bluuebunny/crossref_metadata_2025 huggingface dataset:
A fiber laser using feedback from a linear and stationary cavity for mode locking
Authors: Glas P. , Naumann M. , Reng I. , Schirrmacher A. , Dong L. , Caplen J.
Published: February 2023

Bandwidth limited pulses of <15 ps duration at a repetition rate of 11 GHz with an average power of 20 mW have been obtained by coupling a cw pumped fiber laser to a very short external cavity. In contrast to previous results we have used an external cavity containing no non-linear element, and no moving external mirror, cf. Fig. 1. The light of a 1W, cw diode laser is focused on a fiber possessing an annular active region. The Nd-doped silica fiber is 90 cm long. The main cavity (length lm) is formed by the butt-coupled mirror facing the diode and the uncoated endface (reflectivity R=4%). The linear external resonator (length 1e) is formed by the aforementioned fiber endface and a dichroic mirror. It is noteworthy that the fiber laser does not reach threshold without the dichroic mirror aligned.
Optical pulse generation by manipulations in FM spectra
Authors: Okhotnikov O. G. , Araújo F. M.
Published: February 2023

The method of optical pulse generation described here employs an optical switching of CW phase-modulated signal using Sagnac interferometer incorporating asymmetrically located phase modulator. The phase modulator provides a dual function: (i) optical spectrum broadening and (ii) phase shifting between counterpropagating fields to achieve the switching. Owing to nonreciprocity introduced by the phase modulator, the totally reflecting loop becomes totally transmitting, when an instantaneous differential phase shift ΔΦ=π between counterpropagating fields is attained. It was found that in the frequency domain this switching accomplishes spectral filtering required for pulse formation without the need for filters or etalons. FM-sidebands are fully coupled in sense of being tightly locked together with the phase characteristic corresponding to a constant amplitude in the time domain. By suppression of certain frequency sidebands, one can obtain the optical spectrum with frequency components having relative phases that correspond to optical pulses. In other words, spectral filtering allows the phase modulation to be converted into the intensity modulation. The square-pulse-phasc modulation used here instead of sinusoidal modulation is an efficient method for broadening the FM-spectrum. When pulse risetime τ is much shorter then modulation period T, the switching lime window becomes short and thus high value of duty cycle and shorter pulses can be obtained. Since edges of the electrical pulse could be well fitted by linear approximation, optical pulses generated at the edges are essentially chirp-free.
Modelling of Compound-Cavity Semiconductor Lasers for Passive Harmonic Mode Locking at Terahertz Frequencies
Authors: Avrutin E.A. , Marsh J.H. , Arnold J.M.
Published: February 2023

Passive mode locking (ML) of laser diodes (LDs) at very high frequencies is an attractive subject both for scientific reasons, as it may help understand the mechanisms responsible for mode locking in LDs and limits of their performance, and for possible applications such as generating clock sequences for future TBit communications and developing compact local oscillators for THz frequency conversion.
Multiplexing of volume holograms with the minimum cross-talk noise
Authors: Mazurenko Yu. T.
Published: February 2023

The usual way to realize potentially high storage capacity of volume hologram is the multiplexing of many holograms in the single recording volume while changing the direction of the reference beam or the wavelength. The possibility for ideal multiplexing follows from Bragg conditions. During the hologrram writing. Bragg conditions correlate the wave vector of the hologram grating to the pair of wave vectors of reference and signal radiation. During the reconstruction, Bragg conditions correlate the wave vector of reconstructed radiation to the wave vectors of the hologram grating and of reading radiation. Due to this, the wave vector of reconstructed radiation is uniquely correlated to the wave vector of signal radiation. Yet strict Bragg conditions hold only for the hologram of the infinite size, and, since the size of the reall hologram is limited, these conditions are violated. Because of this, each wave vector of signal radiation is transformed into the set of wave vectors of reconstructed radiation. That leads to the cross-talk noise accompanying individual hologram reconstruction.
Nd3+ DOPED Ba2NaNbO15 Nonlinear Single Crystal Fibers
Authors: Foulon G. , Brenier A. , Ferriol M. , Cohen-Adad M T. , Boulon G.
Published: February 2023

The renewal of the second order nonlinear crystals is very strong in laser material optics. We are involved in the search of new systems based on highly nonlinear niobate crystals family. Among these crystals. Ba2NaNb5O15 is characterized by the highest nonlinear parameters, but it is unfortunately difficult to grow crackless samples.
Mixed Trihydrogen-Selenite / para-Nitroanaline derivatives: a potential family of nonlinear materials
Authors: de Matos Gomes E. , Castro L. , Nogueira E. , Belsley M. , Martin-Gil J. , Martin-Gil F.
Published: February 2023

The majority of organic nonlinear molecules, although possessing high hyper-polarizabilities, tend to crystallize in centro-symmetric structures leading to a vanishing macroscopic second order susceptibility. One possibility of inducing a noncentro-symmetric structure consists of forming hydrogen bonds with an inorganic group. In this context, organic salts of dihydrogenphosphate, such as pyperidine dihydrogenphosphate [1] and 2-amino-5- nitropyridine dihydrogenphosphate [2] have been synthesized and present reasonable second order nonlinear optical responses. In these materials a cation from a polarizable organic molecule forms a hydrogen bond with the dihyrdogenphosphale anion, leading to an alignment of the polar molecules and consequently to the formation of crystalline salts with large bulk nonlinear susceptibilities.
One- and two-dimensional charge-transfer molecules
Authors: Bosshard Ch. , Spreiter R. , Gubler U. , Günter P. , Tykwinski R. , Schreiber M. , Diederich F.
Published: February 2023

Up to now. there is hardly any intuitive assessment on which type of molecules are suitable for third-order nonlinear optics. A complete understanding on how to optimize the third-order nonlinear optical properties and additional properties dealing with applications are still lacking. In this contribution we present third-order nonlinear optical measurements and new structure-property relationships on a series of functionalized tetraethynylethene derivatives that provide further insight into routes leading to large third-order optical nonlinearities.
Doping Modification Of Photorefractive Crystal Potassium Sodium Strontium Barium Niobate
Authors: Chen H. C. , Jiang Q. Z. , Lu X. L. , Chen L.
Published: February 2023

During recent year, the photorefractive materials are attractive in many applications such as optical image processing and optical computing because they have more lower threshold power and easily realize phase conjugation Potassium sodium strontium barium niobate crystal is one of the best candidates. It has open structure and large structure tolerance for dopants with different valence There are two different ways to improve the photorefractive properties of the materials. 1) by adjusting the composition of materials and 2) doping cation ions. This paper is to describe the doping effects on the ferroelectric and photorefractive properties. The composition of potassium sodium strontium barium niobate was chosen as 92% of A-sites occupied by K, Na, Sr and Ba ions. The dopants such as Ce, Pr, Fe, Co, Ni, Cu, Ti and Mn with 0.01-0.1wt% were adopted for modifying the properties. Potassium sodium strontium barium niobate crystals were grown from platinum crucible by Czochralski method with induction heating in air atmosphere. The growth conditions are pulling direction: [001], the rate of pulling/rotation: 0.2-0.4. The size of as-grown crystal is up to ϕ 35 × 35 mm From the shape of hysteresis loops, the doping effect on ferroelectric properties of potassium sodium strontium barium niobate crystals were revealed to have three categories: expansive, stable and shrink for Fe, Cu and others, respectively After the temperature recycle from 100 to 500K, the d33 value for Cu-doped crystal does not change, which suggest that the Cu ion is a good polarization stabilizer. The self-pumped phase conjugation refractivities for Ce, Co and Cu-doped crystals are much higher than the others. They are 70% at 514.5nm for Cu-doped, 73% at 514.5nm for Co-doped and 84% at 632.8nm for Ce-doped respectively.
1.2 J High Energy Diode Pumped 1535 nm Er3+,Yb3+: Glass Laser
Authors: Wu Ruikun , Hamlin Scott J. , Myers Michael J. , Myers John D. , Hutchinson J. Andrew , Marshall Lawrence T.
Published: February 2023

Laser emission at 1535 nm from Er3+: glass is interesting due to its eyesafe wavelength and high atmospheric transmission. Diode laser pumping of the Er:Glass laser rod dramatically reduces thermal effects when compared to flashlamp pumping, allowing operation at higher repetition rates with higher average output power. This technology opens new opportunities for use in many applications such as ranging, target designation, laser radar, environmental sensing, collision avoidance, law enforcement and wind shear detection.
Auto-Stacking of high power laser diode arrays A cost-effective approach for delivering 10 kW/cm2
Authors: Fillardet T. , Brousse E. , Duchemin J. P , Volluet G. , Hirtz J. P.
Published: February 2023

For two dimensional laser diode arrays, microchannel and impingement coolers have been used successfully to produce low thermal resistance actively-cooled packages. For a repetition rate of 100 Hz, stacks with maximum optical power density of 2.5 kW QCW/cm2 are currently under development.
Spatial and time-domain evolution of ultrashort optical pulses in semiconductor flared amplifiers
Authors: Dagens B. , Balsamo S. , Montrosset I.
Published: February 2023

The amplification of ultrashort optical pulses in semiconductor laser amplifiers has been the subject of considerable research interest in recent years, because of the potential applications in high-speed communications and logic systems. Flared single-pass amplifiers have achieved the highest coherent CW output power [l] and can give very good results also for pulsed operation [2]. In this paper we present for the first time a systematic investigation on the contribution of the various physical effects to the pulse amplification and to the temporal, spatial and spectral behavior.
The influence of internally circulating modes on the performance of 980nm pumping laser diodes
Authors: Keh Y. C. , Yu J. S. , Pak G. , Kim T. I.
Published: February 2023

This paper presents a new experimental result about the influence of internally circulating modes(ICM) on the external quantum efficiency of InGaAs/GaAs/AlGaAs based single quantum well laser diodes with the wavelength of 980nm. The influence of ICM on laser performance is much stronger in the case of quantum well structures than in the case of the bulk active layer structures since the super thin active layer(thickness~6nm) allows substantially less absorption in the light travelling path in resonator. This latent ICM in optical resonator obviously deteriorates the external quantum efficiency of the laser emission from front and rear mirror facets.
Inertial Confinement Fusion Applications of High Power Iodine Lasers Iskra-4 and Iskra-5
Authors: Kochemasov G. G
Published: February 2023

In the Russian Research Institute of Experimental Physics (Russian abbreviation is VNIEEF) main purposes of laser fusion activity are development of high power and high energy lasers, creation and investigations of hot dense plasma, determination of ignition conditions.
A two dimensional copper vapor laser code
Authors: Borgard J. M. , Lemaire P.
Published: February 2023

We have developed a 2D axisymetric model of time-dependent simulation of copper vapor discharge with similar assumptions as Kushner [1] for Maxwell equations. The model includes electromagnetic behavior, as well as electrons-atoms collisions, radiative emissions [2], light and heavy species transportation and conductivity, and photonic propagation.
Space-Time Controlling of High-Power KrF Laser Beam During Target Irradiation
Authors: Zvorykin V. D. , Metreveli G. E. , Sychugov G. V.
Published: February 2023

Laser irradiation of a target may be an effective way to initiate phase transitions in the matter, e. g. graphite-diamond transformation during shock loading of a specimen by an ablation pressure. The power density of about 1012 W/cm2 to produce megabar pressure and pulse duration exceeding the time of transformation, i.e. about 100 ns, are needed for such experiments. The spot diameter on a target has to be compared with the extention of a compressed region defined by the product of the front velocity in a specimen and laser pulse duration in order to prevent lateral unloading. It is typically of some hundred microns. By combining these values one can obtain the necessary laser energy of about 100 J. Short-wavelength high-power KrF laser “GARPUN” pumped in a transverse geometry by two counterpropagating relativistic electron beams1 satisfies well these conditions.
Prismless Kerr-lens mode-locked femtosecond Cr:LiSGaF laser
Authors: Sorokina I. T. , Sorokin E. , Wintner E. , Cassanho A. , Jenssen H. P. , Szipöcs R.
Published: February 2023

Cr3+ -doped LiSrA1F6 (Cr:LiSAF) and LiSrGaF6 (Cr:LiSGaF) are especially attractive laser materials for the development of compact and robust ultrafast sources. They provide broad-band gain over a spectral region similar to Ti:sapphire (Ti:S) and are suitable for laser diode pumping. Kerr-lens mode-locked (KLM) Cr:LiSAF laser already allowed to realize pulses as short as 18 fs [1] whereas the Cr:LiSGaF laser has the advantage of substantially higher achievable output powers [2]. Recently, a novel "chirped mirror dispersion control” approach has been suggested and successfully realized in a Ti:S laser [3], allowing to produce stable, sub-10 fs pulses from a prismless Ar+-pumped oscillator [4]. The first prismless diode-pumped Cr:LiSAF laser based on a semiconductor saturable absorber mirror (no KLM action) with Gires-Tournois (GT) coating was realized last year by Kopf et al. [5], producing 160 fs pulses at 25 mW output power, limited by the thermal damage of the semiconductor mirror.
Ultrafast Diode-Pumped Lisaf Lasers
Authors: Falcoz Franck , Balembois François , Georges Patrick , Brun Alain
Published: February 2023

LiSAF crystals (LiSrAlF6 doped with Cr3+ ions) are very interesting amplifier materials due to a large fluorescence bandwidth in the near infrared (800 nm to 1 μm) and an absorption band in the red (600-700 nm). Commercial high power single-stripe laser diodes emitting in this wavelength band are available since a few years. In the field of ultrashort pulses, there is a great interest to develop compact, all solid state diode-pumped ultrafast lasers. Lasers based on LiSAF crystals have the potential to replace Argon-pumped Ti:Sapphire femtosecond lasers for applications where the average power is limited to around 100 mW (seeding an amplifier for example).
Self-Stabilizing Additive Pulse Mode-Locked Nd:YAG Laser
Authors: Groninga H. , Harde H.
Published: February 2023

The coupling of a laser resonator to an external synchronous cavity containing a nonlinear optical element, typically an optical fiber, has proven to be an efficient means for mode­locking of lasers. This concept, originally used in soliton lasers, is known as additive pulse mode-locking (APM) and has also been successfully applied to lamp-pumped Nd:YAG lasers. For these lasers it has been demonstrated that the pulse width can be reduced by more than an order of magnitude compared to an actively mode-locked laser [1,2].
Ultrastable operation of a diode-pumped, passively mode-locked Nd3+ doped fluoride fiber laser emitting at 1.05μm
Authors: Wegmüller M. , Hodel W. , Weber H.P.
Published: February 2023

Regenerative amplifier systems arc attractive for various scientific and medical applications. The growing importance of these systems has led to a considerable advancement in reducing their sizes and costs, resulting in the demand for seed sources that are compact as well. A very attractive way to realise such a seed source for the important lμm wavelength range is presented in this work. It consists of a Nd-doped ZBLAN fluoride fiber laser which is carrier type mode-locked (CTM) by insertion of a saturable absorber (SA) into the cavity. The method of CTM mode-locking is self-starting and allows for a simple and compact set-up. The use of a fluoride host shifts the laser wavelength to a value in the range 1048-1052nm matching optimally the gain peaks of Nd:Glass and Nd:YLF regenerative amplifiers, which is not possible within a silica host.
The Diode-Pumped Monolithic Nd:YAG Laser - a new Tool for High-Resolution Force Sensing
Authors: Holzapfel Wolfgang , Neuschaefer-Rube Ulrich
Published: February 2023

We present a new method of accurate force measurement by applying the intracavity photoelastic effect in Nd:YAG-laser crystals. This technology allows a significant extension of the measurement range and improvement of the relative resolution compared to well-known optical fiber force sensors. Nd:YAG technology also offers the chance to realize high-accuracy force-measuring sensors in a miniaturized and integrated design. Active stabilization of the laser is not necessary.
Spectroscopic Based Oxygen Sensing Using VCSEL and DFB Single Frequency Laser Diodes
Authors: Weldon V. , O'Gorman J. , Pérez-Camacho J. J. , Hegarty J.
Published: February 2023

Gas detection based on direct optical absorption spectroscopy using single frequency distributed feedback (DFB) laser diodes is a well established sensing technique. Only recently, vertical cavity surface emitting lasers (VCSELs) which also provide narrow single frequency emission and arc considered suitable for these sensing applications have become available. We compare such laser structures for use in high sensitivity gas sensing applications and report on some key device characteristics which influence the relative performance of the two laser types for low gas detection limits by targeting the R and P rotational branches of the A band of Oxygen in the b1Σ+g<− X3Σ−g electronic transition which is centred at 762 nm.
Holographic Interferometry Of Superorbital Test Flows
Authors: Wegener Margaret , Bishop Alexis , McIntyre Tim , Rubinsztein-Dunlop Halina
Published: February 2023

The laser-based optical technique of holographic interferometry has been applied to diagnosis of very high enthalpy flows produced in a superorbital expansion tube. This facility, X1, is capable of simulating conditions experienced by spacecraft travelling at superorbital speeds through planetary atmospheres. Holographic interferometry enables visualisation and non-intrusive measurement of integrated gas density.
Applications of Nonlinear Optics Methods in Molecular Dynamics Studies
Authors: Rosenwaks S.
Published: February 2023

The possibility of directing the course of chemical reactions by photoexcitation of specific modes of nuclear motion, so called mode-selective chemistry, continues to intrigue physicists, chemists and biologists. In this presentation we will address the application of stimulated Raman excitation, coherent anti-Stokes Raman scattering, overtone infrared excitation, laser induced fluorescence and multiphoton ionization techniques to preparation and detection of particular rovibrational states of the parent and product species in photodissociation and reactions of small molecules. Bond- and mode- selective processes in these species arc particularly appealing for both theoretical and experimental studies. This is because they are small enough to allow ab initio calculations of potential surfaces and photodynamics and yet retain the complexity of different vibrational degrees of freedom. However, quantitative comparison with theory requires experiments that prepare reactant molecules in specific initial states to avoid the averaging over different quantum states. Also, it is necessary to determine accurately the populations in the various final quantum states of the photofragments.
Tunable Laser Diode for Absolute Distance Measurements
Authors: Hafidi A. , Pfeiffer P. , Meyreuis P.
Published: February 2023

Tunable and narrow linewidth semiconductor lasers are useful in variety of measurement such as a spectroscopy1 and heterodyne optical communication system. Our application is to use this tunable laser diode for absolute distance measurement. At first we have developped an external cavity in the Liftman configuration, composed by a commercial laser diode (without any special antireflexion coating). We focus our theory on the pivot axis position of the external mirror. With this theory only rotary motion is required for continuous tuning. Tunability tests show (fig1) that this laser can be tuned continuously on a frequency range of 60 GHz centered on the axial modes of the external cavity.
Recent Advances in High Power IR Gas Lasers
Authors: Bohn W.L.
Published: February 2023

Before addressing the recent advances in high power infrared gas lasers a general attempt is untertaken to describe the upcoming competing situation between gas lasers on one hand and solid state and semiconductor lasers on the other. Although all solid state coherent light sources show undoubtfully many attractive features, gas lasers still dominate when it comes to very high powers, high beam quality, and high coherence properties.
Opto-mechanical Q-switch shutter with no wearing parts
Authors: Georgiou E. , Papadakis A. , Fotakis C.
Published: February 2023

Mechanical devices for laser cavity Q-switching exhibit desirable features including insensitivity to laser wavelength, beam polarization and laser crystal birefringence, plus absence of background optical losses in the open state. On the other hand, most mechanical Q-switches suffer from wear of moving parts, resulting in limited lifetimes.
Phase and Shape Evolution of Light Pulse Propagating in Birefringent Crystal with Second-Order Nonlinearity
Authors: Belostotsky A. L. , Gorchakov A. V. , Fedjukhin L. A.
Published: February 2023

In this paper we consider the phase and shape evolution of a light pulse that propagates through a birefringent crystal with second-order nonlinearity. We assume the incident light wave to be linearly polarized in the way that at the input of crystal the ordinary and the extraordinary waves are generated. In this case the second-harmonic generation is the result of three-wave nondegenerate interaction (the process of type II). We assume also the process to be phase-matched Δk = k(2ω) - k1(ω) - k2(ω) = 0.
Visible pulsed Optical Parametric Oscillator pumped by Nd:YAG Laser at High Repetition Rate
Authors: Baillon B. , Le Garrec B.
Published: February 2023

Pulsed optical parametric oscillators are efficient sources of broadly tunable coherent radiation. With the recent developments of new nonlinear crystals and efficient pulsed high average power Nd:YAG Lasers, it is now possible to pump OPOs at high repetition rate (from 1 kHz to 10 kHz).
Comparison of Proton Implanted and Selectively Oxidized Vertical-Cavity Surface-Emitting Lasers
Authors: Grabherr M. , Weigl B. , Reiner G. , Ebeling K.J.
Published: February 2023

Performance of vertical-cavity surface-emitting lasers (VCSELs) has drastically improved using selective oxidation for current confinement[1]. Due to the lowered refractive index of the oxide the current aperture also induces lateral optical index guiding Proton implantation offers a planar device structure but the high energy implantation induces vacancies and centers for non-radiative recombnation at the perimeter of the active region. Therefore very small single mode devices with diameters below 5 μm an threshold currents below 100 μA can only be produced by selective oxidation. Thermal conductivity of the implanted material is reduced by a factor of two and a trade off between contact area and shading of the outcoupling facet has to be accepted. Optical guiding in proton implanted lasers is due to a superposition of gain guiding and thermally induced index guiding that changes for different driving conditions.
Investigation on Relaxation of Light-Induced Holographic Grating in Resonant Liquid-Crystal Medium
Authors: Kamanina N.V. , Danilov V.V.
Published: February 2023

On interaction of laser pulsed irradiation with a liquid-crystal (LC), a number of phenomena associated with nonlinear orientation effects, thermal modulation of refractive index, and conformational photo-conversion of molecules can arise.
A Way of Enhancing the Intensity of Radiation in Solid State Lasers with Radiation Loss
Authors: Chemyshev A. V. , Fefelov A. P. , Khomenko S. I.
Published: February 2023

As distinct from conventional linear resonators, in radiation-loss resonators the effective loss is modulated by switching the shutter in an optical assembly incorporating the shutter and mirrors. To achieve the stated mode of operation, the authors have developed an FTIR-effect based shutter [1] with the properties of a dynamic apodizing diaphragm (DAD).
Selection of polarisation and transverse modes in birefringent vertical-cavity surface emitting lasers (VCSEL)
Authors: Valle A. , Pesquera L. , Shore K.A.
Published: February 2023

The polarisation of the fundamental transverse mode of VCSEL can change when the injected current is altered. Switching of the polarisation associated to the excitation of higher order modes has been observed. It has also been noted that the strain induced during the fabrication causes birefringence in VCSEL.
High Sensitive Fiber Interferometric Pressure Sensor
Authors: Belovolov M. I. , Bubnov M. M. , Semjonov S. L.
Published: February 2023

Fiber Fabry-Perot Interferometric sensors (FFPI-sensor) have been shown to possess high sensitivity for the measurement of different parameters. We present the operation of a new extrinsic FFPI-sensor modified for the pressure measurements with high sensitivity and effectively reduced the thermal crosstalk.
Secondary Chemical Reaction Effects Upon Photodissociation of UF6
Authors: Baranov V. Yu. , Dyadkin A.P. , Kolesnikov Yu. A. , Kotov A.A. , Novikov V.P. , Pigulskii S.V. , Razumov A.S. , Starodubtsev A. I.
Published: February 2023

In this paper results of experimental research of UF6 dissociation using repetitively pulsed CF4 laser are presented. The pulse energy was in the range 45-130 mJ and the pressure of UF6 was 0.3-0.6 torr, the cell volume was 16 cm3. From pulse to pulse behavior of UF6 photodissociation relative yield, i.e. fraction of the dissociated molecules for every pulse related to the molecules number before pulse, is investigated. It is revealed that in the irradiated region of the cell where the radiation fluence is more than the threshold one, i.e., Φ ≥ Φ0 = 1 J·cm−2, from 35 to 50% of the UF6 molecules dissociate due to the first pulse and after some following pulses the relative yield sharply decreases. For a moment when the dissociated molecules fraction is a half of their quantity, the relative yield decreases by factors of 4 to 10, depending on initial UF6 pressure in the cell and on the pulse energy. To bring out causes of such effects, we consider here processes upon the photodissociation, i.e., diffusion of its products out off irradiated region, formation of UF5 polymers, recombination of UF5 and UF5 polymers with atomic fluorine, accumulation and losses of the atomic fluorine, ets. Estimations of the appropriate reaction roles and their possible effect upon relative photodissociation yield decreasing from pulse to pulse that was found in our experiments are presented.
Phase - Formation and Mass - Transfer in Alloys under Micro - Floating - Zone Crystallization Induced by Laser Melting of the Surface
Authors: Nishchenko M.M. , Likhtorovich S.P. , Patoka V.I. , Shevchenko N.A.
Published: February 2023

Under the pulsed laser melting of thin surface layer the velocity of solidification front reaches larger values comparable to those of the atoms diffusion rate in the melt. This results in enhancement of the kinetic effects such as the “capture” of the impurity and alloy’s constituent atoms, segregation suppression, “diffusionless” solidification, etc. As a consequence, the heterogeneous non - equilibrium structure is formed in the surface layer which consists of the stable, metastable crystalline or amorphous phases with high defect concentration in particular, structural vacancies specifying specific properties of the layer formed.
CuNiOx Bimetallic Oxides Obtained by Laser Irradiation of Mixed Copper and Nickel Salts
Authors: Alexandrescu R. , Morjan I. , Voicn I. , Pugna G. , Petcu S. , Popescu C.
Published: February 2023

In this work we aim to present our results on the laser production and characterization of mixed oxides of copper and nickel, obtained by irradiation of different metal salt precursors.
Deposition of Elements from Organometallic Compositions under the Action of Laser Radiation
Authors: Mulenko S.A. , Nishchenko M.M. , Ovechko V.S.
Published: February 2023

Deposition of elements from organometallic compositions under the action of laser radiation has a great interest for maskless solid state technology in microelectronics and opto­electronics. Carbonyls of transitional metals such as Cr(CO)6, Mo(CO)6 and Fe(CO)5 were used in the present work. Deposition of elements in conditions of the present experiment was thermochemical - deposition under the action of cw CO2-laser radiation from Cr(CO)6 vapors and photochemical - deposition under the action of KrF-laser radiation (λ
L
= 2 48 nm) from Mo(CO)6, Fe(CO)5 vapors;deoosition under the action of Ar+-laser radiation (λ
L
=488 nm) from Fe(CO)5 vapors.
Numerical and experimental analysis of radiation pressure on micro-objects
Authors: Ohmachi Yoshiro , Baba Kazuhiro , Higurashi Eiji
Published: February 2023

Remote suspension and/or manipulation of micrometer-sized particles can be achieved by subjecting the particles to a laser beam.1 A laser beam can also be used to rotate objects with artificial non-symmetrical structures.2 In this paper we present numerical results for radiation force exerted on a sphere and on a ring. The predictions were confirmed by experimental measurement.
Rotational manipulation of trapped micro-objects about their axes perpendicular to the laser beam axis by radiation pressure
Authors: Higurashi E. , Sawada R. , Ohguchi O. , Tamamura T. , Ukita H.
Published: February 2023

The development of optical trapping by a single focused laser beam, also known as optical tweezers (1), has made it possible to manipulate various particles including biological cells, metallic particles (2), and low-refractive-index micro-objects (3). We recently reported the application of optical trapping to rotational manipulation of artificial micro-objects in micro-mechanical systems (4). Rotation was due to the optical torque from the optical radiation pressure exerted on the outside of micro-objects that had shape anisotropy. The axis of this rotation coincided with the incident laser beam axis (2, 4, 5). In an effort to change the direction of the optically induced torque, this paper investigates the possibility of optical trapping and simultaneous rotation about an axis perpendicular to the incident laser beam axis by illuminating an object with a strongly focused laser beam.
Investigation of CO2-Laser Component Losses Using a Scanning-Interferometer
Authors: Jakob G. , Saetehnikov V. , Schiffner G.
Published: February 2023

A method to measure the reflectivity of laser mirrors and to determine optical losses of laser elements Such as windows, capillaries and especially waveguides including slab waveguides has been developed. Measurements have been carried out using a Scanning-Fabry-Perot-Interferometer wind, forms a stable optical resonator and creates thereby laser-like conditions. One mirror is movable by a circular arrangement of piezo elements to tune resonator length by several laser wavelengths. Laser power is coupled into the interferometer and power transmitted through or reflected by the interferometer can be described by Airy-functions. Both values are functions of interferometer length and depend on optical losses within the interferometer. Evaluating measured Airy-curves enables the determination of losses in stable resonators, in waveguide resonators, and also in hybrid slab-waveguide resonators, the latter using cylindrical mirrors. The reflec- tivity of different laser mirrors, the optical losses of alumina ceramic and copper waveguides and coup bug losses were determined for different wavelengths between 9.2 µm 10.8 µm The standard deviation is about 1% of resonator losses. Losses of ceramic-waveguide resonators have been measured for different mirror-waveguide gaps, varying mirror tilt-angles and with apertures placed close to the mirror. Measured optical losses show some minima and maxima at different mirror-waveguide distances. Moreover, it was observed that an aperture placed between the waveguide and the mirror can reduce measured losses.
Discretely tuned radiation generation via stimulated Raman scattering in Ba(NO3)2 crystal
Authors: Karpukhin S.N.
Published: February 2023

SRS of the neodymium laser radiation in the ion-molecular crystals provides of the discrete set of radiation wavelengths, including, in particular, the emission in the eye-safe range of spectrum. This paper is devoted to study of SRS in barium nitrate [1] (Δω=1046 cm–1) of the multi mode radiation of lasers on YAG:Nd and KGT:Nd. The pump was focused into the crystal with the length of 8 cm by the lens with the focal length of 19 cm. In the Fig. 1 are shown the dependencies of the pump energy conversion efficiency (λp1 = 1.064 µm and λp2= 1.067 µm) to the SRS components. The spectrum width in this experiment equaled Δνp1=0.5 cm–1 (YAG) and Δνp2=l-8 cm–1 (KGT), pulse duration was 10 ns, beam diameter - 5 mm and its divergence - 6′. The maximal conversion efficiency to the first stokes component (λ=1.2 µm) was limited by the excitation of the second stokes component (λ=1.37 µm) at the level of 40 % for both variants of the pump. Opposite directed generation was observed only in the case of pumping by YAG laser. That is why in this case the rate of the conversion to the first stokes component efficiency growth was lower. The maximal total conversion efficiency equaled ~63% for the pumping energy of 10.. 15 mJ for KGT laser.
Experimental Investigation and Mechanism of the Photostimulable Storage Phosphor BaFBr:Eu2+
Authors: Bradford M. , Andrews D.A. , King T. A.
Published: February 2023

BaFBr:Eu plates are commonly used in radiography and crystallography as a reusable imaging device for X-rays, converting the high energy radiation to visible wavelengths. An understanding of the mechanisms involved in the excitation, optical interrogation and storage properties of the phosphor would allow detectors to be designed effectively for specific applications. Environmental radiation monitoring and dosimeter replacements for film badges are possible applications.
The Lidar Facility at Utah State University for Middle Atmosphere Observations
Authors: Wickwar V.B. , Wilkerson T.D. , Collins S.C. , Rees D. , Rees David
Published: February 2023

During the past three years. Rayleigh-scatter lidar observations have been carried out at Utah State University with a small receiving telescope and a powerful Nd:YAG laser (Wickwar et al, 1995). The combination provided a power-aperture product of 3.4 W.m–2 at 532 nm for vertical determinations of the temperature structure between 40 and 90 km. A greatly improved lidar facility is currently under development at this mid-latitude site (41.7 N, 111.8 W, 1.5 km) in the middle of the Rocky Mountains. The major elements consist of a fully steerable, large-aperture telescope (based on four specially designed, 1.27-m minors), two solid stale lasers — a powerful, seeded, Nd:YAG laser operating at 532 nm, as before, and an extremely stable, seeded, alexandrite ring laser tunable between 700 and 810 nm—and modem spectral analysis and signal detection systems. Combining the new pointing capability with a power-aperture product greater than 85 W.m–2, the Nd:YAG laser will be used to determine density, temperature, and wind velocity between 10 and 90 km. A combination of power observations from Rayleigh scatter and spectral observations from both Rayleigh and Mie scatter will be used. Our collaboration with Light Age, Inc., has led to the development of a very stable, spectrally narrow, alexandrite ring laser. By using various combinations of direct emission, Raman shifting, and frequency doubling, resonance-scatter observations can be made from most of the elements, e.g., Na, K, Ca+, Al, Mg, Fe, etc. deposited in the atmosphere between 80 and 110 km by meteoric decay. Furthermore, by precisely stepping the emission from the laser system over the backscatter cross section of one of these elements, the resultant spectral observations can be used to determine the temperature and wind velocity in this altitude region. This upgraded CASS lidar facility will thus provide extensive, high time-resolution observations throughout the middle atmosphere from 10 to 110 km, from the troposphere into the lower thermosphere.
ESA R&D Programmes in Optical Remote Sensing From Space
Authors: Armandillo E.
Published: February 2023

Optical remote sensing from space is an important tool for the study and monitoring of the Earth and its environment. The European Space Agency has specific programmes focused on remote sensing of the Earth for Meteorology and Environmental applications. The present European satellite network relies on data coming from passive optical and microwave imagers and sounders. To meet the requirements posed by Meteorology and Climatology in the years 2000+, new or advanced instrumentation is required, such as lidars, or high resolution optical imagers for example. To timely ensure the availability of key technologies, the Research and Development Programme of the Agency has addressed over the past years critical sensor technologies.
Organic and Inorganic Photorefractive Materials
Authors: Gunter P.
Published: February 2023

The photorefractive effect as space-charge induced refractive index changes in inorganic electro-optic crystals and ceramics has been investigated extensively during almost three decades. In organic crystals the same effect had been discovered in COANP:TCNQ in 1989 [1]. Later on , three other organic crystals prepared in our laboratory have been shown to be photorefractive [2-4]. In addition to the photorefractive effect a similar effect due to the formation of space-charge induced orientational gratings has been found in poled polymers by several authors. Since the origin of the refractive index changes had not been recognized properly at the beginning, this effect was also called "photorefractive".
Photorefractive Sol-Gel Films
Authors: Darracq Bruno , Riehl Didier , Canva michael , Lévy Yves , Brun Alain , Chaput Frédéric , Boilot Jean-Pierre
Published: February 2023

We shall report about photorefractive hybrid xerogel film that were, for the first time to the best of our knowledge, synthesised by the sol-gel process. The silica backbone possesses covalently anchored non-linear optical chromophores (disperse red one) and charge transporting groups (carbazole units). The starling solutions were obtained from copolymerization of carbazole- and DRl-attached silane monomers with tetraethoxysilane (TEOS). A small amount of 2,4,7-trinitrofluorenone was also added to increase the photosensitivity in the visible. Thin films of thicknesses ranging from 0.5 to 5 micrometers were deposited on ITO-recovered glass substrates using the spin-coating technique.
Acoustooptic Modulator for Fibre Optic Gas Sensor Based on Midwave InGaAsSb/InAsSbP Diode Laser
Authors: Kulakova L.A. , Zotova N. V. , Karandashov S.A. , Matveev B.A. , Melekh B. T. , Stus' N.M. , Talalakin G. N.
Published: February 2023

There has been an increased interest in infrared gas sensing using novel LEDs and diode lasers emitting in the mid-IR spectral range. Such sources are especially attractive for fibre optic applications and spectrometers because of small size and high efficiency in the spectral range where most of industrial gases have characteristic absorption bands. For that reason of interest are new light modulators which can be coupled with the above sources operating at CW or pulse mode. The report presents data on new acoustooptic modulator based on amorphous Si-Te alloy and utilized in fibre optic hydrocarbons sensor based on InGaAsSb/InAsSbP diode laser emitting at 3.3 µm.
Novel Cavity Configurations for Self-Mode Locked Kerr-Lens Solid-State Lasers
Authors: Poloyko I.G. , Kalashnikov V.L. , Kalosha V.P. , Mikhailov V.P.
Published: February 2023

It is well known that mode-locking abilities of Kerr-lens mode-locked lasers strongly depend on spatial cavity configuration. A variation of intracavity spacings provides a control for system’s discriminating strength that favors high-intensity radiation against a low-intensity one. So, it is necessary to adjust precisely the system near the boundary of the stability zone. There is a number of publication devoted to the optimal geometries of Kerr-lens mode-locked lasers, mainly, for z-fold four-mirror resonators. However, yet not the whole potential of optimization has been worked out. Also, the possibilities of other than four-mirror resonators, i.e. two- and three-mirror resonators were not addressed at all, except very few experimental works
Spaceborne Incoherent Doppler Wind Lidar: A Review of Progress
Authors: Rees D. , McKay J. , Wilkerson T. , Wickwar V.B. , Gandham I. , Rees David
Published: February 2023

The Technique of Incoherent Doppler Lidar Detection (IDWL) has recently been successfully demonstrated in ground-based systems which use the Rayleigh-scattered or resonance-scattered signals from suitable stable narrow-band pulsed lasers (Rees et al, 1996, von Zahn et al, 1995). The design and engineering concepts and performance of the laser and detection systems will be reviewed, and then extended in the context of the requirements for a space-borne IDWL System.
Semiconductor Lasers: Recent Advancesand Prospects
Authors: Ebeling K.J.
Published: February 2023

Semiconductor lasers have made exciting progress in performance over the last few years with prospective applications e.g. in optical communications and data storage, metrology, display technology, material processing, or solid state laser pumping. The short wavelength limit of semiconductor laser emission has now been pushed to 410 nm using GaN based devices. High power broad area lasers in the well established InAlGaAs material system offer several 10 W continuous output power at power conversion efficiencies above 60%. Beam profile control is obtained in hybrid or monolithic master oscillator power amplifier (MOPA) configurations. Communication laser diodes show small signal current modulation bandwidths 40 GHz and are applied for 20 Gbit/s data transmission. Extremely low laser threshold currents of less than 10µA as well as more than 50% conversion efficiency at 1 mW output power are reported from novel selectively oxidized vertical cavity surface emitting laser diodes (VCSELs).
Status and Future Optical Data Storage
Authors: Bell A.E.
Published: February 2023

Summary not available
Semiconductor Lasers for Short Pulse Generation
Authors: White I.H.
Published: February 2023

In recent years, there has been much interest in short optical pulse generation by diode lasers, particularly in optical communication and signal processing systems, where high repetition rates of over 100 GHz can readily be achieved. However, as diode lasers have been developed with greater optical powers over a wider range of wavelengths, further applications for short pulse generation have been recognized in optical sensing and rangefinding, optical pumping, frequency conversion and spectroscopy.
XeCl Mopa for Shock Hardening
Authors: Branly S. , Godard B. , Fabbro R.
Published: February 2023

An excimer XeCl MOPA has been developed by SOPRA for applications such as X-ray generation and shock hardening of metals and alloys.
High quality electron beams generated from rough Cu cathodes and a KrCl laser
Authors: Nassisi V. , Giannico E. , Rainò A.
Published: February 2023

In this work we studied an electron beam source using an KrCl excimer laser and three Cu cathodes having three different roughness values: 0, 3.5 and 9 µm. The experimental apparatus is shown in Fig.1. The laser beam illuminated the cathodes by a convergent lens accelerating the electrons generated from cathode. The electron beam total current was monitored by a fast Rogowski coil while the beam quality was estimed determining the beam emittance. For this last measurements a slit-slit method was used1. Namely, the electron beam was selected in small beamlets by the first slit array and the beamlet direction spread was monitored moving the second slit arrays and measuring the current by the small Faraday cups, see Fig. 1.
Powerful Lasers Pumped by Discharge from Generators with Inductive Energy Storage
Authors: Tarasenko Victor F. , Baksht Evgenii H. , Lomaev Mikhail I. , Orlovskii Victor M. , Panchenko Alexei N.
Published: February 2023

Earlier we have demonstrated the possibility to use pulse generators with inductive energy storage and opening switches of different types (plasma erosion opening switch, crossatron, semiconducting diodes) for pumping N2, XeCl and Ne Penning plasma lasers1. It was shown that these generators allow to vary pumping regimes and provide optimal excitation of lasers of different types. However, the absence of simple and reliable opening switch providing interruption of a current with amplitude of several units-hundreds of kA and generating voltage pulses of several tens-hundreds of kV limited this pumping technique. The use of industrial semiconducting diodes of SDL type which under certain conditions have the property to interrupt current passing in the opposite direction and development of special semiconducting opening switches (SOS)2 significantly expands the possibilities of application of generator with inductive energy storage (IES).
Experimental Probe of Gaps in Photonic Crystals
Authors: Vos Willem L. , Wijnhoven Judith E.G.J. , Megens Mischa
Published: February 2023

Photonic crystals are 3D periodic composites of dielectric materials with lattice spacings of the order of wavelengths of light. Such crystals show stop gaps in the dispersion relations, that are revealed as optical Bragg reflections. If light interacts strongly with photonic crystals, stop gaps broaden and may merge to form photonic band gaps. In anticipation of band gaps, it is thus important what is a useful experimental probe of stop gaps, especially the widths. Previously, transmission measurements were done, and analyzed in terms of the width or the attenuation of the stop gaps. The interpretation of transmission experiments is severely hampered, however, by polycrystallinity or crystal imperfections, that are difficult to avoid.
Photonic Crystals in Planar Waveguides
Authors: Atkin Dale M. , Russell P.St.J. , Hempstead M.
Published: February 2023

A number of groups world-wide are investigating the use of two dimensional photonic crystals (2-D PC)1 to enhance the efficiency of solid state lasers and light emitting diodes. They hope to suppress the lateral emission of light by creating an in-plane photonic band gap (PBG). The performance of such structures will only be attractive if waveguiding is built into the designs. Previous work has shown that, in planar waveguides with a strong 1-D PC2, novel high-Q resonances occur. In this paper we present measurements of 2-D PC in planar waveguides and consider their relevance to non-linear frequency conversion in semiconductor waveguides.