bluuebunny/crossref_metadata_2025 huggingface dataset:
UV micromachining of polymers with frequency doubled copper vapour lasers
Authors: Coutts D. W. , Glover A. C. J. , Ramsay D. J. , Piper J. A.
Published: February 2023

Copper vapour lasers (CVLs) with their high prf capability (4-24 kHz), high average power (10-100 W) and diffraction-limited beam quality offer a number of advantages for visible machining applications.1 However, many materials (such as clear polymers) are best machined using uv laser sources such as the excimer laser, which, until recently, has been the principal laser used in uv machining applications. The uv outputs available from frequency doubling of CVLs can now be generated with good efficiency to yield multi-watt diffraction-limited output ideal for uv micromachining. Frequency doubling and sum frequency mixing of CVL outputs has been investigated extensively for the last six years; however, it is only recently that reliable, stable, and efficient conversion has been demonstrated. The recent progress has come through a greater understanding of the control of CVL beam quality and improvements in focusing geometries for the nonlinear frequency conversion process.
Imaging and mechanism analysis of high quality drilling by a copper vapor laser
Authors: Pini R. , Salimbeni R. , Vannini M. , Toci G.
Published: February 2023

The growing interest in material processing and micro-machining techniques, which employ copper vapor lasers (CVL) requires specific investigations for the comprehension of the interaction mechanism that can result in a further optimization of the present technology.
Integrated Mach-Zehnder InGaAsP BRAQWET modulators
Authors: Dwir B. , Monnard R. , Sadeghi A. , Carlin J.-F. , Dupertuis M.-A. , Glick M. , Rudra A. , Reinhart F. K.
Published: February 2023

The BRAQWET (Barrier Reservoir and Quantum Well Electron Transfer) modulator is an interesting alternative to quantum well modulators based on the Quantum Confined Stark Effect and the Wannier Stark Effect. The BRAQWET modulator is based on electrorefraction in a tunable electron-density quantum well. It has excellent high speed potential since it involves only one type of carriers (electrons) and the speed of the refractive index change is not limited by carrier lifetime. Realization of this structure in InGaAsP materials has potential for even higher speeds due to higher electron mobility. However, these materials have a lower bandgap offset, which increases enormously the leakage current of a BRAQWET device (tens of A/cm2 at V = 0.5 V).
OEICs: Status in the lightwave communication area
Authors: Leheny R.
Published: February 2023

Summary not available.
10 Gbit/s modules with monolithic electro-absorption modulator and distributed feedback laser
Authors: Kuindersma P. I. , Cuypers G. P. J. M. , van Gestel P. , Binsma J. J. M. , van Dongen T. , Tjassens H. , van Roijen R. , Thijs P. , Hendrix L. , van Roemburg R. , Mols P. P. G. , Tomesen M. , Hummel E.
Published: February 2023

This paper describes the design, fabrication, and testing of transmitter modules for repeaterless long haul transmission of 10 Gbit/s non-return-to-zero (NRZ) data over standard single mode fibre, with a dispersion of 17 ps/km/nm and an attenuation of 0.2 dB/km at a wavelength of 1.554 nm.
Performance improvement of long haul systems by adjustable chirp external modulator and optimum receiver filter design
Authors: Zhou Y. R. , Watkins L. R.
Published: February 2023

It has been reported that appropriate chirp of an external modulator in an IM/ DD system can reduce the chromatic dispersion penalty relative to the chirpless case for middle-length transmission systems.1,2 However, in long haul, high-speed optically amplified IM/DD systems, the major system impairment is caused by the combined effect of chromatic dispersion and self-phase modulation (SPM) due to the nonlinear Kerr effect.3 In this paper, we investigate the influence of external modulator chirp on system performance in the presence of chromatic dispersion and SPM, and in particular, we present the performance improvement attainable by using appropriate modulator chirp combined with optimum receiver filter design.
Two dimensional optoeletronical bus-type interconnection network
Authors: Danzer U. , Zürl K. , Schwider J.
Published: February 2023

Future high-performance computer systems increasingly consist of parallel processing units. For such multiprocessor systems, bus-type interconnection networks for synchronisation and data transfer are required.
Effects of higher harmonic wavelengths of YAG laser on machinability of glass-epoxy composite material
Authors: Watanabe Takehiro , Takano Yoshiyuki , Yoshida Yoshitaro
Published: February 2023

Higher integration of electronic circuits is rapidly progressing by laminating substrates and minimizing through-holes. Micro-drills are currently used to machine the through-holes. However, the drills are not efficient to machine the holes less than 0.3 mm in diameter. Therefore, adaptation of laser beams to small-hole drilling is paid attention.
Pulsed laser processing: novel approach as to fabricate fully isolated transistors for VLSIs
Authors: Ladygin Eugene A. , Usenko Alexander Y.
Published: February 2023

The process technology, which has been called "radiplanar," allows us to improve integrated circuit performance in various points of view. The radiplanar process’ includes two supplementary operations that are not used in usual IS process flow.2 The first one calls for MeV-energy electron irradiation with high dose. The second step comprises a pulsed laser annealing. The additional technological operations are quite compatible with standard process flow and would demand only some minor changes in a few of the standard technological operations for fabricating semiconductors.
Excimer laser sputtering deposition of antireflection coatings for solar cells
Authors: Durand H.-A. , Heilman O. , Makita Y.
Published: February 2023

We have investigated the ArF laser sputtering deposition of several materials, in cluding TiO2 and MgO, for antireflection coating, aiming at large scale production of II-VI and III-V solar cells, the main theme of our research group. Layers were deposited on several semiconductor materials used for solar cells and photodetectors: Si wafers and glass on a first step, followed by GaAs and GaSb substrates. A reasonable growth rate for production was obtained, considering possible pulse frequencies of a few tens of Hertz (0.1 A per 1 J/cm−2 laser energy density per pulse). The structure of the thin films fabricated, as well as diffusion at the interface with the substrate, is investigated using cross-sectional high-resolution transmission electron microscopy, when substrate temperature, nitrogen, and oxygen partial pressure in the atmosphere of the chamber are changed during deposition. The surface optical quality of the deposited films vs thickness and growth conditions is presented, and roughness was measured with a stylus profiler. We have applied this technique to a solar cell prototype and a GaSb based photodetector prototype fabricated in our group.
Laser-induced sputtering of semiconductors due to bound-free transitions of surface atoms
Authors: Agafonov A. I. , Manykin E. A.
Published: February 2023

It has been established that photons can, by a quantum process, cause ejection of atomic particles from solid surfaces.1 Laser-induced sputtering (LIS) of semiconductors has been investigated for photons of both above and below the band-gap energies.2
Using a diode pumped birefringent Nd:YAG microchip laser in heterodyne interferometry
Authors: Czarske J. , Müller H. , Wüste A.
Published: February 2023

The use of a novel two-frequency laser in heterodyne interferometry is proposed. In a heterodyne interferometer two beams of different frequencies have to be generated in order to achieve a directional discrimination of a target movement. The different frequency can be generated by the use of an external frequency shifter, in general a Bragg cell. In order to avoid this additional element a two-frequency laser has to be used. Up to now the Zeeman laser and the two mode He-Ne laser have been used. However, the frequency difference of the Zeeman laser is limited to 2 MHz and both lasers have great amplitude and frequency control efforts.
Luminescence sensors based on ruthenium complexes
Authors: Zemskii V. I. , Veresov A. V. , Kolesnikov Yu. L.
Published: February 2023

The application of luminophores as molecular informators of contents or conditions of environment is a promising trend in sensor design. This trend received a large development effort in the last few years, particularly in the area of fiber optic sensors.1
Laser-optic roughness measurement of high-speed steel strip
Authors: Kim Dalwoo , Oh. K. J. , Lim C. S.
Published: February 2023

Surface roughness1,2 is a measure of topographic relief and is an important quality control parameter in steel sheet for the improvement of paintability, corrosion resistance, and surface friction. Amplitude and spacing parameters are used in describing surface roughness. The typical measure of an amplitude parameter is the average or root-mean-square value of the height of the peaks. A spacing parameter is measured as the number of peaks in an inch. Conventional stylus method can be used in measuring these two parameters only for off-line measurement for the finite section of sheet. Therefore, noncontact optical method is needed in process monitoring of roughness of steel strip.
The cone polarizer: A new concept for fast polarimetry
Authors: Stenkamp B. , Abraham M. , Zetterer Th. , Pokrowsky P.
Published: February 2023

Today, many industrial processes are monitored and controlled by measuring the polarization of light. Ellipsometry, for example, is a well known method in the fields of microelectronics and electrochemistry. Polarimetry is a well established technique for the quantification of optically active species in solutions. Nearly all of the commercially available systems use a rotating analyzer to detect the state of polarization. The mechanical movement limits the speed of the measurement, the size of the system critically determines the price of the devices.
Medium impedance room temperature indium antimonide thin layer detectors
Authors: Padalko A. G. , Lazarev V. B. , Perry F. S.
Published: February 2023

A traditional goal in producing single crystals and thin films of indium antimonide, studying its physical and operational properties, and manufacturing devices based on this material is the development of high-by-sensitive-cooled photodetectors that belong to generations of discrete, linear (one-dimensional), and array (two-dimensional) detectors. Operating temperatures of these detectors are close to liquid nitrogen temperature which requires the use of different cryo- states, and they have background-limited performance.
VUV and X-ray imaging from 25 eV to 8 keV with CCD-based detection systems
Authors: MacPhee A. G. , Denvir D. , Lewis C. L. S. , O'Neill D. M.
Published: February 2023

Sensitivity, dynamic range, and spatial resolution measurements are presented for active imaging systems from Oriel Instruments, designed and optimised for pulsed x-ray diagnostics operating in kilovolt and sub-kilovolt x-ray regimes. Both systems employ cooled, multi- pinned-phase (also known as inverted mode) English Electric Valve company (EEV) charge coupled device detectors for image capture. For photon energies in the range of 25 eV to 1 keV, a rare earth phosphor transducer is coupled to the CCD via a fibre optic faceplate with 6-(µm diameter channels. From 1 keV to 8 keV, direct detection of electron-hole pairs generated in the depletion region of the CCD is employed.
Digitized dual-frequency coupling grating for waveguide displacement interferometry
Authors: Voirin G. , Sixt P. , Parriaux O. , Yan Li
Published: February 2023

Slab optical waveguides are well suited for the monolithic achievement of various sensing and optical preprocessing functions.1 They are of practical usefulness only if free-space beams can easily be coupled to/from the waveguide. Grating coupling is the only access technology compatible with the symmetry and technology of planar waveguides. In the main two noncommunication applications of integrated optics (opto-chemical sensors2 and displacement sensors3), there is a need for coupling a single freespace beam to two guided sensing modes2 and conversely.3
Singular wave fields produced by an achromatic switchable phase element
Authors: Stalder M.
Published: February 2023

Various optical elements were recently described, which allow the formation of optical beams that contain a phase singularity.1,2 Because of this singularity the amplitude of the optical field becomes zero; a dark spot appears in the neighborhood of the singularity. In the referenced articles, binary computer generated holograms (CGHs) are used to create such light beams.
Demonstrator circuitry for optical data transcription and digital optical logic based on differential pairs of optical thyristors
Authors: Thienpoint H. , van de Velde T. , Peiffer W. , Kirk A. , Kuijk M. , Dognin L. , Fernandez J. , Veretennicoff I. , Vounckx R. , Heremans P. , Borghes G.
Published: February 2023

Among the most promising elements for digital parallel optical information processing are differential pairs of PnpN optical thyristors. We have shown very recently that these optical detector-generator type of devices can be switched-on in very short times (typical 10 ns) with very low switching energies (typical 40 fj of absorbed optical energy), while the problem of slow switch-off times, causing unpractical cycle times, was tackled using a double-heterojunction structure that can be completely depleted by means of a simple negative anode-to-cathode low voltage pulse. In this way PnpN thyristors with switch-off times of 10 ns became available.1
Exchangeability test on phase-change disks and testers
Authors: Ito Takuya , Kubo Takahiro , Yamada Seiya
Published: February 2023

We have many international standards for magneto-optical (MO) rewriteable disks. Common experiments and data for standardization of Phase-Change (PC) disks are required, too. To get the data for standardization of PC disks, a tester was developed.
Comparison of different polymeric multimode star couplers for backplane optical interconnect
Authors: Israel D. , Baets R. , Shaw N. , Salik M. , Goodwin M. J.
Published: February 2023

Optical interconnect is very promising for signal transport in advanced digital systems with high data rates at the board and backplane level. In the ESPRIT-HOL-ICS project we aim at interconnecting a number of boards with an optical backplane, which requires a star coupler topology. Multimode polymeric waveguide boards offer an interesting solution for such interconnect problems because they allow for a more complex functionality than is possible with point to point links. Furthermore, multimode waveguides have the advantage of relaxed coupling conditions. However, the design of multimode waveguide elements (bends, junctions, etc.) is often more difficult than that of single mode structures, due to the uncertainty in modal content.
Free space photonic switching using spatial light modulators
Authors: Crossland W.
Published: February 2023

Summary not available.
Engineering of photorefractive polymers
Authors: Malliaras G. C. , Krasnikov V. V. , Bolink H. J. , Hadziioannou G.
Published: February 2023

Photorefractive polymers offer advantages such as their considerable flexibility in synthesis, doping, processing, and low cost. Furthermore, compared to their crystalline counterparts, they offer the possibility of improved value in the photorefractive index change figure-of-merit n3-r/ϵ, owing to the small dc dielectric constant ϵ and reasonable linear electrooptic coefficient r and refractive index n.1
Ultrafast carrier relaxation in low-temperature grown InxGa1-xAs layers
Authors: Krotkus A. , Marcinkevičius S. , Grigoras K. , Pašiškevičius V. , Tellefsen J. A.
Published: February 2023

We present here investigations of the photoexcited carrier dynamics in In
x
Ga1-
x
As epitaxial layers grown by a metal-organic chemical-vapor-deposition technique (MOCVD) at low substrate temperatures (400-430°C, instead of the usual 600°C). It has been reported before1 that under such growth conditions, highly resistive layers with picosecond carrier life times can be obtained. Moreover, this technique can be used for growing alloys of a wide composition range including materials sensitive to infrared radiation.
A cryogenic temperature sensor using the fluorescent decay time of CaF2:Yb2+ and SrF2:Yb2+ crystals
Authors: Bertrand S. , Tribillon G. , Bouazaoui M. , Rouhet J.
Published: February 2023

The needs in temperature control and regulation in chemically and electromagnetically harsh environments lead to the development of optical sensors insensitive to these aggressive surroundings.
Fabrication of long wavelength microresonators
Authors: Corbett B. , Considine L. , Walsh S. , Justice J. , Kelly W. M. , Maltings Lee
Published: February 2023

Spontaneous emission is modified by the presence of an optical cavity. With increasing cavity finesse the fraction of spontaneous emission coupled to the lasing mode can be increased.1 While longer wavelengths (-1.5 μm) place less stringent requirements on device processing with regard to dimensional control there is no practical semiconductor mirror lattice matched to InP as there is for GaAs. With a hybrid approach, useful reflectivity (>95%) may be obtained using metal mirrors (Au, Ag), combination of dielectrics (Si, SiO2, Si3N4) or AlAs/GaAs multilayers. We have used epitaxial liftoff of InGaAs/InP quantum well structures and combined the epilayer with these mirror materials and fabricated high finesse microcavities. The application is towards optically pumped surface emitting devices.
Influence of hydrogen and helium additives on the output power and efficiency of barium vapour lasers
Authors: Halliwell S. N. , Little C. E.
Published: February 2023

We have previously reported large (40%) increases in the output power and efficiency of an infrared (1.13, 1.50 μm) barium vapour laser (BVL) with the addition of ~3% hydrogen.1 We now report more detailed investigations of the mechanisms of hydrogen in the discharge of a BVL, and extend the discussion to BVLs with He, Ne-He, and He-H2 buffer gases.
Strontium recombination laser
Authors: Vuchkov N. K. , Astadjov D. N.
Published: February 2023

The IC-excitation that had been developed in our lab has been applied very successfully in the excitation of CuBr vapor laser.1 The power and efficiency of CuBr vapor lasers have been increased by a factor of 1.5-1.7. In the present work we present the examination of IC-excitation for Sr+ laser.
A diode pumped, continuous wave, frequency doubled neodymium lanthanum scandium borate laser
Authors: Meyn J.-P. , Huber G.
Published: February 2023

Compact diode pumped lasers in the green and blue spectral regions have a great potential for applications like high density optical storage and display techniques. Nd:LSB is an efficient solid state laser at 1.06 μm.1 Now we report on efficient intracavity frequency doubling with potassium titanyl phosphate (KTP).
Microchip lasers and laser arrays: technology and applications
Authors: Mooradian Aram
Published: February 2023

Microchip lasers and laser arrays are miniature diode pumped solid state lasers that can be manufactured in large volume at low cost and can outperform conventional diode-pumped lasers. Semiconductor processing and packaging techniques are used in their manufacture. Some of their characteristics include simple single-frequency and low noise operation, tunability over the gain bandwidth (up to 100 GHz) without a mode jump, short pulse (sub-nanosecond) high peak power capability and high speed (multi-GHz) frequency modulation capability. Power levels of more than 500 mW cw have been demonstrated with a TEM00 output beam. Operation of microchip lasers has been demonstrated in several materials including YAG, YLF, vandate, garnets, glass, and stoichiometric compounds. One- and two-dimensional arrays of microchip lasers can be scaled to high output power with constant brightness while maintaining many of the unique characteristics of the individual microchip lasers. High power 2-D arrays and addressable Q-switched linear arrays have been demonstrated. The manufacturing cost for these devices can be significantly less than for most other lasers and they can be used for high power industrial materials processing, communications, imaging, and laser radar as well as medical applications. The operating characteristics and applications of these laser devices will be discussed.
Two-dimensional simulations of Raman conversion in waveguides
Authors: New G. H. C. , Wilson D. C. , Moreira C. , Hill K. E.
Published: February 2023

The motivation for this work is to model the final Raman conversion stage of the SPRITE KrF laser system as the Rutherford Appleton Laboratory in which several pump beams propagating in a 1-m light guide at small angles to the axis amplify a Stokes pulse travelling down the axis.1-2 The key merit of this configuration is that, in the long pulse regime at least, poor spatial coherence of the pump pulses is eliminated in the Raman conversion process. However, in many experiments, the duration of the KrF pulses is around 10 ps, significantly less than the 28-ps relaxation time of the Raman medium (methane); in this case, the interaction is therefore in the transient regime and the Stokes beam is no longer necessarily insensitive to phase variations in the pump.3
Laser-based methods for hypervelocity flow diagnostics
Authors: Rubinsztein-Dunlop Halina , Barker Peter , Thomas Amberyn , Wegener Margaret , Stalker R. J.
Published: February 2023

Supersonic and hypersonic reacting flows are of current interest in supersonic combustion ramjet (SCRAMJET) propulsion devices and ram accelerators for aerospace launch systems.1
Soliton generation employing passively mode-locked laser diode and erbium-fiber amplifier
Authors: Khrushchev I. Yu. , Dianov E. M. , Deryagin A. G. , Kuksenkov D. V. , Kuchinskii V. I. , Portnoi E. L.
Published: February 2023

Recent progress in laser diodes with an ion-implanted fast saturable absorber resulted in generation of ultrashort optical pulses both in the gain-switching and in the passive mode-locking regimes.1-3 Normally, an implanted laser generates low intensity non-transform-limited pulses or pulse trains. Application of a fiber amplifier to increase the signal intensity and to improve the pulse quality is a promising way of obtaining soliton-like pulses.
Optimized chirp compensation for ultrashort transform-limited pulse generation by a gain-switched DFB laser
Authors: Calvani R. , Caponi R. , Roccato D. , Rosso M.
Published: February 2023

The gain-switching approach to ultrashort pulse generation consists in the direct modulation of a DFB laser with current pulses having a suitable width to excite only the first peak of the relaxation oscillations.1,3 The optical pulses at the laser output exhibit a short duration and a strong chirp which distorts and broadens the corresponding spectrum. A further reduction of the pulsewidth can be obtained by passive compression, coupling the laser beam into a fibre with negative dispersion.
The thin-disc laser: a scalable concept for efficient diode-pumped solid-state lasers with high beam quality
Authors: Giesen A. , Voss A. , Wittig K. , Brauch U.
Published: February 2023

The one-dimensional heat flow in a thin, face-cooled crystal disc avoids thermal lensing and allows the efficient, scalable operation of diode-pumped solid-state lasers with various laser active materials, including quasi-three-level systems.
Development of 1 kW average power excimer laser with UV preionization
Authors: Borisov V. M. , Bragin I. E. , Khristoforov O. B. , Kirykhin Yu. B. , Vinokhodov A. Yu.
Published: February 2023

High-power excimer lasers are of considerable interest for both physical and industrial applications. In 1990 we have reached 1 kW (10 J × 100 Hz) average power emitted by the XeCl laser with active volume 10 × 8 × 80 cm3.1 A creeping discharge on dielectric surface was used as UV preionizer. The LC inversion circuit for main discharge volume was switched by low inductance rail gap switch, equipped own gas flow, and cooling systems. XeCl laser had emitted 1 kW average power in burst mode (2 minutes) at charging voltage 70 kV. Recently, 1 kW average power XeCl laser (10 J/short at 100 Hz or 12,5 J/short at 80 Hz) has been reached by SOPRA'VEL Laser in burst mode (0.5 second).2
A 10 J × 100 Hz XeCl laser for large surface treatment
Authors: Godard Bruno , Murer Pierre , Laborde Patrick , Stehle Marc , Bonnet Jean , Pigache Daniel
Published: February 2023

SOPRA is developing in the frame of EUREKA program EU205, XeCl Laser "VEL" for specific applications.1-5 The data of VEL 1 K are 10 J per pulse at 308 nm with duration of typically 150 ns FWHM and with a pulse repetition rate up to 100 Hz. This laser has been developed in order to treat large surfaces.
Hercules, a large volume XeCl laser facility for high intensity experiments
Authors: Bollanti S. , Di Lazzaro P. , Flora F. , Giordano G. , Sehina G. , Zheng C. E.
Published: February 2023

Short wavelength lasers offer promise in new materials-related applications, as the efficiency and the accuracy of the lasermatter interaction are greatly improved by using ultraviolet (UV) light rather than infrared light. Among them, excimer lasers and frequency-converted solidstate lasers recently acquired a prominent position in both scientific and commercial fields.
Photorefractive and SBS backscattering—a comparison
Authors: Mamaev A. V. , Shkunov V. V.
Published: February 2023

Stimulated Brillouin scattering (SBS) in a backward direction serves for many years as an effective tool of self-phase conjugation (PC) for giant laser pulses.1,2 Recently an alternative type of the stimulated backscattering—the stimulated diffusion scattering (SDS) in photorefractive crystals—has been proposed to be used for PC of low power radiation.3,4 Both effects can be reduced, in principle, to a two-wave mixing of an incident pump wave to be conjugated and of waves that are seeding in a backward direction usually by spontaneous scattering of the same pump wave by randomly distributed small-scale inhomogeneities of a medium (Fig. 1).
Imaging characteristics of near-field optical microscope in reflection
Authors: Bozhevolnyi Sergey I. , Keller Ole , Smolyaninov Igor I.
Published: February 2023

Various scanning near-field optical microscopes (SNOM) with subwavelength resolutions have been developed during the past ten years.1 Near-field optical images are obtained by scanning a subwavelength probe (aperture or fiber tip) very close to an illuminated sample surface and detecting the scattered light. Usually, a shear force technique is employed to maintain the probe-surface distance, which allows one also to obtain a topographical image of the surface studied.1 In such an approach the main problem is to uncouple topographical and optical images so that additional information can be extracted from the optical images. This is especially important for heterogeneous samples, since variations in optical properties can manifest structural changes of sample surfaces. Here we report for the first time results of a systematic study of this problem for the external reflection SNOM.
Laser-based metrology applications and principles of dynamic focusing
Authors: Brown A.
Published: February 2023

Summary not available.
Theory of mode-locked fibre lasers
Authors: Li J. Y. , New G. H. C. , Smith K.
Published: February 2023

Results from a computer model of the mode-locked fibre ring laser of Greer and Smith1 have enabled us to identify the key pulse formation mechanism. This laser is intended to serve as the central component in a signal regenerator for a fibre-optic communication system. An incoming random bit stream, degraded by passage through a long upstream fibre, serves as the external modulation source that drives the actively mode-locked fibre ring laser, and later as the information source in a nonlinear fibre modulator that refashions the original pulse sequence. The real laser cavity contains many kilometres of optical fibre and inclusion of self-phase modulation (SPM) and group velocity dispersion (GVD) is therefore essential.
Pulsed copper vapor laser with high specific output parameters
Authors: Fedorov A. I.
Published: February 2023

Metal vapor lasers pumped by transverse discharge after a conductor explosion in a vacuum seem to be promising from the point of view of their specific output parameters.1,2 This method of pumping can provide high specific output parameters from a number of metal vapors including refractory metals.3
Problems of efficiency and scaling for iodine pulse-repetitive flash-lamp pumping laser
Authors: Danilov O. B. , Artemov A. A. , Zhevlakov A. P.
Published: February 2023

The R & D results of an iodine photodissociative pulse-repetitive flash-lamp pumped laser with 500-W average power are reported, and some problems of its efficiency and scaling are discussed.
Special features of using an unstable resonator in XeCl laser with aperture 12 × 16 cm2
Authors: Ivanov N. G. , Losev V. F.
Published: February 2023

The use of an unstable resonator (UR) for excimer lasers allows essential to rise of an output radiation brightness. However, the improvement of divergence, as a rule, is achieved simultaneously with the decrease of output energy radiation.
Phase-sensitive interferometry with ultrashort optical pulses
Authors: Kop H. J. , Sprik R.
Published: February 2023

The major issue in the characterization of ultrashort-optical pulses is the determination of the chirp, i.e., the relative phase relation between the frequency components within the pulse. We report a novel technique to measure the full phase and frequency properties of an ultrashort pulse.
Gain and threshold current calculations for far-infrared semiconductor lasers
Authors: Yee W. M. , Shore K. A.
Published: February 2023

The optical properties of semiconductor quantum well structures for operation in the infrared have attracted considerable attention. Particular emphasis has been given to the design and implementation of photodetectors based upon intersubband absorption in quantum well structures. With a view to applications in spectroscopy, medicine, and free-space communications, it is of considerable interest to utilise intersubband emission processes to realize infrared semiconductor lasers.
A nonmechanical laser scanner by electron beam pumping of AlGaInP-GaInP semiconductor structures
Authors: Cornelissen H. J. , Savert C. J. , Niesten M. J. H. , Valster A. , van der Poel C. J.
Published: February 2023

An unconventional way of generating laser light with semiconductor structures is to irradiate them with a high energy electron beam of sufficiently high current density. Electron beam pumping thus offers the possibility to scan the exciting electron beam along a bar of semiconductor laser material, moving the lasing spot with the swiftness of the electron beam. This paper describes such a laser scanner. Laser scanners find wide application in laser printers, bar code readers etc. Most of these scanners are limited in their scan rate as they are based on mechanically driven rotating polygons or galvo mirrors. A nonmechanical scanner with increased scan rate will open up new application areas.
Beam quality changes generated by quartic phase distortions
Authors: Martinez-Herrero R. , Piquero G. , Mejias P. M.
Published: February 2023

The spatial characterization of laser beam profiles and the analysis of their quality changes under propagation through optical systems are topics of current interest in the literature.1-4 In this connection, one of the major problems is to find general optimization criteria for beam quality parameters (rigorously defined in terms of the so-called moments of boththe intensity and the radiant intensity of the field) as well as to improve them. In this sense, use of pure phase transmittances, through which the beam is made to propagate, has recently revealed to be an appropriate procedure because the total power is maintained. Thus, it has been shown5 that spherical aberration (or, more generally, quartic phase distortions) could improve the beam quality under certain conditions. This rather surprising conclusion was derived for the bidimensional (2-D) case and symmetric-intensity beams. However, as it is shown in the present work, the generalization of these previous results to 3-D optical systems and non-cylindrical beams involves not straightforward properties, mainly due to the appearance of crossed moments in the analytical expressions. In particular, it is well known in Fourier optics that two identical but orthogonal cylindrical lenses in contact with one another are optically equivalent (in the absence of aberrations) to a single spherical lens of the same focal length. But this equivalence, however, is no longer valid when spherical aberrations take place. In fact, we have found beams (for example, cylindrical Gaussian fields) for which use of the pair of cylindrical lenses produces better output quality parameters than the equivalent single spherical lens (provided that the optical systems were aberrated).
High quality beam generation in multikilowatt cw CO2 laser with all-metal mirror resonator
Authors: Shulyat'ev V. B. , Ivanchenko A. I. , Ponomarenko A. G. , Grachev G. N.
Published: February 2023

A high quality beam is required for many applications of material processing.1 A resonator length and/or power density at a partially transmitting output coupler present limitations on power of cw CO2 lasers with TEM00 mode. A self-filtering unstable resonator (SFUR)2 makes it possible to generate a Gaussian-like intracavity beam. This scheme has been applied to cw CO2 lasers too.3,4 But central obscuration deteriorates the output beam quality.
2.4 J Nd glass laser with a holographic mirror recorded by an external signal
Authors: Betin A. A. , Kirsanov A. V.
Published: February 2023

One of the possibilities of developing high-energy laser systems with the divergence close to the diffraction one is based on the employment of self-phase-conjugation in FWM with feedback (FWMF).1,2 In earlier experiments with Nd glass, the reflected wave energy of 0.4 J was achieved in the Q-switched pulse for the input beam diameter 4 mm.2 The present paper deals with the possibility of increasing the energy output with increasing the operational volume of the active medium.
Circulating pump and single pass pump cw extraction in solid-state lasers
Authors: Peterson P. , Gavrielides A. , Sharma P. M.
Published: February 2023

We develop the cw extraction equations for single and multiple pass pumping and apply these equations to Tm:YAG when the lasing manifold is directly pumped. The lower manifold fractional concentration is fa= (N
a
/N
1
) = exp(–E
a
/kT)/ Z
a
and contains the lower lasing level (a). The upper lasing level (b) is in the N
2
manifold with a fractional occupation fb = (N
b
/N
2
) = exp(–E
b
/kT)/Z
b
. The effective decay time is τ. Furthermore, the absorption cross section is σa(λ
p
) and the lasing cross section at λ
l
is σe(λ
l
). We begin with Fabry-Perot cavity with a single pass pump with transmissive optics at λ
p
. At the lasing wavelength one mirror is perfectly reflecting and the outcoupler has an intensity reflectivity r and the laser field is described by forward and reverse fields.
Ultrashort pulse generation by DFB laser on activated crystals with macrostructures
Authors: Korolkov M. V. , Veremeenko T. V. , Zharikhina L. P.
Published: February 2023

DBF laser of this type is based on the modulation of activator concentration being introduced into the crystal during the growth process.1 As a result, spatial periodic structures of activator concentration

N
a

(
z
)
=

∑

N
m
a

(
z
)
⋅

ℓ

i
m
q
z

and refractive index

n
(
z
)
=

∑

n
m

(
z
)
⋅

ℓ

i
m
q
z

are formed with the period L (q = 2π/Λ) and profile determined by crystal growth conditions.2 Rescattering of the counter-running waves of generation on the structures leads to the DFB.
Models of the 2-µm lasers on the basis of YSGG:Cr,Tm and YSGG:Cr.Tm,Ho crystals
Authors: Alpat'yev A. N. , Smirnov V. A. , Shcherbakov I. A.
Published: February 2023

The theoretical models of active laser media YSGG:Cr,Tm (lasing due to 3H4→3H6 transition of an Tm3+)1 and YSGG: Cr,Tm,Ho (lasing due to 5I7→5I8 transition of an Ho3+)2 that are lasing in 2-µm region are presented.
Self-mode-locked Raman laser
Authors: Mikhailov V. P. , Kalashnikov V. L. , Kalosha V. P. , Poloyko I. G.
Published: February 2023

Last time great progress had been made in the field of the creation and optimization of passive mode-locked lasers producing high-stable trains of ultrashort pulses directly from the cavity of cw solid-state lasers. These systems have the modulators that contain the various nonresonant nonlinearities. Such nonlinearities are self-phase modulation, self-focusing, stimulated nonlinear birefringence, and nonlinear optical Kerr effect. All effects are successfully explored in non-inertial passive modulators for modelocking of cw solid-state lasers1-2 and have been studied theoretically.3-4
Numerical analysis of the DFB dye laser generation kinetics based on the 2-D spatial model
Authors: Korolkov M. V. , Veremeenko T. V.
Published: February 2023

In early works theoretical consideration and numerical simulation of the ultrashort pulses (USP) generation of different types of lasers with distributed feedback (DFB lasers) were made on the basis of various modifications of the rate equations for parameters averaged over the active medium ("point" model’) or equations in partial derivatives for slowly varying amplitudes of counterrunning generation waves and ordinary differential equations for spatial harmonic amplitudes of the generation transition inverse population were used (1-D spatial model of a DFB laser2).
CW dye laser operation at very low flow velocities
Authors: Thiel E. , Drexhage K. H.
Published: February 2023

Until now cw dye laser action has been observed only when the dye solution flows very fast (10 m/s) through the active region. This is realized mostly by using the jet stream technique. Two reasons for the demand of fast dye flow are generally accepted: first, reduction of thermal disturbances and second, mechanical quenching of the lowest triplet state of the dye molecules. A frequently used and high efficient laser dye solution is Rhodamine 6G in ethylene glycol. Employing a new spectroscopic method, we measured a triplet state lifetime of 5 µsec in air-saturated solution at room temperature.1 This is to be compared with the dye molecules, flight time through the active region of a typical cw dye laser. This time is about 2µs. Therefore, owing to the motion of the jet, the triplet state population in the active region is reduced sufficiently so that laser action becomes possible. Moreover it was concluded from the triplet data of Rhodamine 6G1 that no optical gain can be expected in ethylene glycol without mechanical removal of triplet molecules.
A laser system: a Joule exciplex XeCI*-laser-powerful narrow-band dye laser for ecological lidar
Authors: Kopylova T. N. , Kaul' V. B. , Kuznetsova R. T. , Mayer G. V. , Mel'chenko S. V. , Panchenko A. N. , Samsonova L. G. , Sukhanov V. B. , Tarasenko V. F. , Tel'minov E. N.
Published: February 2023

A long-distance monitor lidar should feature high radiation intensity (of the order of hundreds of millijoules), because a scattered light intensity falls with distance more rapidly than R2. The laser radiation spectral width should be sufficiently small (of the order of hundreds small or the order of one tenth of an angstrom).
Spectral multiplexing of diode pumps to solid-state materials
Authors: Lavi R. , Tsadka S. , Jackel S. , Lallouz R.
Published: February 2023

One of the major problems in diode-pumped solid state lasers is the limited brightness of the pump source. A common technique to increase the brightness is to couple the light of two diode lasers using a polarization sensitive optic. This technique has an obvious disadvantage— it will not work with unpolarized sources, such as fiber coupled diode lasers.
The effect of 1.5 mm cascading on 3 mm er3+ laser emission
Authors: Lupei V. , Georgescu S. , Grecu S.
Published: February 2023

Laser emission in various regimes was obtained at room temperature in the three-micron range on Er3+ transition 4I11/2→4i13/2, despite a much larger lifetime of the terminal level. Various mechanisms have been considered in order to obtain efficient depopulation of 4I13/2 necessary to avoid the self-saturation of the laser emission: excited state absorption of the pump radiation from the terminal level,1 energy transfer to impurities,2 up-conver-sion,3 and, most recently, cascading with 1.5µm emission from 4I13/2 to the ground level 4I15/2,4 While the up-conversion is an internal mechanism of the system of Er3+ ions and a high Er concentration is necessary in order to be effective, all the other mechanisms require additional external conditions and could act at any Er concentration.
Laser medium on the basis of calcium niobium gallium garnet doped with Tm3+
Authors: Voron'ko Yu. K. , Gessen S. B. , Eskov N. A. , Ryabochkina P. A. , Sobol' A. A. , Ushakov S. N. , Tsimbal L. I.
Published: February 2023

The peculiarity of the new laser material calcium-niobium-gallium garnet (CNGG) is its low melting point (below 1500°C). That gives an opportunity to synthesize these garnets using technology avoiding the presence of iridium crucibles, which simplifies the crystal growth procedure and reduces the cost of the process of the synthesis compared with other garnets.
Er:YLF crystals as active media for pulse-lamp and up-conversion laser diode-pumped multiwavelength solid state lasers
Authors: Tkachuk A. M. , Shumilin V. V.
Published: February 2023

There is currently interest in the development of solid state lasers that operate in a wide spectral range from visible to IR by pumping both by flash lamp and laser diodes. The most promising materials for UV, visible, and IR lasers are rare earth-doped double fluoride lithium-yttrium crystals (TR3+:LiYF4 or TR3+:YLF). They are characterized by low values of nonlinear refractive index (n2) and high optical damage resistance. Among TR3+: YLF crystals, the considerable interest is in Er3+:YLF crystals that exhibit certain desirable properties such as a wide range of dopant ion concentrations together with material availability in large apertures of excellent optical quality. A Er3+:YLF laser emission is available in the IR and visible spectral ranges at a number of transitions by flash lamp and laser diode pumping, including up-conversion IR pumping.
Crystal growth and optical properties of Er3+ in three melilite-type laser hosts: Ca2Al2SiO7 (CAS), Ca2Ca2SiO7 (CGS), and SrLaGa3O7 (SLG)
Authors: Teisseire B. , Viana B. , Lejus A. M. , Vivien D.
Published: February 2023

Er-doped lasers operating near 1.5 µm are useful for numerous applications (LIDAR, optical fiber communication, eye safe range finder). The development of high power laser diodes lasing around 0.98 pm allowed the pumping of the Er3+ ions through Yb3+, which strongly absorbs in that spectral range. Ca2Al2SiO7 (CAS), Ca2Ga2SiO7 (CGS) and SrLaGa3O7 (SLG) with melilite-type structure are good matrices for rare earth ions and a structural disorder around the RE3+ involves broad absorption and fluorescence bands.1 In this study, two series of crystals with good optical quality are prepared by the floating zone method at various RE3+ concentrations to perform spectroscopy and by the Czochralski process to obtain large laser rods.
Investigation of ArF and KrCl excimer lasers for medical applications
Authors: Denisov V. I. , Razhev A. M. , Vasiliev Zh. V.
Published: February 2023

In recent years UV excimer discharge lasers find wide use in microelectronics, photolithography, and medicine. In medical applications of special interest is the use of these lasers in ophthalmology for reprofiling the external surface of the cornea and healing of eye diseases. The excimer lasers with radiation energy of some joules and pulse frequency of hundreds of hertzs and higher are required for industrial applications. To achieve such radiation parameters, it is necessary to use cooling systems in laser exciting circuits, to use thyratrons as commutators providing their normal mode of operation, and to use saturable reactors and magnetic switch control in the exciting circuits. Unlike industrial lasers, particularly the lasers for ophthalmology, a pulse frequency is limited by 10-20 Hz to avoid thermal damages of operated tissue. In this case the devices are cycled, it is connected with the replacement of patients, and radiation energy is limited by some hundreds of millijoules. The minimum pulse duration and high homogeneity of beam of light are desirable. To attain such parameters of laser radiation it is possible to simplify the laser exciting circuit sufficiently by eliminating not only the cooling system, but also saturable reactors or magnetic switch control by substituting the thyratron on the spark gap that has a sufficiently lower inductance. However, it is necessary to analyze carefully and to optimize the exciting circuit for providing not only the high efficiency of laser (and hence its resource), but the required energy of generation with a high homogeneity of beam.
The effect of anomalous amplification for a nanosecond pulse in a CO2 amplifier
Authors: Kovalev V. I.
Published: February 2023

The unexpected effect of increase by a factor of 1.2-1.5 in the unsaturated gain coefficient for a nanosecond pulse was observed in experimental configuration of double-pass TEA CO2 amplifier with a phase-conjugate mirror (PCM) on the base of InAs in the cavity of a TEA CO2 laser (Fig. 1), being compared to the unsaturated gain in the same amplifier in single pass configuration.1 The factor of amplification rise for nanosecond pulse amplitude exceeded ~4 for amplifier length ~140 cm. The correspondent nanosecond pulses were generated in PCM as a result of mixing of quasisteady single mode signal waves with the chaotically spiking counterpropagating pump waves in InAs plate.2
Excitation transfer between upper SE+ levels in positive column HE-SE+ laser
Authors: Todorov G. T. , Karavassilev P. R. , Sabotinov N. V. , Telbizov P. K.
Published: February 2023

In the recent years, the overall success in handling the lasers working on mixtures metal vapour-noble gas has overshadowed the interest in the details of the processes governing the inverse population in these active media. Most of the metal vapour-noble gas lasers, however, are still susceptible to optimization. An example is the positive column He-Se+ laser. It appears even more attractive due to its three-colour (red-green-blue) mode of operation.1
Resonance optical pumping of carbon monoxide
Authors: Shmelev V. M. , Margolin A. D.
Published: February 2023

This work concerns the process of optical pumping of carbon monoxide using the resonance radiation of electroionization CO-laser affecting the high-lying vibrational levels (v = 4 … 12, where v is the number of a vibrational level).