bluuebunny/crossref_metadata_2025 huggingface dataset:
State of the Art in Optical Stress Analysis
Authors: Rastogi Pramod K.
Published: February 2023

Optical techniques have long been useful for obtaining measurements of flow fields and in experimental solid mechanics. The applications have touched upon a large class of measurement problems. The scope of the present paper will limit to application of these techniques in experimental solid mechanics. A common feature of most of the optical interferometry based methods is that the information is presented in the form of interference fringes in the image of the object under investigation. The interference pattern or the optical phase map provides a visual description of the changes in the optical path length undergone between the initial undeformed and deformed conditions of the specimen surface. While the global visualization of deformation fields is always informative and has been used to advantage in the area of nondestructive testing, there has developed a considerable amount of sustained interest to obtain quantitative information on the measurement of wavefront distortion caused by loading the specimen.
Spatially resolved measurements of density fluctuations with a hybrid Doppler/time-of-flight laser anemometer
Authors: Junker W. , Saffman M. , Lading L.
Published: February 2023

Collective light scattering from density fluctuations is an established approach to optica! velocimetry that is applicable in flows without light scattering particles. It has traditionally been applied to plasma diagnostics [1], while recent interest has considered the use of collective scattering for velocimetry of high speed flows[2,3], where particles are either difficult to introduce, or do not accurately reflect the flow statistics. A generic limitation of this method is that the poor axial resolution results in measurements that are spatially averaged. We have introduced recently a hybrid Doppler/time-of-flight configuration [4], that provides improved axial resolution.
The Remote Analysis Of Nuclear And Non-Nuclear Materials Using Laser Induced Breakdown Spectroscopy
Authors: Young J. , Botheroyd I.M. , Whitehouse A.I.
Published: February 2023

Laser induced breakdown spectroscopy is a form of optical emission spectroscopy and was first proposed in 1962 [1]. The basic experimental set-up of laser induced breakdown spectroscopy is shown in figure 1, where the induced plasma luminescence is spectrally analysed. This in turn provides a unique spectral signature of the target material composition.
A New Model for Orientational Dynamics in Nonlinear Optics
Authors: Andrews David L. , Hands Ian D
Published: February 2023

It is shown how the algebra of weighted orientational averaging1 may be extended to model the temporal evolution of nonlinear optical phenomena Illustration of the technique is made with specific reference to the decay of second harmonic intensity encountered, for example, in chromophore enriched polymers initially poled by application of an electrostatic field.2 Surface specific second harmonic generation (SHG) is also examined with regard to providing, in comparison to other well-established methods,3 a more accurate measurement of the orientations of surface species.
High efficiency Raman amplification in the Dicke narrowed line of hydrogen
Authors: Rodin A.M. , Dement’ev A.S. , Gridline M.V. , Ratcliffe D.B.
Published: February 2023

The creation of a high coherence source of frequency converted laser radiation, for example as required in multi-coloured pulsed holography, requires the use of forward Raman amplification in the Dicke narrowed line of hydrogen at low pressures (3 - 4 atm). However, the conversion efficiency of Raman amplifiers is usually not sufficient even at high pressure. Indeed, in order to address this problem previous workers have used deliberately matched spatial profiles of the pump and seed Stokes beams at 17 atm [1] and superregenerative Raman amplification [2]. In this article we report the experimental observation of forward Raman amplification in the Dicke narrowed line at an H2 pressure of 4 atm with an energy conversion efficiency of up to 68 %, a value close to the theoretical limit of 78 %. given by the Manley-Rowe relation. As such a Stokes pulse (λs - 674 nm) having an energy of ~ 0.7 J was achieved from only ~ 1 J of pump energy (λL = 526 nm).
Trace-Gas Monitoring with a Mobile CO2-Laser Photoacoustic System
Authors: Moeckli M. , Sigrist M.W.
Published: February 2023

Laser photoacoustic spectroscopy is a powerful tool for the monitoring of a large number of gaseous substances at concentration levels varying from the ppb to the percent level. We have developed a fully computer controlled mobile CO2 laser photoacoustic spectrometer which has been involved in several field studies [1,2]. Our system will be presented including some recent developments. Owing to the strong absorption, CO2 laser spectroscopy is particularly sensitive to ethene and ammonia, two trace gases that are important for the production of photochemical smog and of acid rain, respectively, and which are both emitted by road traffic and other sources. These compounds are difficult to detect with alternative methods, particularly if a good time resolution and high sensitivity are required. With the widespread introduction of catalytic convenes in cars, the local concentration of traffic-emitted ammonia could have increased substantially in the recent past. We present first results of a field study performed with our system during a five day period in summer 1995 at a freeway tunnel outlet near Zurich. Tunnel air was pumped continuously through the photoacoustic cell. In order to avoid any adverse effects during sampling which could influence the components to be monitored we used neither CO2 nor H2O scrubbers but preferred to analyse the PA spectra by taking these two substances into account in the fitting procedure for the spectral analysis. The measurements were done at atmospheric pressure and simultaneous monitoring of CO2, ethene and ammonia was achieved with a time resolution of 10 minutes by automatic tuning to the appropriate laser transitions. Detection thresholds of a few ppb were obtained for ethene and ammonia. Furthermore, the CO level was monitored independently by a conventional device. The derived concentration profiles could be correlated with the data from an automatic traffic counting system. Rather high gas concentrations were derived, particularly for ethene and ammonia in the range of up to 250 ppb and 400 ppb, respectively. Even at night the ammonia concentrations stayed well above the background level of a few ppb. Based on these data and the calculated air flow through the tunnel, emission factors (mass of an exhausted component per car and km) from road traffic for the four substances could be determined. To our knowledge it is the first time that ammonia emission factors have been derived in Switzerland. An extrapolation with our emission factor of 15 mg ammonia per km and car indicates that traffic contributes approximately 1 % to the total ammonia emission into the air in Switzerland. A similar percentage was estimated for Austria in 1990. Local relative contributions can be much higher and strongly depend on the vehicle composition of the traffic.
All solid-state compact intracavity spectrometer based on a diode pumped LISAF laser
Authors: Kachanov A. , Stoeckel F. , Yu J. , Frejafon E. , Wolf J.-P.
Published: February 2023

Intracavity laser absorption spectroscopy (ICLAS) is an extremely sensitive method of measurement of very weak absorption spectra. ICLAS is based on very high sensitivity of a broadband laser to narrow absorption lines of the gas tilling the cavity, while the broadband cavity losses are compensated by the gain. This allows to obtain an equivalent absorption path as large as 30000 km and thus to detect absorption lines as weak as 10−11 cm−1. The spectral range of ICLAS is determined by the avalability of broadband homogeneously broadened laser media. Dye, color center and vibronic crystal lasers have been used for ICLAS in the range from 0.4 to 1.5 microns1.
A Copper Bromide Vapor Laser of 120 Watts Output Power
Authors: Sabotinov N.V. , Dimitrov K.D. , Vuchkov N.K. , Astadjov D.N. , Kirkov V.K. , Little C.E. , Jones D.R.
Published: February 2023

Copper bromide vapor laser (CuBrVL) as an alternative of the copper vapor laser (CVL) is successfully being developed. CuBrVL of an average output of up to 10W has already approved as a commercial vanant in the practice [1]. The effect of hydrogen in CuBrVL that increases more than twice its average power and efficiency [2], provided new opportunities for a high-power and efficient CuBrVL to be created.
New Schemes for XUV Laser Pumeed by Charge-Exchange Reactions
Authors: Papanyan V.O. , Ter-Avetisyan S.A. , Nersisyan G. Ts.
Published: February 2023

A complete analysis of suitable pairs of a rare-gas ion and a metal atom is carried out from the point of view of inversion development by selective excitation of an excited metal ion level due to fast charge-exchange reaction Pairs with small energy defect ΔE for the reactions
R

+
+
M
→
R
+
M

+*
,
M

+*
→
M

+
+
hω

VCV
are selected and analyzed.
Laser Action on the Inert Gases Atomic Transitions in the Mixtures with NF3
Authors: Lomaev M.I.
Published: February 2023

Experimental results of the investigation of the laser action on atomic transitions in inert gases mixtures He-NF3, at λ = 706.5 nm, Ne-NF3 at λ = 585.3 nm, Ar-NF3 at λ = 750.4 nm under pumping by a self-sustained discharge are presented. Under laser action at λ = 585.3 nm in Ne-NF3 mixture more than tenfold exceed in radiation power has been achieved as compared to the known mixture of the Penning plasma laser Ne-H2 at the same excitation conditions. Under excitation of mixtures inert gas - halide by a self-sustained discharge it was demonstrated that the electronegative gas simultaneously provided the cleaning of the lower laser level and enhanced the pumping efficiency. Based on the spontaneous radiation and laser action measurements of electron concentration and temperature as well as an analysis of process rates in mixtures of helium, neon and argon with NF3, it is concluded that the population of the upper laser level is carried out due to the processes of electronic excitation.
Injection-Locking of One and Two Dimensional Vertical Cavity Semiconductor Laser Arrays
Authors: Mercier J. , McCall M.
Published: February 2023

Injection-locking of isolated semiconductor lasers has been studied to a considerable extent (see for example [1]), but here we are concerned with an array of lasers. The analytical study of phase-locking via an external tunable source of a multiple element system acting as the slave component is important from the point of view of understanding how the intrinsically out-of-phase operation of evanescently coupled semiconductor laser arrays is modified to produce in-phase operation at both weak inter-slave clement coupling strengths and low injection levels. In this study we are concerned with small numbers of slave elements arranged, in particular, in two-dimensional lattices. The inclusion of carrier dynamics is essential to the understanding of the stable locking regimes and although this limits the analytical progress possible we have established; using the time-dependant coupled mode semiconductor laser rate equations, the locked equilibria of the injected two-clement and three-element (cyclic) slave systems allowing for additional inter-slave detuning. In addition the locking bandwidths and locked phases are described. In particular the transition from an out-of-phase slave system to an in-phase locked system with the resulting single lobed far-field distribution is characterised and found to occur at very low (≃−80dB) injection levels.
Laser resonators with self-imaging waveguides
Authors: Banerji J , Davies A R , Jenkins R M
Published: February 2023

We propose a class of waveguide resonators which are based on the self-imaging properties of multimode waveguides [1],[2]. The resonators consist of waveguides of square cross section 2a × 2a and of length l = 2a2/λ (where λ = wavelength in the core), closed at one end by a plane mirror and bounded at the other by a phase matched mirror of curvature R, placed at a distance z from the guide exit as illustrated in figure 1.
Self-Consistent Approach to the Theory of Spatial Inhomogeneous Effects in a Gas Laser
Authors: RADINA T.U.
Published: February 2023

In the case of a steady-state generation the problem of calculation the laser frequencies, intensities and the spatial disttribution of the field in the resonator reduces to selfconsistent solving of the steady state nonlinear wave equation for the field inducing polarization of the active medium and the quantum-mechanical equation relating the polarization of a medium with the optical wave field. The equations are supplemented by some boundary conditions.
Super-Gaussian output beam formation in a CW CO2 laser by intracavity controlled bimorph mirror
Authors: Cherezova T.Yu. , Kudryashov A. , Bélanger P.-A. , Paré C.
Published: February 2023

The problem of controlling the parameters of laser radiation becomes particularly topical in view of the widespread use of lasers in medicine and technological processes. In this paper, we present the results of investigations of the possibility to form beams with different orders of super-Gaussian profile at the output of a stable laser cavity with the help of an active mirror. As shown in Ref.[1], in order to get these intensity profiles, it is necessary to construct specially calculated profiles of minor surface. As an example, on Fig.1 curve "A" represents such a surface profile. We tried to reproduce this shape with the help of a deformable bimorph minor (curve "B" on Fig.1). Since this profile was symmetrical, we used a minor with ring control electrodes. Such minor was a circular concave semipassive bimorph one with three electrodes. To minimize the root-mean-square (RMS) error between our profile and the necessary one, we combined the real (measured by interferometer) response functions of our minor with different weights. In practice, this amounts to applying a particular voltage to the electrodes of the deformable minor. As shown in Fig.1 (corresponding to a super-Gaussian of order 8), we were able to reproduce the appropriate minor profiles with a corresponding RMS enor of only 0.03% (curve "B"). Figure 2 compares the corresponding calculated near-field distributions (including saturation and edge diffraction effects) for a 2 m long stable cavity. The nearly identical associated far-fields are depicted on Fig. 3. A comparison with a conventional spherical resonator designed to yield a similar output beam divergence allows us to expect ≈ 30% power increase owing to the higher extraction efficiency of super-Gaussian beam profiles. Similar conclusions have been reached for a super-Gaussian of order 6. These calculations make us believe that our intracavity bimorph deformable mirror with only three control elements is able to reproduce super-Gaussian output radiation of the CW CO2 laser with a stable cavity. An experiment to verify this is under way.
Spiral-Type Beams
Authors: Abramochkin E.G. , Volostnikov V.G.
Published: February 2023

Laser beams that have preassigned intensity distribution and conserve their structure under propagation and focusing may be used for laser technology tasks and problem of the light mechanical action on atoms and molecules [1].
Pulse Shortening in Actively Mode-Locked Laser by Using Cascaded Nonlinearity
Authors: Chekhlov O.V. , Zaporozhchenko V.A.
Published: February 2023

The effect of cascaded second-order nonlinearity in two-pass intracavity second harmonic generation has recently been applied for passive mode-locking of lasers both in pulsed /1/ and cw regimes /2/. To achieve stable operation of an intensity dependent mirror reflection by using the cascaded process and reliable formation or shortening of light pulses it is desirable sufficiently high intensity of radiation in the laser cavity. The rise of intensity can be attained with the use of active mode-locking that makes the requirements to nonlinear mirror parameters easy feasible.
Parametric upconversion of tunable femtosecond pulses
Authors: Petrov V. , Noack F.
Published: February 2023

Traveling-wave optical parametric generators pumped by Ti: sapphire regenerative amplifiers at 1 kHz repetition rate represent a convenient tool to produce powerful and highly reproducible femtosecond pulses in the near infrared. [1] Pumping by the second harmonic in order to cover the visible spectral region near 600 nm is, however, considerably complicated because of the substantial increase of the group-velocity mismatch. [2] We demonstrate here a rather simple way to avoid this problem by simultaneous phase-matching of two nonlinear optical processes, optical parametric amplification and sum-frequency generation in a single β-barium borate (BBO) nonlinear crystal.
Saturation of Third-Harmonic Generation in a Plasma of Self-Induced Optical Breakdown due to the Self-Action of 80-fs Light Pulses
Authors: Fedotov A. B. , Loy M. M. T. , Xiao X. , Koroteev N. I. , Zheltikov A. M.
Published: February 2023

Currently, much attention is focused on nonlinear-optical interactions in a laser-produced plasma in the presence of high-power ultrashort light pulses [1 - 3]. Studies in this direction provide an opportunity to reveal specific features of the nonlinear-optical response of a plasma in intense light fields. The results of these investigations are of particular interest for developing sources of short-wavelength radiation.
Spectral programming of temporal pulse sequences using photon echoes
Authors: Luo B. , Elman U. , Kröll S. , Kaarli R.
Published: February 2023

Optical memories based on spectral hole burning (SHB) and stimulated photon echoes (SPE) are attracting much attention. Both approaches add an extra dimension for addressing (frequency and temporal dimension respectively) to the spatial dimensions. With these concepts the storage density can become 103 – 106 times higher than in conventional optical memories. In both approaches, the ratio of the inhomogeneous line width to the homogeneous line width of the ions activated in the storage process determines the improvement in storage density. Compared to the SHB approach, SPE has certain advantages including high R/W rate and ability to process the stored (spatial as well we temporal) information. Using SPE, the authors have experimentally realised the AND, OR and NOT logical operations [1,2]. Further all optical processing, such as temporal pattern recognition, can be done using SPE.
Capabilities of a cw tunable diode laser spectrometer in the 8 -12 µm region based on the difference frequency generation in AgGaSe2 for the detection of trace gases
Authors: Rehle D. , Sumpf B. , Kronfeldt H. -D.
Published: February 2023

Introducing difference frequency generation (DFG) it is possible to create laser sources applicable to high resolution spectroscopy in the mid-infrared. It may become a convenient method for the detection of trace gases. Preferably for this purpose are the atmospheric windows. Whereas with DFG in AgGaS2 the atmospheric window around 4.7 µm could be covered AgGaSe2 allows to produce radiation in the 8 - 13 µm window. In the latter region nearly all atmospheric trace molecules have characteristic bands. Therefore, we developed a spectrometer with the nonlinear material AgGaSe2.
Extreme Concentration of Light Pulse Energy Due to Combined Action of Nonlinear Mode Mixing and Picosecond Stimulated Raman Effects in Silica Fibers
Authors: Nesterova Z.V. , Alexandrov I.V. , Nesterova V.A.
Published: February 2023

The endemic properties of fiber-based Raman convertors consist of the phase correlation between the different Stokes waves and an exclusively wide region of spectral detuning. The application of picosecond pulse pump is very attractive, because some new physical phenomena may be observed. In this communication we report the results of the experiments concerned with the multiwavelength stimulated Raman scattering (SRS) in silica fibers accompanied by the self-action of the picosecond pump and Stokes fields.
Single frequency, electro-optically Q-switched, quasi-cw diode-bar-end-pumped Nd:YVO4 laser
Authors: Jabczyński Jan K. , Żendzian Waldemar , Jankievricz Zdzisław
Published: February 2023

The aim of this work was the experimental verification of Nd:YVO4 crystal as the the high efficient material for Q-switched diode pumped lasers. As a pump source the SDL 3251-Al quasi cw diode bar was used. The beam shaping system forming pump volume of size 1.8 x 0.7 mm2 was worked out [1].
Influence of optical feedback on the static properties of Nd-doped fiber lasers
Authors: Chartier T. , Meziane B. , Sanchez F. , Stéphan G.
Published: February 2023

We report on the static properties of Nd-doped fiber lasers submitted to optical feedback1 in an experimental configuration that gives access to the laser intensity both inside and outside the laser cavity (Fig. 1). We show that optical feedback increases the inner laser intensity and reduces, by up to a factor two, the slope of the output-intensity-versus-pump-level characteristic (Fig. 2). We attribute this unusual phenomenon2 to the spectral selectivity of the external Fabry-Perot cavity composed of the output coupler and the feedback mirror. In the absence of feedback the laser output spectrum consists of thousands of modes, uniformly distributed within the 3000 GHz spectral linewidth. When feedback is applied, the equivalent output mirror reflectivity is modulated at the Free Spectral Range of the external cavity, 1.5 GHz in the case reported here. Because of the important homogeneous linewidth, mode competition takes places. As a consequence the modes with higher reflectivity inhibit the other modes, and non-lasing bands appear in the laser spectrum. The lasing modes undergo lower losses, and the total inner laser intensity increases. In the absence of feedback, the output intensity is directly related to the inner intensity through the transmission coefficient of the output coupler. With back-coupled reflections, this transmission coefficient is frequency dependent. Since the selected laser modes are grouped in the vicinity of the maximum of the effective-reflection-coefficient function, they suffer minimum effective transmission. Based on these physical insights, an adapted theoretical model shows that feedback divides the slope of the output intensity by a factor two, in conformity with the experiments.
Crystalline Air Cooled CW Laser
Authors: Gevorgian G.A. , Kahramanian K.E. , Kostanian R.B. , Kosheverskii E.V.
Published: February 2023

In order to reduce the weight-size dimensions of the lasers and apply their atmospheric low temperetures, it is often needed to use air cooled lasers, instead of traditional water cooled ones. It is known [1], that the heat exchange ratio when cooled diffusely by air, is approximately by two orders of magnitude lower than that for the liquid cooling Therefore, creation of air cooled CW lasers with pump power up to 3kW is one of the actual problems of modern laser techniques. The main problem in creation of similar lasers is to obtain high heat transmission ratios in cooling channels, which will ensure for the lasers working temperature regimes to be near the ones when cooled by liquids. For obtaining such high ratios of heat transmission the authors of this paper succeeded in developing of the turbulence of the flow in the channels with straight flow of the air with Reynolds number

R

e

0.875

=

d
2

−

d
1

v

P

m
a
x
 

(

d
2

−

d
1

)

2
g

k

L
ρ

where d2-d1- is the hydraulic diameter of cooling channel, v-the kinematic viscosity of the air, Pmax-the maximal input pressure of the channel, g-free falling acceleration, k-hydraulic resistance ratio, L-the cooling channel's length, ρ- the air density. The principle of cooling is based on achieving an equality between the times of diffuse propagation of heated air molecule from the cooled object in the plane, perpendicular to the air flow and its running time from the channel's entrance along all its length. Inserting the number Re in the formula for calculating the heat exchange ratio [1]

α
=

λ

d
2

−

d
1

{
…
}
R

e

0.875

P

r
n

, we get its value for cooling channels of various dimensions and configurations, where λ- is the air heat conductivity, Pr - the Prandtl's number,

n
=
0.4
+

0.5

2
P
r
+
1

and figure brackets contain tabulated values of this formula and also constructive-technical parameters of the cooled channel very slightly influencing the heat exchange ratio's value.
Measurement of the displacement of diffuse surface with low reflectivity using angle compensation technique
Authors: Zeng Lijiang , Aoshima Kazumi , Matsumoto Hirokazu , Kawachi Keiji
Published: February 2023

Noncontacting surface sensor based on the principle of laser triangulation has been developed for measuring the displacement of objects that have diffuse surfaces. However, (here are two major drawbacks when such a method is used for diffuse surfaces that have low reflectivity, such as a dragonfly wing. The first drawback is that the measured displacement range is limited by the poor linearity that is due to using a short focal-length lens to collect sufficient light. This problem can be understood by looking at the dashed line in Fig. 1. The second drawback is that, due to light-transfer noise inherent in every position sensor cell, reflectivity variations in the diffuse surface produce measurement errors.
Optical Demodulation Phase Measurement Technique for 3D-Camera Application
Authors: Jetter Volker , Müller René
Published: February 2023

Three dimensional inspection techniques for industrial applications are normally based on either photogrammetric, triangulation or time-of-flight techniques. Combining the latter with an optical demodulation method offers the possibility to obtain 2D and 3D information of a scene. The target is illuminated by a high frequency intensity modulated laser beam. An imaging system forms an intermediate image inside an electro-optic modulator and finally a CCD-camera captures the 3D-image of the object where the intensity of each camera pixel corresponds to the phase shift and therefore the distance between the illuminated object pixel and the optical demodulator.
Scanning Nearfield Optical Microscopy Studies of Organic Materials
Authors: Müller-Zülow Bernd , Kämmer Stefan , Weiss Joachim , Gehring Stefan
Published: February 2023

Scanning Nearfield Optical Microscopy is a relatively young method for viewing materials with a resolution not previously attainable with optical techniques. This microscopy overcomes the conventional Abbe barrier, or diffraction limit, of resolution and allows to enter new optical-characterization fields with submicron resolution. Studies of organic materials using this technique can be found in various fields starting with brightfield imaging of polymer surfaces as well as using fluorescence and polarization contrast. Specific setups of the instrument concerning the sensitivity of detection are even able to study single molecules.
Evanescent field optical sensor for studying ARROW guides
Authors: Borrisé X. , Jiménez D. , Barniol N. , Pérez-Murano F. , Aymerich X. , Domínguez C.
Published: February 2023

Antiresonant reflecting optical waveguides (ARROW) [1] are of current interest both in passive and active optical devices. These guides have unique properties when compared to conventional structures based on total internal reflection. They offer low loss, polarization and wavelength selectivity as well as easy of fabrication. The refractive index and size of the core layer allow flexibility in coupling to an optical fibre with minimal loss. The fact that ARROW guides can be implemented on semiconductor substrate makes them ideal for integration with electronic devices on a single chip.
Integrated-Optic Electric-Field Sensor for Power Utility Applications
Authors: Hui D. , Kato H. , Rahmatian F. , Jaeger N.A.F. , Polovick G.S. , Cherukupalli S.
Published: February 2023

Electric-field sensors based on the integrated-optics version of the Pockels cell (IOPC) [1] have been fabricated and tested. Their high accuracies and wide bandwidths indicate that such IOPC electric-field sensors should find metering, monitoring, and protection applications in power generation, transmission, and distribution systems; as well as being useful in laboratory environments. Past work has concentrated on the linearity and frequency response of such sensors, including their ability to replicate high-speed transient impulses [2]. Here we report on measurements made in the frequency range 1 to 10,000 Hz. Fig. 1 shows the spectral content of an applied signal, including higher order harmonics, and the spectral content of the measured signal in the frequency range 1 to 2,000 Hz.
Calculation of Temperature Cycles, Heating and Quenching Rates During Laser Melt Hardening of Cast Iron
Authors: Grum Janez , Šturm Roman
Published: February 2023

For the case of laser surface-melt hardening, a mathematical model was used to determine the temperature profiles in gray and nodular iron and the depth of the modified layer. The temperature distributions and temperature gradients are presented for the studied depths. The mathematically obtained results ate critically assessed and compared with the results in die experiments. The microstructural changes which can be predicted from the temperature profiles on heating and cooling arc confirmed by microhardness measurements. It was found that in some heal treatment conditions, deviations occur between die mathematical model and experimental results. The factors causing these deviations are analysed and explained.
Laser Effect on Vacuum Deposited Polyimide-Aluminium Composites
Authors: Spassova E. , Assa J. , Jivkov I. , Danev G. , Ihlemann J.
Published: February 2023

Vacuum co-evaporation of polymer materials and metals or their compounds allows the production of thin layers of specific properties. The method is technologically convenient and presents a certain alternative to the "sol-gel" technologies. Composite thin layers (1-1.5 μm) have been obtained by the simultaneous evaporation (10 A/sec) of two monomers (oxydiamline and pyromellitdianhydride) and a metal. As metal a thermally evaporated Al (0.6 A/sec) or an organometalic compound [(CH3)3NAlH3] have been used. The Al-organic compound is thermally decomposed during the first stage of imidization taking place at a temperature of 173 - 177 °C. Electron micrographs exhibit evenly distributed Al particles in the volume of the polyimide matrix with very small dispersivity values (2.5 - 5.0 nm - 90%). The second thermal stage od imidization (270 °C) does not cause coalescence of Al particles. It is assumed that a micro metal synthesis occurs by the build-up of strong C-O-Al bonds which fix the aluminium clusters. The optical parameters of the obtained composites have been measured at the various stages of the imidization process of the matrix. XeCl laser action (308 nm, 30 nsec, 30 to 4000 mJ/cm2) on the materials has been studied envisaging possibilities for micro-structuring. X-ray photoelectron spectroscopy in the exposure area shows a shift of Al2O3 (2.4 eV) which is higher than the Al photoelectron peak (1.7 eV). It is suggested that the laser action does not only break the imide bonds, but also stimulates the course of the chemical reaction on the particles' surfaces. Scanning micrographs demonstrate that the laser ablation process influences the average size of the Al particles.
Oxygen Isotope Ratio Analysis of Silicate and Oxide Minerals by UV Ablation with a Frequency-Doubled Copper Vapour Laser
Authors: Young E. D. , Andrews A. J. , Coutts D. W.
Published: February 2023

Development of reliable and precise methods for measuring the ratios of the isotopes of oxygen, 18O/16O and 17O/16O, in silicate minerals with spatial resolution on the order of tens of microns is of considerable interest to the geochemical community. Laser healing or ablation in a F2 atmosphere releases O2 tram small volumes of mineral material and so affords considerable reduction in sample size relative to conventional methods. A distinct advantage of laser treatment over other methods of microanalysis is that die liberated oxygen can be analysed using highly precise multicollector, magnetic sector mass spectrometers.
Rapid prototyping based on selective laser gluing of metal powder
Authors: Petrov A.L. , Kuprianov N.L. , Levin A.V. , Shishkovsky I.V.
Published: February 2023

The selective laser gluing process for rapid prototyping was proposed and investigated in this work. The main feature of the method is the premixed composition of metal powder and solid thermoplastic glue of low melting point. The scan of a laser beam over the free powder surface gives the local heating and melting of only the polymer component. The melting of thermoplastic glue particles leads to gluing of the nonmelted metal particles.
Proximity x-ray lithography using a droplet-target laser-plasma source
Authors: Malmqvist Lars , Rymell Lars , Hertz Hans M.
Published: February 2023

Laser plasmas are attractive sources for proximity x-ray lithography due to their high brightness and comparatively low cost [1]. However, conventional laser-plasma target systems, e.g., bulk metals or thin film tape targets, limit the applicability of these sources. The limitations primarily concerns repetition rate, operating time, target cost and debris emission. In this paper we discuss the use of microscopic liquid droplets formed by a continuous liquid jet as target [2] and show that this target allows low-cost, uninterrupted operation at high repetition rates and practically eliminates the debris problem.
Optoacoustic monitoring of laser beam welding
Authors: Grad Ladislav , Možina Janez
Published: February 2023

To fully exploit the productivity and flexibility of laser beam welding unit, a reliable monitoring is necessary. Different physical phenomena like light emission and temperature are usually observed and evaluated for that purpose [1]. The aim of this paper is to extend the observed phenomenon to sound which is produced during welding and spread into surrounding air. We were encouraged to succeed by experienced welder who is usually able to distinguish between good and faulty welding procedures by simply listening to the process.
Action of near-field sources on surfaces
Authors: Libenson Mighail N. , Martsinovsky George A.
Published: February 2023

Near-field light sources utilized in near-field optical techniques microscopes can be used for modification of surfaces in microfabrication, nano-electronics, data recording and other technologies [1-2]. Highly localized electro-magnetic field created by such near-field sources, usually designed as tapered fibers, allows one to minimize the area of action of the radiation on the surface. We present theoretical consideration of the processes induced by near-field excitation of surf aces of semiconductors and metals. The consideration is based on diffusion approach, where thermolisation and recombination of light generated carriers are treated separately. The peculiarity of the excitation is that the size of irradiated zone is less than the free path length of generated carriers. This results in heat release at the larger region compared to the irradiated zone. To take into account the structure of the near-field radiation we used exponential approximation in z-direction and Gaussian approximation in x-y plane. The obtained stationary distribution of temperature and noneqilibrium carriers concentration allows us to estimate the overheat temperature and the size of overheated area. The solution shows that the dimensions of two regions associated to heat release due to thermolisation of nonequilibrium electrons and recombination are essentially different.
Sum-frequency generation from molecular monolayers in the mid- and far-infrared employing a free-electron laser
Authors: van der Ham E.W.M. , Vrehen Q.H.F. , Eliel E.R. , Braun R. , Casson B.D. , Bain C.
Published: February 2023

Infrared-visible Sum-Frequency Generation (SFG) has become a widely applied tool for the study of molecular monolayers and interfaces between molecular fluids. By scanning the IR wavelength over the vibrational modes of' the molecule one can independently probe its various subunits in order to gain informal ion on the molecular conformation on the interface and, in specific cases, on the spatial orientation of the subunits.
Internally Teflon-AF Coated Capillary Cell for Optical Fibre Remote Spectroscopy
Authors: Mackenzie Steven J. , Dakin John P.
Published: February 2023

A novel method of enhancing fibre-remote fluorescence and Raman spectroscopic measurements of compounds in aqueous solution is demonstrated. The method uses a water-cored optical waveguide/capillary cell internally coated with Teflon-AF.
Cholesteric Liquid Crystals as Output Mirror for pulsed Nd:YAG-lasers
Authors: Grebe D. , Stengelin T. , Macdonald R. , Eichler H. J.
Published: February 2023

The optical anisotropic molecules of Cholesteric Liquid Crystals (CLCs) spiral around a helical axis forming a Bragg-reflector for circular polarized light with the same screw sense and matching wavelength. Light of a different wavelength or polarization is nearly totally transmitted. Furthermore, liquid crystals are materials with high optical nonlinearities due to electronic or reorientational effects at high intensities E g transverse non-linear optical effects like retro-selffocusing and a pinholing effect were demonstrated using CLC mirrors in a cw-Nd: YAG-laser [1].
Polarization properties of the adaptive loop resonator based on the intracavity degenerate four-wave mixing in Cr4+-doped crystals
Authors: Bufetova G.A. , Klimov I.V. , Nikolaev D.A. , Shcherbakov I.A. , Tsvetkov V.B. , Tuennermann A. , Welling H.
Published: February 2023

The scheme of Nd:YAlO3 laser with adaptive loop resonator (ALR) based on intracavity degenerate four-wave mixing (IFWM) was developed in [1, 2]. It was shown that the influence of IFWM may lead to the significant improvement of energy and spatial output laser parameters. As the nonlinear medium the crystal Cr4+:YSGG was used. The transient gratings of the refractive index are formed in the beginning of the lasing build-up. This fact and strong influence of IFWM to the lasing conditions may make the output emission of the ALR polarized in the case of light scattering under Brewster angle.
Resonators for Mode-locking of Solid-State Lasers by χ(2) - Cascading
Authors: Magni V.
Published: February 2023

The nonlinear amplitude and phase and distortions that arise from cascading of second-order nonlinear processes1 (χ(2)-cascading) have received considerable attention mainly because the self induced effects can be significantly larger than those originated by third-order interactions. This phenomenon is investigated in various contexts including, e.g., solitons and optical switching. In particular, two techniques of passive mode-locking based on χ(2)-cascading have recently been demonstrated lor continuous-wave Nd lasers2−4. In the Cascaded Second order nonlinearity Modelocking (CSM) the spatial phase distortion causes power-dependent cavity mode changes which, in combination with an aperture, provide nonlinear resonator losses, like in the Kerr-lens modelocking. In the Nonlinear Mirror Mode-locking5 the nonlinear losses derive from the parametric interaction of the laser beam with its second harmonic in an intracavity crystal. Various problems remain open with these techniques, among them: resonator design, pulse duration limitation due to the group velocity mismatch in the second harmonic crystal, and application to different active materials.
The Doppler Wind and Temperature System of the Alomar Lidar
Authors: Rees D. , Vyssogorets M. , Nilsen P-E , Gandham I. , Rees David
Published: February 2023

The Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) at Andoya, Norway (69° N. 16°E. von Zahn and Rees, 1994), is a complex multi-instrument facility using lidars, radars and passive IR and Visible-wavelength instruments to study the complex behaviour of the Arctic Stratosphere and Mesosphere (von Cossart et al 1995). ALOMAR has recently been augmented with the commissioning of two large receiving telescopes which can be scanned in azimuth and elevation to permit wind velocity measurements to be obtained by the Doppler Wind and Temperature System (DWTS). The ALOMAR Rayleigh / Raman / Mie lidar uses two powerful Spectra-Physics GCR-6 Nd-YAG lasers. The power lasers are seeded by a LightWavc CW laser which is stabilised against an iodine line generated in an absorption cell. This laser has proved to be extremely stable, with drills of significantly less than lms−1 during periods of 12 hours. Two steerable 1.8 m diameter receiving telescopes recover the atmospheric back-scattered signals, which are fed via libre-optic connections to a complex detection system which includes detectors for the fundamental (1064 nm), frequency-doubled (532 ran), and frequency-tripled (355 nm) laser emissions.
Atmospheric Dispersion Monitoring Using 0.53 um and 1.54 um Satellite Laser Ranging
Authors: Greene B. , Kunimori H. , Hamal K. , Prochazka I.
Published: February 2023

Several attempts have been made to contribute to the existing atmospheric dispersion and optical signal propagation delay models using picosecond high precision multiple wavelength Satellite Laser Ranging (SLR) in visible region [1]. We are reporting, to our knowledge for the first time, on the two wavelengths SLR in visible at 0.53 um and in the near infrared at 1.54 um.
Routine Measurements of Ozone in Planetary Boundary Layer by Differential Absorption Lidar
Authors: Veselovskii I.A. , Bukreev V.S. , Vartapetov S.K. , Cha H.K.
Published: February 2023

During last years the significant progress in the development of DIAL systems for the routine ozone monitoring has been achieved1,2. In our report we present the results of day and night time routine measurements of tropospheric ozone by DIAL system designed on a base of excimer-Raman laser.
Ultracold Atoms - New Approaches and New Perspectives
Authors: Cohen-Tannoudji Claude
Published: February 2023

Laser Cooling now allows one to cool atoms below the single photon recoil limit. It will be shown that subrecoil cooling involves anomalous random walks in velocity space and that new physical insight can be obtained into this problem by using Lévy statistics. New possible applications of such ultracold atoms will be reviewed.
Clinical Laser Diagnostics with Endogenous and Exogenous Dyes
Authors: van den Bergh H.
Published: February 2023

It will be shown how light induced fluorescence is used for the localization of early cancer in the upper serodigestive tract, the tracheobronchial tree, the esophagus and the bladder. Both endogenous and exogenous dyes will be used. Early results with a two wavelengths observation procedure for image enhancements are reported using frequency domain imaging.
LIDAR Atmosphere Monitoring with New Solid State Lasers
Authors: Wolf J.P.
Published: February 2023

3-D-Analysis of pollutant concentrations obtained with all solid state LIDAR systems in industrial, urban, and immission conditions are presented. New developments, including UV-tunable lasers (Ce:LiSAF) and mid-IR OPOs have also been performed to detect VOCs, besides NOx, SO2, and O3.
Performance Characteristics of 500 W Universal Excimer Laser
Authors: Borisov V. , Demin A. , Khristoforov O. , Vinokhodov A. , Vodchits V.
Published: February 2023

At the present time the most commonly encountered KrF/XeCl industrial laser have a maximum of stabilized average power ≈200 W. As an average power and a reliability of these lasers will be increased the economic profit of their application in many technologies is doing obvious. In order to construct next generation of industrial excimer lasers with level of stabilized average power ≈500 W we have developed compact KrF and XeCl lasers with maximum of an average power ≈600 W. Both lasers have the same gas-flow system design. It employs a 120 mm diameter 900 mm long cross-flow fan provided gas velocity ≈45 m/s at interelectrode gap (H) ≈37 mm or 22 m/s at H=70 mm. Excitation systems includes UV preionization systems bazed on sparks or creeping discharge on dielectric (sapphire) surface, electrode structure and LC-inverter and double or three-stages of pulse magnetic compression.
Hybrid Distributed Bragg Reflector laser
Authors: Meliga M.
Published: February 2023

Current and future WDM (Wavelength Division Multiplexing) optical systems for access and transport networks require stable, low-chirp and potentially low cost lasers emitting at predetermined (ITU-T grid) wavelengths. In addition advanced OTDM (Optical Time Division Multiplexing) systems require sources for high quality picosecond pulses on the transmitter side and optical devices for clock recovering on the receiver side The HDBR (Hybrid Distibuted Bragg Reflector) laser, also called FGL (Fiber Grating Laser) can meet all previous requirements.
Simultaneous UV direct writing of channel waveguides and Bragg gratings in planar germanium doped silica
Authors: Marques P.V.S. , Bonar J. R. , Liu X. , Leite A. M. P. , Aitchison J.S.
Published: February 2023

Permanent photo induced refractive index changes by means of UV exposure have been used for laser trimming, fabrication of Bragg gratings [1] and direct writing of channel waveguides [2]. Direct writing is particularly attractive since it allows two-dimensional light confinement without the expensive and time consuming dry-etch stage. In this paper we report on the simultaneous production of both a 2-D waveguide and a Bragg grating.
Non-Linear Methods for High Performance Distributed Optical-Fibre Sensing
Authors: Rogers A. J.
Published: February 2023

Optical fibres offer very special advantages for distributed sensing. They comprise a flexible, insulating, dielectric, minimally-intrusive, one-dimensional measurement medium for installation into critical structures. Examples of such structures are dams, bridges, pressure vessels, oil rigs, aerospace vehicles, mining installations and power system equipment.
Spectroscopic characterization and diode-pumped laser action at 2.7μm of Er:Lu2O3
Authors: Peters V. , Fornasiero L. , Mix E. , Diening A. , Petermann K , Huber G.
Published: February 2023

The sesquioxide Lu2O3 (Lutetia) is isostructural to the comparatively well examined Y2O3 (Yttria). Therefore the thermal conductivity of Lutetia is assumed to be in the same high range as in Yttria (27 W/mK [1]), which makes Lutetia an interesting host material for high power lasing. Due to its high melting point (around 2500°C) is was impossible to grow Lutetia from crucibles in the past so that size and optical quality of existing samples were limited. We have, for the first time to our knowledge, grown Lutetia doped with RE3+-ions from rhenium crucibles using the Nacken-Kyropoulos technique. First samples show monocrystalline regions with rather low stress induced birefringence.
Diode pumping and laser properties of Yb:Ho:YAG at 2 µm operated at room temperature in active mirror mode
Authors: Rothacher Th. , Lüthy W. , Weber H.P.
Published: February 2023

The rare earth ion Yb3+ is an efficient sensitizer for Ho3+ crystal lasers [1]. It has a broad absorption band lying in the emission range of commercially available InGaAs diode lasers and a very efficient energy transfer to Ho3+. In our paper we investigate the laser properties of four Yb3+:Ho3+:YAG laser crystals with 15 at.% and 30 at.% Yb3+ and 2 at.% Ho3+ and two different crystal thicknesses. The laser was operated at 295 K in active mirror mode.