bluuebunny/crossref_metadata_2025 huggingface dataset:
New technique for generating powerful picosecond optical pulses from semiconductor lasers for high-resolution pulsed laser radar systems
Authors: Gorfinkel V. B. , Kompa G. , Sola J. , Volpe F. P.
Published: February 2023

The generation of picosecond high-power single optical pulses is a problem of increasing importance especially in high PRF short-range laser radar systems for fast and reliable 3D-measurements with submillimeter accuracy, and satisfying class-1-laser specification. Presently we report on a novel technique for generating ps high-power optical pulses based on a fast change in the type of optical waveguiding from index- to gain-guiding in the laser structure pumped by nano-second current pulses of high amplitude. This change leads to a very efficient radiation of a gain-switched pulse which may be then followed by an additional Q-switched optical pulse. The new technique can be realized for any laser structure having weak index-guiding and nonmonotoneous dependence of the modal gain on carrier density in the laser active area (like single heterojunction (SH) lasers, single quantum well ridge-guide (SQW RG) lasers with low lateral confinement, etc.).
Present status of mode-locked solid-state lasers
Authors: Sibbett W.
Published: February 2023

Summary not available.
Pulsed laser deposition of high-Tc superconducting thin films for device applications
Authors: Belouet C.
Published: February 2023

Pulsed laser assisted deposition (PLD) has recently emerged as a most promising film-growth technique, at least for basic research, as this has been best demonstrated for the case of superconducting compounds and YBa2Cu3O7–8 in particular. The field of applications of the PLD technique has rapidly spread, and to date, it already covers a broad spectrum of materials. One may anticipate that the PLD technique will soon give birth to a most competitive film-growth technology, in particular in the field of electronics, where it creates new opportunities.
Laser deposition and patterning of diamond
Authors: Obraztsov A. N. , Guseva M. B. , Babaev V. G. , Bregadze A. Yu. , Khvostov V. V. , Valiulova Z. Kh. , Pirogov V. G.
Published: February 2023

Laser beams are finding a lot of applications in diamond technology because of the possibility of versatile control and easy optimization of their parameters.
Airborne backscattering and dial measurements for meteorological and environmental applications
Authors: Pelon J.
Published: February 2023

There is a growing need on mesoscale studies of dynamic and radiative processes in the atmosphere to better understand and model its evolution for meteorological and environmental purposes. To answer it, new observational programmes have been developed, aiming at scale integration analysis. The French research programme LEANDRE is one of these programmes. It supported by the National Scientific Research Centre (CNRS) and by the French Space Research Centre (CNES). It can be considered as one of the steps toward the future implementation of lidar systems on space platforms for climatological studies.
Some examples of photon migration analysis in tissue diagnostic applications
Authors: Avrillier S. , Tinet E. , Ettori D. , Tualle J. M.
Published: February 2023

Many advances in medical care are expected from the actual improvements in the ability to noninvasively monitor and early detect very small changes in tissue function or structure. In optical diagnostic methods, light is directed into tissue and the small amount of emerging (reflected or transmitted) light, bearing clues about the explored tissue, is detected and analysed. Compared to other methods, the main advantages of the optical techniques come from the nonionizing nature of the light and the fact that optical sources are portable, inexpensive, and can be used safely for extended periods of time.
Scattering of photon density waves within the Born approximation
Authors: Hielscher Andreas H. , Jacques Steven L. , Tittel Frank K.
Published: February 2023

Diffraction tomography (DTO) was introduced in the early eighties as an imaging technique in medicine and geology using acoustic waves. This method attempts to reconstruct the internal structure of an inhomogeneous material by the way in which it diffracts waves. It can be used if the wavelength λ of the probing wavefield is in the order of magnitude of the scatterer and when the Born approximation is valid for the scattered field.
Superposition of virtual sources: accelerated modeling of light distribution in heterogeneous tissues
Authors: Ostermeyer M. R. , Jacques S. L. , Hielscher A. H. , Wang L.
Published: February 2023

The modeling of light distribution in tissues is of strong interest both for diagnostics and therapy with light. Under the existing methods, Monte Carlo simulation is known for its accuracy and flexibility in treating complex geometries. However, these advantages are countered by very extensive computation times. Analytical solutions found from diffusion theory can be calculated very fast but are limited to special simple geometries.
Processing of ceramics with copper lasers
Authors: Knowles M. R. H. , Foster-Turner R. , Kearsley A. J.
Published: February 2023

The copper laser is a pulsed visible laser (511 and 578 nm laser lines), which emits intense (50-500 kW), short pulses (20-60 ns) at high pulse repetition frequencies (2-32 kHz). Average power levels from commercial units range from 10-120 W whilst laboratory devices have reached 750 W. Novel unstable resonator designs have yielded near diffraction limited beams,1 which may be efficiently amplified to powers in excess of 2 kW.2 The CVL operates in a unique laser parameter space and consequently has shown new and interesting results in materials processing.
Time-resolved plasma diagnostic through laser diode spectroscopy
Authors: Beverini N. , Strumia F. , Genovesi G. L. , Paganucci F. , Turco A.
Published: February 2023

Semiconductor diode lasers represent an important spectroscopic tool for performing high resolution measurements of spectral lines, from which plasma state parameters can be deduced. It is easy to obtain a fast scanning of the emission frequency of the laser so that the kinetics of the plasma can be followed with a high temporal resolution. The plasma that we want to analyse is produced in a mag- netoplasmadynamic (MPD) thruster, which consists of a coaxial cylindrical Lorentz force accelerator. A pulse of Argon (4 gr/sec) of the length of few msec is injected in the thruster and excited by a current pulse, roughly rectangular, with a typical duration of about 1 msec and an intensity of several KA. A diffusion pump keeps the vacuum at a value of the order of 10−5 torr. The experimental apparatus is shown in Fig. 1. The used diode laser was a Mitsubishi ML64114R. Operational wavelength, corresponding to transition starting from metastable level, was chosen by tuning the temperature of the diode through a Peltier module and the injection current. The laser emission frequency was quickly scanned, every 26 µs over the transition line. The laser output was sent into the vacuum chamber using an optical fiber (200 µm of core). The radiation was collimated into a parallel beam of about 1 cm of diameter through the plasma and finally focused on a fast silicon detector. A beamsplitter sent a fraction of the laser radiation into a low pressure, room temperature d.c. discharge in argon, whose transmission was simultaneously recorded and used as a reference. A typical recording is shown in Fig. 2. A sequence of single frequency sweeps, alternatively forwards and backwards, scanning the transmission profiles of the 1s5−2p8 transition (801.479 nm), are simultaneously observed through the plasma (orthogonal to the thruster axis) and a low pressure argon discharge. We extract from the experimental data the frequency dependent optical thickness. The lineshapes were fit to a Gauss, Lorentz, or Voigt profile to infer atomic density, temperature, and velocity. Two types of measurement were carried out in different points and in two directions (orthogonal and transversal). Figure 3 shows atomic density evolution at 12 cm from thruster anode. Further measurements are in progress. Two crossing beams will be used to obtain the bidimensional velocity profile.
A fast optical method for measuring spatial complexity in speckle fields
Authors: Maksimyak P. P. , Angelsky O. V.
Published: February 2023

No actual optical object is absolutely random in the sense of the probability theory. Therefore, the fields resulting from such objects are not absolutely random but carry information on the degree of ordering in the object.
Performance of the hybrid photomultiplier tube (HPMT)
Authors: Schomaker R. J.
Published: February 2023

By combining state-of-the-art solid-state technology with the latest vacuum photocathode technology, DEP has created a new and innovative range of photodetectors including the DEP hybrid photomultiplier tube (HPMT). This tube is also known as Hybrid photodiode (HPD). As a result of a five-year development program with several CERN groups, DEP now has two types of HPMT tubes available with each having its own field of application. New measurements were performed on the first production tubes and are described in this article. As a result of this development program, the HPMT is now also available for many applications outside the scientific field.
Free-space optical switching and processing using FET-SEED smart pixels
Authors: McCormick F. B.
Published: February 2023

Smart pixel optoelectronic device arrays enable the interconnection and communication advantages of optics to complement the processing power of electronics in computing and switching applications. GaAs multiquantum well (MQW) FET-SEED smart pixels have been used in a 32 input, 16 output multistage switching fabric prototype1 using 5 stages of (2,1,1) node arrays2 (16 nodes/stage), as shown in Fig. 1(a). Optimization of the initial system experiment has increased the fabric's bit rate from 50 Mb/s to 155 Mb/s per channel. As shown in Fig. 2, these FET-SEED systems incorporate smart pixels using GaAs MQW modulators and detectors, computer generated holograms, 2-D fiber bundles, external cavity semiconductor lasers, high resolution bulk and microoptics, and custom optical bench optomechanics.
Improvements in a gas discharge XeF (B→X) laser
Authors: Peters P. J. M. , Mei Q. C. , Witteman W. J.
Published: February 2023

The technology of electrical discharge gas lasers has improved greatly in the last decade. High repetition rates excimer lasers with operating powers of 100-300 W are commercially available now. However results on the XeF (B→X) discharge excimer laser are scarce although e-beam pumping of this laser transition has been studied extensively. This certainly has to do with the increased probability of discharge instabilities in the NF3 or F2 doped laser gas mixtures compared to the HCl-doped gas mixtures for the competing XeCl excimer laser under the same pumping conditions. With the use of new and powerful excitation techniques these problems are addressed.
Q-switching of high power continuous wave and pulsed Nd:YAG lasers
Authors: Danileiko Yu. K. , Denker B. I. , Kertész I. , Korchagin A. A. , Kroó N. , Musatov A. G. , Osiko V. V. , Plosz B. , Sidorin A. V. , Sverchkov S. E. , Tihonova T. L.
Published: February 2023

Nd:YAG laser of 500-W power, continuous wave or pulsed at 10-800 Hz repetition rates with duty cycle from 0.1 up to 0.8 was Q-switched by two different ways. In the first frustrated total internal reflection (FTIR); in the second tunable, small base Fabry-Perot (TFP) was used for switching. In both cases piezoceramies served for the displacement of the switching optical elements. Between 50 and 150 kHz, the measured amplitudephase characteristics have shown resonance at Q ≈ 5, which limit the applicability of these modulators above resonance. Special attention was paid to damp the mechanical resonances up to 200 kHz, using an electro-mechanical model calculation with strong electrical damping parameter. The damped and undamped characteristics are given.
Improvements in excimer laser performance and safety
Authors: Baughan A. K. , Ferguson A. H. , Kearsley A. J. , McGrady G. S.
Published: February 2023

There has been a considerable amount of work performed over the last ten years on extending excimer laser gas lifetimes and improving laser performance by various means. One of the most successful has been cryogenic trapping of the detrimental contaminants of the excimer laser mixture. Significant improvements over current laser performance have been obtained using this method combined with a novel source of fluorine for use with fluoride-based lasers (ArF, KrF etc.).
Frequency modulated external cavity diode lasers: a theoretical and experimental study
Authors: Willis A. P. , Kane D. M. , Langley L. N. , Shore K. A.
Published: February 2023

A theoretical and experimental study has been undertaken of a frequency modulated (FM) external cavity diode laser (ECDL). Operation as an FM laser is achieved using an intracavity electrooptic phase modulating crystal driven at a frequency close to but not equal to the cavity longitudinal mode spacing. FM lasers have applications in optical metrology, spectroscopy, and laser cooling of atoms.1
300-W Nd-YAG laser with reduced output beam divergence
Authors: Dimakov S. A. , Gorlanov A. V. , Kliment'ev S I. , Kovalchuk L. V. , Orlova I. B. , Sventsitskaya N. A.
Published: February 2023

Usually power Nd-YAG lasers with stable resonators work in multimode operation and show divergence 20–100 times larger than the diffraction limit. Use of unstable resonators in such lasers is not trivial because of strong thermal lenses induced in active crystals. In Ref. 1 an unstable resonator for a laser based on two active rods was proposed and investigated. Output beam divergence in excess of the diffraction limit by 2 times with output power of 160 W was obtained.
Possibilities of depopulating the final level of 3 µm self-limited laser transitions in Er-and Ho-doped fluoride crystals
Authors: Razumova I. K. , Tkachuk A. M. , Sandulenko A. V.
Published: February 2023

Recently developed 3-µm lasers on erbium- and holmium-doped crystals are of great interest for laser physics and biomedicine. Achieving the frequency operating mode and increase of the pulse repetition rate for pulse-periodic mode are urgent. However, there are still unsolved problems of the studies of such 3-µm lasers.
Quantum cascade lasers: coupled quantum well optoelectronics in the 4-100 µm wavelength region
Authors: Capasso Federico , Faist Jerome
Published: February 2023

A new semiconductor injection laser, which differs in a fundamental way from diode lasers, has been demonstrated using quantum structures grown by MBE and designed by band-structure engineering.1 Called the quantum cascade laser (QCL), this device relies on only one type of carrier (it is a unipolar semiconductor laser), and on electronic transitions between conduction band states arising in quantum wells. This is to be contrasted with diode lasers (including quantum well lasers) where the lasing transition occurs between electron and hole states across the semiconductor bandgap. Such pure quantum confinement unipolar lasers were originally proposed 25 years ago, but despite considerable effort this is the first structure to achieve laser action.
High power low confinement AlGaAs/GaAs single quantum well laser diode operating in the fundamental lateral mode
Authors: Petrescu-Prahova I. B. , Buda M. , Iordache Gh. , Karouta F. , Smalbrugge E. , van de Roer T. G. , Kaufmann L. M. F. , Wolter J. H. , van der Vleuten W. C.
Published: February 2023

It was recently proposed,1,2 that the power density related to the window width (in W/μm) of a laser diode can be substantially improved using a low confinement epitaxial structure. Keeping a reasonable high value of the intrinsic gain in the active region, a low confinement structure shall work also with a low modal gain value. The power optimization process is essentially connected to the attenuation coefficient of the laser waveguide α. When operating with an α value around 1 cm−1 and pursuing a high differential efficiency, the modal gain should have a value around 5 cm−1 and the laser length should be increased accordingly.2 A beneficial consequence of the low modal gain value is the possibility to increase the stripe width while preserving well the operation in the fundamental lateral mode above the threshold.
Media effects on image transfer
Authors: Kokhanovsky Alexander A. , Zege Eleanora P.
Published: February 2023

The optical transfer function (OTF) is the basic characteristic responsible for image transfer through scattering media (aerosol atmosphere, clouds, fogs).1 The mutual coherence function (MCF) of the light field is of great importance for the coherent communication systems. The MCF and the OTF of a scattering medium depends on its microstructure and thickness. To study the effect of the microstructure on the image transfer characteristics the Mie calculations are used to obtain single scattering characteristics and then the Monte Carlo simulations provide OTFs. It is a reliable but cumbersome and time-consuming technique.
The multicomponent air pollutant photoacoustic gas analysis using a cw 13CO2-laser
Authors: Kulikov V. V. , Starovoitov V. S.
Published: February 2023

In the last few years, the photoacoustic spectroscopy with using CO2-lasers has proved promising for local air pollution monitoring. The application of rare isotope carbon dioxide species lasers permits to both reduce the absorption background caused by the atmospheric CO2 and increase the number of substances to be detected. The use of 13CO2 specie in active medium of an exciting laser makes it possible to determine the concentrations of substances, absorbing the radiation in the range of 9.6-10.2 and 10.6–11.4 μm.
Spatial dynamics of self-consistent waveguides near to interfaces between linear and nonlinear media
Authors: Aliev Y. M. , Boardman A. D. , Smirmov A. I. , Xie K. , Zharov A. A.
Published: February 2023

The present report is devoted to an investigation of the influence of radiative losses upon the spatial dynamics of self-consistent waveguide channels that are localized near to the interface between linear and Kerr-type nonlinear dielectric media. It is shown that the radiative effects, through their dependence on the intensity of the electromagnetic fields, the initial channel position, and the angle of incidence, can lead either to the total disappearance of nonlinear formations or to their displacement, deep into the nonlinear medium, as the result of loss of some part of the initial energy. The nonlinear interaction of the self-consistent channels with the externally incident, stimulating beams is studied and stability of resulting steady states is determined. In order to carry out these investigations, an original perturbation approach is suggested that is based on the assumption of a small overlap between the externally incident waves and the internal, nonlinear quasilocalized eigenmode. It is shown that this step permits equations that determine the spatial dynamics of channel energy and position, to be obtained, together with the structure of scattered fields. The results obtained enable an interpretation of some effects, previously demonstrated by extensive 2-D numerical calculations, to be given.
Porous silicon
Authors: Canham L.
Published: February 2023

Summary not available.
Compact free electron lasers in the far infrared-millimetre region
Authors: Doria A. , Gallerano G. P. , Giovenale E.
Published: February 2023

Conventional free electron lasers (FELs) suffer from some drawbacks related to the large size of most electron beam (ebeam) accelerators that implies high costs, system complexity, and shielding requirements. However, in the far infrared (FIR) and millimetre (mm) wave region the FEL can meet the demand of compactness. For example, the low ebeam energies required (<10 MeV) allow the use of small size accelerators like radio-frequency (rf) linacs or microtrons. The increased performance in terms of gain at wavelengths in the FIR and mm also requires a shorter length of the interaction region, thus allowing the use of short period undulators and a small number of periods which results in a better efficiency. Moreover, the presence of a dispersive element inside the undulator, like a waveguide needed for operation at long wavelengths, alters the radiation generation mechanism introducing new tuning possibilities in addition to those traditional for the FELs. The performance of such a device shows very peculiar characteristics like the possibility of changing the central frequency and the spectral bandwidth for spectroscopical purposes or the high peak power for applications in nonlinear optics. Following the above considerations the FEL group at the ENEA Frascati Research Centre has started a development program for compact FEL devices. A first prototype is now running, since 1992, in the mm wave region, and a second development step to move toward the FIR region is in progress.
Physics of microcavity lasers
Authors: Yamamoto Y.
Published: February 2023

Summary not available.
Micromachining with Copper Lasers
Authors: Knowles Martyn
Published: February 2023

The copper laser is a pulsed laser which emits intense (50 - 500 kW), short (20 - 60 ns) pulses at high pulse repetition frequencies (2 - 32 kHz). The laser radiation is in the visible with laser lines al 510.8 nm (green) and 578.2 nm (yellow). Average powers from commercial units range from 10 - 120 W whilst laboratory devices have reached 750 W. Novel unstable resonator designs and amplifier configurations have yielded near diffraction limited beams which may be efficiently amplified to powers in excess of 2 kW with typical wall-plug efficiencies of 1 %. It is this combination of laser parameters that differentiates the copper laser from other laser types.
Real Time Day Light Holography, Holographic Interferometry and Speckle Photography Well Suited to Medical Environment
Authors: Petrov Valery
Published: February 2023

Medical data acquisition utilizing laser sources meets growing demand in ophthalmology, dentistry, orthopaedics, endoscopic inspections and other fields. Simple, cheap and reliable systems operating in real or quasi-real time and friendly to medical environment are needed now. Holography and holographic interferometry in spite of their unique features are rather rarely used in medical practice due to relative complexity, costs, lengthy multi-stage procedures, need of dark rooms and vibration insulation. But most of these drawbacks can be easily avoided.
High-power end-pumped composite Nd:YAG rod
Authors: Weber R. , Neuenschwander B. , Weber H.P. , Albers P
Published: February 2023

Finite Element simulations of different methods for cooling of the pumped rod surface in longitudinal Nd:YAG pumping schemes predicted a superior behavior of the composite rod concept, i.e rods with doped and undoped parts. Due to the undoped pumped end, the surface contribution to the thermal lens caused by rod expansion is almost eliminated. Therefore, also the deviation of the phase front distortion from spherical is significantly reduced, facilitating to compensate for the thermal lens.
Photorefractive properties of an organic salt
Authors: Follonier S. , Bosshard Ch. , Pan F. , Günter P.
Published: February 2023

Inorganic photorefractive materials are widely used for applications in the visible spectral range. The lack of sensitive photorefractive materials at telecommunication wavelengths (λ=800- l500nm) where low cost semi-conductor laser diodes are commercially available opens a new field of interest. Due to the shift of the absorption cut-off towards longer wavelengths with increasing nonlinearities, the newest organic materials fulfill the sensitivity requirements at near infrared wavelengths. Among the organic crystals, 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) is a promising candidate to investigate the photorefractive properties of organic materials. Combining very large nonlinearities (r111 of 92 pm/V at λ=720nm) with an absorption cut-off at around 700nm along the dielectric axis x1, DAST shows promising results in the standard two-beam coupling experiments. Using the light interference pattern of two incoming coherent laser beams (ratio of pump to signal beam > 100), an index grating could be generated at a wavelength of λ =720nm. Due to the 90° phase shift of this index grating with respect of the light intensity pattern, an asymmetric energy exchange could be observed and qualitatively analyzed (Fig. 1). Using polished b-plates with dimensions up to axbxc= 12x1x4 mm3, a gain of up to 1.4cm-1, corresponding to a net gain of (Ί−α)≥0.2cm_l, was measured for light polarized along the dielectric axis x1 at a pump intensity of 85mW/cm2. Writing times of the order of one second have been measured. These first results point out the promising properties of the organic salt DAST for photorefractive applications at near infrared wavelengths. Further experiments of the dependence of the photorefractive gain on the applied electric field, the wavelength, and the grating period will also be reported.
Heterodyne interferometric optical estimation of turbulent liquid media characteristics
Authors: Haudidier N. , Cariou J. , Lotrian J.
Published: February 2023

The heterodyne technique is particularly appropriate to the evaluation of coherence characteristics of the optical wave fronts after propagation through random media. We have studied an inverse problem for the estimation of the liquid media turbulence characteristics.
Application of a copper laser monitor for the observation of laser induced instabilities during the treatment process of material
Authors: Klimovskii I.I. , Abramov D.V. , Galkin A.F. , Prokoshev V.G. , Grigoriev A.V. , Arakelian S.M.
Published: February 2023

Investigation of physical processes induced under powerful laser radiation interacting with surface of metal are very important to understand the mechanisms of the energy transport during the melting processes. The essential deviations from equilibrium state of the system are a vital point for discussed highly nonlinear phenomena. These deviations could not be described within the frameworks of common (weakly nonlinear) linearized dynamic models. First of all it is concern to such a most general and fundamental nonlinear problem as an excitation of stochastic and turbulent movement in dissipative systems and as a result the definite spatial and temporal structures (often with contrast to fluctuations) arise in considered nonlinear material. But experimental study of discussed phenomena during the melting process under powerful laser radiation as well as under development of electron-beam, electric arc and plasma technologies is limited due to absence of reliable methods for observation of zone of interaction where excited flows come out from the bulk to surface of illuminated material. In the first place it is connected with the formation of blazing plasma directly above the zone of interaction. The experimental unit reported by us for analysis of dynamic processes during the laser treatment of materials consists of two pieces, i.e. the laser technological plant and the laser monitor.
Channel capacity of uni-directional self-healing ring network
Authors: Park S. Y , Park C. S.
Published: February 2023

A self-healing ring is a network to survive during a cable cut [1]. This paper describes an architecture of remote node for uni-directional self-healing ring network, each of which consists of an optical add-drop multiplexer (ADM), three optical switches, and three erbium-doped fiber amplifiers (EDFAs). We estimate the channel capacity of the ring network whose channels are spaced 0.8-nm apart in the amplifier band.
Characterization of Excimer Laser Beam Parameters
Authors: Mann K. , Ohlenbusch J. , Westphal V. , Albrecht H.S.
Published: February 2023

For a variety of excimer laser applications, e.g. in material micro-processing, precise control over the spatial profile of the laser beam is essential. This strongly requires high resolution techniques for acquisition of energy density distributions and accurate methods for subsequent evaluation of the relevant laser beam parameters.
Current Status and Trends in Active Matrix LCD’s
Authors: Ayres J.R.
Published: February 2023

Active matrix LCDs have a significant and expanding position in the overall display market This talk will first review the current status of AMLCDs. Key trend in technology which are likely to be realised in future displays will also be highlighted.
Liquid Crystal Projectors Architectures
Authors: Marcellin-Dibon E. , Joubert C. , Loiseaux B.
Published: February 2023

Among many display technologies, projection TV is the only one which can provide large size images with high quality. Liquid Crystal projection is the emerging technology that will extend the ranger of projection TV products, and which is already widely used for institutional front projectors. Many advantages like the compactness and the good image quality are making this new technology very attractive.
Design of computer generated beam shaping holograms
Authors: Beyerlein M. , Dresel Th. , Schwider J.
Published: February 2023

For the design of computer generated holograms reconstructing certain intensity patterns with phase freedom we use an object-oriented approach. The given pattern is decomposed into elementary objects for which appropriate phase-only hologram functions can be found. The total hologram function is received by subsequent superposition of its constituents with a relative amplitude and phase weighting, respectively. Thus, the degrees of freedom are dramatically reduced compared to sampling approaches. The design algorithm allows to compensate for the intensity and phase distribution of the impinging laser beam and for the shape of the hologram aperture. The phase-only hologram function for an elementary focal object is found by a raytracing approach for the light beams propagating from point x at the hologram plane to point

u
¯

at the focal plane. To get the correspondence

x
¯

(

u
→

)

the equation for light flux transformation,

I
(

x
¯

(

u
¯

)
)
det

∂

x
¯

∂

u
¯

 
=

I
0

(

u
¯

)

, is integrated with respect to the intensity distribution

I
(

x
→

)

of the laser beam within the hologram aperture and the intensity distribution

I
0

(

u
¯

)

of the desired focal pattern at the distance z. Moreover, conservation of total energy is assumed. The equation for the slope of the light ray in paraxial approximation,

∇
ψ
(

u
→

)
 
=
 

x
→

(

u
→

)
−

u
→

z

, is integrated to get the phase

k
ψ
(

u
→

)

immediately behind the hologram. This phase function has to be encoded in the hologram together with a phase compensation for the input beam. The phase-only hologram functions for the elementary objects which are implemented so far are eiven in table 1.
Low threshold 2.01 µm Y3Al5O12:Yb-Tm laser
Authors: Nikitichev A.A. , Pysmenniy V.A.
Published: February 2023

Sensibilization of Tm ions by Cr ions is today the usual operating scheme of the lamp-pumped Tm laser. High concentration of Tm ions results in efficient Cr→Tm energy transfer and in cross-relaxation of absorbed energy quanta, resulting in term in double quantum efficiency of absorbed energy conversion. At the same time, high concentration of the activator and the three-level lasing lead to the high energy threshold, limiting thus the pulse repetition rate. High energy threshold, accompanied by the low intensity of the Tm ion absorption band at the wavelength of AlGaAs laser diode emission prevents also the use of Y3Al5O12:Tm crystals in lasers with the transverse diode pumping.
Ultra-Violet HeCd Laser with Pumping by Microsecond Electron Beam
Authors: Novoselov Yu.N. , Uvarin V.V.
Published: February 2023

Exciting the HeCd mixture by nuclear reaction products has permitted laser generation on green (533.7 nm and 537.8 nm) and blue (441.6 nm) Cd-ion lines. However, lasing on λ = 325.0 nm (a 5s22D3/2 - 5p2P1/2 transition similar to the 5s22D5/2 - 5p2 P3/2 transition for λ = 441.6 nm) has not yet been obtained with nuclear pumping. Inasmuch as the processes of excitation of the atmospheric-pressure HeCd medium by nuclear pumping and electron beam pumping are alike and are determined primarily by the power of the energy contribution, electron beams can be used to simulate nuclear pumping.
Excited state absorption of erbium-doped crystals
Authors: Le Boulanger P. , Doualan J.-L. , Girard S. , Margerie J. , Simondi-Teisseire B. , Viana B.
Published: February 2023

Excited state absorption can be used to obtain up-conversion lasers (with sequential two-photon absorption or avalanche absorption) but it can also reduces laser performances if this absorption occurs in the pumping or emission light domain.
Broad-Area InGaAs/AlGaAs Quantum-Well Lasers with High Efficiencies
Authors: Heerlein J. , Jost G. , Joos J. , Morgott S. , Reiner G , Unger P.
Published: February 2023

High-power lasers emitting at a wavelength of 980 nm are preferred pumping sources for Er3+-doped fiber amplifiers and are widely used in communication systems. We have fabricated MBE-grown strained In0.2Ga0.8As/AlGaAs GRIN-SCH lasers with different number of quantum wells (1-3). The 8-nm-thick quantum wells are surrounded by 40-nm-thick GaAs barrier layers and AlxGa1-xAs graded index layers where the Al mole fraction x is linearly graded from 14 to 50 %. We have varied the thickness of the GRIN-SCH region in the range of 250 nm and 600 nm. The top contact consists of a highly doped (1020cm-3) 50-nm-thick cap layer and an evaporated TiPtAu contact metallization. The active areas with a width of 20 – 150µm have been defined by wet chemical etching. To obtain a high reliability, the structures have been passivated by a Si3N4 layer deposited by plasma-enhanced chemical vapor deposition (PECVD). Especially in high-power devices, the continuous optical power is limited by thermal heating. Besides a low series resistance, an effective cooling mechanism is necessary. For lowering the thermal resistance, the laser diode has been soldered junction-side down on a diamond heat spreader because of the high thermal conductivity which is about 20 times higher compared to GaAs. A 3-µm-thick eutectic AuSn layer is used as solder.
Output Coupling Hole Optimization of the Waveguide Submillimeter Laser
Authors: Gurin O.V. , Degtyarev A.V. , Svich V.A. , Tkachenko V.M. , Topkov A.N.
Published: February 2023

The output power and polarization degree increase has been investigated as a result of the output coupling hole displacement from the axis of submillimeter (SMM) laser resonator based on the circular metal waveguide.
Electrode power losses in the pulsed discharge of CuBr laser
Authors: Astadjov D. , Sabotinov N.
Published: February 2023

Copper vapor lasers being a source of hundreds of watts laser power in the visible range have been developed in various options. Electrical power of order of ten kilowatts is normally deposited in the laser tube. This power goes not only to the discharge plasma but to the electrodes as well. However, information of the energy dissipation in electrodes is not reported so far. We present our study on that subject under typical conditions for CuBr laser.
Guided and radiation Modes of a Graded-Index Waveguide with Defocusing Nonlinearity
Authors: Petrov Dmitri V.
Published: February 2023

In waveguides with defocusing nonlinearity the effective refractive index (ERI) of guided modes decreases with mode’s power down to mode cutoff; they are not guided below certain value of mode’s power. In this work the ERI behavior near its cutoff value in self-defocusing nonlinear graded-index waveguides. These waveguides can be realized in strongly nonlinear materials. In the nonlinear graded-index waveguide the turning point of the guided mode and, hence, the size of the region, where the most part of power propagates, is changed with mode’s power. Radiation modes that are necessary in describing any radiation phenomena in the region around waveguide, and a dark fundamental wave at the smooth refractive index interface are also analyzed.
The initiation of the optical breakdown by pigmented melanosomes in the anterior chamber of eye under the laser pulse action
Authors: Pustovalov V.K.
Published: February 2023

The purpose of this paper is to estimate the influence of melanosomes in the anterior chamber of the eye on the results of short laser pulse action on the eye biotissue in the case of glaucoma of adult patients and children. In the case of glaucoma of adult patients the biotissues in the anterior chamber of the eye mostly contain melanosomes (pigmented granules), which act as absorbing inclusions when irradiated with laser pulses. In contrast to the eye of adult in the case of hydrophthalmia (congenital glaucoma), there are practically no melanosomes in the anterior chamber of the children’s eyes. A model is proposed for the heating of a pigmented melanosome in eye biotissues by a laser pulse. Analytical and numerical calculations based on this model are made.
Mathematical modelling of dynamic cooling and pre-heating, used to increase the depth of selective damage to blood vessels in laser treatment of port wine stains
Authors: Sturesson C , Andersson-Engels S
Published: February 2023

Based on the assumption that the maximum irradiance allowed during laser treatment of port wine stains is limited by the temperature rise at the dermoepidermal junction (DEJ), we theoretically investigated how much the irradiance could be increased by dynamically cooling the skin surface. The heat condution equation was solved numerically in cylindrical coordinates using a skin model composed of four layers. The laser-light absorption was calculated using Monte Carlo simulations. The transient thermal behaviour of the skin was modelled when cooling with water at a temperature of 0°C and with liquid nitrogen at a temperature of -196°C. With cooling, an increase in the maximum irradiance by a factor 2.33.6 was theoretically permitted depending on the irradiation time, wavelength and mode of cooling. The corresponding increase in vessel selective damage depth was predicted to be 0.4-0.5 mm.
Electroluminescent Polymers: Progress Through Polymer and Device Engineering
Authors: Bradley D.
Published: February 2023

Summary not available.
Frequency doubling of a 1560 nm diode laser in a periodically-poled waveguide and locking to the Rb D2 lines
Authors: Mahal V. , Bruner A. , Kiryuschev I. , Arie A. , Arbore M. A. , Fejer M. M.
Published: February 2023

Optical frequency standards operating at 1.55 µm are required for fiber-optic wavelength division multiplexed communication systems and for 'cold start' coherent optical communication. Unfortunately, transitions near 1.55 µm are rare and difficult to probe. One may overcome the difficulties associated with frequency references at 1.55 µm by second harmonic generation (SHG) and locking to Rb D2 line near 780 nm. This reference was already used to stabilize 1560 nm laser diodes using the internally generated second harmonic of diode lasers and by bulk external SHG in KNbO3, however the SHG power levels were in the pW range and the nW range, respectively, hence locking to Doppler broadened line was possible, but the power level was not sufficient for locking to sub-Doppler lines.
Photorefractive CdTe:V homodyne detector at 1.06 and 1.55 µm.
Authors: de Montmorillon Louis-Anne , Delaye Philippe , Launay Jean-Claude , Roosen Gérald
Published: February 2023

Real time holographic materials are ideally suited for use as adaptive beam-combiners to coherently superpose a phase-modulated signal beam and a local oscillator beam in a homodyne detection scheme. Photorefractive crystals are among the most sensitive materials for real-time holography.
Fiber Grating Stabilized Single-Mode Semiconductor laser
Authors: Pan J. J. , Jing X. , Shi Y.
Published: February 2023

Narrow linewidth semiconductor lasers find important applications in lightwave communication systems. The available DFB laser diodes (LD) have difficulties of wavelength selectivity and stability for dense WDM applications. This paper reports a low cost single-mode LD, stabilized by a fiber Bragg grating (FBG) and integrated in a hermetically sealed standard butterfly package. The device provides excellent wavelength and power stability and sidelope suppression.
Compact CO2 Lasers with Slab and Annular Geometries of Active Elements
Authors: Orlov L.N. , Gaiko O.L. , Nekrashevich J.I. , Nevdah V.V.
Published: February 2023

Transversal RF excitation of molecular active media offers a lot of advantages for laser design, but the realization of them both in a slab or an annular geometries requires new types of resonators. For a slab laser we have investigated a 3-mirrors stable multipasse resonator; in out recent experiments we have a possibility to vary the effective length of the active medium from 3 to 21 double passes between two wall’s mirrors. It is shown, that the optimum number of such passes depends on the media amplification, mirror’s reflection losses and overlapping of the beams inside the cavity. This type of resonator is preferable for the active media with a moderate gain; it gives a higher power extraction from the large volumes of the active gases and a better quality of the output beam then other known stable and unstable resonators.
Accounting for absorption saturation effects in pulsed z-scan measurements
Authors: Kozich Valery P.
Published: February 2023

Z-scan technique is sensitive method for measuring the sign and magnitude of light induced changes in the refractive index. These changes could be due to such mechanisms as local heating, Kerr effect, changes in the local temperature and population of excited states.
Lidar and in situ Study of the Vertical Structure of the Atmospheric Planetary Boundary Layer Over Urban Area
Authors: Kolev I. , Parvanov O. , Kaprielov B. , Donev E.
Published: February 2023

Monitoring of ambient air quality can be carried out either measuring the various pollutants in the atmosphere or sounding the planetary boundary layer (PBL), assuming that the number and distribution of the air pollutant sources remain the same. In terms of PBL meteorology low level stability, inversion distribution, buoyancy, turbulence strength, mixing height, wind velocity and direction are some of the meteorological parameters that need to be monitored. The remote sensors, in comparison to the in situ sensors, can provide such data continuously in both space and time with a better resolution.
Multihertz table-top Petawatt fs-lasers: fiction or conceivable reality?
Authors: Korn Georg , Barty C. P. J. , Rose-Petruck C. , Squier J. , Wilson K. R.
Published: February 2023

This paper has been withdrawn.
Lamp pumped 1,5 μm generation on a new active medium - LaSc3(BO3)4:Cr,Yb,Er
Authors: Ageev A. Yu. , Balabaev S. I. , Kuzmin O. V. , Kutovoi S. A.
Published: February 2023

The paper presents the results of preliminary investigations of spectral-luminescent and generation properties of LaSc3(BO3)4:Cr,Yb,Er (LSB:Cr,Yb,Er) crystal. LSB single crystals with different Cr,Yb,Er concentrations were grown by Czochralski technique in iridium crucibles. LSB crystallizes into a structure of monoclinic syngony with spatial group C62h.
Delayed Self Heterodyne Linewidth Measurement of Vertical-Cavity Surface-Emitting Laser Diodes
Authors: Jung C. , Schmid W. , Weigl B. , Reiner G. , Miclialzik R. , Ebeling K.J.
Published: February 2023

Recently, record low linewidths of 30 MHz have been reported for proton-implanted vertical-cavity surface-emitting laser diodes (VCSELs) [1]. However, the value obtained was near the resolution limit of the available Scanning Fabry-Perot interferometer, thus underlining the need for a more refined measurement technique. We have employed the delayed self heterodyne method in the setup of Fig. 1 to accurately determine the linewidth of VCSELs. With a single-mode fiber of 1 km length in the delay and modulation arm of the interferometer, a resolution of 150 kHz is easily offered. For the measurements, VCSELs lasing on a single longitudinal and transverse mode as well as with stable polarization state have to be selected in order to avoid excess mode partition noise. In Fig. 2, the linewidths of a proton-implanted InGaAs-AlGaAs VCSEL with 16 μm active diameter and a lasing wavelength near 960 nm is plotted as a function of the inverse output power, reasonably well displaying the linear relationship expected from theory. The linewidths are deduced from the heterodyne spectra, an example of which is depicted in the inset of Fig. 2 for an output power of 0.8 mW and an intermediate frequency of 1 GHz. Thermal rollover and the onset of higher order mode lasing limit the output power to 1.1 mW. A relatively large linewidth-power-product of 14 MHz-mW is obtained, however the minimum linewidth of 20 MHz and the residual linewidth of about 4 MHz are the lowest values reported so far. Future work will be devoted to investigations of highly efficient selectively oxidized single-mode VCSELs and might result in further improvements of device performance.
Nonlinear Frequency Conversion of Nd: glass and Yag Laser Radiation in Crystalline, Gaseous, Ionic and Plasma Media
Authors: Ganeev R.A. , Kulagin I. A. , Begishev I. A. , Redkorechev V. I. , Usmanov T.
Published: February 2023

Frequency conversion of high-intensity radiation of Nd: glass and YAG lasers in different media have been investigated. Various factors leading to limitation of conversion efficiency are examined. An investigation was made of cascade generation of the second, fourth and fifth harmonics of radiation from a wide-aperture Nd: glass laser in KDP and ADP crystals. The efficiencies of energy conversion of Nd: glass laser radiation to the second and fourth harmonics were 0.87 and 0.92. It was found that the main factor limiting the efficiency of the fifth harmonic generation is two-photon absorption of radiation. The efficiency of conversion to the fifth harmonic was 0.19.
New Class of Multiple Wavelength High Efficiency Solid State Lasers
Authors: Kostanian R. B.
Published: February 2023

Lasers simultaneously operating at several wavelengths have good prospect for medical, scientific, technological and other applications. Multiple wavelength lasers reported so far have a common shortcoming: they have low efficiency. Creation of effective multiwavelength lasers, which would simultaneously radiate at several wavelengths may widen the field of their applications. They may successfully be used in problems where either a multifunctional action is needed or an irradiated object is multicomponent. For example, lasers radiating at two different wavelengths could be used in medicine to provide both cutting and coagulation simultaneously.
Comparison of CW Lasing Operation of Nd:YAG, Nd:KGW and Nd:BEL with Laser Diode Pumping
Authors: Demidovich A. , Shkadarevich A. , Danailov M. B. , Apai P. , Gasmi T. , Gribkovskii V. , Kuzmin A. , Ryabtsev G. , Batay L.
Published: February 2023

New efficient solid-state laser materials - lanthanum beryllate (Nd:BEL) and potassium gadolinium tungstate (Nd:KGW) - for laser diode pumping were compared with the most popular Nd:YAG crystal. Nd:YAG, Nd:BEL and Nd:KGW were pumped in the same cavity conditions suitable for intracavity frequency doubling: Rin>99.98% and Rout=99.9%. The relation between the output power and pump radiation wavelength was investigated in the range 807.5 - 811.5 nm. Both for Nd:BEL and Nd:KGW the obtained dependence is much weaker than the one expected from the absorption spectra. An interpretation of this behavior for high Nd -doping crystals is proposed.
Mixing and Detection of 10µm Infrared Laser Radiation by the First Nanometer Thin-Film Ni-NiO-Ni Diodes with Integrated Antennas
Authors: Fumeaux C. , Herrmann W. , Rothuizen H. , De Natale P. , Kneubühl F.K.
Published: February 2023

Thin-film Ni-NiO-Ni diodes with a contact area of (110nm)2 are integrated with 110nm to 5µm dipole, bow-tie and spiral antennas which couple to 30THz (≈10µm) CO2-laser radiation and permit detection and mixing at difference frequencies over75MHz.