bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractal Transmission Properties of a Quasiperiodic Sequence of Directional Couplers
Authors: Rahman Lutfur , Winful Herbert G.
Published: February 2023

Quasi-periodic structures, structures which are intermediate between
the periodic and disordered systems, have been a subject of
considerable theoretical interest in recent years1–3. It
has been shown theoretically that such structures display exotic
behavior such as weak localization and scaling. Experimental
realization of such structures and identification of these exotic
features is needed. One potentially simple experiment towards this end
has recently been proposed2 where a stack of dielectric
layers is constructed using two types of dielectric layers arranged in
a Fibonacci sequence. The transmission coefficient, as a function of
the wavelength of incident light, was demonstrated to be multifractal
and displayed scaling. Our work is concerned with a quasi-periodic
optical system consisting of waveguide directional couplers which
under certain resonant conditions displays localization and scaling.
The energy exchange between the guides is codirectional as opposed to
the contradirectional energy exchange of Ref. 2.
All-Optical Cross Switching of Modes of a Strip Loaded GaAs/GaAlAs Multiple Quantum Well Waveguide
Authors: Wa P. Li Kam , Burke S.V. , Pate M. A. , Roberts J.S. , Robson P.N.
Published: February 2023

We have already demonstrated all-optical operation of a nonlinear directional coupler(1) as proposed by Jensen(2) and more recently we have reported optically induced switching between two vertical modes of a SiNx loaded waveguide(3). In this presentation, we describe the experimentally observed nonlinear switching between two transverse modes of a strip loaded GaAs/GaAlAs multiple quantum well waveguide.
Second-Harmonic Generation in Poled Optical Fibres: Dynamics and Phasematching Techniques
Authors: Fermann M.E. , Li L. , Farries M.C. , Payne D.N. , Russell P.St.J.
Published: February 2023

The dynamics of pulsed and cw excitation poling in germanosilicate fibers are studied using a novel phasematching technique for second-harmonic generation.
Length Dependence of Second Harmonic Generation in Optical Fibers Prepared with 1.064µm and 532nm Light
Authors: Batdorf B. , Krautschik C. , Österberg U. , Stegeman G. , Morse T.F.
Published: February 2023

Efficient frequency doubling in phosphorous doped optical fibers has been widely observed. A conversion efficiency of 13% at 951 watts peak power at the fundamental frequency has been reported [1]. Fibers prepared with only fundamental light (1.064µm) have previously been studied [2] and found to have the characteristic input intensity squared dependence on second harmonic (SH) output associated with χ(2) interactions. However, the growth of the SH is not quadratic with length [3], implying a length dependent χ(2) in the optical fiber. The purpose of this study is to determine what parameters are important during the preparation of the fiber for the final length dependence of the SH.
Cerenkov Second Harmonic Generation of Semiconductor Laser Radiation (λ=1.3 μm) in Ti: LiNbO3 Waveguide
Authors: Buritskii K.S. , Garbuzov D.Z. , Dianov E.M. , Zaitsev S.V. , Ovchinnikov A.V. , Tarasov I.S. , Chernykh V.A. , Scherbakov E.A.
Published: February 2023

A number of works [1,2] have recently appeared, where Cerenkov second harmonic generation in LiNbO3 waveguides is considered. Proton-exchanged H+:LiNbO3 waveguides were mainly investigated, featuring high value of refractive index difference and small waveguide depth and hence strong optical confinement. The high Cerenkov SHG efficiency (μ=1% at pump power P=20 mW) was obtained in such waveguides. The efficiency of this process in waveguides produced by Ti diffusion into LiNbO3 is not yet estimated.
Three-dimensional modes in planar nonlinear structures
Authors: Akhmediev N.N. , Nabiev R.E. , Popov Yu.M. , Lebedev P.N.
Published: February 2023

A wave equation for light propagation in nonlinear planar structures has solutions eingϕ (x), limited in x direction perpendicular to the interface, and propagating in the form of a wave along the interface in the direction z. These waves may be excited by light beams, which are incident to the interface from a linear interface at grazing angles /1/. Some properties of these waves are considered in /2,3/, namely, they are unstable with respect to the development of small-scale transverse perturbations.
Chanńel Waveguide with Parabolic Coupling Horns on Semeconductor Doped Glass
Authors: Mai Xu , Yan Li , Chang-hong Ma , Ning An
Published: February 2023

Semiconductor doped glasses are now being considered the ideal material for making sub-picosecond nonlinear optical devices. Experiments performed on bluk glasses have shown its larger optical non-linearety(1) and demonstrated carrier recombination times in the range of 80 to 16 ps(2). Recently, nonlinear response of semiconductor doped glass has been obtained to be about 3.5 ps by indirect method of measuring moving grating(3). So it has great potential for use in high qualitv nonlinear guided wave optical devices such as ring resonantors, directinal couplers and distributed feedback channel waveguides, etc.
Integrable Optical Correlator; its Temporal Resolution, Spectral Response, and Power Sensitivity
Authors: Vakhshoori D. , Walker J. , Wang S. , Smith J. S. , Soccolich C. E. , Islam M. N.
Published: February 2023

To realize the future opto-electronic integrated circuits the functions that are available by discrete devices should also be present in an integrated forms. One of these functions is optical correlation which is used in time division multiplexing system and other schemes where optical pulses are used. Here we present a new class of integrable optical correlator and experimentally study its temporal resolution and power capability. The correlator (a special GaAs/AlGaAs waveguide) is shown to be broadband capable of correlating pulse trains with average power in the correlator in sub mW range with wavelengths ranging from 1.06μm to 1.7μm. The correlator device was also used to generate sum frequency signal from mixing l0mW cw beam of 1.06μm Nd:YAG laser with 7mW cw beam of 1.3μm semiconductor laser diode. The latest result shows the potential of direct measurement of optical pulses from semiconductor laser diodes at different wavelengths with a single integrable compact correlator without any mechanical translation. The power levels involved are 200μW (1.06μm) to 3 mW (1.7μm) average power in the correlator device. The longest pulses measured are 12psec centered at 1.43μm and the shortest pulses are 400fsec centered at 1.7μm with an indication of even shorter correlation trace of 150fsec. For the 150fsec pulses the resolution was limited by the 10X objective lens that was used to image the correlation signal on to the detector.
Large Nonlinear Phase Shifts in a Nitrobenzene-Cored Single-mode Fibre
Authors: Kashyap Raman , Finlayson Neil
Published: February 2023

The availability of picosecond mode-locked pulses and low loss optical fibre has made it desirable to use the effects of self-induced phase-shifts for applications in all optical processing. There have been several successful demonstrations of all-optical switching in fused silica fibres in recent years. What is common amongst most of these devices is that they use long lengths of fibre, typically 25m to km, high optical powers or both. No demonstration of all optical switching in short lengths of optical fibre at relatively low powers has so far been demonstrated. This limitation is mainly due to the low nonlinearity of silica (3 x 10-20 m2/W). Recently, 29cm long fibres made with new glasses have been reported which yield 17π nonlinear phaseshift with an input power of 1kW [1]. This paper reports on the observation of self-induced polarisation instabilities in 10cm lengths of nitrobenzene-filled silica-capillary single-mode waveguides. Large phase changes of at least 12π are reported at peak input powers of only 14W, with no saturation of the nonlinearity.
New polymers for nonlinear optics
Authors: Kishimoto Manabu , Zou Dechun , Seo Iwao
Published: February 2023

Poled polymer films with nonlinear optical (NLO) chromophores doped or covalently attached to the polymer chain have been the subject of recent study1–3. These materials have potential as electro-optic switching/modulator and second harmonic generator (SHG)4,5. Their usefulness is determined by their temporal stability and other physical and mechanical properties. For NLO processes, such as SHG, it is essential to achieve noncentrosymmetric molecular assemblies. In addition the material must provide ease of processability.
Amplification of Nonlinear Waves in a Symmetric Planar Waveguide
Authors: Akhmediev N.N. , Mitskevich N.V. , Nabiev N.N.
Published: February 2023

The study of nonlinear waves in layered structures proposed in Refs.[1] and [2] has become widespread, stimulated by the progress in the early 1980’s. The possibility of using such waves in optoelectronic devices spurred advances in both theory and experiment [3-7]. Propagation of waves in nonlinear waveguides is usually considered in passive optical systems Ca case of transparent media).
Cross-phase-modulation-induced nonelastic collisions of optical solitons
Authors: Höök A. , Lisak M. , Anderson D. , Serkin V. N.
Published: February 2023

A new class of problems has recently appeared; nonelastic interaction of solitons at different polarization states or different wavelengths. Recently[1] it was predicted that the so-called effects of shadows should appear in the process of collisions between solitons in birefringent fibres. The same behaviour is observed in computer simulations of NLSE solitons at different wavelengths in single-mode fibres[2].
Second Harmonic Generation in Optical Fibres - the Role of the Longitudinal Fields in Symmetry Breaking
Authors: Sceats Mark G , Poole Simon B
Published: February 2023

Seeded SHG in fibres is quantitatively explained by the proposition that the longitudinal field of the pump mode is involved in the ionisation of Ge-Si wrong bonds through a 3-photon ionisation process invoving two pump photons and one seed photon. This interference produces a grating of defects which has the correct inversion asymmetry to produce SHG. Optical pumping of the trapped electrons in Ge(l) centres developes an electrostatic field which produces SHG by the EFISH mechanism.
The Soliton Frequency Stabilization and Raman Self-Frequency Shift Suppression in Fibers Doped Er And Tm Ions
Authors: Dianov E M , Konstantinov K K , Pilipetskii A N , Starodumov A.N.
Published: February 2023

The possibility of the Raman self-frequency shift [1-3] suppression is of great interest for both the high bit rate communication lines and the lasers with fiber cavities [4]. In the communication lines for picosecond pulses the frequency shifts are small. Frequency drift toward a maximum of the gain profile in an active fibers can compensate to some extent the effect of self-frequency shift. The possibility of frequency stabilization by the effect of frequency pulling under the gain profile was investigated by Blow et al [5]. The frequency pulling to some fixed frequency was predicted instead of the growing with the fiber length soliton frequency shift. The suppression of self-frequency shift due to Raman amplification in the field of external pump wave was experimentally investigated by Gouveia-Neto et al [6].
Nonlinear bent directional couplers with asymmetrical distribution of nonlinearity
Authors: Karpierz Mirosław A.
Published: February 2023

Recently, the nonlinear directional couplers have been extensively investigated as optical devices for ultra high-speed data processing [1-7]. They were analyzed for parallel waveguides [2-5] as well as for configuration with bending waveguides [5-6], which is more insensitive with respect to fabrication tolerances of the device length. In most of previously analyzed nonlinear directional couplers there was assumed the symmetrical distribution of nonlinearity. However, it has been shown that for asymmetrically placed nonlinear material the required switching power is lower than for symmetrical case [7].
Nonlinear Directional Coupler Switched by the External Wave
Authors: Weinert-Raczka Ewa , Petykiewicz Jan
Published: February 2023

A typical Nonlinear Directional Coupler (NLDC) permits power dependent energy transfer between two adjacent waveguides. The output of the device can be controlled by the input power solely for high energy signals. For weak fields NLDC works like a linear coupler with the output dependent only on the device design. NLDC working with weak modes and controlled by a strong field at a different frequency guided by the central region of the coupler was proposed by Lederer et al. [1] .
Dynamic Effects of Kerr Nonlinearity and Spatial Diffraction on Self Phase Modulation of Optical Pulses
Authors: Karlsson M. , Anderson D. , Desaix M. , Lisak M.
Published: February 2023

It is well known, cf [1] that the optical Kerr effect can give rise to self - focusing and is responsible for self phase modulation of optical pulses. The formal analogy between the phenomena of spatial diffraction and temporal dispersion of optical pulses was pointed out very early [2]. However, only recently the two aspects have come together in the strong interest which has focussed on optical pulses propagating under the combined influence of nonlinearity, temporal dispersion and spatial diffraction [3-7]. Of particular interest is the possibility of generating optical pulses which collapse simultaneously in space and time due to the inherent instability of solitons in higher dimensions.
Three Photon Absorption Coefficients of Al0.18Ga0.82As Below Half the Band Gap
Authors: Kang J. U. , Villeneuve A. , Al-hemyari K. , Aitchison J. S. , Ironside C. N. , Stegeman G. I.
Published: February 2023

Recent all-optical switching experiment have shown the usefulness of AlGaAs used below half the band gap.1–3 This spectral region is useful because the two photon absorption (2PA) vanishes below half the band gap, and that 2PA was shown to be detrimental to all-optical switching.4 However, the three photon absorption (3PA) becomes the limiting factor for nonlinear guided wave when the influence of the 2PA can be neglected.5 The previously measured value included some absorption by free carriers that were generated by 2PA.2 Such a process has the same behavior versus intensity as 3PA. In the present experiment the two photon absorption is negligible, therefore only the 3PA coefficient has been measured. We will show that AlGaAs satisfies the figures of merit and hence is a prime candidate for the study of nonlinear guided wave phenomena at 1550 nm.
Experimental Measurement of Multiple Brillouin Stokes Orders in a Fibre Amplifier Under Pulsed Excitation
Authors: Wait P.C. , Newson T.P. , Pannell C.N. , Russell P.St.J.
Published: February 2023

In long passive optical fibres excited by narrow linewidth sources, stimulated Brillouin scattering (SBS) is the first non-linear effect to reach threshold [1]. In optically amplifying fibre, the SBS characteristics are drastically modified, and the threshold power can reach μW levels [2]. This is particularly important in long lengths of fibre lightly doped with Erbium to provide distributed gain, as has been proposed for practical amplifier systems [3]. Above a certain threshold power, the electrostrictive phonon gain provided by interference of the forward pump and backward Stokes waves coherently amplifies the phonon population at the resonant frequency, resulting in a sudden stimulated surge in Stokes power. At sufficiently high pump powers, this process can continue, producing a cascade of successive Stokes orders. In passive fibre, the threshold power at which SBS becomes significant is governed by the temperature, the modal area and the pump laser linewidth [2]. In this paper, SBS in a 60 m long Erbium-doped fibre amplifier (EDFA) is explored for excitation by 80 nsec pulses at various different levels of EDFA gain. A cascade of first, second, third and fourth Stokes orders is observed; previous work reported only two Stokes orders under similar conditions [4].
A scheme for high-contrast, low power all-optical gate using spatial solitons
Authors: Afanasjev V. V. , Serkin V. N.
Published: February 2023

The optical solitons (temporal and spatial) are very promising for all-optical switching and logic gates due to stability and uniform phase along the pulse. Various schemes have been demonstrated (see, for instance, [1-4]), however in all those schemes the power of the control wave was more or comparable with the power of the signal wave. We propose a scheme where the control wave power is approximately 2-4% of the signal wave power. This scheme is based on the control of the bright spatial soliton interaction.
The Three-Waveguide Soliton Coupler
Authors: Hernandez-Figueroa H.E. , Di Pasquale F. , Ettinger R.D. , Fernandez F.A. , Davies J.B.
Published: February 2023

The numerical demonstration of spatial multisoliton emission from a nonlinear waveguide [1] immediately opened new possibilities for the design of nonlinear optical devices. Two of these are particularly notable: the soliton coupler [2] and the soliton scanner [3]. The former, designed with the help of the equivalent-particle theory [2],[4], performs exchange of energy between two waveguides by transfer of solitons. The scanner, on the other hand, makes use of a tapered nonlinear slab which terminates in a nonlinear medium. A spatial soliton excited in the thinner (output) end can follow different routes depending on the power and relative phase of aTE1beam which is added as a probe to the mainTE0input mode.
Properties of input nonlinear grating couplers
Authors: Yokota Mitsuhiro
Published: February 2023

Recently, nonlinear guided-optical phenomena have attracted the attention of many workers to establish the all-optical signal processing. As one of the nonlinear media, the Kerr-type medium whose refractive index depends on the light intensity is usually used. This medium shows the interesting phenomena such as self-focusing, generation of self-phase modulation and optical bistability [1], [2]. The grating couplers are one of the most important elements for the optical integrated circuits. Under some approximations, the mode conversions [3], the beam scanner [4], [5] and the optical bistability [6], [7] are examined. For the more complete interpretation of the properties of the nonlinear grating couplers, the precise analysis is needed.
Nonlinear Directional Coupler with Externally Controlled Grating
Authors: Weinert-Rączka Ewa
Published: February 2023

The efficient power exchange between waveguides in a directional coupler occurs when the propagation constants of their guided modes are equal. The coupling between nonidentical waveguides can be accomplished with the help of a power dependence of the propagation constant in a nonlinear waveguide. For low energies phase matching of different waveguides modes can be obtained with the help of a grating formed by a periodic perturbations of the refractive index [1,5]. The gratings in so called Grating-Assisted Couplers are usually formed during a fabrication process and have constant, immutable parameters.
Theory of The Active Nonlinear Coupler Laser
Authors: Walton Donnell T. , Winful Herbert G.
Published: February 2023

In a recent paper we proposed a mode locking scheme based on an active nonlinear directional coupler.1 This scheme relies on the saturable absorber-like action of a nonlinear coupler along with the soliton shaping and amplification effects that occur in an erbium doped fiber laser. Pulses shorter than 100 fs were shown to be feasible in a simple dual-core fiber geometry. Since erbium fiber lasers operate in the negative group velocity dispersion regime, the formation of soliton-like pulses in this system is not unexpected. For fiber lasers with positive group velocity dispersion, the creation of solitary pulses without the benefit of dispersion compensation is not obvious. This work, then, has two objectives: to show that the active nonlinear coupler laser is capable of creating soliton-like pulses even in the positive GVD regime, and to extend the model of the laser in the negative group velocity dispersion regime to include the effects necessary for pulse durations shorter than 100 fs.
NL-FDTD Modeling of Linear and Nonlinear Corrugated Waveguidess
Authors: Ziolkowski Richard W. , Judkins Justin B.
Published: February 2023

With the continuing and heightened interest in linear and nonlinear semiconductor and optically integrated devices, more accurate and realistic numerical simulations of these devices and systems are in demand. Such calculations provide a testbed in which one can investigate new basic and engineering concepts, materials, and device configurations before they are fabricated. The time from device conceptualization to fabrication and testing should therefore be enormously improved with numerical simulations that incorporate more realistic models of the linear and nonlinear material responses and the actual device geometries. It is felt that vector and higher dimensional properties of Maxwell’s equations that are not currently included in existing scalar models, in addition to more detailed materials models, may significantly impact the scientific and engineering results.
Brillouin Gain Spectrum Measurements using a Single Laser Source
Authors: Niklès Marc , Thévenaz Luc , Robert Philippe
Published: February 2023

Stimulated Brillouin scattering (SBS) is a non-linear process that occurs in optical fibres at much lower pump power than most other non-linear effects. The pump wave is scattered into a backward-propagating Stokes wave that experiences a frequency shift lying in the 12-13 GHz range at 1300 nm. This shift is proportional to the acoustic velocity within the fibre, making SBS an efficient tool for sensing applications, e.g. for monitoring strains in installed fibres [1].
Soliton Pulse Train Generated by Integrated All Optical Fibre Technique Using Comblike Dispersion Profiled Fibre
Authors: Chernikov S. V. , Kashyap R. , Taylor J. R.
Published: February 2023

Generation of optical pulses at repetition rates in 10s-100s GHz range beyond the limits of conventional electronics can be achieved using all optical passive techniques. Here, we report a 60 GHz soliton pulse source utilizing all optical fibre technology. The principle of operation is based on the use of dual frequency beating as a source of periodic optical signal and the transformation of the beat half-periods into optical pulses using nonlinear propagation in a novel optical fibre design which we call a Comblike Dispersion Profiled Fibre (CDPF). This fibre consists of many alternating segments of two fibre types with high anomalous dispersion and minimum absolute dispersion at the operational wavelength. In fact, the dispersion-length profile of this fibre has a comb-like shape. Previously, transformation of the optical beat signal into pulse train was demonstrated in a Dispersion Decreasing Fibre (DDF) [1]. However, the implementation of CDPF has a number of advantages: CDPF can provide significant suppression of Stimulated Brillouin Scattering (SBS) enabling the use of a narrow linewidth, low phase noise beat signal; it can provide pulse train generation over a much wider range of repetition rates and a reduction of the necessary input power; and a CDPF can be accurately produced with in advance determined properties using conventional standard types of optical fibres - Standard Telecommunication (STF) and Dispersion Shifted Fibres (DSF) and thus does not require any special technology.
Stepwise Dispersion Profiling of Periodically Amplified Soliton Systems
Authors: Forysiak W , Doran NJ
Published: February 2023

Stable soliton propagation over many amplification periods, as currently envisaged for future communication systems, requires the soliton period, zo to be a few times the amplifier spacing, za [1,2]. This condition arises because the fibre loss removes the continuous balance between group velocity dispersion (GVD) and self phase modulation (SPM), normally associated with the nonlinear Schrodinger equation, introducing a periodic perturbation to the propagating solitons. As zo approaches za, the magnitude of these perturbations increases, setting limits on the admissible pulse width and corresponding data capacity. The results presented here consider the potential application of stepwise dispersion profiling to minimise these perturbations. We derive a simple scheme for optimal profiling and demonstrate numerically that it allows average soliton propagation beyond the usually accepted limits.
Optical Double Layers
Authors: Kivshar Yuri S. , Turitsyn Sergei K.
Published: February 2023

As is well known, the stimulated Raman scattering (SRS) in nonlinear optical fibers precludes the existence of stable solitary waves both of bright and dark soliton types. For bright solitons, the SRS effect can affect the temporal evolution even for pulses as wide as a few picoseconds causing a continuous frequency down shift1,2. For dark solitons, the SRS effect leads to a soliton acceleration with a subsequent decay3,4. However, new regimes of nonlinear wave dynamics may be expected to exist in the presence of the SRS effect, e.g., propagation of shock waves or kinks3,5. The nonlinear wave in the form of a kink may be treated as a particular case of a shock corresponding to a jump between two uniform background waves having different amplitudes of the envelopes. As a matter of fact, such a type of nonlinear waves is known in plasma physics as a double layer6,7.
Off-axis pulse propagation in a gradient index medium with Kerr nonlinearity — a variational approach
Authors: Lai Yinchieh , Chien Chih-Hung , Wang Jyhpyng
Published: February 2023

A gradient index medium is a medium with a parabolic refractive index distribution: Here G is the index gradient constant and the axis is in the z-direction. A recent analysis[1] by one of the authors (J. Wang) and his student has shown that continuously adjustable negative group-velocity dispersion up to hundreds of square femtoseconds can be produced by propagating the optical beam off the axis of a gradient index medium (see Figure 1). The idea is that the dispersion caused by the frequency dependence of G(ω) (the index gradient dispersion) is of a different sign compared to the dispersion caused by the frequency dependence of no(ω) (the material dispersion, usually positive). The net effect of index gradient dispersion is proportional to the square of the offset distance from the beam center to the axis, as can be guessed from the form of equation (1). Therefore, by off-axis propagating the light with a big enough offset, the net dispersion can be made negative. In a subsequent paper[2] they further show that optical solitons in a broad spectral range can be produced by such off-axis propagation after taking into account the Kerr nonlinearity. In the present paper we develop a variational approach to study the general off-axis pulse propagation problem in a gradient index medium with Kerr nonlinearity. Compared to the method used in Ref[1,2], our variational approach has the advantages of being more general and more physically clear. Simple expressions that describe the existence criteria and properties of this new type of solitons are obtained.
Self-guided Waves – Bright and Dark
Authors: Poladian L. , Mitchell D.J. , Snyder A.W.
Published: February 2023

A self-guided wave (or spatial solitary wave) propagates without diffraction in an homogeneous nonlinear medium because the tendency to diffract is balanced by containment due to the nonlinearly induced refractive index change.1,2 We have developed a simple method for understanding the conditions under which self-guided waves can exist and their qualitative properties. We emphasize that the results obtained here for self-guided waves apply to homogeneous media with any arbitrary intensity dependent nonlinearity, not just to Kerr law media.
Polarization Dynamics of Pulse Formation in a Passive Fiber Ring Cavity
Authors: Haelterman M. , Trillo S. , Wabnitz S.
Published: February 2023

In nonlinear fiber optics scalar modulational instability (MI) gain in the anomalous dispersion regime has been exploited to compensate for the losses in a sinch-pumped passive ring cavity in order to have lasing action [1]. MI in dissipative systems such as lasers is indeed a general mechanism for the generation of stable pulse trains [2]. Morover, in a sufficiently detuned cavity the domain of Mi-induced pulse formation extends to the normal dispersion [3]. In this work we show that removing the scalar approximation (i.e., including in the description the state of polarization of the field) leads to new phenomena such as cw multistability and a new kind of MI where the polarization of the growing sidebands is orthogonal to the pump. Our approach allows us to predict and characterize a rich variety of behaviors including cw polarization switching, the emission of stable pulse trains with different polarization, and chaos.
Harmonic Partitioning of a colliding pulse modelocked erbium fiber laser cavity for the generation of high repetition rate pulse trains
Authors: Fermann M. E. , Stock M. L. , Yang L. -M. , Andrejco M. J. , Harter D.
Published: February 2023

Passively modelocked fiber lasers[1-3] are a potentially very attractive source of ultrashort pulses for ultra-high bit rate communications. However, despite the large variety of suggested cavity configurations, passively modelocked fiber lasers have to date been limited to operation at low repetition rates. The reason is the low gain cross section of rare-earth doped fibers and their tendency to energy loss via cross relaxations at high rare-earth doping levels. As a result useful active fiber lengths are typically not shorter than about 1 m for the case of erbium ions4 (neodymium fibers can be substantially shorter, but fiber lengths shorter than 1 m are still uncommon due to handling difficulties). Thus passive mode-locking in fibers at the fundamental cavity frequency is typically limited to about 100 MHz. Higher repetition rates may in principle be obtained by the insertion of sub-cavities5; however, the laser then becomes sensitive to phase fluctuations between the major and the sub-cavity, which makes stable operation nearly impossible. Therefore, to date, higher-harmonic modelocking was only possible by resorting to active modulating schemes, which are phase insensitive and hence can provide stable pulse trains at repetition rates up to a few GHz.
Optical Beat Signal Switching in a Nonlinear Fibre Loop Mirror.
Authors: Chernikov S.V. , Taylor J.R.
Published: February 2023

A nonlinear fibre loop mirror [1, 2] (NFLM) has recently been paid considerable attention as a fast optical switch for various applications. The use of the NFLM for optical signal processing [1-4], for optical pulse shaping [5] and in passively mode locked fibre lasers [6] have been demonstrated. In this paper , we investigate generation of a pulse train relaying on switching of a dual frequency optical beat signal in the NFLM. The idea of pulse train generation through optical beating is based on reshaping the half-periods of the sinusoidal beat signal into well-separated pulses [7]. The reshaping was previously achieved using nonlinear propagation in an optical fibre influenced by "slow" amplification or dispersion decreasing along the fibre length [8], or, alternatively, by exploiting the soliton Raman self-scattering effect [9]. Here, we demonstrate theoretically and experimentally how the nonlinear switching characteristics of the NFLM in conjuction with a dispersion delay line can provide a mechanism for the transformation of a beat signal into a train of well separated transform-limited pulses at multigigabit/s repetition rates.
Dark spatial solitons for guiding light by light using thermal non-linearities in slab waveguides
Authors: Luther-Davies Barry , Yang Xiaoping , Fotheringham David , Krolikowski Weislaw , Woodruff Maneerat , Samoc Anna , Samoc Marek
Published: February 2023

Previous work 1 has shown that it is possible to use dark spatial solitons to write reconfigurable waveguides in self-defocussing non-linear media.
Thermally Stable NLO Polymers Based on Thermal Crosslinking
Authors: Shi Yongqiang , Steier William H. , Chen Mai , Dalton Larry R. , Yu Luping
Published: February 2023

The relaxation of the dipole alignment over time and particularly at elevated temperatures of electric field poled second order NLO organic materials is one of the problems facing this technology. The limited temperature range makes it difficult to process the material into devices and difficult to package the devices into circuits. The prospects for hybrid circuits of combined semiconductor and organic devices on semiconductor substrates are promising but will require organic materials with improved thermal stability.
Nonlinear Polarizabilities of Symmetric and Non-symmetric Polyene and Cyanine-Like Organic Molecules
Authors: Perry J. W. , Marder S. R. , Cheng L.-T. , Bourhill G. , Mansour Kamjou , Gorman C. B. , Gilmour S. , Tiemann B. G.
Published: February 2023

There is considerable interest in understanding the origin of the molecular nonlinear polarizabilities. Recently, the important role of bond alternation (difference in the carbon-carbon double bond and single bond lengths) in influencing the second order polarizability, β, of asymmetric conjugated dyes has been pointed out.[1] It was suggested that there is an optimal degree of alternation needed to maximize β. The connection between bond-alternation and the electronic, optical and chemical properties of conjugated molecules has also been recognized previously.[2] These studies as well as the results of prior experimental studies[3] have led us to investigate the affect of bond alternation on the third-order polarizability, γ. One aim of the present work is to gain insight into the differences between the magnitude and signs of γ for simple polyenes and cyanines. For moderate length to long polyenes, nonresonant electronic γ is positive, whereas for comparable cyanines γ is negative.
Fluorescence Seeding of Stimulated Raman Scattering in Microdroplets
Authors: Kwok Alfred S. , Chang Richard K.
Published: February 2023

Simulated Raman scattering (SRS), in the absence of external seeding, builds up from spontaneous Raman noise. When the pump-laser pulsewidth is much longer than the dephasing time of the vibrational relaxation, the SRS spectrum is dominated by the vibrational mode with the maximum Raman gain. The depletion of the input-laser intensity by the SRS-buildup of the Raman mode with the largest gain prevents the SRS-buildup of other Raman modes with weaker gain. Selective feedback in a two-mirror resonator geometry was used to enhance the growth of SRS of the weaker 801 cm1 mode of cyclohexane in an optical cell by lowering the feedback for the strong 2929 cm–1 mode. In a Raman gain experiment, a Raman amplifier is used to amplify a weak seeding beam generated by a Raman oscillator or a tunable laser.
Cascading of χ(2) for χ(3) Nonlinearities
Authors: Van Stryland E.W. , Stegeman G. , DeSalvo R. , Hagan D.J. , Sheik-Bahae M.
Published: February 2023

The cascading of second order nonlinearities (χ(2): χ(2) to induce a nonlinear phase distortion on the input beam has recently received considerable attention[1,2] We estimate that materials with large second order nonlinearities (≃102 pm/V) will give rise to effective nonlinear refractive indices,

n
2

eff

, of 10–12 to 10–10 esu. These nonlinearities are truly nonresonant and can be in a lossless spectral region (i.e. loss determined by impurities and defects). An important difference between this nonlinearity and a true χ(3) nonlinearity is that the sign is readily changed by, for example, changing the phase matching condition.
Application Specific Self Electro-optic Effect Devices
Authors: Lentine Anthony L.
Published: February 2023

A few years ago, the predominant area of research in optical computing devices was to try to develop devices that could behave as optical logic gates or more specifically NOR gates. In theory, one could optically interconnect these NOR gates to implement arbitrary digital functions and ultimately a digital optical computer. Bistable devices based on non-linear optical materials in Fabry-Perot etalons were among those proposed, for these NOR gates [1,2] A variety of optoelectronic devices have also been investigated. One group of devices called self electro-optic effect devices (SEEDs) rely on changes in the optical absorption that can be induced by changes in an electric field perpendicular to the thin semiconductor layers in quantum well material [3,4]. If we place the quantum well material in the intrinsic region of a reverse biased diode, then as we apply a voltage across the diode we can change its absorption. We can also use the same device as a detector, generating photocurrent in response to an incident light beam. In a SF.FD, the photocurrent generated by one or more of these detectors causes the voltage to change across one or more modulators. Thus, a SEED has optical inputs for controlling optical outputs. One particularly useful device, the symmetric SEED (S-SEED) [5] consists of two of these quantum well p-i-n modulator/detector diodes connected electrically in series. It has the inherent characteristics of a set-reset latch, but can also do logic functions (such as NOR) by using a preset beam. It uses pairs of complementary optical signals, so it is insensitive to optical power supply fluctuations and operates with a wide dynamic range (1 nW - 500 μW). Uniform arrays of devices with as many as 32768 S-SEEDs have been made [6] and several system demonstrations have now been built using these devices [7].
Single-Shot Measurement of the Intensity and Phase of a Femtosecond Pulse Using the Optical-Kerr Effect
Authors: Kane Daniel J. , Trebino Rick
Published: February 2023

We report and demonstrate the first technique for measuring the full, time-dependent intensity and phase, E(t), of an individual femtosecond pulse. This new technique, which we call “frequency-resolved optical gating” (FROG), uses the polarization-spectroscopy optical-gate arrangement with an instantaneously responding χ(3) sample medium, such as glass. Here, however, the pulse is split and one version of the pulse gates the other (see Figs. 1 and 2). We then measure the signal spectrum as a function of the delay between the two input pulses. Because the signal pulse is shorter than the input pulses (by a factor of √3 for Gaussian pulses), the signal pulse reveals, for a given delay, the frequency of a particular temporal component of the ultrashort pulse (See Fig. 2). For reasonably well-behaved pulses, the output plot of signal intensity vs. frequency and delay graphically displays the pulse instantaneous frequency vs. time (See Fig. 3). More importantly, inversion of ω(t) to obtain t(ω), followed by integration of this result, yields the phase vs. frequency, φ(ω). In conjunction with the pulse spectrum, I(ω), which is also naturally obtained in FROG, this result yields the full amplitude and phase of the pulse field in the frequency domain, E(ω). Simple Fourier transformation yields E(t). We have demonstrated the method using a microscope slide as a nonlinear medium and ~620-nm, ~200- μJ, nearly transform-limited ~100-fsec pulses and ~200-fsec chirped pulses.
Analysis of Transient Beam Fanning in Photorefractive Media
Authors: Banerjee Partha P. , Liu Jaw-Jueh
Published: February 2023

Photo-induced light scattering in photorefractive materials has been extensively studied due to the wide variety of applications that utilize this effect, such as optical limiters, self-pumped phase conjugate mirrors, unidirectional ring oscillators and bistable optical devices [1-4].
Nonlinear Optical Properties of a novel organic crystal: 2-Furyl Methacrylic Anhydride (FMA)
Authors: Horinouchi S. , Kinoshita T. , Sasaki K. , Okamoto T. , Tanaka N. , Fukawa T. , Goto M.
Published: February 2023

We report a new organic nonlinear optical crystal, 2-Furyl Methacrylic Anhydride (FMA). Fig.1 shows the molecular structure of FMA. The crystal, whose cut-off wavelength is located at about 380nm, is almost transparent in visible region. The refractive indices were measured by employing Brewster angle method. One of second harmonic generation (SHG) coefficients, d33, was determined by Maker fringe method.
Refractive Indices and Dielectric Properties of Deuterated Zinc Tris Thiourea Sulfate
Authors: Zelmon David E. , Ramabadran Uma B. , Hopkins F. Kenneth
Published: February 2023

Semiorganic materials have recently become the subject of extensive research because of their potential for applications for nonlinear optical devices. Among the recently descovered materials are allyl thiourea cadmium chloride, thiosemicarbazide cadmium chloride, and zinc tris thiourea sulfate. Knowledge of the linear optical properties of these materials, such as the refractive index and dielectric constant, is necessary to determine their relative merit for optical applications such as frequency conversion and electro-optic devices. We report measurements of the spectral dependence of the refractive indices and temperature and frequency dependence of the dielectric constant for deuterated zinc tris thiourea sulfate (d-ZTS).
Recent Progress in Measurement of Molecular Hyperpolarizabilities
Authors: Moylan Christopher R. , Twieg Robert J. , Miller Robert D.
Published: February 2023

Progress towards working polymer-based optoelectronic devices must include progress in chromophore design and characterization. In this work, several dozen organic compounds have been specially designed and synthesized, and their hyperpolarizabilities (β) have been measured by electric field-induced second harmonic generation (EFISH). The compounds were designed not only so that their β values would be sufficient, but also so that they would be thermally stable if incorporated into polymer matrices, and so that they would not absorb too far into the red. Naturally, there are tradeoffs between these characteristics. A simple figure of merit, μβ0/λmax (where λmax is the peak absorption wavelength), is used to account at least in part for the nonlincarity/transparcncy tradeoff. Comparison of the molecular structures of chromophores and well-known thermally robust polymers is used to estimate the thermal stability of both guest/host and chemically bonded systems.
Evaluation of Nonlinear Optical Host-Guest Systems with Long Lifetime
Authors: Suzuki A. , Matsuoka Y. , Kitahara Y. , Ikushima A. J.
Published: February 2023

Host-guest systems which consist of transparent polymer matrices and optical nonlinear active molecules, are one of the key materials for optical nonlinear devices. For practical use, the materials should have both large nonlinearity and long lifetime. Such host-guest systems, made of poly-acrylamide derivatives and p-nitroaniline, have been developed in the group of present authors1). The lifetimes at room temperature are expected to be more than several 10 years, as were estimated from the changes in nonlinear susceptibility over 180 days. Such a conventional evaluation might not be sufficiently accurate for long lifetime materials, because the lifetime is 10~1000 times longer than the ordinary available experimental period. In this paper we estimated the lifetime at room temperature from the Arrhenius plot based on the lifetime data at elevated temperature. This method seems to be more accurate and timesaving than the conventional one.
The Linear and Nonlinear Optical Properties of the Organic Material (+)2-(α-methylbenzylamino)-5-nitropyridine (MBA-NP)
Authors: Bourhill G. , Cruickshank F. , Pugh D. , Simpson G. , Sherwood J. , Bailey R. , Wilkie S.
Published: February 2023

Nitropyridine derivatives have long been known as potential materials for nonlinear optical applications [1]. The chiral molecule (+)2-(α-methylbenzylamino)-5-nitropyridine (MBA-NP) was identified as a promising material by the powder technique [2]. MBA-NP possessed a powder efficiency 20 times that of a urea reference when the fundamental wavelength was 1064 nm. This value is in good agreement with that reported by other authors [3].
Multilayer, Nonlinear Arrow Waveguides for Surface Emitted Sum-Frequency Mixing
Authors: Normandin R. , Dai H. , Janz S. , Delage A. , Brown J. , Chatenoud F.
Published: February 2023

When used with conventional communication optical fibers, with a typical core diameter of 8µm, conventional channel waveguides geometries need to present similar thicknesses for good mode overlaps between the two. This has been a difficult goal to achieve with semiconductor waveguides due to their high index of refraction. The waveguides were typically much thinner than the fiber core and, consequently, input efficiencies were quite low. This problem was addressed some time ago with the demonstration of the antiresonant reflecting waveguide (ARROW) geometry(1). Although these are intrinsically leaky waveguides quite acceptable losses were feasible in silicon(2) and GaAs(3) geometries. On the other hand when dealing with nonlinear interactions in semiconductor waveguides, it was realised quickly that in other to maintain acceptable overall efficiencies the waveguide thickness had to be kept unreasonably small (4). This obviously led to input coupling difficulties. In our previous work, presented two years ago at this topical meeting (5), we demonstrated a new multilayer AIGaAs waveguide geometry with surface harmonic emission efficiencies well above what was possible in uniform films. This led to the development of several devices (6,7) such as correlators, spectrometers and intracavity diode laser second harmonic generators(8). However, little attention has been given to the problem of fiber input coupling to the nonlinear waveguide. We present the first results, to our knowledge, of multi-layer core ARROW waveguides and their use in nonlinear harmonic generation. There has been little mention of the ARROW geometry in a nonlinear context, with the recent exception of inter-guide coupling(9), since they tend to be thick guiding structures.
Crosstalk and Error Probability in Counter-Beam λ-Multiplexed Digital Holograms
Authors: Yariv A. , Glasser Lance , Rakuljic George , Leyva Victor
Published: February 2023

The recently proposed method for wavelength multiplexed holograms(1) raises the fundamental issues of crosstalk and error probability in such holograms. As a result we pose the following question: A crystal with N stored λ-holograms is illuminated with, say, λ1 in order to project out (read) hologram #1.
Orientation dependence of the picosecond nonlinear optical signals in KTa1-xNbxO3 crystals.
Authors: Liu Huimin , Reeves Roger J. , Powell Richard C. , Boatner L. A.
Published: February 2023

The mixed-crystal system of KTa1-xNbxO3 (KTN) has been the subject of. numerous laser studies due to its promise as a nonlinear optical material. However, the optical properties of KTN crystals change with composition due to different structural phases. As the niobium concentration x increases from 0 (KTaO3) to 1 (KNbO3) the perovskite-structure of KTN undergoes a phase transition from a cubic paraelectric phase to the tetragonal and orthorhombic ferroelectric phases.1-6 Experimental data on these structural changes support a model where the Ta,Nb ions are displaced from central positions in the octahedron of oxygen ions to one of eight equivalent positions along the cube diagonals. The different structural phases are a consequence of the preferential occupation of a certain set of sites by the Ta,Nb ions.1-6