bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Assessment of Single Crystal Fibres
Authors: Sinclair A G , Ruddock I S , Illingworth R
Published: February 2023

Single crystal fibres are grown by the Laser Heated Miniature Pedestal Growth technique [1] in lengths of up to ~ 50mm and with diameters in the range 50-500 μm. By this method, doped fibres, for example Cr3+ and Ti3+ in sapphire (alumina) for use in solid-state lasers or fibres of various nonlinear crystals may be produced. For laser action to be possible or for a fibre to be used in an optoelectronic device, there are several requirements to be met:-

(i) the fibre diameter and cross-section must be uniform,

(ii) the direction of the optic axis in an anisotropic crystal should be known,

(iii) the fibre ends should be flat and preferably normal to the fibre axis,

(iv) the fibre surface should be smooth so as to minimise scattering losses, and

(v) for a fibre to be incorporated into a laser cavity a polarised Gaussian beam entering the fibre at one end must emerge from the other as a Gaussian beam of a known state of polarisation.
Error Sources and Performance Limits in Digital Holographic Data Storage
Authors: Heanue John F. , Daiber Andrew , Snyder Ray , Colvin James , Bashaw Matthew C. , Hesselink L.
Published: February 2023

Starting with the work of van Heerden1, many estimates of the potential storage capacity of a holographic data storage system have been made. While some effort has been made to theoretically predict2–3 and to measure4–5 the practical limits imposed by noise sources, most results deal with fundamental limits imposed by the finite spatial frequency resolution of the recording medium and the optical system. We are interested in characterizing the noise statistics in a typical holographic storage system and using these statistics to predict the ultimate limits on system performance. Toward this end, we have developed theoretical models to describe several fundamental noise sources. These models are used to predict limits on the storage capacity and transfer rate achievable in a practical device. We have constructed an experimental system that is used to obtain data on bit-error-rate performance and to verify theoretical predictions. Finally, we are using the experimental system to develop efficient techniques for overcoming noise sources so that we can achieve performance closer to the theoretical limits.
Optical correlation of phase- and amplitude-encoded objects using wavelength-multiplexed holographic storage elements
Authors: Sayano Koichi , Zhao Feng
Published: February 2023

Optical image correlation has been demonstrated for recognition of patterns and images by comparing against stored reference filters corresponding to known images. Optical implementation of this operation is highly desirable because image correlation can be generated in an analog fashion using common optical elements, providing considerable speed advantages over digital computation. Spatial light modulators have been used as the filters in a vanderLugt correlator configuration, but low throughput and slow download times, particularly for a large number high resolution images, were major drawbacks. Using a wavelength multiplexed holographic element for storage of the reference image filters provides increased access speed, and the recent availability of visible wavelength, tunable external cavity semiconductor lasers, wavelength multiplexing becomes practical. In this paper, we report on an optical image correlation system using a holographic storage element for fast access speed and translation tolerance. Amplitude and phase encoded transparencies, as well as spatial light modulators, were used as the input image sources.
Off-Bragg Analysis of Diffraction Efficiency of Photorefractive Holograms
Authors: Nonaka Koutarou
Published: February 2023

A photorefractive medium is widely used for multiplexed holographic recording1. Although the diffraction properties for off-Bragg conditions are important in evaluating cross-talk noise and wavelength and angular sensitivities for multiplexed holographic recording, most previous analyses have focused on the on-Bragg readout conditions. In a photorefractive medium, a photorefractive phase shift and fringe bending effect2 appear within the medium. These phenomena make off-Bragg analysis for photorefractive hologram gratings very difficult. Consequently, off-Bragg analysis has been reported only for special cases3. A numerical calculation for the off-Bragg condition has also been reported4, but an analytical formula for calculating the diffraction efficiency for the off-Bragg condition is essential in order to easily evaluate the cross-talk noise and wavelength and angular sensitivities for the multiplexed holographic recording.
Theory of Two-Species Transport in Photorefractive Crystals Using Two Wavelengths for Nondestructive Readout
Authors: Liu A. Y. , Bashaw M. C. , Paraschis L. , Hesselink L.
Published: February 2023

Holographic storage offers many advantages over conventional storage methods, however, readout of information cannot be made non-destructive without special fixing procedures, such as thermal and electrical fixing. Several other techniques enabling non-destructive readout of information have been investigated, including two-photon recording in singe species crystals[1], and sensitizing with a short wavelength and recording and reading with a long wavelength with two species[2,3]. The last method has the advantage of allowing each species to be chosen, so that the photorefractive properties can be optimized while retaining the information during readout.
Form-stable pulse propagation in 3-level media: adiabatons and matched pulses
Authors: Fleischhauer Michael
Published: February 2023

The resonant interaction of pulse-pairs with multi-level atoms has attracted some attention in recent time because of the possibility of a quasi-loss-free propagation in otherwize optically thick media. The pulse-pair propagation in Λ-type atoms as shown in Figs. 1 is here discussed in terms of the adiabatic coupled and decoupled superpositions of the lower levels.
Experimental Progress in Cascading Nonlinear Optics
Authors: Stegeman G.I. , Torruellas W.E. , Schiek R. , Lawrence B. , Fuerst R. , Baek Y. , Trevino-Palacios C. , Baboiu D. , Baumann I. , Sohler W. , Assanto G. , Torner L. , Baldi P. , De Micheli M. , Ostrowsky D.B.
Published: February 2023

Cascading refers to phenomena associated with the multiple interchange of photons between beams which interact parametrically via second order nonlinearities. [1] Although second harmonic generation (SHG) is the most common example, it also involves sum and difference frequency mixing, optical parametric amplification etc. It has been known since the early days of nonlinear optics that two successive second order interactions can contribute to a third order nonlinearity via χ(2)ijkχ(2)kmn ➔χ(2)ijmn(effective) [2,3] We have found that the effects are more subtle than this and they can give rise to many interesting effects in nonlinear optics. They are essentially of two types, one based on the nonlinear phase shift accumulated by the fundamental beam on transmission through a second order medium and the second is a consequence of the strong coupling which occurs at high intensities between the fundamental and harmonic beams. The second leads to the generation of spatial solitary waves. [4] Here we discuss our progress in studying these effects.
Ultrashort-pulse generation in the ultraviolet using ionization-induced harmonic generation
Authors: Kapteyn H.C. , Backus S. , Peatross J. , Zeek E. , Read K. , Murnane M.M.
Published: February 2023

In recent work, we have demonstrated that ionization-induced harmonic generation in gasses is a useful source of very short duration pulses in the ultraviolet and vacuum ultraviolet. Using millijoule-energy, 25 fs driving pulses at 800 nm wavelength, we can obtain a third harmonic pulse duration of under 16 fs, measured using the technique of self-diffraction frequency resolved optical gating. Microjoule pulse energy and milliwatt average power can be produced, and the conversion efficiency can be optimized by adjusting the chirp of the input pulse.
Third-Harmonic Generation in a Plasma of Self-Induced Optical Breakdown in Air Using 80-fs Laser Pulses: Self-Action of Light Beams and Spectral Broadening
Authors: Fedotov A. B. , Loy M. M. T. , Xiao X. , Krylov V. N. , Rebane A. K. , Koroteev N. I. , Zheltikov A. M.
Published: February 2023

Recently, much attention has been focused on the generation of high-order harmonics using high-power laser pulses. Optical harmonics of extremely high orders were detected in experiments using high-power ultrashort laser pulses focused into rare-gas jets [1 - 4]. For the most part, experiments on harmonic generation both in rare gases [1 - 4] and in a laser-produced plasma [5 - 12] use pulsed high-power systems. First experiments on third-harmonic generation at a high repetition rate, which used 1-kHz laser pulses with a duration of 200 fs, demonstrated that the efficiency of third-harmonic generation (THG) in a plasma of self-induced optical breakdown can be as high as 7*10-4 [13].
Nonlinear Optics of Nanostructured Materials: Fractal Nanocomposites and Self-Affine Surfaces
Authors: Shalaev Vladimir M. , Mercer J. , Safonov V. P. , Botet R.
Published: February 2023

Optical phenomena experience a giant enhancement in metal nanocomposites and rough thin films consisting of small nm-sized particles and roughness features, respectively. The enhancement is associated with excitation of surface plasmons which are collective modes and strongly depend on the morphology (geometrical structure) of the material. Fractal structures are prevalent in composites and cold-deposited thin films. The emergence of fractal geometry was a significant breakthrough in the description of irregularity. Fractal objects do not possess translational invariance and, therefore, cannot transmit running waves. Accordingly, collective excitations, such as surface plasmons, tend to be localized in fractals [1,2]. Formally, this is a consequence of the fact that plane running waves are not eigenfunctions of the operator of dilation symmetry characterizing fractals.
Chirality in Nonlinear Optics
Authors: Verbiest Thierry , Kauranen Martti , Maki Jeffery J. , Persoons André
Published: February 2023

Second-harmonic generation (SHG) can be used to study the chiral properties of isotropic thin films1. The efficiency of SHG is highly dependent on the handedness of incoming circularly-polarized light. This phenomenon is referred to as nonlinear optical activity. In addition, linearly-polarized fundamental light can also be used as a probe of chirality. Recently, we showed experimentally that the second-harmonic efficiency is different upon radiation with fundamental light that is linearly-polarized -45° and +45° with respect to the p-polarized direction2. We also developed a theory of SHG from isotropic chiral surfaces that includes contributions of electric- and magnetic-dipole transitions to the surface nonlinearity3.
Femtosecond to nanosecond dynamics in C60: implications for excited-state nonlinearities
Authors: McBranch D. , Klimov V. , Smilowitz L. , Robinson J. M. , Koskelo A. , Grigorova M. , Mattes B. R.
Published: February 2023

Recently, many studies have emerged on optical power limiting (OL) in buckminsterfullerene (C60).1 OL occurs when the absolute transmittance of a material decreases with increasing laser fluence; in C60, the dominant mechanism for OL is reverse saturable absorption (RSA), in which the absorption cross section from excited-state electronic energy levels is significantly higher than the ground state absorption cross section. For limiting of nanosecond pulses, the lifetime of the excited-state responsible for the nonlinear absorption is a crucial parameter. In this work, we provide a detailed study of the relaxation dynamics of the excited-state absorption for C60 in toluene solution, as a thin solid film, and entrapped within an inorganic sol-gel glass matrix. Our results demonstrate that the microscopic morphology of the C60 molecule plays a crucial role in determining the relaxation dynamics. We find that the dynamics of the C60-glass composite occur on long (ns) timescales, comparable to those in solution; thin film samples, by contrast, show rapid decay (<20 picoseconds). Combined with intensity-dependent transmission measurements on the same samples, these results demonstrate that the C60/sol-gel glass composites contain C60 in a molecular dispersion, and are suitable candidates for solid-state optical limiting.
Enhancement of Second-Order Optical Nonlinearity by Supramolecular Engineering
Authors: Kauranen Martti , Verbiest Thierry , Boutton Carlo , Houbrechts Stephan , Persoons André , Samyn Celest
Published: February 2023

Only noncentrosymmetric molecules can possess a second-order nonlinear response, i.e., they have a nonvanishing first molecular hyperpolarizability. Polar molecules with donor and acceptor groups connected by a conjugated π electron system are traditional organic second-order materials. For macroscopic noncentrosymmetry, such molecules are incorporated in, e.g., a polymer host and poled with a static electric field. The nonlinear coefficients of poled materials are proportional to the product μβ where p is the permanent dipole moment of the molecules and β is the vectorial part of the first hyperpolarizability [1].
Vertical couplers: all-optical switch design
Authors: Geatches Rachel M , Dewar Susan V , Penty Richard V
Published: February 2023

Nonlinear directional couplers (NLDCs) have been shown to have great potential as the basis for all-optical switching devices (reviewed, for example by Agrawal and Boyd [1]). The potential for nonlinear switching has been demonstrated in InGaAsP NLDCs, by utilizing resonant non-linearities near the band gap, i.e., λ = 1.55μm, thereby requiring moderate switching powers [2]. However, the required swiching power is higher than that ideally required for semiconductor laser optical sources and so it is important that this is minimised. Significant reductions in switching power have been predicted in coupled fibers with asymmetric configurations when compared to corresponding symmetric designs [3]. Chen et al also forecast further reductions in switching power by matching gain in one guide to loss in the other. We have studied the design of asymmetric semiconductor couplers, where the coupling is finely balanced, and predict the switching power to be substantially reduced when compared with symmetric designs. These investigations are now being extended to vertical configurations, which are expected to have significant advantages over the more conventional horizontal designs. By adopting a vertical configuration, the waveguiding regions can be realistically closer together, thereby reducing the coupling length, which will allow for a minimum of loss over the distance required for switching. Furthermore, the geometrical asymmetry of the coupler can be maximized, by coupling a planar-guide to a rib-guide. Likewise material asymmetry can be introduced easily into a vertical configuration. Finally, by having the guides in different planes, the doping requirements needed for biasing in order to induce gain (at transparency), can be more easily realised.
Coherent transient in optical lattices: Application to quasi-periodic optical structures
Authors: Guidoni L. , Triché C. , Guibal S. , Verkerk P. , Grynberg G.
Published: February 2023

We present a new method of spectroscopy for atoms cooled and trapped in an optical lattice. This method which makes use of coherent transients permit to improve the signal to noise ratio by more than one order of magnitude by comparison with the previous optical detection methods such as probe transmission or atomic fluorescence [1]. We apply this method to the spectroscopy of cesium atoms first in a four-beam lattice [2] and second in a quasi-periodic structure obtained by adding supplementary incident beams. These structures are strongly connected with the field of quasi-crystals [3] which is very active in solid-state physics. Because of the topological invariance of the optical potential, the same spectra are obtained whatever the phases of the incident beams. Additional information about distribution of atoms among the potential wells can be deduced from the analysis of the coherent transients.
Localization and coupling dynamics in nonlinear waveguide arrays
Authors: Aceves Alejandro B. , Santagiustina Marco
Published: February 2023

Several efforts have been made to study the pulse dynamics in nonlinear waveguide (WG) arrays. Steady-state solutions are known for N-periodic WG arrays [1] and the dynamics of 2-coupled WG’s have been investigated by means of variational methods [2, 3].
Degenerate Backward Optical Parametric Oscillators and Amplifiers: Conversion Efficiencies and Gain Saturation
Authors: Ding Yujie J. , Khurgin Jacob B.
Published: February 2023

Since quasi-phase matching (QPM) was proposed in Ref. [1], there have been many demonstrations [2] of achieving second-harmonic generation (SHG) based on QPM. Recently, due to rapid development of poled nonlinear materials such as LiNbO3, optical parametric oscillators (OPOs) and amplifiers (OPAs) have been intensively studied [3]. In these investigations, the thickness of each domain is usually much larger than the wavelengths of the parametric and pump wave based on QPM. Recently, GaAs/AlGaAs multilayers [4] and asymmetric coupled quantum-well domain structures [5] were used to achieve SHG. Most recently, we proposed transversely-pumped counter-propagating OPOs and OPAs (TPCOPOs and TPCOPAs) based on semiconductor structures [6], which is the reverse process of surface-emitting sum-frequency generation. In this configuration, the parametric waves counter-propagate in a waveguide along the epitaxial layer plane while pump waves propagate along the surface normal. Oscillation can occur without an external feedback. Such a concept was first introduced for nondegenerate backward OPO based on conventional phase-matching [7]. Recently, we investigated the conversion efficiency vs. the pump intensity in this configuration, however, based on QPM [8]. Here, we present our result of the first study of the degenerate backward optical parametric oscillators (DBOPOs) and optical parametric amplifiers (DBOPAs) in a waveguide based on QPM. DBOPO can occur without an external feedback. This is fundamentally different from conventional OPO. A second-order nonlinear optical material consists of many domains in which the adjacent domains have the opposite signs of second-order susceptibilities, but the same magnitude [χ0(2)], see Fig. 1. The spatial period of the domains is l0 = λ0/n0, where n0 is the effective refractive index the domains at the wavelength λ0. A pump wave at the wavelength in vacuum λ0ω = λ0 propagates along the positive z axis and is reflected by a mirror attached to the right-side facet with the reflectivity R2ω. These two counter-propagating pump waves interact with the nonlinear medium. As a result, DBOPOs can occur in the nonlinear medium, i.e. forward and backward parametric waves are generated and propagate along the positive and negative z axes, respectively, see Fig. 1(a).
Chaos stabilization via pulse train generation in dispersive optical parametric oscillators
Authors: Trillo Stefano , Haelterman Marc
Published: February 2023

Optical parametric oscillators (OPOs) are devices of growing importance for several applications [1]. In the degenerate configuration OPOs permit to enhance the conversion between the pump (2ω0, SH) and the subharmonic or fundamental (ω0, FF) fields, both being close to two resonance modes of the cavity. However, cw-operating degenerate OPOs undergo different instabilities, such as bistability and self-pulsing. These instabilities, predicted in the framework of the dispersionless mean field model, give rise to hysteresis and chaotic self-pulsing, respectively [2-4]. In this communication we are aimed at showing that this scenario changes drastically as long as dispersion is included in the mean-field description. In particular dispersion allows for nonlinear phase-matching of nondegenerate processes, which results into a novel instability of the OPO steady-states, namely the build-up of sideband pairs equally detuned (say, by ±Ω) from both the FF and SH carriers. This novel mechanism is analogous to modulational instability recently predicted for cavityless parametric amplification [5]. In the OPO, however, the dissipative nature of the problem favours the stable formation of periodic patterns (i.e., pulse trains) at a repetition rate Ω. The stability analysis reveals that these periodic trains are stable at power much larger than the threshold for the competing chaotic self-pulsing, and hence constitute an intrinsic mechanism of stabilization of the OPO. Moreover the formation of periodic trains via modulational instability turns out to be a preferential mechanism even when the OPO is bistable, or, unexpectedly, even when it operates below the cw threshold for conversion to the subharmonic.
Brillouin-Enhanced-Four-Wave-Mixing Vector Phase Conjugate Mirror
Authors: Bowers M. W. , Boyd R. W. , Hankla A. K.
Published: February 2023

Most laser applications require very good beam quality. Many components in lasers and laser systems can degrade the laser quality below what is acceptable. Optical phase conjugation is one method in which a highly aberrated optical beam can be restored to near diffraction limited quality. Stimulated Brillouin scattering (SBS) is a nonlinear process which can produce a phase conjugated optical wave. Simple SBS phase conjugators typically cannot correct for polarization distortions. Polarization restoration has been accomplished by phase locking orthogonal polarizations together in an SBS cell1,2,3,4. We have designed and tested a new method of polarization restoration which is easy to implement and can passively alter the phase or polarization of the return beam for output coupling.
Generalized Master Equation Models for Kerr Lens Mode-Locking
Authors: Dunlop A. M. , Firth W. J. , Wright E. M.
Published: February 2023

We recently presented [1] the following “master equation” [2] applicable to any nonlinear cavity with linear properties describable by an ABCD matrix and with one nonlinear interaction per round trip: The intra-cavity field E is a function of fast (t) and slow (T) times, as well as

r
→

⊥

, the transverse position vector. ∇⊥ is the transverse gradient operator, and cosψ = S. Here S = (A + D)/2. We have included typical operators for gain and dispersion [2], and so the round-trip time TR is that based on the group velocity. To describe KLM, we specialize the nonlinear function N(E) to the Kerr form N(E) = iη|E|2E, which requires that the ABCD elements be calculated at the Kerr lens.
Effective Suppression of Amplified Spontaneous Emission by SBS Phase Conjugation
Authors: Ni C. K. , Kung A. H.
Published: February 2023

Optical phase conjugation using stimulated Brilluoin scattering (SBS) is widely used in high average power solid state lasers and multipass amplifiers for correction of problems brought on by thermally induced birefringence and depolarization and for pulse compression.1 Multi-kilowatt average power with diffraction-limited beams are now routinely obtained in Nd:YAG laser systems where a SBS mirror is an integral part of the system. The pump lasers used in these systems all have narrow bandwidths, typically <1 GHz. The reason for this is well-known2,3: the SBS threshold for a noisy (multi-frequency) pump is higher than that for a single-longitudinal-mode pump or one with just a few modes. So, in order to obtain high reflectivity for the SBS mirror using minimal power, narrow-bandwidth lasers are used. We have taken note of this property of SBS and explored its utility to solve another important problem in laser amplifiers: the suppression of amplified spontaneous emission.
Quasi-Phasematched Singly Resonant Parametric Oscillation in Periodically-Poled Lithium Niobate Waveguides
Authors: Arbore M. A. , Fejer M. M.
Published: February 2023

Diode-based sources of near or mid-IR radiation are finding applications in communications, spectroscopy, and process monitoring. Nonlinear optical frequency conversion to shift diode laser outputs to the desired wavelength has attracted significant attention as a means to meet these needs. Periodically-poled lithium niobate (PPLN) has proven to be a nonlinear material offering an excellent combination of efficiency, wavelength accessibility, ease of fabrication, reproducibility, and cost. Waveguide geometries significantly increase conversion efficiencies of nonlinear devices by tightly confining the optical fields over long interaction lengths. Combining annealed proton-exchanged (APE) waveguide technology with PPLN allows the application of nonlinear frequency conversion to low power sources.
Influence of Mirror Curvature on Pattern Formation in Nonlinear Optics
Authors: Harkness G. K. , Lega J. , Oppo G.-L.
Published: February 2023

Study of pattern formation in the transverse section of lasers with plane cavity mirrors of infinite size shows that the fundamental solutions are transverse travelling waves [1]. In the case of Optical Parametric Oscillators (OPO), instead, rolls [2] or squares, or hexagons [3] are the fundamental patterns close to threshold. With curved cavity mirrors, however, both cases of lasers and OPO produce outputs which look like a combination of empty cavity modes, generally of Gauss-Laguerre type. These are the most commonly observed experimentally; a typical example of output intensity is shown in Figure 1 for the laser case.
Control of Spatio-Temporal Dynamics in Nonlinear Optics
Authors: Martin R. , Oppo G.-L. , Scroggie A.J. , Firth W.J.
Published: February 2023

The ability to control spatio-temporal dynamics of nonlinear optical systems is of great interest due to the possibilities of obtaining stable outputs without losing essential power and also to achieve pattern selection for information processing purposes.
Comparison of Molecular Hyperpolarizabilities Measured in Gas and Liquid Phases
Authors: Kaatz Philip , Shelton David P.
Published: February 2023

Hyper-Rayleigh Scatttering (HRS) measurements have become an important method for measuring the first hyperpolarizabilities β of organic chromophores [1]. This technique is more flexible and much simpler than the alternative Electric-Field-Induced Second Harmonic Generation (EFISH) method for determining β. However, unresolved difficulties with the absolute calibration of solution EFISH measurements [2] have not been avoided, but only compounded, because the uncertain EFISH values are used to calibrate HRS, and because different combinations of tensor components are measured in the two experiments. Furthermore, HRS signals from liquid phase samples can include large intermolecular contributions [3], which have usually been ignored.
Lasers Without Inversion and Ranman Oscillators Comparative Analysis
Authors: Khurgin Jacob B. , Rosencher Emmanuel
Published: February 2023

In the last few years there has been substantial interest in the lasers capable of operation without inversion (LWI). Numerous schemes have been suggested [1],[2], which, if realized in practice, can expand the range of laser devices in spectral regions where for various reasons inversion is difficult to achieve - among them vacuum UV, using atomic vapors as an active medium, and mid-to-far IR., using intersubband transitions in quantum wells. Until recently, the research has been mostly limited to the theoretical work, but lately there had been a conclusive report of laser oscillation without inversion in Rb [3]. A number of LWI proposals based on intersubband transitions in quantum wells, that seem to be ideally suited for the practical implementation of LWI concept, have also been made.
Resonance and bright-dark solitons in group-velocity mismatched second-harmonic generation
Authors: Trillo Stefano
Published: February 2023

Waves interacting parametrically in quadratic media experience nonlinear phase changes which, under appropriate conditions, may be compensated for by dispersion or diffraction, resulting into mutually trapped (temporal or spatial) solitary envelopes or simultons. Although this trapping was predicted in the seventies [1], it was observed only recently for second-harmonic generation (SHG) in the 3D spatial case [2], motivating renewed interest for applications oriented to all-optical processing. Usually these solitons survive in the presence of moderate walkoff [3]. Here we investigate the opposite case for which the group-velocity difference or walk-off dominates over dispersion (or diffraction). This occurs whenever the beam widths are large enough so that the walkoff length zw is much shorter than dispersion length zd. The purpose of this communication is to show that, in this case, group-velocity difference may be offset by velocity-locking due to new types of solitons. We consider two specific cases of SHG. First, we show that type I bulk SHG, supports only dark-bright pairs whereas bright-bright solutions are not permitted. Conversely we show that when type II forward SHG occurs in a grating structure which couples the two fundamental polarization components, new types of stable solitons which fullflll the Bragg condition (i.e. resonance solitons) are supported.
Soliton Propagation in Two-Photon Resonant Region
Authors: Kitahara R. , Ishi J. , Ema K.
Published: February 2023

The stability of soliton propagation in nonresonant region has been studied extensively. The temporal and spatial evolution of pulses in such region can be analyzed with the nonlinear Schrödinger equation (NSE). The effects of the third-order dispersion term can be analyzed in the frame of NSE, however the dispersion of nonlinearity is usually ignored except for some extreme cases such as shock term.1) When we consider the propagation of ultrashort pulse or the propagation in resonant region, the effects of nonlinear dispersion reveal themselves remarkably. Nevertheless, the dispersion of nonlinearity have not been fully explored. In this paper, we examine the pulse propagation characteristics with dispersive nonlinearity using nonlinear wave equation in frequency domain. We show that, when pulses propagate at the two-photon resonant region, the effects of the third-order dispersion is compensated by the dispersive nonlinearity and solitonlike propagation of femtosecond pulses can be achieved.
Industrial Laser Ultrasonic Inspection System Using A DPCM for Wavefront Compensation
Authors: Dunning G.J. , Pepper D.M. , Mitchell P.V. , Klein M.B. , O’Meara T.R.
Published: February 2023

We present the results of a prototype laser-based ultrasound inspection system combining a wavefront-scrubbed laser receiver with a pulsed laser ultrasonic generator. Laserbased ultrasound [1] represents a noncontact, long-standoff-distance technology to remotely inspect materials for integrity of bonds, surface treatments, thickness, defects, microcracks, and temperature. The ability to employ lasers for the diagnostic enables one to perform the inspection under harsh industrial conditions, including high temperature, radiation, and vacuum environments. The basic system involves one laser to generate acoustic modes in a material via thermoelastic and/or ablative excitation, and a second laser to sense the resultant, transient surface displacements of the workpiece, induced by the ultrasound. Neural network post-processing or rule-based algorithms can be employed to classify the detected ultrasonic signatures.
Optical switching based on singlet-singlet excited state absorption
Authors: Yang Miao , Si Jinhai , Wang Yuxiao , Li Chunfei
Published: February 2023

Progress in optical computing, optical communication and optical information processing depends on a large extent of the availability of fast all-optical switches. Most of the all-optical switches utilize nonlinear FP cavity1,2,3. Its absorptive loss is very large because of working on the resonant wavelength, and the switching time is districted by the response time of cavity. In 1990 K. W. Beeson4 presented a novel all-optical switch based on the triplet-triplet absorption in Eosin Y using a CW laser as a pump beam, and obtained μs scale switching time. We developed this kind of switches in C605 whose switch off time was about 250 ns which depends on the lifetime of the first triplet excited state.
All-Optical Switching in Waveguide Structures Due to Cascaded Nonlinearities
Authors: Schiek R. , Baek Y. , Krijnen G. , Stegeman G. I.
Published: February 2023

The second-order nonlinear interaction between a fundamental light wave and its second harmonic causes energy transfer between the interacting waves (second harmonic generation (SHG)) and modifies their phases nonlinearly (cascaded nonlinearity) [1], This implies that all-optical switching can be implemented on the basis of cascading in phase-sensitive waveguide structures [2].
Proposed system for a solid-state, tunable 2.5 TeraHertz laser
Authors: Herman Gregory S. , Barnes Norman P.
Published: February 2023

Research efforts two decades ago attempted to produce TeraHertz sources using all optical technology [1] - [4]. Many authors reported widely tunable THz generation using difference frequency generation, however, many of these early efforts were unable to achieve the output powers needed for a practical device. Since these early experiments, the state-of-the-art of both the solid-state laser industry and the nonlinear crystal industry have improved dramatically. In April 1996, Kawase et. al. reported successful generation of coherent tunable THz-waves using a Q-switched Nd:YAG laser and a LiNbO3 crystal [5]. To this authors knowledge, this was the first reporting of successful generation of TeraHertz waves using this method since 1976. However, the implementation that they chose can be significantly improved upon through a different choice of nonlinear crystal as well as with other techniques.
High efficiency, long lifetime volume holographic gratings in LiNbO3
Authors: Sayano Koichi , Zhao Feng , Hendow Sami T. , Kukhtarev Nickolai V.
Published: February 2023

Volume holographic gratings have been demonstrated for narrow bandwidth, high spectral selectivity filtering in both the visible and IR.1,2 For 1.5 μm these filters are of particular interest for telecommunications devices for wavelength division multiplexing. Recently, the lifetime of volume holographic gratings in LiNbO3 was presented for the weak screening case that is primarily encountered in holographic data storage applications. In this paper, we address the issue of lifetime for the high efficiency filter application, such as filters, standards, and couplers. Useable lifetimes at 25°C of 20-30 years have been obtained from accelerated measurements at elevated temperatures for these high efficiency IR holographic gratings.
Nonlinear Spatial Correction of A Light Beam Shape In Photorefractive Planar Waveguides
Authors: Shandarov V.
Published: February 2023

Self - actions of light beams in photorefractive media have attracted significant interest recently. Similar phenomena, like nonlinear optical surface waves [1], spatial solitons [2], self - focusing and self - defocusing effects can be realized in photorefractive materials at optical powers some orders less than in Kerr media. It makes possible applications of these effects to needs of optically - controlled photonic elements, optical interconnects and memories. Photorefractive optical waveguides suggest in that way some additional advantages compared with basic 3D media. It is due to the potential larger concentration of active impurities provided by surface doping, the possibility to combine different dopants within separate areas of the same sample, larger light intensity within waveguides. Besides, nonuniform light fields and photorefractive properties over waveguide depth can result a number of effects having no analogs in bulk configurations [3,4]. In this work some features of confined light beam self - actions in lithium niobate optical waveguides doped by Fe and Cu are experimentally investigated and discussed.
Self-Pumped Phase Conjugation of Low Power Ar+-Laser Beams in Dye-Doped Nematic Liquid Crystals
Authors: Eichler H.J. , Macdonald R. , Meindl P.
Published: February 2023

Since the discovery of optical phase conjugation in 1972 researchers tried to generate phase conjugated beams with different nonlinear media and various techniques for many applications1-3. Self-pumped phase conjugation (SPPC) is obtained by stimulated Brillouin scattering or wave mixing in photorefractive crystals. The SBS-effect is observed with pulsed lasers at a high threshold power in the range of about 10 kW whereas photoreffactives operate with continuous powers in the mW-range. These crystals are expensive and available only for small optical apertures of about 1 cm2. In contrast liquid crystal cells may have much larger dimensions and offer also high optical nonlinearities. It was shown4 that self-pumped phase conjugation in liquid crystals can be realized by wave mixing effects with threshold powers less than 1 W.
Efficient Stimulated Raman Conversion in Crystals from 532 and 1064 nm to 500-1150 nm
Authors: Grebe D. , Macdonald R. , Eichler H. J. , Kaminskii A.A. , Bagayev S. N. , Butashin A. V. , Pavlyuk A. A.
Published: February 2023

The frequently used Neodymium-doped solid-state laser materials emit in the near infrared. Stimulated Raman scattering and parametric effects are useful to increase the spectral range. Laser materials which show strong Raman conversion are promising materials. A Q-switched Nd3+:KGd(WO4)2 -laser was demonstrated emitting the laser line at 1067 nm and more than 60 % of the total energy in the first two Stokes lines at 1180.8 nm and 1321.5 nm. [1]
Passive Cavity Dumping with Liquid Crystal Mirrors in Q-Switched Nd:YAG-lasers
Authors: Grebe D. , Stengelin T. , Macdonald R. , Eichler H. J.
Published: February 2023

Cholesteric Liquid Crystals (CLCs) show a selective reflection for circularly polarized light. Radiation with different polarization or wavelength is nearly fully transmitted. Furthermore, liquid crystals show strong optical nonlinearities due to electronic effects [1] or reorientation of the anisotropic molecules [2]. In cholesteric liquid crystals transverse non-linear optical effects like retro-self-focusing and a pinholing effect were demonstrated with a cw-Nd:YAG-laser[3,4].
Rapid Growth of Large-Scale (20-50cm) KDP Crystals
Authors: Zaitseva N.P. , Dehaven M.R. , Vital R.L. , Carman M.L. , Spears R. , Montgomery K. , Atherton L.J. , De Yoreo J.J.
Published: February 2023

KH2PO4 (KDP) and K(DxH1-x)2PO4 (DKDP) crystals are at present the only nonlinear crystals which can be grown to the sizes (30-80 cm) needed for laser radiation conversion in laser fusion systems. There are many problems associated with the growth of such crystals by the traditional technique, due primarily to the low growth rates (1 mm/day) and long growth periods. A new, fast-growth technique recently developed at Moscow State University, allows us to grow KDP crystals at rates that are an order of magnitude or more larger than those achieved with traditional methods [1]. This technique is based on the method of temperature reduction starting from a "point seed" with a size of about 1 cm3 independent of the final size of the crystal.
Amplification of Optical Signals in Bi12TiO20 Crystal by the Fanned Beam
Authors: Khomenko Anatoli V. , García-Weidner Alfonso , Kamshilin Alexei A.
Published: February 2023

The photorefractive sillenite crystals (Bi
12
TiO
20
, Bi
12
SiO
20
, and Bi
12
GeO
20
) been possess the high sensitivity, but the experimentally achieved gain for optical signals amplification by two-beam coupling does not exceed 1,500.1,2 This value is more than one order of magnitude less than the gain recently measured with BaTiO
3
crystals.3,4 The main limitation for the gain in sillenites is introduced by the beam fanning.
Phase Mismatched Modulation Instability in Birefringent Fibres
Authors: Murdoch S. G. , Harvey J. D.
Published: February 2023

In the normal dispersion regime, two forms of modulation instability have been observed when birefringent single mode fibres are subjected to intense pump pulses. These instabilities are the cross phase or XPMI process [1,2] and the coherent or PMI process[3,4]. In both of these processes, the generated sidebands develop at the peak of the gain, which occurs corresponds to the phase matching condition between the pump and the sidebands corrected for the optical Kerr effect. In this work we report on the development of modulation instability in birefringent fibres, using fibre winding geometries in which phase mismatches are deliberately induced. The results are in accord with theoretical predictions.
Measuring Weak Laser Pulses Using Frequency-Resolved Optical Gating
Authors: Fittinghoff David N. , Krumbügel Marco A. , Sweetser John N. , Trebino Rick , Tsang Thomas
Published: February 2023

Frequency-Resolved Optical Gating [1] (FROG) measurements based on polarization gating [2] (PG FROG), self diffraction [3] (SD FROG), and second-harmonic generation [4] (SHG FROG) have been used successfully to measure ultrashort laser pulses with spatially uniform temporal pulse shape and phase with durations from 9 fs to 2 ps and with wavelengths from the ultraviolet to the near infrared. Temporal Analysis by Dispersing a Pair of Light E-fields [5] (TADPOLE), a combination of FROG and spectral interferometry, has been used to measure pulse trains with average pulse energies of 42 zeptojoules (42 × 10-21 J). None of these techniques, however, has proved capable of measuring the pulses from a Ti:sapphire laser without a temporal ambiguity or an amplified reference pulse. The difficulty lies in the fact that the pulses from such oscillators are too weak for PG or SD FROG, and SHG FROG has a time-reversal ambiguity due to the symmetry of the second-harmonic signal in time. TADPOLE, while capable of measuring extremely weak pulses, uses FROG to measure a reference pulse and thus has the same restrictions Here we use surface third-harmonic generation (THG) to make an unambiguous measurement of the intensity and phase of pulses from a Ti:sapphire oscillator. In addition, we describe a new method for using TADPOLE for measuring ultrashort laser pulse fields that vary arbitrarily in time and in space.
Nonlinear cw Pump-Probe Investigations for Semiconductor Microcavities Exhibiting Normal-Mode Coupling
Authors: Nelson T. R. , Khitrova G. , Lindmark E. K. , Wick D. V. , Berger J. D. , Gibbs H. M. , Tai K. , Lai Y.
Published: February 2023

Normal-mode coupling (NMC) or vacuum-field Rabi splitting has been studied for many years. Early experiments used many atoms or even a single atom in a high finesse cavity. Recent observations of NMC in semiconductor microcavities [1] have led to a flurry of investigations. We present here the results of high excitation cw pump-probe experiments which show a new nonlinear behavior, in which the transmission of the two NMC peaks disappears with no appreciable change in NMC splitting.
Strong Optical Nonlinearities and Ultrafast Carrier Dynamics in Luminescent and Nonluminescent Porous Silicon
Authors: Klimov Victor I. , McBranch Duncan , Karavanskii Vladimir A.
Published: February 2023

Since the first experimental observation of efficient visible photoluminescence (PL) from porous silicon (PS) [1] this material has attracted much interest for its possible applications in all-silicon-based optoelectronics. Until now experimental studies of PS have mainly concerned PL, yielding information on the energy structure and population dynamics of the low-energy relaxed states in the material. Time-resolved nonlinear-transmission measurements can provide complementary information to conventional PL spectroscopy, revealing the structure of the higher-lying states and fast carrier dynamics in the initial stage after photoexcitation. In the present paper we report studies of the optical nonlinearities and ultrafast carrier dynamics in free-standing porous silicon films performed by femtosecond pump-probe experiment. The large photoinduced absorption observed in the spectral range 1.2–2.65 eV is attributed to molecular like complexes (clusters) which are most likely intrinsic to PS layers. Comparison of the transient absorption in samples of luminescent and nonluminescent PS shows that PL and photoinduced absorption originate from different species inside PS layers.
Femtosecond Nonlinear Optical Response of CuBr and CuCI Nanocrystals in Glass in the Optically Transparent Region
Authors: Thantu N. , Melinger J. S. , McMorrow D. , Justus B. L.
Published: February 2023

Because large third-order refractive nonlinearities, γ, are expected, much study on nanocrystal doped glasses has focused on the nonlinear optical properties at or near the single photon resonance.1 Although γ is smaller in the single-photon transparent region, its temporal response is expected to be pulse-width limited. More importantly, since the potential use of these materials as optical devices depends on the figure-of-merit ratio proportional to γ/(ατ or (βτ), where α and β are the linear and nonlinear absorption coefficients, respectively, and τ is the response time, a possibly larger figure of merit in the transparent region warrants studies far from the absorption edge. Recent studies2,3,4 performed on photodarkening CuBr nanocrystal doped glasses in the transparent region indicate a sizable two-photon enhanced nonlinearity which should scale with the concentration of CuBr nanocrystals in the glass. Time-resolving the nonlinear optical response3 with 60 fs, 620 nm optical pulses revealed a nearly pulse-width limited response followed by a subpicosecond decay. The CuBr and CuCI nanocrystals with the band edge in the 370-400 nm region are single-photon-transparent to the 620 nm light, but are two-photon-resonant at this wavelength or at 800 nm, the wavelength of interest in this study.
Progress in Reducing Loss of Diffusion Bonded Stacked GaAs for Mid Infra-Red Generation
Authors: Zheng D. , Gordon L. A. , Wu Y. S. , Eckardt R. C. , Fejer M. M. , Byer R. L. , Feigelson R. S.
Published: February 2023

Mid infra-red (IR) sources between 1 μm and 10 μm have wide applications in spectroscopy, remote sensing and military countermeasures. Established nonlinear IR crystals such as AgGaSe2, and AgGaS2 have poor thermal properties, and low damage thresholds. ZnGeP2 appears promising for high power applications, but its growth technology is still being developed, and crystals are expensive. In comparison, GaAs has a large nonlinear coefficient, good optical transmission between 1 μm and 12 μm, and high optical damage threshold. It also has good chemical stability, good mechanical properties, and a well developed growth technology. Unfortunately, single crystal GaAs is linearly isotropic; therefore, nonlinear interactions cannot be birefringently phase-matched. However, the interacting waves can be quasi-phasematched (QPM) by periodically modulating the nonlinear coefficient in a stack of rotated plates1,2. By diffusion bonding individual plates together, we can minimize scattering and reflection losses at the air-GaAs interfaces. Preliminary diffusion-bonded-stacked (DBS) GaAs devices demonstrated close to theoretical conversion efficiency3,4, but had high transmission losses. We report improved processing, leading to a significant reduction in the transmission loss to less than 0.2% per layer at 5 μm.