bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of air flow in hollow bricks using holographic interferometry
Authors: Vennin C. , Watson J. , Imbabi M. S.
Published: February 2023

Natural convection is a topic of considerable interest in many engineering applications. To improve the thermal insulation of walls, hollow bricks in which this kind of convection occurs could be used. Thus a good understanding of the free convection of the air inside this type of bricks is valuable. Theoretical studies consisting of computer simulation have already been carried out and give a good understanding of the flow movement, velocity, and temperature variation in different types of fluids.1-2 The aim of our study was to perfect a good holographic interferometric method to visualise the isothermal lines of a free air flow convection inside a hollow brick. By viewing and understanding the heat transfer inside, it will be possible to define a cavity shape that reduces heat exchange between the cold outdoor and the hot indoor surface (and vice versa). The hollow brick cavity dimensions were 180 × 60 × 60 mm, two walls were in aluminium, two in Tuffnal and the two windows were in a Plexiglas. Temperature differences, ΔT, of 7 to 30°C were obtained with the heater on the vertical side. The temperature was measured with four thermocouples inside the two aluminium walls.
Photorefractive grating fixing and enhancement in multidomain ferroelectric crystals
Authors: Cudney R. S. , Fousek J. , Zgonik M. , Gunter P. , Garrett M. H. , Rytz D.
Published: February 2023

Photorefractive gratings can be fixed in ferroelectric crystals if a complimentary “grating" of ferroelectric domains is somehow created,1-4 i.e., the direction of the spontaneous polarization Ps of the crystal is selectively reversed such that the bound charge located on the domain walls electrically compensates the light-induced space-charge distribution of the original grating. Usually the selective reversal of the direction of Ps is accomplished by first creating a space-charge distribution by the usual manner (interfacing two light beams in the crystal) and then applying an electric field in the direction opposite to Ps.
Observation of misalignment of the subharmonic grating in photorefractive Bi12SiO20
Authors: Pedersen Henrik C. , Johansen Per Michael
Published: February 2023

Subharmonic generation in photorefractive crystals has experienced an increasing interest since the discovery of this effect by Mallick et al.1 Further experimental results2,3 and theoretical models4,5 have all contributed to the understanding of this rather peculiar phenomenon. The aim of this paper is to present new experimental results showing a rather surprising behavior of the subharmonic grating.
Ultrafast trapping and slow recombination in Auston switches observed via THz spectroscopy
Authors: Brorson S. D. , Zhang J. , Keiding S. R.
Published: February 2023

We have performed two different types of femtosecond pump and probe measurements on THz transmitting antennas.1 The devices were "10-30-10" antennas fabricated on ion-bombarded silicon-on-sapphire (SOS) chips and pumped with a mode-locked Ti:Al2O3 laser. The experimental setup is similar to the usual configuration for THz spectroscopy1 except that the transmitting antenna is excited by two laser pulses, a "pump" and a "probe."2 The emitted THz pulse is monitored at the receiving antenna by activating the receiver with a "gate" pulse from the laser.
30 dB gain in vertical cavity amplifying photonic switch
Authors: Raj R. , Oudar J. L. , Bensoussan M.
Published: February 2023

Major progress has been made in the processing of optical signals in recent years, due to the development of high-quality epitaxial Fabry-Perot (FP) structures with multiple quantum wells active medium sandwiched between Bragg reflector mirrors. A wide range of innovative use has been made of these structures.1 We have recently demonstrated2 a fast vertical cavity amplifying photonic switch (VCAPS), which might overcome the problem of losses likely to be encountered in cascading different functions for achieving active optical interconnects. Here we show a dramatically improved performance of the VCAPS with 30 dB gain with switching times better than 20 ps in a GaAs-based structure operating at 847 nm. We also show that the amplification configuration is a powerful method for studying carrier induced refractive changes.
Generation of ultrashort electrical pulses with variable pulse widths
Authors: Keil U. D. , Gerritsen H. J. , Haverkort J. E. M. , Wolter J. H.
Published: February 2023

Short electrical pulses have conventionally been generated with photoconductive switches on short carrier lifetime material such as low temperature grown GaAs. Another approach is nonuniform illumination of a photoconductive switch.1,2 Both methods yield electrical pulse widths of less than 1 ps. The first method, however, is usually not compatible with active devices on the same wafer. The disadvantage of the second method is that the generated pulse forms are difficult to reproduce.
On the influence of material properties on the high speed behavior of metalsemiconductor-metal photodetectors
Authors: Sickmöller Markus , Kowalsky Wolfgang
Published: February 2023

With respect to today's optical communication systems using bitrates in the regime of several 10 GHz, the understanding of ultrafast processes in semiconductor devices with sub-micron dimensions is of growing importance for device optimization. MSM photodetectors commonly fabricated on semi-insulating materials are very promising for system applications,1,2 because of their simple planar structure, high frequency response, low dark currents, and process compatibility to MESFET technology. However, the pulse response with very short rise- and FWHM-times of the detectors is often deteriorated by a long exponential tail.
Modulation, chirp, and tunability properties of vertical cavity surface emitting lasers integrated with quantum-well modulators
Authors: Khan A. , Woodbridge K. , Roberts C. , Parry G.
Published: February 2023

We show that use of quantum-well absorbers within the Bragg reflectors of GaAs/AlGaAs-based vertical cavity surface emitting lasers results in improved chirp and modulation characteristics. Further enhancement can be obtained using strained InGaAs/GaAs.
Chirp and periodic spectral structure in the light reflected from nonlinear mirror
Authors: Kabelka V. , Masalov A. V.
Published: February 2023

The spectral characteristics of nonlinear mirror based on parametric process ω → ω1 + ω2 are analyzed. The nonlinear mirror consists of parametric crystal, glass plate for phase compensation, and trichroic mirror for ω, ω1, ω2 waves.1,2 Up to now the analysis of nonlinear mirror was focused mainly on the dependence of reflection coefficient on input radiation intensity. We report results of spectral-characteristics calculations of nonlinear mirror. The first attempt to consider spectral properties of nonlinear mirror was made in Ref. 2, where the authors found occasional mode resonances in the laser with nonlinear mirror. Our calculations give the whole spectral picture of nonlinear reflection, and moreover they elucidate the phase properties of nonlinear mirror, which is very important for chirp formation of ultrashort pulses generated by laser with passive mode-locking by such a mirror.
Gain-mode coupling in diode-array end-pumped microchips
Authors: Okulov A. Yu. , Lebedev P. N.
Published: February 2023

Recent realization of diode-array end-pumped microchips1 reveals a possibility of fabricating a single-frequency solid-state laser arrays. In contrast to fiber end-pumped Nd:YAG arrays,2 the short cavity microchips provide a stable selection of the single longitudinal mode.3 The arrangement of a gain pixels in the form of a spatially periodic array with period p makes it possible to synchronize them by means of self-imaging,4 placing the output mirror at the distance being multiple of p
2
2λ from the active slice. The small value of self-phase modulation raises the threshold of transverse chaotic instabilities.5 A weak gain-guiding within the active slice offers the possibility of using a simple numerical model based on the Fox-Lee algorithm with a nonlinear mirror (rather than a coupled-mode model6) for calculation of the stationary eigenmodes of the system, taking into account transversely inhomogeneous gain saturation and thermal lensing. The validity of this model had been tested by the split-step FFT method.7 It was shown also by 1-D numerical modeling that such a system is sensitive to small transverse phase fluctuations that lead to the ramification of a wavefront on several domains where the wavefront is almost flat, but somewhat tilted; the waves emitted by this domain interfere in the far field, increasing the beam divergence beyond the diffraction limit.8
The correction to the paraxial approximation for the laser cavity modes
Authors: Skryabin D. V. , Radin A. M.
Published: February 2023

The well known Hermite-Gaussian beams represent the leading, or paraxial, approximation to the high-frequency asymptotics of the field in an optical cavity. In calculating the correction to the paraxial approximation for the field inside of the cavity, it is necessary to take into account small deformations of the beam intensity profile after reflection from the parabolic mirror. These deformations reveal themselves in the higher terms of the high-frequency asymptotics. The leading asymptotic term obeys the well-known Fredholm homogeneous integral equation
Suppression of multiple pulse formation in actively mode-locked laser diodes by incoherent optical feedback
Authors: Kawaguchi Hitoshi , Hatayama Hitoshi , Takahashi Yutaka
Published: February 2023

The actively mode-locked laser diode (LD) with an external mirror configuration suffers from trailing pulses, which are caused by the residual reflection at the LD facet even with an antireflection coating (Ra < 10-4).1 To avoid the undesired trailing pulses, two possibilities were shown to exist:2 (1) increasing the LD length and/or decreasing the injection current fall time until the LD roundtrip time is longer than the injection current fall time; and (2) decreasing the internal facet reflectivity Ra well below 10-4. However, these are not so easy to realize. Insertion of a saturable absorber into the laser cavity was also proposed.3 When the cavity length is relatively long (~ few GHz) and the bias and RF currents are large, we also observe trailing pulses caused by the excess gain, which is similar to the relaxation oscillation of direct modulation.
Spatial behaviour of population density measurements and wall phenomena in a barium vapour laser
Authors: Mildren Richard P. , Brown Daniel J. , Carman Robert J. , Piper James A.
Published: February 2023

The barium vapour laser, as well as being a high average power source of near to mid-IR radiation, is also a useful test system for studying kinetics of metal vapour lasers. The barium atom and ion ground states have visible upward transitions of sufficient oscillator strength suitable for hook spectroscopy. In contrast, the more popular copper vapour laser requires broadband uv sources and detectors to access the copper ground state, and the copper ion density is impossible to measure by conventional techniques (absorption, emission, and anomalous dispersion spectroscopy). Hook studies of metal vapour lasers have been popular in the last ten years, however, there has been little work on spatially resolved density measurements, particularly of the ground state.
Wavelength tuning of a 1300 nm semiconductor laser in a fibre ring configuration with a single-stage electrooptic lyot filter
Authors: Frison Thierry , Porte Henri , Goedgebuer Jean-Pierre
Published: February 2023

Tunable semiconductor lasers1 that can be tuned over a broad spectral range are of great interest for a number of applications. Multisection DBR or DFB laser diodes having tuning range of several nanometers have been reported. Another attractive solution is to use cavity extended lasers in which tunability is performed with an intracavity spectral filter such as a rotating grating,2 an acoustooptic cell,3 or an electrooptic modulator.4 We describe here another type of extended cavity laser diode in which the resonator is an optical fibre loop and the active medium is a semiconductor amplifier.5 The wavelength tuning system is an intracavity electrooptic biréfringent element.
Time-resolved dephasing measurements of dyes using incoherent light
Authors: Kummrow A. , Lau A. , Woggon S.
Published: February 2023

The dephasing times T2 of vibrational transitions were determined by interferometric coherent anti-Stokes Raman spectroscopy (ICARS).1 The broadband incoherent pump laser (centered at 510 nm, matching to the long wavelength absorption edge of the dyes) has a coherence time of 40 fs, which defines the time resolution for ICARS. The broadband laser beam is split by an interferometer in two twin beams, which join in the sample with a narrowband Stokes laser. A typical oscillation of the ICARS intensity as a function of delay between the two twin beams is depicted in Fig. 1 for narrow-band detection. The sample was bis-(di-methylaminojheptamethine iodide in ethanol (10−3 M). The oscillation frequency is the difference between the detection frequency and the twice Raman transformed Stokes laser frequency (Rabi detuning oscillation). This allows to determine the vibrational frequency(ies) of the excited vibration(s). The damping is given by 2T2. Corresponding results are listed in Table 1. The data obtained are in good agreement with those calculated from lineshapes and frequencies observed in multiplex-CARS experiments. This indicates a predominantly homogeneous broadening of the Raman lines. The two different fits in Fig. 1 demonstrate the high accuracy obtainable with ICARS. The accuracy is mainly limited by errors in the calibration of the monochromator applied for narrowband detection.
Intracavity laser spectroscopy with Ti:sapphire laser: Sensitivity limitations and applications
Authors: Kachanov A. A. , Charvát A. , Campargue A. , Permogorov D. , Stoeckel F.
Published: February 2023

Intracavity laser spectroscopy (ICLAS) is known as a very sensitive and multispectral technique for very weak absorption measurements.1 This technique is based on the high sensitivity of the spectro-temporal dynamics of a high multimode laser to intracavity frequency dependent losses, when the line width of the absorbing species are narrower than the gain curve.
Transmissive and reflective optical bandpass filters using guided-mode resonance effects
Authors: Magnusson R. , Wang S. S.
Published: February 2023

Novel filters based on the guided-mode resonance properties of planar, dielectric waveguide gratings have received some attention in the literature recently.1–5 This type of diffractive optical element can couple externally propagating waves to waveguide modes resulting in complete energy exchange between forward and backward propagating lightwaves. This efficient interaction is achieved by using a waveguide grating with high spatial frequency such that only the zero orders propagate, with all higher diffraction order cut off. It is the purpose of this paper to present new optical filter designs that are based on guided-mode resonance effects in planar dielectric structures. With near-ideal reflection and transmission filters achievable, it is believed that these will find numerous applications in many fields such as laser design, optical sensing, and spectroscopy.
Single-mode optical parametric oscillator system of BBO and KNbO3 tunable from the visible (0.42 μm) to the infrared (4 μm)
Authors: Fix A. , Goeritz G. , Urschel R. , Wildt D. , Borsutzky A. , Wallenstein R.
Published: February 2023

As has been demonstrated in previous investigations,1,2 Nd:YAG laser-pumped optical parametric oscillators (OPO) of beta-barium borate (BBO) are powerful all-solid-state sources of coherent radiation with a large tuning range (300–3000 nm), high internal conversion efficiency (60–70%), and high output energies (100–200 mJ). Narrowband operation was achieved by injection seeding with low power monochromatic radiation.3
Tunable dye-doped xerogel lasers
Authors: Canva M. , Georges P. , Dubois A. , Brun A. , Chaput F. , Boilot J.-P.
Published: February 2023

The easiest route to produce tunable optical pulses is to use a broadband fluorescent gain medium. For this purpose organic dye molecules are very suitable and have been widely used in solution during the past 30 years. Today, new crystals such as titanium sapphire, and nonlinear techniques such as optical parametric oscillation, may provide solid state systems. For dyes to remain competitive, it would be interesting to disperse the molecules in solid host matrices, instead of diluting them in solutions. This may be achieved by using the sol-gel process.1–3
Inorganic liquid hosts for mid-infrared lanthanide lasers
Authors: Brocklesby W. S. , Coleman A. P. , Rutt H. N. , Sarkies J. R.
Published: February 2023

Inorganic liquids such as phosphorous oxytrichloride and selenium oxychloride were very heavily researched as laser hosts many years ago. The only laser ion used was Nd3+, and as more convenient solid hosts such as glasses and YAG became available work on the liquids ceased. In this early work the lasers were large flashlamp pumped systems, and in this application there are further disadvantages arising from thermal expansion and high stimulated Raman cross sections, aside from the corrosion and toxicity problems in circulating systems sometimes containing litres of material.
Generation of focused shock waves in medicine using lasers
Authors: Andrienko Yu. A.
Published: February 2023

Nowadays, noninvasive destruction of kidney concrements using focused shock waves is a routine procedure in medicine. A patient is immersed in the water bath under the tomographic control, and then electric discharge and acoustic reflector are used to produce a series of focused shock waves to destruct the concrement.1 Authors of the technique also supposed that laser beams can be used instead of electric discharge.
Laser diagnostics of organic matter in snow and ice
Authors: Fadeev V. V. , Glushkov S. M. , Panchishin I. M. , Vorontsov D. Yu.
Published: February 2023

Many original methods are available for studying various parameters and components of liquid water including aquatic humic substances; however, there are no remote methods for measuring organics in snow and ice. For several years, we perform a program aimed at the development of such technique.
The growth and studies of photorefractive Bi12TiO20 single crystals
Authors: Prokofiev Victor V. , Kamshilin Alexei A. , Jääskäläinen Timo
Published: February 2023

Photorefractive crystals of the sillenites (Bi12GeO20, Bi12SiO20, Bi12TiO20) have the promising applications in optical information processing, including spatial light modulators, optical memories, phase conjugation, image inversion, and optical interconnects.1 In comparison to other sillenities, bismuth titanium oxide (Bi12TiO20, BTO) exhibits a higher sensitivity for red lights that permit the use of a cheap HeNe laser. In addition, BTO crystals have a lower optical activity ρ, which is favourable for many applications. However, some technological problems (the incongruent melting of Bi12TiO20, the high tendency of Bi2O3-containing melts to the supercooling, etc.) created difficulties for producing large single crystals of high optical quality.
Determination of oil film thickness on water surface by laser spectral methods
Authors: Dolenko T. A. , Petrov P. S. , Serdobolskaya M. L. , Deydan T. A. , Fadeev V. V. , Chubarov V. V.
Published: February 2023

The problem of the remote determination of the oil film thickness on the water surface is actually remined and it is not solved yet. In this paper we compared the four laser spectral methods, which had been offered for decision of this problem. These laser methods are based on the measurements: (a) of absolute oil fluorescence spectral conversion efficiency; (b) of suppression of Raman back- scattering signal from water by oil film; (c) of oil fluorescence signal, which is normalized on Raman backscattering signal from water volume;1 and (d) of deformation of Raman backscattering water band because of oil film absorption.
Enhanced third-order nonlinear susceptibility of semiconductor-doped glass
Authors: Mizumoto T. , Kimura N. , Tonami S. , Naito Y.
Published: February 2023

All-optical switches are generally designed to operate with intensity-dependent refractive index, which results from the third-order nonlinear susceptibility χ(3). In this paper, the real part of χ(3) observed at a signal wavelength λs is examined in CdS
x
Se1-
x
-doped glass pumped at λ
p
≠ λ
s
. It is shown that, comparing to the case of being pumped at λ
s
, which is longer than a band gap wave-length, larger Reχ(3), typically by a factor of 103, is obtained at λ
s
when pumped at the wavelength close to the band edge. The large χ(3) obtained at low absorption wavelength gives us flexibility in designing a variety of all-optical devices.
Noise limitations to Brillouin amplifier efficiency
Authors: Glick Yaakov
Published: February 2023

Brillouin two-beam coupling has been used to achieve gains as high as 109.1 The limiting factor in amplifying a weak signal is the presence of spontaneously scattered noise at the Stokes-shifted frequency. This noise arises from scattering of the pump light by acoustic fluctuations in the medium and will be amplified by the same factor as the input signal.
Feedback-induced polarization-switching in the Nd-doped fibre-laser
Authors: Meziane B. , Sanchez F. , Besnard P. , Stephan G. M. , François P. L.
Published: February 2023

The use of coherent optical sources as pumps in solid-state lasers has led to the experimental feasibility of long fibrelasers, thus allowing for the study of coherent effects on increased time-scales. The fabrication process and the wired geometry of the host matrix induce a small birefringence which defines two polarization eigenstates along the eigenaxes of the host glass. The pump diode-lasers are usually linearly polarized. Such a linearly polarized pumping in bi-axial lasers introduces polarization-related effects which are masked out when conventional unpolarized optical pumping, such as flashlamps, are used.
Vibrational states of native and photoinduced colour centers in silica fibers
Authors: Aleksandrov I. V. , Nesterova Z. V. , Petrovskii G. T.
Published: February 2023

The problem of microdefects (or colour centers) in transparent glasses is very actual now. In a more common sense this question connects with the fundamental aspects of a glass structure. As the confirmation of such proposal it must be mentioned about the presence of a mutually exclusive model of silica glasses. The most known theories operate with local microdefects, such as non-bridged oxygens or ring groups in silica network, but the same physical experiments were used to establish the microclaster model (see Ref. 1 and references therein). In a last case the term "defect" is absent at all. So, the formulation of the new spectroscopic tools for glass structure investigation is needed.
Photoacoustically generated ultrasound as a new guidance modality for laser angioplasty
Authors: Pang K. F. , Chen Q. X. , Davies G. A. , Dewhurst R. J. , Kuhn A. , Payne P. A. , Shan Q.
Published: February 2023

Laser angioplasty is an alternative to the established balloon angioplasty techniques for the treatment of stenotic lesions and short occlusions in arterial disease. Because it does not require the lesion to be traversed, laser angioplasty, in some cases, offers treatment of longer occlusions; but in this situation the risk of complications is high,1 arising from intimal dissection through the lack of appropriate guidance during the angioplasty procedure. Laser energy is able to burn through healthy tissue just as effectively as through atherosclerotic plaque.
Status of optical processing in the telecom environment
Authors: Barnsley Pete
Published: February 2023

Optical processing has been the topic of research and study for many years. The prospect of potential control of light with light has long been seen as the means to replace electronic bottlenecks within computing or telecommunications processing equipment. Light travels fast (like electronic signals), fibre has very low attenuation, wavelength is an extra degree of freedom, light can be highly parallel and signals can be made to interact strongly or weakly, and many technologies allow the interaction between the electronic and optical signals. Rapid research progress has, however, been limited in its commercial success; optical processors and optical computers are still far off.
Upgrading standard fibre communication links to 10 Gbit/s using solitons and dispersion compensation
Authors: Knox F. M. , Forysiak W. , Doran N. J.
Published: February 2023

Current interest in the use of optical solitons in high data rate communications centres around their use in long distance, typically trans-oceanic, systems with low group velocity dispersion fibres.1 The potential application of solitons in nondispersion shifted fibre systems is not often considered as the dispersions of such systems (around 15 ps/(nmkm) at the low loss, 1.55 μm wavelength region) leads to short soliton periods, giving pulse breakup from amplifier perturbations,2 pulse walk-off, and collisions from soliton interactions, and requires high optical powers to support fundamental solitons. Amplifier output powers of a few milliwatts are typically considered for systems applications, whereas solitons in standard fibre systems may require greater than 10 mW.1 There is much interest in upgrading the large existing standard fibre base to higher data capacity.3 This paper studies the use of solitons in upgrading such systems to 10 Gbit/s and considers the use of dispersion compensation to overcome the problems found.
Technique for Measuring Ultrashort Laser Pulses in Time and Space
Authors: Krumbügel Marco A. , Fittinghoff David N. , Sweetser John N. , Trebino Rick
Published: February 2023

We developed a new method for measuring ultrashort laser pulse fields that vary arbitrarily in time and in space. Previously, we have made measurements using Temporal Analysis by Dispersing a Pair of Light E-fields (TADPOLE) on extremely weak (42 × 10-21 J) pulses with spatially uniform temporal pulse shape and phase [1]. TADPOLE involves combining at a beam splitter an unknown pulse and a reference pulse characterized by Frequency-Resolved Optical Gating (FROG) [2] and performing spectral interferometry.
Double Cascade Erbium Fiber Laser at 1.7 μm, 2.7 μm, and 1.6 μm
Authors: Schneider J. , Frerichs Ch. , Carbonnier C. , Unrau U. B. , Pollnau M. , Lüthy W. , Weber H. P.
Published: February 2023

The output power of the erbium fiber laser at 2.7 μm (4I11/2 → 4I13/2) is enhanced due to simultaneous laser action at 1.7 μm (4S3/2 → 4I13/2) and 1.6 μm (4I13/2 → 4I15/2) an Er3+-doped fluorozirconate fiber. The laser cascade overwhelms the saturation effect for the transition at 2,7 μm by suppressing the laser transition at 850 nm (4S3/2 → 4I13/2) with lasing at 1.7 μm |1|. The population of the level 4S3/2 occurs for pump wavelengths around 800 nm due to strong pump excited state absorption (ESA).
Diode-Pumped Laser Operation of Nd3+: CaGdAIO4
Authors: Lagatsky A.A. , Kuleshov N.V. , Mikhailov V.P. , Ostroumov V. , Huber G.
Published: February 2023

So long as diode-laser-pumped solid-state lasers are gaining importance, research on new materials with improved spectral properties for diode pumping is of increased interest. Here we report on the spectroscopic properties and diode-pumped laser performance of Nd-doped CaGdAlO4. This crystal has tetragonal lattice structure with the space group I4/mmm [1]. The Nd3+ ion enters the ninefold coordinated Gd3+ site of C4v point symmetry. The single crystals doped with 2 at. % of neodymium were grown by the Czochralski technique.
Direct bonding between laser wafers and magneto-optic waveguides
Authors: Yokoi Hideki , Mizumoto Tetsuya , Maru Koichi , Naito Yoshiyuki
Published: February 2023

Wafer direct bonding is an attractive technique for the integration of different materials The authors have applied this technique to the bonding between III-V compound semiconductors and magneto-optic crystals with the aim of the integration of a laser diode and an optical isolator because it overcomes the issues associated with the lattice mismatch between the two different materials [1,2]. In a previous study, we demonstrated the bonding between InP and several kinds of garnets [3] which are essential to an optical isolator. When the optical isolator is integrated with the laser wafer as shown in Fig. 1, the surface of garnet wafer where a rib waveguide is formed is to be bonded with an etch stop layer for the vertical alignment. In this paper, we report the direct bonding between GalnAsP etch stop layer and Gd3Ga5O12 (GGG) which is used as a substrate for magneto-optic crystal growth. The bonding is also described between InP and the garnet rib waveguide.
Q-Switching of A Diode-Pumped Nd:Yag Laser by GaAs Saturable Absorber
Authors: Kajava T. T. , Gaeta A. L.
Published: February 2023

Q-switching of a diode-pumped laser is an attractive technique for generating relatively short pulses with high pulse energies. Compact pulsed lasers in the visible region are of particular interest for communications, micromachining, remote sensing, microsurgery, and as pump sources for other laser materials. Fully passive Q-switches have considerable advantages in terms of device simplicity and overall efficiency since fast high-voltage modulators are not required. Cr-doped YAG crystals have been the standard solution. In this work, we study the Q-switching behavior of a single-crystal GaAs wafer in a Nd:YAG diode-pumped laser.
Transverse mode characteristics in amorphous-GaAs-antiguided vertical-cavity surface-emitting lasers
Authors: Yoo B.-S. , Chu H.Y. , Park M.S. , Park H.-H.
Published: February 2023

Stable single-mode emission of vertical-cavity surface-emitting lasers (VCSELs) is one of the imperative characteristics for application to optical computing and fiber communication. Several attempts have been reported to stabilize transverse mode emission for VCSEL.1,2 In this work, transverse mode characteristics for an antiguided VCSEL structure using amorphous-GaAs (a-GaAs) clad with high refractive index have been investigated. For 10 μm-diameter device, we observed stable transverse mode emission, indicating the effective antiguiding of high order transverse mode in the a-GaAs clad. Using a finite difference beam propagation method, we studied the transverse field profiles of the antiguided stnicture and the effects of mirror loss at the transverse mode.
Solid-State Distributed Feedback Dye Laser with Fan-Shaped Grating
Authors: Efendiev T.Sh. , Katarkevich V.M. , Rubinov A.N. , Ryzhechkin S.A.
Published: February 2023

In this report we are presenting a new compact and efficient tunable laser source - holographic distributed feedback (DFB) laser [1] with fan-shaped grating and dye doped epoxypolymer matrix as an active element.
Q-switching of Nd-lasers with high repetition rates by SBS phase conjugation
Authors: Ostermeyer Martin , Heuer Axel , Menzel Ralf
Published: February 2023

The beam quality of high-power solid state lasers can significantly be improved by using phase conjugating mirrors. These mirrors can easily be realized by stimulated Brillouin scattering (SBS) in liquids or gases. Such SBS phase conjugating mirrors were used in single-rod Nd:YALO double pass amplifier systems with average output powers of 100 Watts [1] and 140 Watts [2].
Materials and Performance Issues in the Practical Implementation of Vertical-Cavity Lasers
Authors: Schneider R. P. , Corzine S. W , Tan M R T. , Hahn K. H. , Hummel S. G.
Published: February 2023

Vertical-cavity surface-emitting lasers (VCSELs) are rapidly nearing practical widespread implementation in key applications such as data communications. Because of numerous advantages relative to either edge-emitting lasers or light-emitting diodes, even broader application of this device technology is anticipated with further improvements in performance characteristics and wavelength coverage. In many cases, such advances hinge on advances in the underlying materials and process technology. This talk will overview the impact that different epitaxial design and process approaches, including selective oxidation, have had on improving VCSEL performance benchmarks over a broad wavelength range.
Continuous-wave diode-pumped Yb3+:S-FAP laser
Authors: Gloster L. A. W. , Dickinson M. R. , Hopps N. W. , King T. A.
Published: February 2023

Ytterbium-doped crystals hat e emerged recently as impressive solid state laser media emitting in the 1 μm region. The apatite structure S-FAP serves as an excellent host for the Yb3+ ion. Recently. Yb3+:S-FAP has been pumped by a Ti:sapphire laser [1], a Cr:LiSAF laser [2] and a pulsed diode laser [3] generating l.047 μm. However, due to its long storage lifetime of 1.26 ms, small quantum defect and absorption linewidth. Yb3+:S-FAP is ideally suited to CW diode pumping.
Room Temperature CW Yb:GGG Laser Operation at 1,038-μm
Authors: Belovolov M.I. , Dianov E.M. , Timoschechkin M.I. , Barashov L.V. , Belovolov A.M. , Ivanov M.A. , Morosov N.P. , Prokhorov A.M. , Timoschechkin K.M.
Published: February 2023

Yb-doped materials, whith typically lase around 1.03 μm, have the simple electronic structure of Yb3+ and have attracted considerable attention over the past few years. Only a several Yb-doped crystals have been extensively studied as laser media to date: Yb-YAG/1/, Yb-FAP,Yb-S-FAP /2/ and Yb-GSGG /3/.
Fiber Bragg Gratings for Strain Sensing in Smart Structures
Authors: Schena A. , Falciai R. , Fontana R.
Published: February 2023

Intracore fiber Bragg grating are suitable for strain sensing in smart structures because they can be easily incorporated into complex structures such as composites without compromising the integrity of the material. These gratings reflect a very narrow linewidth light signal at a wavelength determined from the grating period and the effective index of the fiber core. When a stretch is imposed on a fiber grating, the peak wavelength moves towards higher values. High resolution in measuring the Bragg wavelength is required over a wide range in order to interrogate wavelength multiplexed sensors in a single optical fiber.
Future Potential of Surface Treatment with Lasers
Authors: Dausinger Friedrich
Published: February 2023

Despite convincing technical advantages, surface treatment with lasers has found only a very limited number of industrial applications, up to now. The comparison with competing conventional methods on the one hand and with more successful laser techniques on the other hand shows inherent weaknesses:

• low coupling efficiency,

• low thermal efficiency,

• inappropriate use of expensive heat sources.
Use of Laser-Driven Ion Sources for Low-Cost Reduction of Dry Friction
Authors: Boody F. P. , Höpfl R. , Hora H. , Kelly J. C.
Published: February 2023

Extensive studies of implantation of ions into near surface areas of materials have demonstrated significant improvement of such properties as surface tension, friction and durability. The cost of implanted ions is currently rather high due to the limited ion current density of the usual ion sources, especially if ions from other than gaseous plasma sources must be used. The advent of laser-driven ion sources, with 2-3 orders of magnitude higher currents than classical ion sources, may change the scenario for a wide range of applications, making ion implantation as crucial a manufacturing technology in the future for other industries as it is today for microelectronics.
A novel high-performance continuously tuneable Optical Add-Drop Multiplexer in micro optic technology
Authors: Bcndelli G. , Donati S. , Lano R.
Published: February 2023

Optical Add-Drop Multiplexers (OADM) are key devices for the development of Wavelength Division Multiplexing (WDM) fibre optic networks [1]. The OADM allows, in the optical domain, to extract one channel (Drop function) from a WDM transmission link and to insert another one (Add function), at the same wavelength, carrying new information. A critical feature of an OADM is the isolation between Add and Drop ports since even a low level of leakage (< -25 dB) of the inserted channel into the Drop port generates homo-wavelength interference with the extracted channel, leading to unacceptable degradations of the transmission performance [2]. In this paper we report the proposal and realisation of a new structure of OADM [3] optimised with respect to the isolation features and the tuneability.
A 1×8 Supergrating Tap-off WDM Device
Authors: Chik H. , Bismuth J. , Xu J.M.
Published: February 2023

The growing interest in fiber to home technologies has motivated research into devices that can select and tap off a small portion from wavelength channels carried by the fiber. To accomplish this function, a beamsplitter and a wavelength demultiplexer are both necessary (see Fig. 1). In this paper, we present a new device, a tap-off WDM based on the concept of superimposed Bragg gratings, which offers the combined functionalities.
Silicon backplane-flc based routing crossbar switch: design and performance
Authors: Moignard R. , Kerouèdan S. , Defosse X.
Published: February 2023

This study is an extension of the British OCPM (Optically Connected Parallel Machines) collaborative project funded through the LINK Optoelectronic Systems Programme [1]. In a recent paper, we described the particularities of our project with respect to the OCPM project [2]: the wavelength is the usual telecommunication one (λ=1.55µm), the input and output fibers are single-mode (in order to provide a realistic telecommunication demonstrator). The routing is performed by the key-component, a Silicon Backplane Spatial Light Modulator (SBSLM) [3]. This SBSLM is a CMOS 1µm Integrated Circuit (IC) with Ferroelectric Liquid Crystal (FLC) SCE13 (Merck) on the top. The system forms a 8×8 crossbar.
Optical Single-mode Fibres Array Switch Using Polarization Controlled Vertical Cavity Surface Emiting Laser Arrays for packet switching
Authors: Plouzennec L. , Cambon P. , Daniel E. , Piernas B. , Perrot M. R.
Published: February 2023

Vertical-Cavity Surface-Emitting Laser arrays (VCSELs) are low cost components and attractive devices for association with free space interconnects. The opto-clectronics characteristics of GaAs VCSELs are already interesting for local-area networks implementation. For long-haul telecommunications applications, first results on InP based VCSELs are encouraging. Thus, in order to evaluate the advantages and drawbacks of the use of VCSELs in an optical fibres switch, we have developed a self-routing crossbar architecture.

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single mode optical fiber) [1]. Our study is divided in three parts: i) optical interconnects; ii) a photo-addressed switch node; iii) an header decoder.
A Novel Scheme for Increasing Transmission Distance of Soliton Communication Systems by Selective Frequency Shifts
Authors: Teixeira Antonio Luis Jesus , Ferreira Da Rocha José R. , Agrawal Govind P.
Published: February 2023

The soliton format has important advantages (long-haul transmission, stability, high bit rates) but also some inherent limitations, such as soliton interaction[1], that can cause practical problems and limit the bit rate. To minimise soliton interaction, several techniques such as amplitude shifts [2] and phase shifts [3] have been suggested during the last few years. In this paper, we propose a novel method for soliton interaction control in which selective solitons of a bit sequence are frequency shifted. It is shown that this technique can significantly increase the collision distance.
All-optical demultiplexer with 19 dB inherent amplification utilizing fiber four-wave mixing
Authors: Hedekvist Per Olof , Andrekson Peter A.
Published: February 2023

Two methods that have been suggested for a fiber based all-optical demultiplexer are with a nonlinear optical loop-mirror (NOLM) [1] or to use four-wave mixing (FWM) [2]. The first or this methods have a theoretical maximum efficiency of 100 % and a rectangular, well defined switching window. With the second method, on the other hand, we show that more than 100% efficiency can be achieved. At the same time the switching window is highly dependent on longitudinal variations of the fiber zero-dispersion wavelength, λ0. Two 10 GHz mode-locked external cavity lasers were used as pulse sources in our measurements. The signal was modulated at 10 Gbit/s and multiplexed optically to 20 Gbit/s, and its wavelength, λs, was a variable parameter in the experiment. The pump wavelength was fixed at λp=λ0+0.5 nm to achieve phase-matching by compensating for nonlinearities [3].
On-line synthesis of diffractive elements by optical-computer feedback
Authors: Piestun Rafael , Zaoui Igal , Tamir Einat , Spektor Boris , Shamir Joseph
Published: February 2023

The implementation of diffractive optical elements (DOE) on spatial light modulators (SLM) is a subject of growing interest. SLM’s permit to achieve reconfigurable and programmable electro-optical systems with wide applications in photonic switching, optical computing, beam shaping and beam steering. However, current SLM’s usually suffer from relatively low space-bandwidth product and various non-ideal characteristics. In addition, when utilized as part of an electro-optical system, other aberrations should be also considered. When a DOE is designed by computer, it is difficult if not impossible to take into account all these factors. Therefore, the practical result will present a reduced performance: wave-front distortion, poor signal-to-noise ratio and low efficiency. Some of the well defined system limitations could be taken into account by using optimization algorithms, but they are computationally intensive and they cannot consider all system parameters, some of which are not known.
Spectroscopy and CW Laser Emission at 1.54µm from Yb-codoped Er:KY(WO4)2
Authors: Mikhailov V.P. , Kuleshov N.V. , Lagalsky A.A. , Shcherbitsky V.G. , Neumann E. , Jensen T. , Dienning A. , Huber G.
Published: February 2023

Recently, room temperature cw laser action around 1.6 µm was demonstrated in Er,Yb- doped YAG and Y2SiO5 under pumping by Ti-sapphire laser [1] and by InGaAs laser diodes |2|. Here we report, for the first time to our knowledge , room temperature cw operation of Er,Yb:KY(WO4)2 (KYW) in the eye-safe spectral range near 1.5 µm under both Ti-sapphire and diode laser pumping.
Threshold analysis of semiconductor lasers: novel parameter extraction method
Authors: Toffano Z. , Destrez A. , Bozorgui S.
Published: February 2023

Semiconductor laser evolution throughout threshold is continuous in both power and linewidth showing a phase transition like behaviour. It is not correct to consider the below threshold behaviour as that of a light emitting diode and the above one as a fully coherent laser. The two regions obey to different mechanisms such as cavity filtered amplified spontaneous emission and carrier recombination below threshold and gain, photon lifetimes and linewidth enhancement above threshold. Few measurements of coherence behaviour have been made in the threshold region. We have previously developed a method using the Schawlow-Townes slopes below and above threshold in order to extract the linewidth enhancement factor α. [1]. Coherence evolution at threshold has been studied for classical detuned lasers based on analysis of the Fokker-Planck equation [2] but no useful expression adapted to semiconductor lasers has been given so far. We use here an analytical model enabling us, by fitting, to extract all major internal parameters of a semiconductor laser.
Study of ZnCdSe/ZnMgSe Multiple Quantum Wells Structures
Authors: Dianov E.M. , Trubenko P.A. , Shcherbakov. E.A.
Published: February 2023

The ZnMgSe ternary alloys are materials for blue-green electron-beam-pumpcd multiple quantum wells (MQW's) structures [1]. Quantum well structures with ZnMgSe have a number of advantages over ZnSc based structures. On one hand, ZnMgSe has higher bandgap than ZnSc and therefore improves separate carrier-confinement, on the other hand the capability of the tailoring Mg concentration exists to produce matched lattice to the ZnCdSe active layer, i.e. to obtain unstrained heterostructures. There are only a few papers devoted to study of ZnCdSe/ZnMgSe quantum well structures [2].
A Qualitative Improvement of the Passive Self-Injection Locking Method for Spectral Control of Dye and Ti:Al2O3 Lasers by Dual-pulse pumping
Authors: Nenchev M. , Geneva M. , Slavov D. , Stoykova E.
Published: February 2023

Passive self-injection locking (PSIL) laser control yields efficiency close to that in the optimized non-selective cavity [1]. The principle of PSIL lies in the spectrally selective reinjection through the one of the outputs in two-outputs cavity. Its main problem is the wideband free lasing at high pump levels. We show (theory, experiment) that die background emission in a PSIL-controlled dye or Ti:Al2O3 laser can be reduced drastically by dual-pulse pumping when the laser is pumped first by a near threshold pulse and second by the main pulse which is X=30+50 times the threshold. The scheme of the dual-pulse pumped PSIL-controlled two-wavelength dye laser is presented in Fig.1. The cavity is formed by the laser output mirror M1 (R=0.9) and two interference structures - M2 (R=0.7), IW1 and M3 (R=1) selects λ1 and M2 IW1 as an intermediate reflector, IW2 as a selector and M4 (R=1) selects λ2- The IW1,2 are interference wedges (thickness 5µm, reflectivity of the coatings 0.9, wedge angle 3.10-5 rad).
Highly Scattering Effect of Substituted Intralipid on Dye Doped Microdroplets for Lasing Enforcement
Authors: Taniguchi Hiroshi , Tanosaki Shinji , Tsujita Kazuhiro , Inaba Humio
Published: February 2023

Microdroplets are known to act as high-Q optical cavities with optical feedback provided by total internal reflection at the sphere-surrounding media interface. Using the spherical cavities, lasing and stimulated Raman scattering (SRS)1 have been observed when liquid microdroplets are irradiated by intense laser beams. These lasing and SRS emissions occur at discrete wavelengths corresponding to morphology-dependent resonances of the sphere.
4f-5d Transitions of Ce3+ Ion in LiBaF3 Single Crystal
Authors: Semashko V. V. , Abdulsabirov R. Yu. , Galjautdinov B. M. , Korableva S. L. , Naumov A. K. , Dubinskii M. A.
Published: February 2023

There has been recent progress in tunable solid state UV lasers due to the development of new Ce3+ doped single-crystal active materials [1,2]. Hence, the search for new laser materials based on the 5d-4f transitions of the Ce3+ ion is of high practical value.
Stability and gain properties of dye-doped polymeric active elements in a solid-state dye laser
Authors: Popov S. , Kaivola M. , Nyholm K.
Published: February 2023

Solid-state dye-doped materials offer obvious advantages over traditional liquid solutions as active medium of tunable lasers [1]. Although these materials have been under extensive investigation for a long time, considerable improvement in their lasing properties has not been achieved until recently [2]. The low stability of the dyes impregnated into the solid-state host matrices has been a disadvantage which has restricted the commercial promotion of polymer materials as the active medium in tunable lasers. Also, a complete picture of the processes responsible for dye destruction in solid solutions is still to be presented.