bluuebunny/crossref_metadata_2025 huggingface dataset:
Field mechanism of simultaneous oscillation on several transitions in cw CO2 and CO lasers
Authors: Gorobets V. A. , Petukhov V. O. , Tochitsky S. Ya. , Churakov V. V.
Published: February 2023

The obtaining of the steady-state regime of simultaneous oscillation on several given lines in CO2 and CO lasers presents difficulties because of the competition between transitions. In Ref. 1, it is shown theoretically and experimentally that the steady-state multiwave regime in a TEA CO2 laser is possible at sufficiently high intensities of the light fields in the cavity. Due to the effect of “rotational or vibrational bottleneck" the competition between the transitions becomes considerably weaker. To weaken the competition, it is necessary to purposely create the conditions under which the field intensity in the cavity exceeds the saturation intensity of the CO2 molecule operating transitions, which is determined from the expression: Is = cπγ/τB, where c is light speed, γ is the collisional half width of the line, τ is the characteristic time of collisional relaxation, B is the integral Einstein coefficient for the centre of the vibrational-rotational transition. The field mechanism considered is applicable to multiwave oscillation at rotational transitions of both one band and various bands. In the last case, it is much easier to weaken the competition between the transitions. The effect of "vibrational bottleneck" comes into action at far lower saturation intensities, because it is determined by slower processes of vibrational exchange.
A long pulse 250 kV electron gun for high-pressure gas lasers
Authors: Ustinovskii N. N. , Peters P. J. M. , Gielkens S. W. A. , Witteman W. J.
Published: February 2023

Large cross-section e-beams proved to be efficient for preionization and excitation of high-pressure gas laser media. This paper describes an e-beam gun with a secondary electron emission (SEE) cathode and a wire ionised plasma (WIP) as anion source for the production of the secondary electrons that has been developed to meet a broad range of requirements.
Power limitation of a large-bore copper vapor laser due to inadequate penetration of the electric field
Authors: Blau P.
Published: February 2023

It is well known that the specific mean power in a copper vapor laser falls considerably when scaling from a small-bore tube to a large-bore tube. Several mechanisms were proposed to explain this fact. The major ones are thermal population of the lower laser levels due to excessive heating of the gas and disturbance of the plasma relaxation by long diffusion time to the walls. We found that the combination of the high gas temperature and the high residual electron density results in high electric conductivity, especially near the tube axis. Thus the diffusion constant of the electric field decreases, and in a large-bore tube only a small portion of the electric field penetrates into the plasma.
High energy electron beam and electromagnetic field interaction modelling for high-speed electro-optical applications
Authors: Sabry R. , Chaudhuri S. K.
Published: February 2023

In order to look beyond the conventional optoelectronics technology, a high energy particle and radiation interaction scheme is considered for use at the electro-optical interfaces. Introduced interactive medium, which utilizes a relativistic electron beam to create coupling among different electromagnetic field signals (from an operating wavelength and/or frequency point of view) in the vacuum or low density materials, exhibits milder response limitations than solid-state media. Relaxation of the described material dispersion, which imposes constraint on the speed and strength of interaction (i.e., electro-optical coupling) due to the signal distortion, offers an opportunity to gain access to a higher range of the available spectrum.
Effect of optical feedback and light injection on transient dynamics of singlemode semiconductor lasers
Authors: Mirasso Claudio R. , Hernández-García Emilio , Dellunde Jaume , Sancho José María , Torrent Maria del Carme
Published: February 2023

Timing jitter and frequency chirp are of considerable importance for practical applications of semiconductor lasers and for pulse generation and propagation in optical fibers. They cause a degradation of the temporal resolution and severely limit the distance of propagation of optical pulses inside the fiber. On the other hand, optical feedback is an important effect to take into account in optical communication systems. Feedback coming from short external cavities appears to be important in optical integrated devices, where reflexions from the different components of the circuit can influence the laser performance. Recent works1 have shown that timing jitter strongly increases for certain positions of the external reflector in short external cavities (≲ 10 mm).
AlGaInAs metal-semiconductor-metal photodetectors and modulators for GBit/s systems
Authors: Kummetz T. , Fricke A. , Sowada D. , Mähnß J. , Kowalsky W.
Published: February 2023

Planar metal-semiconductor-metal (MSM) structures prepared on GaAs have attained outstanding frequency limits as high speed photodetector and light modulator due to the low capacitance of the planar electrode design. The operation wavelength of 1.3 µm and 1.55 µm for applications in optical communication systems are obtained by solid source MBE growth of the quaternary material system AlGaInAs under lattice-matching conditions on InP. To achieve high-quality Schottky contacts with low dark currents and high breakdown voltages, an AlInAs barrier enhancement layer has to be inserted between the AlGaInAs active layer and the PtAu metal contact. Integration of the basic MSM structure with a Fabry-Perot resonator results in wavelength selective photodetection and modulation.
Novel resonator geometry with non-equal mirror reflectivity interference wedge for tunable unidirectional ring lasers
Authors: Stoykova E. , Nenchev M.
Published: February 2023

We draw attention (theory and experiment) to the interference wedge (IW)1-3 property to present a strong asymmetry in reflection, when it is built of non-equal reflectivity mirrors and we show how this failure permits to develop attractive unidirectional ring lasers. In proposed ring cavity schemes a single IW is used simultaneously as a tuning element, as an element introducing asymmetry and as a laser output coupler. This is an advantage in comparison with the conventional schemes with Faraday rotator4 or a reinjecting extracavity mirror.5
Structural stability and array modes of odd number cyclic vertical cavity semiconductor laser arrays
Authors: Fishman T. , Orenstein M.
Published: February 2023

Arrays of Vertical Cavity Surface Emitting Lasers (VCSELs) were prepared by patterning the reflectivity of the laser's back mirror.1 The latter was accomplished by the deposition of metal layers on top of the Bragg mirror, employing a predefined spatial pattern. High quality and very large laser arrays were obtained using this method.2 The cyclic arrays of this paper are “real" two-dimensional (2D) arrays, since cyclic boundary conditions cannot be implemented in one dimension. Cyclic (ring) arrays are of practical interest since, by applying symmetry consideration, it is obvious that the near field (NF) and the far field (FF) intensity patterns of the dominant mode should have the same number of intensity lobes. This is in contrast to rectangular arrays, where the number of FF lobes is always 4. As a consequence, array illumination by multiple beams can be generated using the ring arrays. Odd number ring arrays are of a special interest, since the regular anti-phase mode cannot be supported by odd cyclical symmetry. Thus, spontaneous symmetry breaking is expected. The study presented in this paper explores the self modes of such arrays, their structural stability, and manifests the linear mechanism for spontaneous symmetry breaking with its general implications.
Advances in high power semiconductor diode lasers and their applications
Authors: Welch D. F.
Published: February 2023

Semiconductor laser diodes continue to advance in the field of high power lasers. Output powers of monolithic sources have been demonstrated in excess of 120 W cw, while stacked arrays of diodes have exceeded 400 kWatts peak output power. Several areas of advancement have been dramatically impacted by the technologies over the past 3 years including wavelength access of, single mode coherent operation of, and high reliability operation of laser diodes.
Enhanced lateral-mode selectivity of a broad-area semiconductor laser with an external cavity
Authors: Mailhot S. , McCarthy N. , Champagne Y.
Published: February 2023

External-cavity schemes have been recognized as efficient ways for controlling the lateral-mode content of the output beam emitted from high-power broad-area (BA) semiconductor lasers.1,2 The external cavity can act as a mode-selecting device provided that the beam fed back into the BA laser is allowed to be wider than that of the free-running BA laser. Due to the limited lateral dimension of the gain medium, a wider beam is expected to experience higher losses, so that the fundamental lateral mode will be favored, compared to the higher-order lateral modes having larger sizes. We have investigated, both theoretically and experimentally, the lateral-mode behaviour of a BA GaAlAs semiconductor laser (stripe width W = 75 μm, length L = 370 μm) operated with an anamorphic external cavity comprising a collimation lens system (f1 = 8 mm) and a cylindrical lens (f2 = 25 mm). This lens is spaced from the collimation lens by the distance d = 30 mm, and the external cavity is bounded by a uniform 30%-reflecting plane mirror M1. Figure 1 illustrates schematically the external-cavity configuration. For the lateral direction parallel to the junction plane, the size of the beam incident upon the antireflection (AR) coated facet of the BA laser can be adjusted by changing the distance L2 between the cylindrical lens and the external mirror. The curvature of the cylindrical lens lies along the lateral direction, so that the beam size along the transverse direction, perpendicular to the junction plane, remains unchanged after propagation in the external cavity.
Switching of Raman scattering
Authors: Heeman R. J. , Godfried H. P.
Published: February 2023

In transient stimulated Raman scattering (SRS), efficient conversion of short pump pulses to Stokes radiation is difficult to obtain. A short seed pulse at the Stokes frequency increases the efficiency and may induce full depletion of the pump pulse, even when the pump power is too low to scatter efficiency without seed. However, for low pump powers the Ra­man polarizability induced by the pump and seed pulse decays, which results in a terminating Stokes pulse, even when the pump pulse itself is long. Nevertheless, the Stokes pulse can be wider than the dephasing time of the Raman polarizability or the width of the seed pulse by an order of magnitude. Applying a second seed may once again induce a sufficiently large Raman polarizability but only if the phase of the Stokes seed matches the phase difference between the pump and remaining Raman polarizability. If not, the polarizability induced by the first pulse and consequently the conversion efficiency for the Stokes radiation decreases. Therefore, it is possible to switch off the Stokes pulse by applying a second seed with appropriate phase and intensity.
Reverse saturable absorption and saturable absorption in doped xerogels
Authors: Brunel M. , Canva M. , Brun A. , Chaput F. , Boilot J.-P.
Published: February 2023

Organic molecules often present, at given wavelengths, reverse saturable absorption behavior:1–5 at low fluences, the absorption is weak; at high fluences, some molecules are excited to the first excited state whose absorption is greater. Aluminophthalocyanines encaged in solid inorganic xerogel silica matrices obtained from tetraethoxysilane precursors present this behavior.5 Similar results are also obtained with mixed organic/inorganic doped matrices.
Waveguide modulators based on the Franz-Keldysh effect with linear transmission-voltage characteristics
Authors: Kiesel P. , Kneissl M. , Linder N. , Knüpfer B. , Quassowski S. , Dankowski S. U. , Riel P. , Döhler G. H.
Published: February 2023

For many applications in opto-electronic integrated circuits (OEIC) and for optical analogue modulation, there is a strong interest in waveguide modulators with linear relation between transmission and applied voltage. In recent years much effort has been devoted to studying the different effects that can be used for intensity modulation in waveguide structures. Most of the suggested devices are based on the quantum-confined Stark effect (QCSE). In our opinion the Franz-Keldysh effect (FKE) is even more attractive for waveguide applications. Compared to the QCSE, the FKE exhibits a lot of advantages and shows only slightly lower absorption changes, which is quite unimportant for waveguide modulators. The absorption changes due to the FKE can be obtained in relatively simple structures (e.g., double hetero (DH) p-i-n structures) that are well-suited for integration in OEICs. The absorption changes due to the FKE extend over a broad wavelength range. Therefore, FK-modulators are quite insensitive to temperature variations. A possible temperature drift can be compensated nearly perfectly by a small dc bias. Furthermore, in such devices there are no problems with trapping photo-generated carriers in quantum wells. This results in much shorter transit times. Saturation problems under high speed and high power operation are largely avoided. In addition, FK-modulators show a weaker polarisation dependence of the switching contrast compared to devices based on the QSCE.1 Finally, FK-modulators are particularly well suited for analogue optical modulation.
Dispersively Q-switched Er-fiber laser with 1.48-μm intracavity laser diode as pump source and nonlinear Fabry–Perot modulator
Authors: Okhotnikov O. G. , Salcedo J. R.
Published: February 2023

An attractive technique to design pulsed fiber lasers can be realized by current modulation of the laser diode (LD) used as the intracavity pump source. Recently, this approach was demonstrated to mode-lock the Er-doped fiber laser due to phase modulation in the intracavity pump LD1,2 or to synchronize the relaxation oscillations.3 It was shown there that a high level of phase modulation can be obtained with a MQW LD operating at 1.48 μm. Here, we show the Q-switched operation of a Er-doped fiber laser with pump LD used as a nonlinear etalon to switch the cavity finesse.
High-repetition-rate β barium borate visible range femtosecond optical parametric oscillator
Authors: Driscoll T. J. , Gale G. M. , Hache F.
Published: February 2023

High-repetition-rate femtosecond optical parametric oscillators (OPO) are potentially very useful devices in many areas of science due to their wide tunability, relatively short pulse duration, and automatic synchronisation with the pump laser, which can allow, for example, sum and difference frequency generation, further extending the range of tunability of the OPO. To date, continuous wave fem­tosecond OPOs have mostly employed KTP,1–3 mainly pumped by the fundamental wavelengths of a Ti:sapphire laser. These sources operate in the near- to mid-infrared, although intracavity frequency doubling of a KTP OPO has been described recently.4
Tunable noncritically phasematched cw KTP-OPO
Authors: Scheldt M. , Boiler K.-J. , Wallenstein R.
Published: February 2023

We report on the investigation of the spectral properties of a noncritically phase-matched cw optical parametric oscillator (OPO) of kaliumtitanylphosphate (KTP). The OPO is pumped by a single­mode Tbsapphire laser. Because of the tunability of this pump source the wavelengths of the signal and idler waves are, in principle, tunable in the range of 1.05–1.37 μm and 2.2–3.1 μm. The collinear pumping maintains perfect alignment of the tuned OPO.
Kinetic processes in copper HyBrID lasers
Authors: Jones D. R. , Maitland A. , Little C. E.
Published: February 2023

A large-bore (6-cm) copper HyBrID laser has been demonstrated to produce average output powers at 510.6 nm and 578.2 nm of up to 201 W at an efficiency (based on stored energy) of just under 2%, and 120 W at an efficiency of 3.2%.1
Pulsed discharge excitation processes in the CuBr vapor laser
Authors: Vuchkov N. K. , Astadjov D. N. , Sabotinov N. V.
Published: February 2023

In our previous papers1,2 we have suggested two novel excitation circuits for CuBr vapor laser (IPC and IC circuits). The effect of these new circuits is an essential increase of the laser efficiency.
Atomic populations and electron densities in an operating copper vapour laser
Authors: Hogan Geoff P. , Webb Colin E.
Published: February 2023

We have measured many of the internal parameters (excited state and ground state atomic populations, electron densities, etc.) as functions of time in the pulse repetition cycle, and of radial position in the plasma tube, in a 42-mm bore 40-W copper vapour laser (CVL) running under standard operating conditions. This has enabled us to compile the most complete and comprehensive parameter map of the CVL yet assembled in which all of the measurements refer to a single device, operating under identical conditions and with all timings accurately referenced to a well-defined datum.
Impact of the electronic distribution function on the copper vapor laser kinetic
Authors: Borgard J. M. , Goossens J. P. , Lemaire P. , Valrho C. E.
Published: February 2023

We have studied the impact of the electronic energy distribution function on the copper vapor laser kinetic through a coupling between kinetic equations and a Boltzmann code.
Optical characterization of vertical-cavity surface-emitting lasers by photoluminescence spectroscopy
Authors: Sebastian J. , Gramlich S. , Weyers M.
Published: February 2023

Vertical-cavity surface-emitting lasers (VCSELs) are only lasing if the emission wavelength of the quantum wells (QWs) coincides with maximum reflectivity of the Bragg reflectors. This puts stringent demands on the control of the epitaxial growth process. Additionally, it calls for a thorough characterization of the grown layer structures especially with respect to the QW emission wavelength and the spectral reflectivity of the Bragg mirrors before processing them into lasers. For this characterization optical methods are the most feasible since they are fast and usually nondestructive. We have used photoluminescence spectroscopy (PL) to characterize the emission both from the surface and from cleaved facets. This combined approach allows for a more complete characterization of the structures.
Recent progress in vertical-cavity laser diodes
Authors: Ebeling K. J.
Published: February 2023

Vertical-cavity surface-emitting lasers (VCSELs) have shown considerable improvement in their operating characteristics during the past few years of concentrated investigations. These new laser diodes offer great potential as a compact light source for optoelectronics, optical communications, and optical storage. Among the various designs of surface-emitting laser diodes VCSELs have the lowest threshold currents and provide the highest packing density in two-dimensional arrays. VCSELs of submilliamp threshold currents,1 above 100-mW cw output power2 and high electrical to optical conversion efficiency of 15% as well as monolithic high-performance planar two-dimensional arrays of independently addressable VCSELs have been demonstrated. Most efficient VCSELs are being fabricated in the InGaAs-AlGaAs material system with emission between 800 and 1000 nm wavelength. Very recently, VCSELs with red and near-infra-red emission at 670 nm3 and 1.3 μm wavelength,4 respectively, have been realized.
Transverse modes and patterns in electrically pumped vertical cavity surface-emitting semiconductor lasers
Authors: Li Hua , Lucas Timothy L. , McInerney John G. , Morgan Robert A.
Published: February 2023

Vertical-cavity surface-emitting semiconductor lasers (VCSELs) show considerable promise as high-speed spatial light modulators, high-brightness displays, and light sources for parallel optical computing or free-space communication systems. In each of these applications, it is essential to control the transverse mode characteristics. From a more fundamental aspect, VCSELs can provide very large Fresnel numbers (>100), enabling study of a rich variety of spatio-temporal dynamics.1 One important question relates to the symmetry of the modes relative to that of the laser structure, any defects or nonlinear phenomena (self-focusing, many-body effects, gain saturation etc.). Here we report the results of measurements of transverse mode spectra well above lasing threshold, and how these mode spectra can be controlled by external light injection. Our results differ from observations in other lasers,2 in that both Gauss-Hermite modes and Gauss-Laguerre modes were excited in the same laser under the same operating conditions.
Thermally stable highly efficient electrooptic polymer modulator
Authors: Liang J. , Levenson R. , Chemla Y. , Zyss J.
Published: February 2023

Electro-optic polymers provide an interesting alternative to bulk materials such as Lithium Niobate for a range of applications encompassing electro-optic modulators, switches, or directional couplers. The ability of polymers to be spin-coated on semiconductor substrates and their compatibility with such processing techniques as photolithography or reactive ion etching, now classically used in III-V semiconductor-based optoelectronics, provide a relevant technological background towards their integration in optronic circuits.
Low loss passive polymer waveguides at 1300 and 1550 nm
Authors: Knoche Th. , Müller L. , Klein R. , Neyer A.
Published: February 2023

For the fabrication of low cost optical waveguides with low transmission loss polymeric materials and mass fabrication techniques are very promising. A further advantage of using polymers in combination with replication techniques is that waveguides together with structures for the passive alignment of fibres and possibly microoptic and optoelectronic components can be fabricated. With new waveguide polymer systems, low-loss buried integrated optical waveguides at 1300 and 1550 nm have been realized.
Characterisation of the intensity dependent refractive index of nonlinear polymers in solution
Authors: Offrein B. J. , van Wolferen H. A. G. M. , Hoekstra H. J. W. M. , Driessen A. , Popma Th. J. A.
Published: February 2023

Polymers form, besides semiconductors, a class of interesting optically nonlinear (ONL) materials. The nonresonant nonlinearity of π-conjugated polymer systems can be relatively large and the nonlinear response time is often in the ps-regime, even in the resonant case. We use a Fabry-Perot to determine both the real and imaginary part of the intensity dependent refractive index of ONL polymers in solution. The etalon converts changes in the refractive index and absorption coefficient of the material inside the resonator (the polymer solution) into a transmission change.1 It is useful to characterise the nonlinearity of the material in solution as it may be difficult to grow crystals or spin waveguides of newly developed nonlinear polymer systems. The Fabry-Perot is inserted in a pump-probe type setup, as shown in Fig. 1. The change of the optical parameters is induced by a 527-nm 35-ps pump pulse and detected with a 660-nm 5-ps probe pulse.
Very large cubic nonlinearities in quadratic molecular media induced by cascading second order processes
Authors: Vidakovic P. , Zyss J. , Kim D. , Toruellas W. , Stegeman G. , Moerner W. , Twieg R. , Bjorklund G.
Published: February 2023

Cascading has been recently proposed1 and demonstrated in KTP-based structures as a means to achieve significant optically induced phase shifts because of coupled second-harmonic and down-conversion processes in a mismatched configuration. In view of record high quadratic nonlinear susceptibilities of organic materials,2 we have extended this approach to molecular crystals, which had been previously developed toward such applications as three-wave mixing and optical parametric oscillation. Their potential toward outstanding performance in the realm of χ(3) processes based on cascading3 and eventually outperforming other type of materials and nonlinear effects toward all-optical signal processing is being currently established as follows.
Electroluminescence in conjugated polymers
Authors: Friend R.
Published: February 2023

Summary not available.
The effects of the wavefront dislocations on the atmospheric adaptive optical systems performance
Authors: Fortes Boris V. , Lukin Vladimir P.
Published: February 2023

When optical wave propagates through an inhomogeneous medium the finite number of points occurrence is possible, where irradiance intensity equals to zero as consequence of partial waves interference.2 The phase of the wave cannot be defined in these points and in their vicinity the phase surface can be described either as a multilist, three-dimensional surface or as a broken two-dimensional surface. In the last case the branch cuts connect the pairs of the screw dislocations with opposite sign.4
Oil film thickness measurement using two water Raman contours
Authors: Patsayeva S. V.
Published: February 2023

Detection and quantification of oil pollutions in natural water is now a very real problem for environmental monitoring. Some investigators use intensity depression of Raman backscattered signal from water under an oil film for film thickness measurement. This technique has one essential shortage: the remotely detected intensity ratio depends on laser power output, experimental conditions variations, laser beam penetration into the water column, etc.
Lidar monitoring of air pollution over urban area
Authors: Kolev I. , Parvanov O. , Kaprielov B.
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 mesoscale flow patterns 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.
Atmospheric trace gases detection by absorption spectroscopy using near infrared diode lasers
Authors: Destombes J. L. , Bachir I. Hadj , Tranchart S.
Published: February 2023

During the last 10 years, the availability of tunable diode lasers in the near infrared region has led to many spectroscopic applications. Because of their advantages (single mode output, room temperature operation, low cost, and compatibility with fiberoptics), one emerging application of these sources is the monitoring of molecular species in the atmosphere by optical absorption since many gases of interest have absorption bands in the 600-1600-nm wavelength region. Gases such as H2O, CO2, NO2, CH4 can be detected at parts-per-million level by using commercial diode lasers.
An adaptive system for unidirectional communication through a waved water-air interface
Authors: Beń V. , Ivakin E. , Kitsak A. , Lazaruk A. , Rubanov A. , Rutkovski F.
Published: February 2023

The paper deals with an adaptive system for collimated light beams transfer through a distorted interface of two media with nonequal refractive indexes (e.g., n and 1). The proposed method is based on real time searching for quasiplane parts of the boundary appropriate for the transmission of strictly directed beams without a significant increase of their divergence. The reflection of a probe field is used to locate these areas and to govern a signal beam formation procedure.
Dual wavelength 1.44 µm/1.06 µm Nd: YAG laser for medicine
Authors: Kubeček V. , Jelínkova H. , Hamal K. , Zanzottera E.
Published: February 2023

It has been demonstrated that pulsed operation of the Nd:YAG laser is possible with good efficiency at 1.44 µm wavelength.1 This wavelength is particularly interesting for atmospheric propagation and medical applications because it is eye-safe and coincides with absorption peak of water in this spectral region. It has been shown that the same effects on tissue can be obtained with 1.44 (µm Nd: YAG laser as with 2.12 µm Ho:YAG laser.2 For technical reasons, the power output and pulse repetition rates from many holmium lasers are limited. Thus, an alternative laser that provides similar tissue effects but more flexibility in laser parameters would be advantageous.
All-optical, efficient fusion technology of biological cells incorporating near-IR laser beam manipulation and UV laser beam processing
Authors: Inaba Humio , Sato Shunichi
Published: February 2023

Various kinds of biological cell fusion techniques such as based on biological, chemical, and physical methods have been developed up to now, and they are widely used as essential means for basic research and applications in biotechnology and life sciences. However, whole cell damage associated with these fusion techniques is unavoidable because stimulations like high concentration polyethylene glycol and high voltage electric field are collectively applied. These collective treatments also do not make possible a fusion of specific cells that are desired for particular purposes. As an alternative to these techniques, the laser- induced fusion scheme realizing a one-to- one fusion of desired cells in an enclosed and safe chamber, with cell damage limited to a small region irradiated by the laser pulse, has been studied and developed by some groups including us.1,2
Pulsed laser deposition of biocompatible coatings
Authors: Antonov E. N. , Bagratashvili V. N. , Sobol E. N. , Howdle S. M.
Published: February 2023

Hydroxyapatite (HA) is a mineral basis of bone tissue and is used for medical and dental implants.
Application of the UV excimer lasers in ophthalmology: the Russian experience
Authors: Razhev A. M.
Published: February 2023

Since 1983 some hundreds of publications appeared in literature, which showed promise for using the UV excimer lasers in medicine. Of particular interest is the application of these lasers in ophthalmology (photorefractive keratectomy).
Forsterite laser system for tumour therapy and diagnostics by means of HpD method
Authors: Jankiewicz Z. , Skripko G. A. , Zajac A. , Tarazewicz I. G.
Published: February 2023

Elaboration of the efficient set for hema- toporphyrin derivative photodynamic therapy [HpD-PDT] diagnostic and therapy, require the knowledge about the absorption spectrum of a photosensibilizer. Our work is based on HpD synthesized by A. Graczyk's team,1 and spectrum is presented in Fig. 1. As it is known the absorption spectrum of HpD depends on the composition and kind of absorbing tissue as well as on the individual features of a patient.1,3 The efficient use of the HpD for diagnosis and therapy of tumours requires an application of the light sources with a relatively narrow spectral line, enabling a radiation emission within the range of 610-630 nm (therapy) and of 350-420 nm (diagnostics). Red radiation is used for therapy, in spite of a weak absorption for Hp, considering its relatively significant penetration in the tissues.
Photoreversible photochromic molecules for spatial light modulation and optical switching
Authors: Dantsker David
Published: February 2023

Progress in photonic technology for application in signal processing and in optical computing is made possible by the aid of suitable optoelectronic hardware. Organic materials and especially various organic dyes1 show a promising nonlinear optical behaviour by presenting enhanced nonlinear effects, which exceed those of known optical materials and thus become excellent candidates for utilization in optical devices. Organic dyes are characterized by their strong optically induced nonlinear resonant coefficient of absorption, which alters the readout light absorption, and thus enables them to become the most appropriate candidates for spatial light modulation (SLM) and optical switching.
Linear-, nonlinear-, and electro-optic properties of CdS nanocrystals embedded in a polymer
Authors: Sperling V. , Woggon U. , Wind O. , Bogdanov S. V.
Published: February 2023

A review about the linear-, nonlinear-, and electro-optic properties of CdS nanocrystals embedded in films of polyvinyl- alcohol (PVA) are given. The preparation of CdS crystals using a polymer matrix is shown to be an alternative method to produce 3D-quantum confined structures, instead of, e.g., the usual growth in glasses. To characterize the optical properties, degenerate four-wave mixing and absorption-saturation experiments have been carried out. Additionally, the electric field-induced absorption change has been measured at different laser excitation intensities. Comparing different glass matrizes with the polymer, the nonlinear-optical experiments show a considerable decrease in the bleaching efficiency with increasing trap density. This behaviour can be explained by an additional term introduced into the two-level system representing the properties of the interface. The probability of localisation, capture, and transfer of carriers into the surrounding matrix rises with increasing density of traps in the interface region. This is in agreement with a theoretical model describing the probability to find an excited electron-hole pair near the interface.1 The measurements of degenerate four-wave mixing show an astonishing result if comparing the values of nonlinear susceptibility χ(3)- For the PVA-film the susceptibility is about twice the value of χ(3) reported for the experiments carried out at CdS-doped in glasses.
Bulk crystals of ferroelectric niobates with periodic domain pattern
Authors: Aleksandrovski A. L. , Naumova I.I.
Published: February 2023

Ferroelectrics with periodically arranged antiparallel domains are very attractive for applications in nonlinear optics,1 the major difficulty being the fabrication of perfect periodic structures. To produce bulk crystals we used Czochralski growth of lithium niobate crystals doped with Y, Dy, and with Mg as a second dopant, and barium-sodium niobate. Both crystals were grown along the ferroelectric z-axis, and lithium niobate along

[

01

1
¯

2

]

-direction as well (at 57° to z-axis in YZ-plane).
Charge density capacity limitation of volume storage in photorefractive materials
Authors: Alves Clara , Aing Phannara , Pauliat Gilles , Roosen Gérald
Published: February 2023

The calculation of the storage capacity of volume holographic materials conducted by P. J. van Heerden1 is quite often quoted to highlight the large storage capacity of photorefractive materials. If V is the volume of the material and λ is the optical wavelength, then this capacity is expressed by:
Photorefractive effect in nematic liquid crystal
Authors: Rudenko E. V. , Sukhov A. V.
Published: February 2023

The reorientation of optical axis (so-called director) of nematic and cholesteric mesophases by electric field of optical waves was investigated thoroughly during the last decade. It is well known (see, e.g., Ref. 1) that such reorientation leads to extremely high values of effective third-order optical susceptibilities, up to 1 cm3/erg, the proper mechanism being called orientational optical nonlinearity of liquid crystals (ON).
Room temperature photorefractive effect and self electro-optic effect device (SEED) in II-VI CdTe/CdZnTe multi-quantum wells (MQWs)
Authors: Haas H. , Magnea N. , Pautrat J. L. , Gosselin S. , Baron T. , Dang Le Si
Published: February 2023

We report on a MQW-device operation under electric field at room temperature. The samples are grown by MBE on a transparent substrate (up to 770 nm) of CdZnTe (Zn = 24%). The strain symmetrized intrinsic QW-region of 20 periods of 10 nm/13 nm CdTe/CdZnTe (Zn = 38%) with two insulating barriers of Zn = 54% (3.3 nm) is grown on an n+ (5 1016cm-3) indium-doped buffer layer matched to the substrate. The optically active layer is partially removed to give access to the highly doped layer, and electrical contacts are made by evaporation of indium on the n+-type CdZnTe. In the first type of samples, a semi-transparent Gold contact (1 mm) is deposited on top of the structure to provide the m-i-s structure with a Schottky barrier. The second type of samples uses a p-i-n structure (p-dopant is atomic nitrogen), which presents a higher built-in field. These two configurations provide a highly resistive depletion layer.
Threshold effects in photorefractive waveguides on lithium niobate
Authors: Kostritskii S. M.
Published: February 2023

In this work a photorefractive effect in proton-exchange planar waveguides on LiNbO3 crystals is discussed. These waveguides are doped by copper with the help of a new original technique using the low-temperature ionic substitution.1 The copper and hydrogen contents are determined by absorption spectra measurement by visible and infra-red regions.
Lidar studies of fluctuation spectra of the coefficient of backscattering in the atmospheric surface layer
Authors: Razenkov I. A. , Rostov A. P. , Shefer N. A.
Published: February 2023

It is now customary to consider atmospheric aerosol as a passive conservative admixture in the atmosphere, that is, it does not disappear and fully floats by the wind vortexes. A serious argument in favor of that statement is the fact that the spectrum of fluctuations of backscattering is similar to that of wind speed, that is, in spectrum, as a rule, the extent region is present, corresponding to inertia interval of the Kolmogorov-Obukhov spectrum. The first was E. Eloranta, which by laser sounding of the atmospheric aerosol had derived the fluctuation spectra of lidar signal similar to that of wind speed.
Estimation of soliton parameters in variational analysis of nonlinear propagation
Authors: Burak D. , Nasalski W.
Published: February 2023

The variational analysis of the Gaussian beam propagation in a nonlinear Kerr medium has been proven to be a very convenient and efficient method.1 The propagation of an intense electromagnetic beam in a medium with planar symmetry can be modeled by the normalized nonlinear Schrödinger equation (NSE)2
Nonlinear optical properties of porous silicon: the experimental studies by means of second harmonic generation
Authors: Aktsipetrov O. A. , Melnikov A. V. , Murzina T. V.
Published: February 2023

Last year porous silicon (PS) was shown to be a very promising material with unique properties. Its main peculiarity is an intensive photoluminescence in the visible spectrum range while the mechanism of this phenomenon is still argued.
Second harmonic in reflection in material science of ferroelectrics
Authors: Stefanovich S. Y.
Published: February 2023

The area of application of Second Harmonic Generation (SHG) technique is broadening now. Besides the search for new nonlinear crystals there are examples of SHG researches of equilibria of ferroelectric solid solutions and investigations of kinetics of noncetrosymmetric phases formation in the course of chemical reactions in mixtures and gels or during crystallization in glasses. In order to solve these problems on the basis of SHG data it became necessary to suggest a more unified approach to SHG measurements for the variety of non-centrosymmetric and ferroelectric substances. To provide standard conditions for SHG measurements, the materials prepared either by growth of crystals, sintering of ceramics, or by "wet" chemical synthesis should in all cases be reduced to thin powders. When powders with size partides (L) smaller than the maximum coherent length are used the intensity of second harmonic (I2ω) appears to be a good quantitative measure of nonlinear polarizability. In most oxides this is guaranteed if L < 3 mcm. Under this condition coherent length can be eliminated from the equation for the SH-intensity. The effect of the sample thickness on I2ω is eliminated by measuring the radiation from sample in the backward direction.
Laser-acoustic investigations of turbulent flows of aerosol particles in the atmospheric surface layer
Authors: Shefer N. A. , Rortov A. P. , Razenkov I. A.
Published: February 2023

At present there are not many data about behaviour of the coefficient of the turbulent exchange for the atmospheric aerosol admixture. A practical significance of this information is explained in its application for prognostication of admixtures propagation in the atmosphere. In this report, results of the experimental investigations of coefficient of the turbulent exchange and the turbulent flow of phone atmospheric aerosol are represented.
Metal-electrolyte interface: about the mechanism of the optical second harmonic generation
Authors: Aktsipetrov O. A. , Melnikov A. V. , Murzina T. V. , Nikulin A. A. , Rubtsov A. N.
Published: February 2023

The nonlinear electroreflectance (NER) is a very promising phenomenon of nonlinear optics of surfaces. This effect consists of the modulation of second-harmonic (SH) intensity reflected from the surface of centrosymmetric media under the influence of the electrostatic field. A conventional method of the electrostatic field application to the surface is the electrochemical technique, which allows one to apply the dc electric fields of the strength of 106 – 107 V/cm. The mechanism of NER in metals is not clear yet, as well as the general character of NER behavior in this case.
Polarisation-sensitive coherent anti-Stokes and spontaneous Raman spectroscopy of caiix[4]arene films
Authors: Vardanyan A. G. , van Hulst N. F. , Ranger J. , Otto C. , Greve J.
Published: February 2023

Novel organic molecules with high nonlinear optical properties are an important subject of investigation because of their potential application in optical communication, frequency conversion, etc.1 Here, we present the experimental results of spontaneous Raman, polarisation sensitive CARS (PS-CARS) and waveguide CARS of the newly synthesised organic molecule tetranitro-tetra-(n-propoxy)calix[4]arene (c40h44n4o12) in thin films. For assignment of most specific strong Raman bands of calix[4]arene, a comparative analysis and different derivatives of this molecule were used. In addition, the depolarisation ratios for most of the bands were estimated by polarisation sensitive spontaneous Raman and CARS independently. Several strong bands are present in the Raman spectrum of calix[4]arene: Ω = 1095 cm−1, Ω = 1265 cm−1, Ω = 1340 cm−1, Ω = 1584 cm−1. The strongest band at Ω = 1344 cm−1 (ρ = 0.25) corresponds to the symmetric NO2 stretch. In Fig. 1 the PS-CARS spectrum for calix[4]arene in chloroform (C = 20 mg/ml) is shown. The result of fitting the spectrum with depolarisation ratios, taking into account the various settings of the polarizers is also shown. The observed line shape changes at different analyser settings around the position of background suppression illustrate the polarised character of the different bands. For example, the different dispersive shape of the chloroform band at Ω = 1214 cm−1 with ρ = 0.7 deviates from the bands of calix[4]arene with ρ < 0.7. In Table 1 the depolarisation ratios for calix[4]arene, as determined from the polarised Raman and PS-CARS spectra are summarised. The values agree well for both techniques.
New geometry for quasi-phase-matched frequency conversion in lithium niobate with periodic domain structure
Authors: Aleksandrovsky A. L.
Published: February 2023

Quasi-phase-matched concept of frequency conversion was introduced for collinear geometry, with pump propagating normal to layers in periodic structures. Some useful deviations from this case were pointed out recently.1 Here an alternative geometry is proposed: with pump propagating nearly along the layers.
Photo- and electroinduced effects on optical second harmonic generation in thin oriented films of bacteriorhodopsin
Authors: Aktsipetrov O. A. , Fedyanin A. A. , Murzina T. V.
Published: February 2023

In the last decade the interest in optical and nonlinear optical properties of thin films rose considerably. These systems are of significant importance not only from a fundamental point of view but also because of possible applications. In the present report the second-order nonlinear optical properties of thin oriented films of bacteriorhodopsin molecules (bR) are studied by means of the second-harmonic (SH) generation technique. The choice of this type of films is dependent on the topical interest since a better understanding is needed of the bR behavior in such systems, their nonlinear optical properties, and their changes under the external subjections—the CW radiation and the DC electric field.
Temporal cross-phase modulation as a tool for picosecond parametric amplification in a single-mode fiber
Authors: Maillotte H. , Gindre D. , Lantz E. , Monneret J.
Published: February 2023

Parametric amplification in a single-mode silica fiber is studied by means of temporal cross-phase modulation between a strong picosecond pump and a weak signal pulse. The theoretical study deals with the nonlinear Schrödinger equation (NLSE), well-known to describe pulse propagation along single-mode fibers under the combined influences of optical Kerr effect, group-velocity dispersion (GVD) and, eventually, birefringence. In the present work, the time-varying input field results from two superimposed pulses whose spectral decays, relative intensities, and temporal shapes can be varied. The parametric gain is then calculated by means of Fourier transform of the beating pulse at the end of the fiber. Different cases are studied in the normal dispersion regime of the fiber.
Gas detector measures parts per trillion: periodic CH4 and H2O release from a single cockroach
Authors: Bijnen F. G. C. , Harren F. J. M. , Reuss J. , Hackstein J. H. P.
Published: February 2023

Atmospheric methane is an important component in the process of global warming and ozone depletion. The biogenic sources are responsible for the majority of CH, fluxes (>70%). The contribution of each different source is still a question of debate. Insects like termites and cockroaches may contribute up to 20% of the total budget. Our trace gas detector (Fig. 1), consisting of a photo acoustic (PA) cell placed in the cavity of a CW liquid nitrogen cooled CO-laser, permits measuring methane (detection limit 1 ppb) and water vapour release together with CO2 during the respiration of a single cockroach. This way the complex breathing pattern of this animal is observed, which demonstrates the sensitivity and speed of the detector (Figs. 2 and 3).
Remote, in-vivo monitoring of blood oxygen saturation of patients using optical fibres
Authors: Scully P. J. , Holmes R. , Jones G. R.
Published: February 2023

Monitoring of patients in magnetic resonance (MR) scanners is complicated by the effects of the static magnetic field, the radio frequency field, and time-dependent magnetic field gradients. Conventional electronic sensors malfunction under these conditions, and optical fibre-based sensors are increasingly being used because of their immunity to electromagnetic interference and intrinsic safety.1 Conventional pulse oximeters have been reported to malfunction when used in the vicinity of MR scanners.2
ZnMgSSe-based blue laser diodes
Authors: Okuyama Hiroyuki , Ishibashi Akira
Published: February 2023

Since the first operation of II-VI laser diode (LD) by Haase et al.,1 much effort has been devoted to studies on II-VI semiconductors for realization of short-wavelength LDs. Recently, a continuous wave (cw) operation of a few seconds was achieved by using ZnMgSSe as the cladding layer.2 In this presentation, we show the latest results of II-VI LD.