bluuebunny/crossref_metadata_2025 huggingface dataset:
ChAOS: The University of Chicago Adaptive Optics System
Authors: Kibblewhite Edward , Wild Walter , Carter Barbara , Chun Mark , Shi Fang , Smutko Michael , Farmiga Nestor
Published: February 2023

We describe an affordable sodium laser beacon adaptive optics system for near IR astronomical research at the Apache Point 3.5m observatory.

The successful incorporation of adaptive optics technology to major astronomical observatories for near IR and visible operation demands that these systems ultimately be: (a) functional over the entire sky, (b) affordable, maintainable, reliable, and reasonably compact, and (c) possess a well-designed user interface for ease of operation. Motivated by these considerations, we have designed a system (ChAOS) that will use a high altitude sodium beacon as a reference source. This will enable full-sky coverage as long as an 18th magnitude natural star resides within the isoplanatic patch for tip-tilt correction. The sodium star will be created with an MIT Lincoln Laboratories laser-diode-pumped sum frequency laser operating with 15W average output power at 589nm. A dc lateral shearing interferometer wavefront sensor has been designed, and is under development in our laboratory, which uses low read noise CCD arrays. Detailed calculations have been made of the performance of this wavefront sensor, a quad-cell Hartmann array system, and minimal variance (Cramer-Rao bound) wavefront sensors, for beacons formed by optimally focused Gaussian laser beams propagating through the atmosphere; results of these calculations will be summarized. A vigorous program is underway for the development of low-cost, repairable, and reliable continuous facesheet deformable mirrors. The control system, real-time wavefront digital reconstructor, and a high-voltage deformable mirror multiplex interface driver are also being built for ChAOS. An overview of these ChAOS components and the design and expectations of the integrated system will be presented.
Wide field-of-view astronomical imaging using wavefront sensor deconvolution with a Laser Guidestar Reference
Authors: Gonglewski J.D. , Dayton D.C.
Published: February 2023

It was recently suggested that a simple atmospheric distortion correction method using a laser guidestar reference (LGR) produces a potentially simpler compensation method than adaptive optics (AO) systems, with some loss in performance.1In addition, there are several advantages other than simplicity and cost, including the possibility of widening the field of view (FOV) of the compensations system, and compensating for multiple layers of turbulence. This paper extends this earlier work to the wide field of view problem in astronomical imaging.
Adaptive Optics Development at Lincoln Laboratory
Authors: Greenwood Darryl P.
Published: February 2023

For almost two decades Lincoln Laboratory has been developing adaptive optics for the purpose of improving the quality of propagated laser beams. Results of significance in this program have been: (1) compensation for atmospheric turbulence on a ground-to-space link; (2) proof-of-principle of the use of mesospheric sodium as a source for synthetic beacons; and (3) demonstration of synthetic-beacon adaptive optics using Rayleigh backscatter as a source. These events are all “firsts” in the development of adaptive-optics technology. As a result of a 1990 decision by the U.S. Air Force, we are now in the position to make the results of these programs available to the astronomical community, for whom adaptive optics is clearly a boon in highresolution imaging of celestial objects. In particular, the systems used in the aforementioned experiments are being applied to astronomy at both the Mount Wilson Observatory and the Firepond Optical Site in Massachusetts.
Large Telescopes and Integrated Adaptive Optics for Directed Energy Programs
Authors: Wildt Daniel R. , Prater Ronald F.
Published: February 2023

Since the beginnings of the Strategic Defense Initiative Organization (SDIO) programs in Directed Energy Weapons, specifically high energy laser (HEL) based systems, this organization has supported programs that extend the state-of-the-art in adaptive optics. These concepts have been closely woven with the development of very large mirrors that play an active role in the "beam control" adaptive optics system. These mirrors are very lightweight for space application and their demanding design requirements raised early questions about whether scalable technology could even be developed and whether these optics could be economically manufactured. Though the requirements for beam projecting systems are different than astronomical imaging applications, there are enough similar technologies involved that these systems should be of interest to this audience.
Requirements for Adaptive Optics in Large Astronomical Telescopes
Authors: Beckers Jacques M.
Published: February 2023

The incorporation of adaptive optics in large astronomical telescopes to provide diffraction limited imaging promises to revolutionize ground based optical astronomy in the next decade. The gains are especially impressive for large aperture telescopes where the large increase in diameter D results both in a decrease of the area of the telescope point spread function proportional to D2 and in an increase in collected photons within that smaller area of D2. The availability of adaptive optics will thus pay off handsomely in many astronomical uses of large telescopes.
Low-Cost Tip-Tilt and Deformable Mirrors for Astronomy
Authors: Arnold R. , Cuellar L. , Rego A. , Smith G. , Trissel R. , Barrett T. K.
Published: February 2023

We have developed low-cost tip-tilt and segmented deformable mirrors for use at astronomical telescopes. The design of the mirrors and performance test data will be presented.
Real-Time Corrected Long Baseline Interferometer System Concept
Authors: Vernon R.G.
Published: February 2023

A design concept and analyis for a long baseline interferometer imaging system that uses real-time higher order wavefront control, tilt and piston control has been developed to: (1) stabilize the fringe field associated with the visibility phases, (2) measure visibility amplitudes and closure phase, and (3) allow investigation of celestial sources beyond 15th magnitude. Pupil plane phase difference control and closure phase measurement on three telescopes is accomplished simultaneously using differential phase modulation and Fourier de composition. Atmospheric wavefromt sensing is accomplished in all three telescopes using Rayleigh scattered 15 watt laser guide stars focused at 20 km. Tilt sensing and correction is accomplished using the imaged source field. A method for obtaining good pupil plane coverage using only three 1 meter apertures is presented. Analysis is performed on the adaptive optics assemblies to trade-off laser guide star power requirements, optical train efficiency, wavefront sensor measuring accuracy, track sensor accuracy, number of wavefront sensor subapertures, deformable mirror actuators and servo bandwidth requirements. Analysis is performed on the piston control subsystem to optimize the measurement of closure phase and visibility amplitude over a narrow spectral bandwidth, to trade-off source irradiance requirements, piston measuring accuracy, and visibility amplitude accuracy.
Application of Blue-green Lasers to High Data Rate Underwater Communications
Authors: Snow Judith B. , Longacre Jacob R.
Published: February 2023

High data rate underwater laser communications are highly constrained by laser propagation characteristics in the marine environment. Many of these limitations are mitigated by using an optimally designed laser for seawater transmission, namely a compact blue-green laser. Digital data can be transmitted through seawater by an amplitude modulated laser beam that is detected by a remote optical receiver. The primary technical issue for this application is the distance over which error-free optical communication is possible. Maximum range for a laser beam propagating through seawater is in the hundreds of meters. Achievable distances are limited because optical signals transmitted through seawater are exponentially attenuated according to where I is the received optical signal strength, Io is the initial optical signal strength, r is the transmission range, and c is the beam attenuation coefficient.
Linear and Nonlinear Optical Properties of Annealed Proton Exchanged LiNbO3 Waveguides
Authors: Bortz M. L. , Eyres L. A. , Fejer M. M.
Published: February 2023

Quasi-phasematched frequency conversion in LiNbO3 waveguides is an efficient method for the generation of short wavelength radiation from infrared laser diodes. While many techniques are used to form the ferroelectric domain grating necessary for quasi-phasematching, waveguide confinement is usually provided by the annealed proton exchange (APE) process. The optical properties of APE waveguides are not well understood and accurate models relating the modes of the waveguide to processing parameters are not available. Also, effects of the APE process on the nonlinear optical properties of LiNbO3 have yet to be understood. In this presentation we discuss two sets of experiments. First, we report a nonlinear diffusion coefficient for protons in LiNbO3 and the relationship between concentration and index change, which allow a quantitative prediction of the modes of APE waveguides.1 Second, we report depth profiling of the d33 nonlinear coefficient in proton exchanged (PE)2 and APE waveguides which, in conjunction with the optical modes, allows accurate calculation of the overlap integrals and normalized conversion efficiencies for guided wave nonlinear optical interactions. These models make possible the optimization of APE waveguides for maximum normalized conversion efficiency, noncritical phasematching, or efficient coupling to a laser diode for any guided wave nonlinear optical interaction.
Displays, High Definition Television and Lasers
Authors: Glenn William E.
Published: February 2023

High definition television for both commercial and consumer use is critically dependent on the development of new display technology that can be manufactured at a reasonable price. There is a strong demand for new high definition displays for the theatre conference rooms and for other commercial applications. These applications need inexpensive high resolution projection displays with 3,000 to 10,000 lumens output. Only light-valve projectors have been able to come close to the technical requirements - but at a very high cost.
Blue, green and red, Tm3+, Ho3+ doped upconversion laser glasses, sensitized by Yb3+ and Er3+
Authors: Izumitani T. , Peng B. , Lin Y.
Published: February 2023

In order to get blue, green and red laser beam, we applied upconversion process1). We used Tm3+, Ho3+ ions which give three energy level lasers. As the difference between emission and absorption peak wavelength is small, the sensitizers were applied to get higher emission intensity. The base glass was fluoro-zirco, aluminate glass(AZF)2), because the phonon energy is small and the chemical durability is excellent.
Generation of 369.4 nm Radiation By Efficient Doubling of a Diode Laser
Authors: Williams A. , Seidel D. J. , Maleki L.
Published: February 2023

The trapped ytterbium ion frequency standard1,2 under development at JPL requires at least 10 μW of continuous-wave (cw) laser radiation at 369.4 nm. Only diode lasers meet the requirements of low power consumption and small size for use aboard spacecraft1, but diode lasers are not currently available at this wavelength. It is therefore necessary to employ frequency doubling methods to reach 369.4 nm with diode lasers.
Cooperative Energy Transfer in A Yb-Pr Doped ZBLAN Fiber
Authors: Remillieux A. , Jacquier B. , Poignant H.
Published: February 2023

Upconversion pumping of rare earth doped materials has been extensively studied over the two past decades. Most of mechanisms for converting infrared radiation to short wavelength output are quite well known and relative strengths of these processes have already been reported in bulk materials [1]. However, due to length of interaction of laser ligth with luminescent centers in a fiber, Excited State Absorption (E.S.A.) can dominate the Addition of Photons by Energy Transfer (so-called A.P.T.E.). This is mainly true because of low doping of fibers. Such low concentration is required to prevent from clustering or agregation which causes losses along the fiber.
Near Infrared Pumped ZnSe and ZnSSe Blue Lasers
Authors: Yang X.H. , Shan W. , Hays J.M. , Song J.J.
Published: February 2023

ZnSe and ZnSe-based materials are receiving a great deal of attention for their potential blue opto-electronic applications.1,2 We have previously reported observations of room temperature blue laser oscillations from ZnSe and ZnSSe single crystals employing the above-the-band-gap one-photon pumping method.3,4 Here we report our recent study of blue laser action in these crystals where optical pumping was achieved via two-photon transitions. In particular, we have used near-infrared (~850 nm) excitation with two photon energies in the vicinity of the fundamental energy gaps in these wide gap materials.
Upconversion Fiber Lasers
Authors: Hanna D. C.
Published: February 2023

Progress on development of upconversion fiber lasers, in particular those based on Thulium-doped and Praseodymium-doped ZBLAN glass fibers, will be described.
Upconversion Green Laser Operation of Yb,Ho:KYF4
Authors: Thrash R.J. , Jarman R.H. , Chai B.H.T. , Pham A.
Published: February 2023

Energy upconversion provides an attractive alternative to second harmonic generation as a route to compact visible laser sources.
Lasers for Advanced Optical Storage Applications
Authors: Lenth Wilfried
Published: February 2023

This talk will review the performance, reliability and cost requirements of short-wavelength laser devices for future optical recording systems in commercial data storage as well as consumer applications.
Very High Efficiency of Frequency Doubling in QPM Waveguides of KTP
Authors: Eger D. , Oron M. , Katz M. , Zussman A.
Published: February 2023

Frequency doubling of infrared diode laser light by nonlinear QPM waveguides has become one of the leading techniques for developing compact blue light sources.
Time-Dependent Change of the Phasematching Wavelength Due to Refractive-Index Instabilities in Proton-Exchanged LiTaO3 Waveguides
Authors: Åhlfeldt Henrik , Laurell Fredrik
Published: February 2023

Quasi-phasematching (QPM) waveguides fabricated through annealed proton exchange (APE) in LiTaO3 are promising candidates as the frequency-converting elements in blue frequency-doubled diode-laser devices [1].
Review of Currently Available Compact Blue-Green Solid-State Lasers
Authors: Baer Thomas M.
Published: February 2023

The current status of commercially available solid-state sources in the blue-green spectral region will be reviewed.
Blue light generation using a high power modelocked tapered stripe laser
Authors: Goldberg Lew , Mehuys David
Published: February 2023

A novel type of a high power modelocked laser based on a tapered stripe diode amplifier is frequency doubled to generate 25 mW average and 1.4 W peak 430 nm power.
Compact Frequency Doubler of Diode Laser Light
Authors: Eger D. , Oron M. , Zussman M. Katz A. , Shachna A.
Published: February 2023

Compact blue laser sources are required for several applications such as optical recording, printing and metrology.
Optical resonators for high power lasers
Authors: Wittrock U.
Published: February 2023

An overview is given on resonators for high power solid state lasers, optimized for beam quality and efficiency. The obstacles to achieve fundamental mode operation in the kW-range are discussed and the principle limits are given.
High-energy, single-longitudinal-mode solid-state oscillators using gain-gratings
Authors: Damzen M. J. , Green R. P. M. , Crofts G. J.
Published: February 2023

We present the results of a laser resonator design that uses 3-D volume gain gratings formed by spatial hole burning1 and initiated by spontaneous cavity emission. The induced gain-gratings can be considered dynamic holographic elements with diffractive properties that provide both spectral and spatial mode control of a high-gain flashlamp-pumped Nd:YAG laser system. The dynamic parametric growth of the grating initiated from amplified spontaneous emission in the cavity produces a self Q-switching resulting in short pulse formation.
Spiral phaseplate used to produce helical wavefront laser beams
Authors: Beijersbergen M. W. , Kristensen M. , Woerdman J. P.
Published: February 2023

A spiral phaseplate1 has been developed that can be used to produce helical-wave front laser beams. The phase of such a beam has a screw dislocation at its center, also called a topological charge, which is associated with orbital angular momentum.2,3 The plate is a transparent plastic disk with a helical surface (Fig. 1). The azimuthal thickness variation is 0.72 mm over 2π, but this is scaled down by immersing the plate in index-matching fluid. By changing the temperature, the effective step can be tuned from zero to a few wavelengths, so that the immersed plate operates as a diffractive-optical element.
Metal island film polarizer
Authors: So Daniel W. C.
Published: February 2023

Many integrated optical devices are sensitive to the polarization of light. A thin film polarizer1,2 which transmits the transverse magnetic (TM) mode with a low insertion loss (<1 dB) and which attenuates the transverse electric (TE) mode with a high extinction ratio (>30 dB) is considered. The basic planar device structure consists of a dielectric waveguide which is separated from a parallel metal island film waveguide by a buffer region (Fig. 1). The difference between the TE and the TM modes arises due to the distribution of the metal islands in the film. Because of the excitation of the local surface plasmon in the metal particles, the attenuation of the TE mode is two orders of magitude greater than that of the TM mode. The physical parameters of the metal film waveguide are adjusted such that the TE mode is phase-matched with that of the TE mode of the dielectric waveguide. The TE mode of the optical waveguide is coupled distributively to the metal film waveguide and is attenuated, whereas the TM mode is not coupled due to significant phase mismatch and also is attenuated by two orders of magnitude less than that of the TE mode. Thus, an efficient TM mode pass on-line polarizer can be realized.
UV from IR: multistep upconversion in Tm:YbAG
Authors: Morris P. J. , Lüthy W. , Weber H. P. , Zavartsev Yu. D. , Studenikin P. A. , Umyskov A. F. , Zagumenyi I.
Published: February 2023

Yb is an ideal sensitisor due to desirably broad and strong absorption and the possibility of energy transfer to other rare earth ions. Multistep upconversion followed by blue fluorescence is already known in Yb:Tm:glass. The process begins with absorption of a pump photon by an Yb ion and energy transfer to the Tm 3H5 level. Relaxation to the Tm 3F4 level is followed by Yb-Tm upconversion, where an Yb ion de-excites from the 2F5/2 level to the ground state and causes the Tm ion to be excited to the 3F2,3 levels. Relaxation to the 3H4 level is followed by a second Tm-Yb upconversion process which populates the 1G4 level, producing blue fluorescence due to transitions to the ground state. Low Tm concentrations (<0.5%) are required to prevent the 3H4 + 3H6 → 2 3F4 cross relaxation process. With high Tm concentrations, however, other Tm-Tm interactions become possible. One such interaction is 3F3 cross relaxation whereby one ion relaxes to the ground state and a second is excited to the 1D2 level, followed by UV fluorescence due to transitions to the ground state.
Remote diagnostics of the plant leaf structure features: the spectropolarizational nephelometry technique
Authors: Belyaev B. I. , Shuplyak V. I. , Sikorsky V. V. , Stelmakh G. F.
Published: February 2023

It is shown that the laser and optical nephelometric measurements including the spectropolarizational ones at different angles are highly informative for non-contact plant diagnostics. Before recent time the traditional view on the polarization of plant-reflected radiation was a formation of the polarized component due to a specular reflection on the leaf surface exceptionally. Our detailed studies on the spectral and angular dependences of the reflected light polarization degree for the different plant leaves have shown that the singly and multiply scattering on intraleaf structure elements combined with chlorophyll molecular absorption is very essential for the formation of polarized light component. It is also found that the polarizational characteristics are more sensitive for the changes of plant structure as compared with the traditionally measured bidirectional reflectance factors. We have discovered and theoretically substantiated a spectral shift of a main maximum of the polarization degree angular dependence and an appearance of the additional (non-Brewster) maxima at the incident angles of 65-75°, 15-20°, 30-35° and 40-45°. The features of polarization degree angular function are resulted from single scattering processes and concerned with such factors as intraleaf water concentration, leaf's age, size, and concentration proportions of the lipid and protein components. The experimental and theoretical obtained results give the basis of optical and laser remote diagnostics of the intraleaf structure; in particular, make possible to obtain the refractive indexes of leaf structure elements, intracell particle concentrations, and particle size distribution functions. It is shown that the plant illness (in particular, bacterial cancer), ontogenetic development of plants, and ecological state of vegetation may be diagnosed from analysis of the polarization degree angular functions.
Potential of autodyne lidars for study of the atmosphere
Authors: Gordov E. P.
Published: February 2023

Nowaday usage of laser autodyning, i.e., usage of a laser as a transmitter of probing signal and as the receiver of its frequency shifted echo, is quite attractive area for the lidar community (see, for example, Ref.1). Such an approach to laser sensing of the atmosphere looks very beneficial since information on atmospheric path losses and on retroreflector (mirror, topographic targets, aerosol) properties is retrieved from characteristics of the laser intracavity field. As a result of intraresonator mixing, the following positives take place: (1) high noise immunity; (2) enhanced sensitivity quite comparable with those achieved at heterodyning; (3) possibility to neglect by short noise of a photodetector; (4) simple lidar design since the same optical path is used for the probing signal and its echo; (5) absence of local oscillator, hence robustness and self-alignness of the lidars; (6) possibility to retrieve a set of optical and dynamic characteristics of the distant retrorflector and atmospheric path from signal measurement.
Low threshold current in InGaAlP/InGaP visible laser diodes
Authors: Lee J. W. , Shin D. H. , Kang S. J. , Kim T. K. , Kim T. , Oh M. S. , Kim J. Y. , Kim T. I.
Published: February 2023

InGaAlP/InGaP visible laser diodes emitting in the 600 nm range are considered to be promising optical sources for use in optical information systems such as high density optical disks, laser beam printers, and bar-code readers.1 One of the important problems to be solved for practical use is high threshold current of this system. Among many methods, high doping in the clad layer and compressive strain in the active layer2 are considered the most effective ones to reduce a threshold current. This study demonstrates that a very low threshold current can be obtained for simple one step epitaxial structure by applying these two effects.
Reduction of linewidth enhancement factor in strained 1.55-μm InGaAsP lasers
Authors: Summers H. D. , White I. H. , Rees P. , Blood P.
Published: February 2023

The linewidth enhancement factor, α, is an important parameter of semiconductor laser operation as it affects the spectral linewidth, increasing it by a factor of (1 + α2) compared to the value predicted by the Schalow-Towns formula. Bulk lasers typically show α-values of 6–7; however, this value has been reduced by the use of quantum well structures to 3-4. Recently, the introduction of strained layers into quantum well lasers has led to further reductions in the α-value. In this work we analyse from first principles, for the first time, the physical mechanisms responsible for the reduction of the α-parameter in strained layer lasers operating in both cw and dynamic regimes. We measure α-values of ~2 in 1% compressively strained lasers operating d.c. and under modulation conditions. Agreement between experiment and theory is found.
GaInAsSb Mid-infrared diode lasers
Authors: Spears D. L.
Published: February 2023

For the past six years, Lincoln Laboratory has been developing mid-infrared diode lasers based upon GaInAsSb/AlGaAsSb heterostructures grown on GaSb substrates by molecular beam epitaxy.1-4 Compactness and efficiency make diode lasers very desirable in the mid infrared for optical pumping solid-state lasers and for direct sources in this spectral range, which is eyesafe and contains may strong molecular absorption lines. Band gaps and lattice constants of the III-V alloys used in this work are shown in Fig. 1. GaInAsSb alloys lattice matched to GaSb lie along the dashed line and can have band gap wavelengths ranging from 1.7 to 5 μm by adjusting the composition. As was found for GaAs and InP lasers, quantum-well active regions (particularly those under compressive strain) have led to many mid-infrared laser performance breakthroughs.1-3 In addition, early life-tests on these devices have indicated good reliability.
Slab-CO2 laser employing a hole-coupled waveguide resonator
Authors: Yelden E. F. , Morley R. J. , Horn H. K. , Abramski K. M. , Baker H. J. , Hall D. R. , Taghizadeh M. R.
Published: February 2023

Recent progress in high power, slab waveguide CO2 lasers, using RF excitation, has achieved specific power output approaching 30 kW·m-2 and absolute laser output powers in the kilowatt regime. These devices commonly employ a hybrid unstable resonator, or a plane mirror waveguide resonator containing a partially reflecting output coupler. Unstable resonators have the advantage of all-reflective mirrors and edge coupling, but are unable to provide sufficient frequency purity and beam quality for some applications, such as lidar and remote sensing. For large aperture devices using stable cavities, partially transmitting output mirrors, usually of ZnSe become expensive and are more readily damaged than full reflectors, whilst the large output beam provides difficulty with the subsequent beam handling. There is thus a need for a new resonator approach, which can deliver a small aperture beam from wide slab lasers, with good beam quality and spectral purity, using all-reflective optics.
Upgraded mobile DIAL laboratory for air quality measurements
Authors: Biccola M. , Corio W. , Marzorati A.
Published: February 2023

Optical and laser remote sensing techniques provide powerful tools for environmental monitoring. In particular atmospheric pollution concentration and meteorological parameters can be determined, with range resolution, using laser sources and DIAL (Differential Absorption Lidar) methods.
High repetition rate, short pulse, diode pumped solid-state laser for space communications
Authors: Larat Christian , Pocholle Jean Paul , Schwarz Muriel , Feugnet Gilles , Papuchon Michel
Published: February 2023

Laser systems deliver low divergence light beam with high quality mode. This feature leads to a small emission antenna diameter, which is of great interest for future free-space communication systems. Today, diode pumped solid-state lasers are under intense research and development.1 Indeed, in comparison with flash lamp pumped laser, they offer significant advantages in terms of efficiency, compactness, lifetime, and high beam quality.
Perturbations analysis of a laser beam propagating in turbulent water by an interferometric method
Authors: Perennou A. , Cariou J. , Lotrian J.
Published: February 2023

Optical heterodyne detection will be severely perturbed by the refraction effects caused by the turbulent medium. The price of high optimum sensitivity in heterodyne detection is the strict alignment of the local oscillator beam and the signal beam. To study the influence of turbulences on an optical wave front, we have used an experimental method based on an interferometric technique (Mach-Zehnder interferometer).
UV to near IR solid-state narrow-band laser for a mobile differential absorption lidar
Authors: Nava E. , Garbi M. , Mombrini G.
Published: February 2023

A narrow-band solid-state laser source for remote sensing of atmospheric pollutants and meteo parameters from a truck-mounted Differential Absorption Lidar system (DIAL) has been realized. The laser source, based on a Ti:sapphire laser, was originally designed for measurement of H2O and temperature (O2) profiles in the Near IR (767–830 nm). During the work the design has been modified to allow for measurement of gaseous pollutants (NO, SO2, O3, NO2) with absorption in the VIS-UV region (225–450 nm). To extend the tunability of the Ti:sapphire beyond the original design range (750–850 nm) up in the VIS-UV region, a frequency-mixing/conversion scheme using three BBO crystals has been selected. The block diagram of the laser is shown in Fig. 1.
Crystalline visible upconversion lasers
Authors: Heumann E.
Published: February 2023

Summary not available.
Laser shock-hardening, physics and applications
Authors: Fabro Rémy
Published: February 2023

The laser shock-hardening is a rather recent process that is still under research in several laboratories. The shock wave generation uses the "confined regime" where the plasma expansion is delayed by using a laser transparent coating deposited at the target surface. Typical shock wave pressures of 50 kbars are then generated at laser intensities about 10 GW/cm2 with water confinement. The physics of this mechanism is discussed and the main limiting process for pressure generation, which are the breakdown mechanisms of the dielectric, is analysed. In a second part, the basic principles of shock wave propagation inside materials are recalled and allow the determination of the thickness of plastified material and of the residual stresses field generated inside the material. Also, the effect of different processing parameters such as the geometry of interaction, pulse repetition, and spatial separation are analysed. We will also present some applications devoted to the improvement of several properties for different materials such as their fatigue life or corrosion resistance. Comparisons of this treatment with a conventional surface treatment such as shot-peening will be also discussed. Finally, the key points for the achievement of an industrial laser processing machine will be defined.
Theoretical description of pulse laser deposition as a new thin film technique
Authors: Völlmar S. , Mai H. , Dietsch R. , Granse G. , Lenk A.
Published: February 2023

Pulse-laser deposition techniques provide a variety of thin films with special structural and functional properties useful for application. The method is suitable for the preparation of layers and layer stacks of virtually all substances, including refractory and nonconducting materials as well as stoichiometric compounds. It is distinguished from other methods by its very high instantaneous deposition rate and by particle energies up to 1 keV.
Recent achievements in ultrafast optoelectronic devices in Russia
Authors: Mak Arthur A.
Published: February 2023

General peculiarities of investigations in Russia in the field of short power radiation pulses are analyzed.
Near-field optical imaging of human blood cells
Authors: Bozhevolnyi S. I. , Smolyaninov I. I. , Keller O.
Published: February 2023

Scanning near-field optical microscopy (SNOM) is a new imaging technique that allows one to obtain spatial resolution far beyond the classical diffraction limit.1 Analysis of biological samples may be one of the most exciting applications of such a technique. Here we present the first near-field optical images of various cells of human blood and discuss further improvement and possible applications of our SNOM.
Flexible workstation for laser surface treatment
Authors: Cantello M.
Published: February 2023

Summary not available.
Powder flow from novel nozzle design for laser cladding and alloying
Authors: Carty S. , Owen I. , Bastow B. , Steen W. M.
Published: February 2023

This paper describes some laser alloying/cladding nozzles that are being investigated, with the objective of alloying and cladding in any direction and at any angle of inclination.
Improved drilling and cutting with copper vapour lasers
Authors: Bergmann H. W. , Mayerhofer R. , Slunecko T. , Hartmann M. , Gan E.
Published: February 2023

Laser beam cutting and drilling using pulsed CO2- and Nd:YAG-laser systems is a very well-known and established industrial technique. Short pulsed lasers such as copper vapour lasers (CVL) have shown a potential in achieving precision machining (accurate circular drill holes, narrow kerf-widths, small heat affected zones) due to its high pulse power, high repetition rate, and good focusability.1
Soliton generation and transmission under periodic and pseudorandom word modulation of laser diodes
Authors: Mirasso Claudio R. , Pesquera Luis
Published: February 2023

Recently several groups1,2 have reported error free soliton transmission over more than 9,000 km at Gb/s rates. When solitons are generated by gain-switched lasers, the pulses are severely chirped and a narrow-band optical filter must be used.1 It has been observed3 a large pulse spreading for distances greater than a few thousand kilometers when using a DFB laser and a bias current (C
b
) above threshold. We have recently shown4 that this pulse spreading is due to the pulse-to-pulse frequency jitter originated in the laser diode (LD). In this work the effect of C
b
on soliton generation and transmission is studied. We numerically obtain that when the laser is biased slightly below threshold pulse spreading is strongly reduced for any frequency of modulation in the GHz range. With this bias current we can generate solitons under both periodic modulation (PM) and pseudorandom word modulation (PRWM). When the laser is biased above threshold it is not possible to generate solitons under PRWM for frequencies >2 GHz due to pattern effects.
Conoscopic optical probes: a new generation of metrological instruments
Authors: Bucourt Samuel , Le Falher Eric , Malet Yann , Sirat Gabriel Y.
Published: February 2023

Conoscopic holography is an interferometric technique based on light propagation in crystals. Conoscopic optical probes overcome the main limitations of 3D optical measurement, namely complexity, unreliability, and low precision. Although some systems were designed before, conoscopic probes are operational today as industrial items due to the availability of new improved optical components and the new capacities of low cost numerical processing.
The analysis of field-effect waveguide device with thick-film three electrode configuration
Authors: Pan J. J. , Li Y. Q. , Lee Edward
Published: February 2023

Field-effect waveguide devices have many attractions because of their advantages of fabrication simplicity, highpower handling capability, wide-operational bandwidth, etc. The previous theoretical analysis on this topic is mainly concentrated to the conventional infinity thin electrode configuration.1−3 Since the field-effect waveguide with simple thin electrode configuration can only perform some basic applications, a field-effect waveguide device with more complicated electrode configuration is needed for better performance characteristics and more advanced applications. A field-effect waveguide with the embedded thick-film three electrode configuration is analyzed here. This electrode configuration gives us more freedom to control both the position and the profile of the induced waveguide. Just like the field-effect transistor (FET), the field-effect waveguide utilizes two electrodes (similar to “source" and "drain" in FET) to build up (induce) and control the induced-waveguide shape, while it uses the third electrode (similar to "gate" in FET) to control the induced-waveguide position.
The ultrashort light pulse handling in electrooptic modulators with Raman-active media
Authors: Arkhireev V. O. , Nesterova Z. V. , Nesterova V. A.
Published: February 2023

The electrooptic modulators (EOMs), which contain the liquid-filled capillary optical fiber (OF), are very attractive as model systems in the investigation of the light manipulations in nonlinear waveguides and in the various fiber-based sensors. The marked properties of liquid-filled OF are the ideal step-index profile in a core and the possibility of mode content variation due to change of the core temperature. Moreover, there is a great number of the neat organic liquids with strongly different nonlinearities, which are suitable to these investigations. The key problem discussed is the role of real and imaginary components of the third- order susceptibility of the liquid core during the light pulse handling in the EOM by the external electric field. In the present paper the experimental results of an effective manipulation by the spatial, temporal, and spectral content for the picosecond light pulses (λ = 0,53 µm, Δt = 35 ps, P = 0,1 – 104W) in the EOM were demonstrated. The typical dimensions of the inner core diameter and the capillary length were 50 µm and a few centimeters correspondingly. As a rule, the liquid derivatives of benzene and halogen-substituted methanes were used to hollow-core filling. The pulse energy and the spectra were registered in an ordinary manner. The amplitude and temporal characteristics of the ultrashort light pulses were measured using the streak camera with picosecond time resolution.
A high-speed multiquantum well-based optical header reader for fiber network packet switching
Authors: Zia O. , Singh J. , Bhattacharya P. K. , Sen S.
Published: February 2023

Despite significant advances in optical information transfer, routing decisions in optical networks are still made by electronic devices.1 The matching of an optical "header" to a local address, a key requirement in packet switching, is presently performed by converting the optical header to an electronic data stream and then carrying out the comparison. This operation at every node on the network is now recognized as a communications bottleneck, ultimately limiting network performance. To circumvent this problem, a simple optoelectronic architecture has been implemented at high speeds to perform an optical data comparison in a manner which avoids the electronic bottleneck. Demonstrated at a data rate of 200 Mbits/sec, surpassing current FDDI standards, this architecture is a promising method for optical header reading in a packet switching network.
A software tool for investigating optical signal processing
Authors: Keating J. G. , Halligan J. , Adamson K. , Gleeson D. J. , McKenna-Lawlor S. M. P. , Klima M.
Published: February 2023

Classical signal processing functions such as spectrum analysis, correlation, convolution, filtering, mixing, and noise reduction can be performed optically using optical signal processing devices and systems. The signal media, i.e., light waves, not only have a higher information-carrying capacity than electrical wires, but may pass through each other without interference, thus providing an increased interconnection capacity. This property facilitates improved communication and ease of reconfiguration between processing elements in highly parallel optical computing architectures.1
Algorithm of invariant image description using modified Gabor transform
Authors: Kaliteevskij N. A. , Semenov V. E. , Glezer V. D. , Gauselman V. E.
Published: February 2023

We propose an algorithm of image coding which is invariant to scale transformation due to a method of scale weighting function (SWF) described below. So it could be a base for an algorithm of pattern recognition. We get an image code at the output—a set of 60 numbers which are independent on the image size. Let's describe the algorithm briefly. An input image I(x,y) is processed in some channels which have identical organization and different scales forming logarithmic series with the step 1/2 octave. Processing of an image in K-th channel includes two steps: (a, b). Then using SWF method the image code is built in two steps: (c, d).
Waveguide optical bistable devices with weighted distributed feedback structure
Authors: Mizumoto T. , Ibusuki Y. , Nakatsuhara K. , Naito Y.
Published: February 2023

Nonlinear optical devices have been studied for their possible uses in various all-optical functions. The optical bistable devices, which employ intensity-dependent refractive index change, have been demonstrated in a GaAs—GaAlAs superlattice etalon1 and in a CdS
x
Se1-
x
doped glass etalon.2 A pioneering work on its waveguide version was also reported for the Fabry-Perot resonator constructed with a GaAs/GaAlAs MQW waveguide.3 In order to integrate the bistable device with other optical functional devices, it is essential to use distributed Bragg reflectors for optical feedback.
Ultrafast erasable optical storage in Sb-Rich GeSb films
Authors: Afonso C. N. , Solis J. , Morilla M. C. , Ollacarizqueta M. A.
Published: February 2023

Phase change optical storage is the most promising alternative to magneto-optical recording. This technology is an all-optical one and has a much better signal to noise ratio and a simpler reading mechanism that simplifies the optical head. This leads to a decrease in the access time and to make the phase change disks interchangeable with the earlier optical storage products, the CDROM and WORM discs. The most significant drawback with phase-change materials has been the need for materials with highspeed crystallization, crystallization triggered by <100 ns laser pulses being usually required.
Erasable zone plate in bacteriorhodopsin film for photonic switching
Authors: Okada-Shudo Y. , Ujihara K. , Tomioka H. , Yamaguchi I.
Published: February 2023

The photochromic protein bacteriorhodopsin (bR), which is related to the human visual pigment, is found in the purple membrane of Halobacterium halobium in two-dimensional crystallized form. The absorption of a visible photon by bR triggers a photocycle as shown in Fig. 1. Both the forward and reverse photoreactions produce stable products in less than 3 picoseconds at 77 K. Its photochromic properties, i.e., the light-driven reversible color changes, are used in real-time holographic recording.
Single frequency lasers and efficient cladding-pumped lasers using YB3+-doped silica fibre
Authors: Dawes J. M. , Pask H. M. , Archambault J. L. , Townsend J. E. , Hanna D. C. , Reekie L. , Tropper A. C.
Published: February 2023

Yb3+-doped germanosilicate fibre has been demonstrated to be a versatile host for laser action at wavelengths from 1 to 1.2 μm.1 It can be pumped at wavelengths from 800-1064 nm, and the emission band extends from 970—1200 nm, including wavelengths of interest for specific applications, e.g., 1020 nm for pumping of 1.3 μm Pr3+-doped fibre amplifiers, 1140 nm for pumping of Tm3+-doped fluoride fibre upconversion lasers, and 1083 nm for optical pumping of 3He.
Shallow trap modelling of infrared sensitive BaTiO3
Authors: Ross Graeme W. , Jeffrey Philip M. , Eason Robert W. , Damzen Mike J. , Ramos-Garcia Reuben , Troth Roger , Garrett Mark H. , Rytz Daniel
Published: February 2023

Recent interest in photorefractive BaTiO3 has turned toward near infrared wavelengths compatible with solid-state laser diodes. The demonstration of applications, such as diode injection locking and brightness enhancement1 in this region of the spectrum using modest laser powers has renewed interest in the ferroelectric material.
Time-resolved piezoelectric nonlinearities and exciton dynamics in strained [111] p-i-n multiple quantum well structures
Authors: Harken D. R. , Huang X. R. , McCallum D. S. , Smirl A. L. , Sánchez-Rojas J. L. , Sacedón Arthur , Muñoz E. , Calleja E.
Published: February 2023

We report the first time-resolved measurement of the optical nonlinearity formation and of the carrier dynamics in strained piezoelectric multiple quantum wells (MQWs). Strained, [111]-oriented MQWs are attractive for novel optical and electronic device applications1,2 because they contain large, built-in piezoelectric fields. Exploitation of these materials will depend on a detailed knowledge of the dynamics of photogenerated carriers. In the ultrafast optical experiments that have been performed to date, the shot-to-shot accumulation of carriers, which are long-lived because they are spatially separated at the ends of the MQW structure, has prevented the time resolution of the piezoelectric nonlinearity formation and the elucidation of carrier dynamics.3
Two-photon absorption semiconductor waveguide autocorrelators for ultrashort pulse measurements
Authors: Barrow David A. , Laughton Frances R. , Karkhanehchi M. Mehdi , Marsh John H.
Published: February 2023

A conventional autocorrelator consists of a Michelson interferometer, which splits an incident train of laser pulses into two paths. Both beams are then combined in a second-harmonic generating crystal and the pulsewidth is obtained by measuring the intensity of the second-harmonic generated (SHG) light as a function of the time delay between the two beams.
A new CW self-mode-locked Cr:LiSrGaF femtosecond laser
Authors: Sorokina I. T. , Sorokin E. , Wintner E. , Cassanho A. , Jenssen H. P.
Published: February 2023

Researchers nowadays pay increased attention to the development of compact ultrashort-pulse lasers (i.e., all-solid-state and with minimum intercavity elements).
Photorefractive materials and applications
Authors: Buse K. , Krätzig E.
Published: February 2023

Tailoring of photorefractive crystals and optimization for certain applications requires detailed knowledge on microscopic origins of the photorefractive effect. Illumination generates movable charge carriers that migrate in the crystal and are trapped at different sites; a charge redistribution happens and a space charge field appears that modulates the refractive index via the electrooptic effect. For transition metal doped LiNbO3 and moderate light intensities sources and traps of the charge carriers have been identified, e.g., Fe2+ and Fe3+ ions in LiNbO3:Fe. However, up to now in many important photorefractive materials, e.g., in BaTiO3, KNbO3, Sr1-xBaxNb2O6 (SBN), KTa1-xNbxO3 (KTN) and Bi12TiO20 (BTO), the photorefractive centers are not known. Several experimental hints (light-induced absorption changes, nonlinear dependence of photoconductivity on light intensity, dark buildup of holograms, activation of crystals for infrared recording by green illumination, transient dark conductivity phenomena) indicate that at least two different interacting centers contribute simultaneously, each of them occurring in different valence states.
Nondestructive testing with TV-holography and shearography
Authors: Ettemeyer A. , Honlet M.
Published: February 2023

New materials and components can only be certified as good as long as their quality can be checked. Therefore it is of main importance that the development of techniques for nondestructive testing (NDT) can keep pace with the development of new materials. Holographic and shearographic measuring techniques are well suited for NDT purposes of new materials. These techniques offer big advantages, especially for the inspection of composite materials and geometrically complicated structures.