free-space configuration of Ref.3. Interconnection capacity of the proposed planar system and the optimum number of internal reflections in an optical substrate are also derived by analyzing aberrations of the CGH’s.
An optoelectronic hybrid multi-stage interconnection network
Authors: Jiang Jie , Tietgen Karl Heinz
Published: February 2023

Multi-stage interconnection networks (MINs) can be employed in switching systems and in interconnections of processors. The interconnection patterns in MINs, "perfect shuffle", "butterfly" or "crossover", are particularly appropriate for optical implementation [1]-[4].
“Broadcast and Switch” – A New Class of WDM Networks for High Switching-Speed, High Connectivity Applications
Authors: Sharony Jacob
Published: February 2023

Optical networks can be categorized into two main types: "Broadcast and Select" and “Wavelength Routing” [1]. The main building blocks in these networks are: star couplers in the former and wavelength-selective switches (WSS) in the later. The WSS is a switch that can independently switch different wavelengths. In both networks, tunability of transmitters or receivers is usually needed to provide the desired connections. In current technologies optical networks experience a “tunability bottleneck”: tunable lasers, although fast, are limited to a narrow region resulting in a relatively small number of wavelengths, and tunable filters are relatively slow for high speed applications.
Turnover-type Free-space Multichannel Optical Switch
Authors: Sakano Toshikazu , Noguchi Kazuhiro
Published: February 2023

Free-space optical switches are attractive candidates to replace conventional electrical switches in future supercomputers and telecommunication systems[1]. The switches have the potential to handle a large number of high speed signals without suffering from such problems as electromagnetic interference, signal delay, and clock skew. Liquid crystal light modulators which can control the polarization state of light are promising as the switching devices in such switches, because they make it easy to construct large arrays, and they are transparent to the lights being switched over a wide wavelength region. Several free-space multichannel optical switches based on these devices have been proposed for multistage optical switching networks [2],[3]. The optical switches are the one-way type in which optical signals enter one side of the switch body and are output from the other side. Input and output fiber arrays must, therefore, be situated on both sides of the switch. In applying such switches to intra-board chip-to-chip interconnects in a multiprocessor system, the input and output links of each processor have to be connected to the optical switch via input and output optical fibers, respectively [4]. This scheme causes wiring congestion and restricts the architecture of the system if the number of processors is increased.
Polarization Independent Optical Modulation with Tensile-Strained GaAs-InAlAs Quantum Wells Grown on GaAs Substrate
Authors: Chan Yuen-Chuen , Tada Kunio
Published: February 2023

Polarization independent optical modulation at a wavelength range of around 860nm with tensile-strained GaAs-InAlAs quantum wells grown on a relaxed non-pseudomorphic InAlAs grid layer has been studied and demonstrated by theoretical simulations and waveguide absorption measurements.
Single-Mesa Optical Memory and Logic Pixels for Highly Parallel Arrays
Authors: An Xilin , Geib K. M. , Hafich M. J. , Beyette F. R. , Feld S. A. , Robinson S. Y. , Wilmsen C. W.
Published: February 2023

A new family of optical logic gates is presented. The two inputs of these devices are separated by wavelength, thus isolating the two signals and reducing cross talk. Experimental results showing the operation of the optical set-reset memory, optical inverter, optical gated latch, optical AND gate and NAND gate are presented. Output on/off contrast ratios ranging from 6 up to over 50 have been obtained.
Ultra-fast Photonic Packet Switching with Optically Processed Control
Authors: Glesk I. , Prucnal P.R. , Wang Baolin
Published: February 2023

In ultra-high speed networks individual address bits are spaced only picoseconds apart, and address recognition can be made by an ultra-fast demultiplexer which allows the packet to be routed without any opto-electronic conversion. One low-power device capable of performing the critical operation of reading address bits in an optically compressed packet header is the Terahertz Optical Asymmetric Demultiplexer (TOAD)1.
Low-voltage electroabsorption in InGaAsP/InP multiple-quantum-well electron transfer structures
Authors: Olin Ulf , Varga Dana , Fröjdh Krister , Wallin Johan , Landgren Gunnar
Published: February 2023

Fast low-chirp electro-optic modulators are essential for applications as external modulators in long-haul communication systems. For integration with high-speed drive electronics, the modulation voltage should be restricted to preferably the sub-volt region. Barrier reservoir and quantum well electron transfer structures (BRAQWETs) have shown a great promise for these applications, due to its large electro-refractive effects[1] and fast intrinsic speed, which make them particularly suitable for high-speed Mach-Zehnder interferometric amplitude modulators[2].
8x8 Array of optoelectronic switching nodes comprised of flip-chip-solder-bonded MQW modulators on silicon CMOS circuitry
Authors: Lentine A. L. , Goossen K. W. , Walker J. A. , Chirovsky L. M. F. , D’Asaro L. A. , Hui S. P. , Tseng B. T. , Leibenguth R. E. , Kossives D. P. , Dahringer D. W. , Miller D. A. B.
Published: February 2023

One approach to improving the performance of large processing or telecommunications switching systems is to interconnect integrated circuits using optics. Smart pixels, with integrated optical detectors, modulators, and electronic logic, could potentially be used in these systems. The FET-SEED, consisting of the monolithic integration of multiple quantum well (MQW) optical modulators and detectors with GaAs field effect transistors, is one design platform for these smart pixels [1,2]. Another potential design platform uses the hybrid integration of MQW modulators and detectors with commercial electronic circuits [3-7]. This latter approach allows one to design circuits with greater complexity and circuit yield, because it uses available established VLSI processes.
Development of a 16 x 16 reconfigurable holographic interconnection system
Authors: Gravey P. , Bonnel L.
Published: February 2023

The use of arrays of reversible holograms is an attractive method to perform reconfigurable free-space interconnections of N inputs x N outputs high bit rate communication channels. Indeed, when the number of channels N increases, holographic switching systems have in principle less optical losses than those based on shuttered geometries such as vector-matrix or matrix-matrix architectures [1]. All the holographic switching system reported until now are made with a single deflection stage and they are therefore not suited to single mode fibre interconnections [2-4]. However, using single mode output fibres is very important because it enables the insertion of single mode optical amplifiers (either semi-conductor amplifiers or doped-fibre amplifiers) in order to compensate the switching losses and to realize quasi-transparent sytems for cross-connects applications.
Experimental High-Speed Optical Cell Selector for Photonic ATM Switch
Authors: Maeda T. , Hironishi K. , Kuroyanagi S. , Kondo Y. , Tsuyama I. , Murakami K.
Published: February 2023

This paper describes an experimental optical cell selector with fiber delay lines and semiconductor optical amplifier gates for a photonic ATM switch. It handles 10 Gb/s optical ATM cells.
All-optical selection of 160-Mb/s channels from a 51.2-Gb/s data-stream
Authors: Keating Adrian J. , Tsukada Masato , Hiramatsu Atsushi
Published: February 2023

Contemporary all-optical demultiplexers can convert data-streams from rates of typically 100 Gb/s to 6.3 Gb/s, equivalent to 1 in 16 channel selection [1-3]. A wide range of techniques to achieve all-optical demultiplexing have been reported [1] which have a variety of applications in communication systems. These applications include receiver front-ends in long-haul transmission systems [2] and high-throughput network gateways [4]. However, the use of all-optical demultiplexing in peripheral network equipment, operating at low data rates, is rare [5]. In peripheral equipment these demultiplexers should function as selectors, with the ability to select any (authorized) channel from the input data-stream.
High Contrast Nematic Liquid Crystal Polarisation Controllers: Application to a 4 x 4 Free Space Optical Switch at 1.5 μm.
Authors: Pain F. , Coquillé R. , Vinouze B. , Wolffer N. , Gravey P.
Published: February 2023

Free space optical switches are very attractive because of their high-density interconnections, transparency to signal format and bit rate. Recently, multistage optical switches using liquid crystal (LC) cells have been demonstrated at the telecommunication wavelengths [1] [2] [3], By alternately cascading polarisation controller arrays (LC cells) and routing elements (bireffingent plates, polarising beam splitters, prisms, diffractive optical elements), a N input N output optical switch can be realized. To create an optical switch with low insertion loss and good crosstalk, we must resolve some technical issues such as the development of low-loss and high- contrast polarisation controllers.
Optoelectronic Switching for Virtual Wavelength Paths
Authors: MacDonald R.I. , Corazza D. , Sharma R. , Clegg D.D.
Published: February 2023

Optical transmission with wavelength division multiplexing (WDM) opens the possibility of "transparent" networks that can carry virtually any signal between any pair of network terminals. The advantages for upgrading, reconfiguration and service provision are obvious. Foreseeable WDM technology provides only a few tens of wavelength channels for use in the whole network. These are most efficiently used if wavelength assignments can be independently made on each link. A nodal "wavelength crossconnect" (WXC) function is then required to assign new wavelengths to the incoming signals on outgoing links. If this function can be done transparently a "Virtual Wavelength Path", analogous to the "virtual path" concept of ATM routing is created. However methods of wavelength translation that provide optical transparency tend to be expensive, polarization dependent, hungry for optical power, and in an immature state of development.