bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient intracavity frequency doubling of a passively modelocked diode-pumped Nd:LSB laser
Authors: Braun B. , Hönninger C. , Zhang G. , Keller U. , Heine F. , Kellner T. , Huber G.
Published: February 2023

We report for the first time a stable and simple method for intracavity frequency doubling of a solid-state laser passively modelocked by using a low-finesse antiresonant Fabry-Perot saturable absorber (A-FPSA [1]). With a Neodymium-Lanthanum-Scandium-Borate laser (Nd:LSB) as gain material and a beta-Barium-Borate (β-BBO) nonlinear crystal with type I phase matching, we achieved a conversion efficiency of 48% resulting in 190 mW output power of TEM00 green light at modest pump powers of 1.2 W. Intracavity frequency doubling is favourable for the low to intermediate power regime, where the typical peak intensities of the output beam are not sufficient to obtain high single pass nonlinear frequency conversion efficiencies. But random noise fluctuations in cw intracavity requency doubled lasers, caused by nonlinear coupling between the laser modes and referred to as the green problem [2], made these lasers inappropriate for many applications. This problem can be overcome with a ring laser approach, where 780 mW of green light at a pump power of 4 W could be shown [3], by the use of additional intracavity elements, which make the laser rather complex and critical to operate, or with the use of an external resonator, where up to 200 mW of green light were produced at a diode pump power of 1 W, but which requires electronic frequency locking elements [4], Another possibility to obtain stable output are modelocking techniques, which lock all longitudinal modes together in phase. We describe an all solid-state, completely passive approach for intracavity frequency doubling of a solid-state laser, which is stable, non critical to align, and does not require any electronic control elements.
Efficient blue light generation by frequency doubling and sum-frequency mixing of laser diodes in KnbO3
Authors: Fluck D. , Günter P.
Published: February 2023

Direct second-harmonic and sum-frequency generation (SHG, SFG) with near infrared semiconductor laser diodes (LDs) offers the possibility of robust, compact and reliable blue lasers. KNbO3 crystals are very attractive for frequency conversion of near infrared DLs into the blue spectral range due to its high nonlinear optical coefficients, its favourable noncritical phase-matching (PM) configurations, and the absence of any optical damage and gray tracking effects for cw blue power levels of up to 200 mW1. Efficient blue light generation at 430 nm and 490 nm by noncritical type I PM SHG with LDs in KNbO3 has been reported for single-pass2,3, resonant4,5, and waveguide configurations6. Other wavelengths in the 415 to 475 nm spectral range can be efficiently generated by making use of the nonlinear optical coefficient d32 of KNbO3 for noncritical type I PM SFG with commercially available single-mode AlGalnP, AlGaAs and InGaAs laser diodes.
Laser-diode Pumped Intracavity Frequency Doubled Nd:YLF-laser at 455nm
Authors: Kellner T. , Heine F. , Huber G.
Published: February 2023

The development of an all-solid-state coherent blue light source is an widely investigated topic nowadays, especially for applications in the display technology. One possibility to realize such a light source is the intracavity frequency doubling of neodymium doped laser crystals at the ground-state transition1,2. In Nd:YLF the laser transition from the 4F3/2- to the 4I9/2- -manifold is at 910nm (Eω ┴ c). This yields in a frequency doubled radiation of 455nm, which is a suitable wavelength for display technology A 1.8mm long Nd:YLF crystal with a dopant concentration of 1% was used in the experiments. The laser crystal high reflection coated at the fundamental wavelength was pumped by a fiber-coupled 10W laser diode at 792nm Nd:YLF posesses a strong absorption for E||c at 792nm. The pump radiation was unpolarized, so that only 47% of the available pump power was absorbed. The laser crystal was mounted on a Peltier-cooler to achieve efficient cooling. Efficient cooling is important to prevent excessive reabsorption losses caused by the thermal population of the lower laser level To reduce the thermal loading of the crystal the laser diode was operated in a quasi cw-mode (50% duty-cycle). A maximum output power of 620mW with a slope efficiency of 17.3% was achieved in a nearly confocal linear resonator with a 0.7% output coupler (Fig. 1)
Ion-Implanted KNbO3 Channel Waveguides for Efficient Blue Light Second-Harmonic Generation
Authors: Pliska Tomas , Fluck Daniel , Günter Peter , Beckers Lutz , Buchal Christoph
Published: February 2023

Frequency doubling of near infrared diode lasers in channel waveguides offers the potential of robust, compact and reliable blue laser sources. Potassium niobate (KNbO3) is one of the most promising materials for blue and green light second-harmonic generation (SHG) thanks to its high nonlinear-optical susceptibilities and favourable phase-matching properties [1].
Beam quality improvement of transversally diode-pumped Nd:YAG lasers by additional longitudinal pumping
Authors: Muller Nicolas G. , Weber Rudolf , Weber Heinz P.
Published: February 2023

In this work, additional relatively weak longitudinal pumping was used to improve the beam quality of a transversally diode-pumped Nd: YAG laser
Comparative Response Times of Space-Charge Field and Reorientational Enhancement in Highly Diffractive Photorefractive Polymers
Authors: Cox A. M. , Blackburn R. D. , Shakos J. D. , Wade F. A. , West D. P. , King T. A.
Published: February 2023

All presently reported photorefractive polymer composites of high efficiency rely on the orientational enhancement mechanism. We have identified conditions in which the speed of re-orientational response is the limiting factor in holographic diffraction efficiency rise-times, not the dynamics of the space-charge field.
Improved photorefractive response in ZnTe through co-doping with vanadium and manganese
Authors: Brost George , Trivedi S.B. , Jagnnathan G.V. , Schwartz R.N.
Published: February 2023

ZnTe has the potential to be an outstanding photorefractive material. In earlier work(1) it was found that incorporation of vanadium in vapor grown ZnTe was very difficult. Even when vanadium was incorporated as an active impurity the doping usually was not uniform. In this paper we report on improved photorefractive response in ZnTe through co-doping with vanadium and manganese.
Active Media for Up-conversion and Multi-Wavelength Solid State Lasers
Authors: Tkachuk A. M.
Published: February 2023

Rapid improvement of high power red and IR laser diodes induced new interest in the search for new materials and optimization of the known rare-earth doped crystals which are promising for lasing in a wide spectral range from UV to IR under laser diode (LD) and lamp pumping.
Application of Photoinduced Long-Period Fiber Gratings in Optical Sensors
Authors: Dianov E.M. , Kurkov A.S. , Medvedkov O.I. , Vasiliev S.A.
Published: February 2023

At present the photoinduced in-fiber Bragg gratings are widely used as a sensitive element of optical fiber sensors. Their operation is based on the vanation of the reflection peak under an outer action. The sensitivity of silica glass to variations of temperature or applied strain is very small, therefore the operation of sensors based on the Bragg gratings are possible only due to the narrowness of the reflection peak. We propose to apply die pholoinduced long-period cladding-mode-coupled fiber grating as a sensitive element of optical fiber sensors The sensitivity of this type of the grating can be increased by its loading in an additional medium.
Midwave Two-Wavelength Radiation from Tunable InAsSb(InAs)/InAsSbP DH Diode Lasers
Authors: Zotova N.V. , Karandashov S.A , Matveev B.A , Stus’ N.M. , Talalakin G.N.
Published: February 2023

Mid-IR diode lasers emitting in the 3-4 pm region where most of the gases have absorption bands can be used for gas spectroscopy and fibre optic sensors. Electro- and photoluminescence of the InAs/InAsSbP and InAsSb/InAsSbP double heterostructures (DH) have been studied and mechanisms of radiative recombination in DH lasers operating at 4.2180 K in the 3-3.6 µm spectral range including their temperature and current tunability are discussed.
Correction of segmented mirror aberrations by phase conjugation and dynamic holography
Authors: Bogdanov M.P. , Dimakov S.A. , Gorlanov A.V. , Goryachkin D.A. , Grigor'ev A.M. , Irtuganov V.M. , Kalinin V.P. , Kliment’ev S.I. , Kozlovskaya I.M. , Orlova I.B. , Sherstobitov V.E. , Venediktov V.Yu.
Published: February 2023

A problem of designing laser telescopic systems with the dynamic correction of distortions brought on by individual components (mainly, by the large-size primary mirror) is so far the issue of attention. Systems of such kind are typically employ a special diffraction structure on the surface of optical element to be corrected thus providing nonreciprocal propagation of the beams in a system incorporating a phase conjugate mirror as well.
Investigation into the Modulation and Duty Cycle Effects in Al-Alloy Welding with High Power Nd-YAG Laser
Authors: Kathuria OY P , Tsuboi Akihiko
Published: February 2023

An experimental study has been undertaken for the weldability of Al-alloy A5052-HR32 using the modulation effect to overcome the cracking problem. The experiments were carried out with a multiwave Nd-YAG laser of which power could be varied from CW to pulse mode with square and sine wave modulation function. The samples ranging in thickness from 1 mm to 2mm were bead on plate, butt and lap welded. For the efficient coupling and to prevent the back reflection into the cavity, the incident beam angle was set at 10 degrees to the normal (Fig.1). A cross flow nozzle was used against the spattering and to suppress the plasma plume, thus enhancing the penetration depth. The shielding gas, argon was applied in the front, back and bottom groove of the fixture so as to shield the hot newly soldified weld metal as it emerges from the laser beam. The result indicate that because of high solidification rate, a very fine dendritic microstructure is developed in the fusion zone (Fig.2). Besides that microstructural characterization of the weldment revealed urn order porosity that occured in the welded region. The level of cracks and porosity in the high duty cycle welds were significantly less than that encountered in the low duty cycle weldment. Whereas the microhardness data result indicate that the weld metal and the heat affected zone were as hard as the base metal.
High Speed Uncooled Photoconductive Detectors Based on Doped Thin Insb/Al2o3 Layers
Authors: Padalko A.G. , Shevchenko V.YA. , Pashkova O.N. , Perry F.S.
Published: February 2023

Opportunity of standard photolithography using has led to creation of photoconductive detectors with labyrinth layout, which have an impedance up to tens of kOhms at 300 K, with some advantages under direct matching to preamplifier curcuits without transformers. So that doping is the .most important technique of photoelectric parameters improving of such type devices, the purpose of present work is understandable.
Recent progress on high power laser diode arrays at THOMSON-CSF Composants Specifiques (TCS)
Authors: Hirtz J.P. , Fillardet T. , Marquebielle G. , Vassilakis E. , Duchemin J.P. , Volluet G.
Published: February 2023

THOMSON-CSF Components spécifiques (TCS) has recently developped a set of products of high power Laser diodes, covering CW & QCW linear bar arrays emitting at 808 nm and 980 nm, fiber-coupled CW bar arrays, stacks with passive and active coolings, and more recently high brightness autostacks structures delivering up to10 KW/ cm2.
Industrial fast flow coaxial high power CO2-laser
Authors: Bohrer Markus , Schuöcker Dieter , Basalka Heinz
Published: February 2023

Due to the fact that there is a need in the industry for compact and reliable laser sources with high beam power, the demands for efficiency and stability have to be input factors for the design process, as well as high output power and good beam quality. Hence a new coaxial CO2 laser with fast axial gas flow, which satisfies all these requirements, has been developed and realised at the Technical University of Vienna in cooperation with an Austrian company. After two years of design and development, output powers up to 7 kW and diameters of the focused beam down to 300µm could be achieved with one single module. Besides the availability of new and improved mirrors and an ultra strong turboblower, the simplicity of this laser concept made it possible to build up a size-reduced and cost saving industrial laser device. However due to the high RF power input of 5*104 W in a small spatially limited coaxial discharge volume, a lot of mechanical, optical and thermodynamical investigations for the improvement of RF-matching, plasma performance and resonator stability have been necessary. In detail a very accurate thermodynamical analysis has been carried out. Numerical evaluation of the resonator has proved necessary to provide operation stability and satisfactory beam quality for industrial applications.
Laser-Diode Pumped High Average Power Nd:YAG Green Laser
Authors: Oba Masaki , Maruyama Yoichiro , Kato Masaaki , Muramatu Toshiaki , Arisaw Takashi
Published: February 2023

For the pumping of tunable lasers such as Ti:Al2O3 and dye lasers, the second harmonic of a LD-pumped Nd:YAG laser is a very attractive pump source because of the its high repetition rate, high beam quality, compactness, reliability, etc. We have been charring out the research and development of LD-pumped high average power Nd:YAG green laser for the pumping of the tunable laser.
Laser Radiation as Universal Stimulus for Skin Receptions
Authors: Nemenov Michael I. , Vekshin Aleksei A. , Tsimlnikov Efim M.
Published: February 2023

The role of skin reception in human life activity is great. Unlike the case with hearing and sight, the loss of skin sensations is life-threatening. However, until recently there were no suitable methods and instruments for investigation of dynamic and threshold properties of skin reception.
Polarisation Effects in the Electroluminescence and the Electroabsorption of Ordered GalnP Layers
Authors: Greger E. , Gulden K.H. , Schweizer H.P. , Moser M. , Schmiedel G. , Kiesel P. , Döhler G.H.
Published: February 2023

Under certain growth conditions GalnP tends to exhibit spontaneous superlattice ordering with atoms arranging in GaP/lnP monolayers along two of the possible four [111] crystal directions. The superlattice ordering leads to significant changes in the electrical and optical properties of the crystal most prominently decreasing the energy band gap. In ordered material optical transitions between the highest valence band and the conduction band are not allowed for polarisation parallel to the ordering directions. In order to demonstrate the potential device applications of this polarisation effect we have studied the electroluminescence (EL) and the electroabsorption of (Al0.3Ga0.7)0.52In0 48/Ga0 52ln0.48P p-i-n double hetero structures. Samples with ordered (o-samples) and disordered (d-samples) GalnP active layers have been grown lattice matched to GaAs by metal organic vapour phase epitaxy (MOVPE). The o-samples were grown at 650°C on exactly oriented GaAs substrates while for the d-samples a growth temperature of 710°C and 6° toward [111A] tilted substrates have been used. Moreover, thermal disordering of the o- samples was achieved by rapid thermal annealing (RTA) at 900°C for 30 sec after growth (a-samples). This technique allows to compare ordered and disordered material made from the same epitaxial wafer. Surface emitting light emitting diodes (LED) with chemically dry etched mesas have been fabricated. The EL spectra of o- and a-LED show peaks at 673 nm and 650 nm respectively. This corresponds to an energy shift of 65 meV and is in very good agreement with PL measurements. The a-samples exhibit a significantly decreased EL-efficiency compared to the o-LED which can be explained by damage caused by RTA. Polarisation measurements of o-LEDs exhibit a contrast of 1.4 dB between polarisation parallel to the

[

01

1
¯

]

and [011] crystal direction respectively. This effect is nearly independent of diode current and mesa geometry, but not observed for a-LEDs. This lifted degeneracy of polarisation states associated with the ordered GalnP phase has to be considered as a very promising feature for polarisation control in VCSELs.
Picosecond and Femtosecond Travelling-Wave Parametric Lasers: Tuning from UV to Mid-IR
Authors: Danielius R.
Published: February 2023

Summary not available.
Highly Efficient UV-Generation from a 1 kHz Diode-Pumped Solid-State Laser System
Authors: Stamm U. , Zschocke W. , Deutsch N. , Schröder T. , Basting D.
Published: February 2023

By frequency-quadrupling the output of a nanosecond Q-switched diode-pumped Nd:YAG laser average powers of 2.2 W have been generated at 266 nm. The conversion efficiency 1064 nm to 266 nm is 22 %.
Noncritically phase-matched KTP optical parametric oscillator with near diffraction limited signal beam
Authors: Dubois Arnaud , Lépine Thierry , Georges Patrick , Brun Alain
Published: February 2023

Optical parametric oscillators (OPO’s) are of particular interests to produce radiations in the mid-infrared [1]. Nevertheless, output beams with high qualities seem to be difficult to obtain together with high average powers [2].
Er Doped Active Waveguide Films Prepared by in-Situ Doping During Pulsed Laser Deposition
Authors: Afonso C.N. , Serna R. , Ballesteros J. M. , Zschocke A. , Polman A.
Published: February 2023

Optically active thin films have many potential applications as waveguide lasers and amplifiers. Since the recent development of the Er doped fiber amplifier for telecommunications, there has been an intense research activity in the production of Er doped active waveguides for operation at 1.5 µm. The most common approaches to produce waveguides are ion exchange, in-diffusion or ion implantation which require a two step process and produce a non uniform doping profile. This work reports on the successful growth of in-situ Er doped active films with a step dopant profile by pulsed laser deposition. A comparison between two different approaches is presented which involve the use of a single doped target or two targets (one for the matrix and one for the dopant) which are alternatively ablated.
Dynamic Holography: Applications in Information Processing
Authors: Vainos N. A.
Published: February 2023

All optical methods still represent, an attractive alternative for providing solutions in information storage and processing capacity problems in the long term. However materials requirements are becoming very strict for such methods to compete with current electronics, pushing the integration of all optical technology even further in the far future. Holographic methods represent the shorter term exploitable means in the field, in particular where applied, not in their passive but, in their dynamic form.
Spectropolarization Characteristics of Optical Radiation Reflected by the City Tree Leaves Grown in Different Conditions
Authors: Atrashevsky Yu.I. , Shuplyak V.I. , Sikorsky V.V. , Stelmakh G.F.
Published: February 2023

This work is development of spectropolarization nephelometry technique which allows to investigate the most essential mechanisms of formation of radiation flux reflected by the plant leaf: the specular reflection on the leaf surface, the singly and multiply scattering on intraleaf structure elements, the chlorophyll molecular absorption, and the cuticle refraction of radiation going out from the leaf. It was found that the polarization characteristics are more sensitive to the changes of plant structure as compared with the traditionally measured bidirectional reflectance factors. A spectral shift of a maximum of the polarization degree angular function have been discovered and theoretically substantiated.
Influence of Potato Leaves Variety on the Spectropolarization Characteristics of Leaf Reflected Radiation
Authors: Belyaev B.I. , Belyaev Yu. V. , Chumakov A.V. , Kurikina T.M. , Nekrasov V.P. , Shuplyak V.I.
Published: February 2023

Studies of the spectropolarization characteristics angular dependencies of radiation reflected by the plant leaves allow to investigate the mechanisms of reflected radiation flux formation: the specular reflection on the leaf surface, the singly and multiply scattering within leaf, the leaf pigment absorption, and the cuticle refraction of radiation going out from the leaf. The polarization characteristics are most sensitive to the changes of plant structure as compared with the other factors. We have discovered and theoretically substantiated a spectral shift of a maximum of the polarization degree angular dependence.
Two- and four-wave mixing in iron-doped BaTiO3 by grating recorded via orthogonally polarized waves
Authors: Jullien P. , Mathey P. , Lompre P. , Novikov A. , Odoulov S.
Published: February 2023

The coupling of two orthogonally polarized waves, one ordinary and other extraordinary, because of the recording of a grating by spatially oscillating photovoltaic current is studied in iron-doped BaTiO3 crystals.
Gas Lasers with the Phase Conjugation
Authors: Kulikov S.M.
Published: February 2023

A review is presented of researches carried out at Institute of Experimental Physics (Russian Federal Nuclear Center) on creation iodine (wave length 1.315 mcm) and chemical lasers (wave lengths 2.5-4.2 mcm) with SBS - mirrors since 1973. We investigate the operation of the lasers with phase conjugation (PC) for free running mode (pulse duration 1-100 mcs) and Q - switch mode (pulse duration 0.5 -5ns). The competition of the "useful” PC Stokes radiation generation and the "parasitic" generation at the laser transition central frequency at multistage lasers with the high (10^6) gain was studied. We are investigating PC in a wide range of wave lengths. SBS and PC was obtained for wave length up to 4.2 mcm and for radiation with the spectrum width near 700 1/cm. Processes competing with SBS and the methods to suppress them were investigated.
Statistical Criterion for Speckle Averaging
Authors: Sadi John , Vukicevic Dalibor
Published: February 2023

Both coherent optical processing and holographic data storage systems, as well as SAR, ultrasound and endoscopic holography imaging suffer from loss of data due to speckle. This can't be overcome easily, so it is usually averaged out without the use of a proper criterion giving the number of speckled images to multiplex. Young proposed a coherent resolution criterion for a single image [1] while another one was given by us for multiple images [2], based on contrast considerations. Here we provide a new one. dealing with intensity statistics.
InSb Diode Lasers at 5μm Grown by MBE
Authors: Ashley T
Published: February 2023

Semiconductor laser diodes operating at visible and near infrared wavelengths have revolutionised electro- optic applications because of their small size, high spectral purity, high modulation frequency, ruggedness and long lifetime. There is considerable interest in longer wavelength devices operating in the mid-infrared for several applications, including remote detection of pollutant and toxic gases, general spectroscopy, eye- safe range finding and secure communications. There are several alternative material systems and device structures for lasers in the mid infrared band, including intersubband devices in GaInAs/AlInAs; strained or unstrained type II superlattices or quantum wells in several InAs based systems; and a variety of II-VI and IV-VI bulk or quantum well structures. We have chosen to develop lasers based on InSb, which is the only direct gap III-V system for wavelengths in excess of 4μm and for which very high quality epitaxial growth and fabrication techniques exist.
Active Medium of CO2 Laser Under Degenerate Four-Wave Mixing
Authors: Afanas'ev L. , Ionin A. , Klimachev Yu. , Kotkov A. , Seleznev L. , Sinitsyn D.
Published: February 2023

Degenerate four-wave mixing (DFWM) and phase conjugation (PC) of pulsed CO2 laser radiation inside its own laser medium were studied experimentally. The operational mode of the e-beam controlled discharge CO2 laser has been chosen in such a way (CO2:N2:He gas mixture, p=0.1 -0.56 atm, tin=30 μs) that the laser pulse length (τout~10 - 20 μs) is comparable with the relaxation time of the upper laser level (τrel~l5 - 30 μs). The interaction length of DFWM was about 100 cm.
Continuous-wave mode-locked AgGaSe2 optical parametric oscillator tunable from 4 to 8 μm
Authors: Grässer Ch. , Marzenell S. , Beigang R. , Wallenstein R.
Published: February 2023

Synchronously pumped optical parametric oscillators (OPOs) using AgGaSe2 are well suited for the generation of high power ps and fs light pulses in the mid infrared region up to 12 μm1. In this contribution we report on the characterization of a AgGaSe2-OPO pumped by a Nd:YLF laser pumped KTP-OPO at 1.55 μm.
Atmospheric Pollution Measurements by DIAL
Authors: Milton Martin
Published: February 2023

Atmospheric remote sensing is one of the most challenging application areas for new laser sources. Amongst the most widely-used techniques in this area is Differential Adsorption Lidar (DIAL) which uses repetitively pulsed narrow bandwidth lasers to make range-resolved measurements of species in the atmosphere. The most widely- used applications of DIAL use ultraviolet and visible lasers to measure a limited range of species, including ozone,sulphur dioxide, the oxides of nitrogen, toluene and benzene. More recently the applications of DIAL have increased significantly with the availability of tunable high-powered infrared laser sources including OPO's. DIAL measurements in the infrared including methane, propane, hydrogen chloride, hydrogen sulphide and hydrogen fluoride.
Influence of the resonator mirrors thermal deformation on mode structure of radiation of the laser.
Authors: Kaptsov L.N. , Kudryashov A.V. , Rostovtsev A.V.
Published: February 2023

One of the important problems in laser design is receiving a laser radiation, correspond to fundamental mode TEM00 of resonator. Different effects prevents formation of such radiation. One of them is heating of laser resonator mirrors under action of radiation. At heating, the mirrors are deformed and a configuration of the resonator and also mode structure of radiation changes.
New Developments in High Average Power, Intra-cavity Frequency Doubled Nd:YAG Lasers
Authors: Thro P. Y. , Le Garrec B. , Razé G.
Published: February 2023

High average power, intra-cavity frequency doubled Nd: YAG lasers at high repetition rates are of considerable interest for pumping Ti: Sapphire and dye lasers or OPOs. Due to the quality improvement of doubling crystals and optimization on the cavity parameters, reliable 100 Watts of green radiation are now reachable.
A cw tunable infrared spectrometer based on the difference frequency generation in AgGaS2 and the application for trace gas detection and line broadening investigations in the 5 µm region
Authors: Kelz T. , Nägele M. , Basar G. , Sumpf B. , Kronfeldt H.-D.
Published: February 2023

A cw tunable spectrometer based on the difference frequency generation (DFG) using the nonlinear crystal AgGaS2 (1 = 40 mm, non-critical type 1 phase matching) and two diode lasers was constructed. With this system we are able to cover the wavenumber region around 2050 - 2150 cm-1. In this region molecular gases like CO, N2O and NO have pronounced absorption lines excluding interferencies from other atmospheric gases. With diode lasers as pump source (690 and 810 nm) we arc able to detect this trace gases as well as to measure line broadening coefficients and spacing of several NO-doublets
High Speed Two Dimensional Bar Code Detection System
Authors: Wakaumi Hiroo , Ajiki Hiroshi
Published: February 2023

A high speed two dimensional (2D) bar-code detection system (BCDS) with two visible-light laser diodes (LDs) driven by a complementary light emission (CLE) method and by a pulse modulation one with bias current (PMBC), has been newly developed to realize highspeed scanning. The CLE method enables a high effective scanning speed, while still retaining the size of the 2D BCDS small. And also, the PMBC method enables a high-frequency drive of LDs, that is. high-speed scanning. This paper experimentarily demonstrates the effectiveness of these CLE and PMBC drive methods.
Corrosion Resistance Improvements of Metallic Alloys Using One-Step Excimer Laser Treatment
Authors: Sarnet T. , Autric M.
Published: February 2023

This study concerns the structural modifications of metallic alloys such as aluminum alloys, titanium alloys and steels in order to improve their mechanical and physic-chemical properties. These modifications induce changes in the lifetime of these metallic samples as far as the corrosion resistance is concerned. Effects have been studied as a function of incident energy density, overlapping, number of pulses using a KrF excimer laser (20 ns; 80 W; 248 nm). Structural modifications analysed by low-incidence X-ray diffraction have been observed for all materials with micro and nano-structures formation due to the high values of the cooling rate (>108 K.s−1). The most interesting structures were, for instance, the titanium Ti6Al4V (α+β) which after processing becomes a fine lath martensitic structure which has a thickness of approximately of 250 nm, and also steel 35NCD16 (ferrite+perlite) which is austenitic+martensitic after treatment. An investigation was carried out after scanning large surfaces into corrosion resistance of these metallic materials. Electrochemical tests -anodic polarisation- revealed a significant increase in the resistance to pitting of the aluminum alloys. This improvement is due to the dissolution of khatyrkite phase in the matrix leading to a redistribution of the copper atoms within the melted layer (few microns). On the other hand, 2017A aluminum can be slightly softened by the processing. In the opposite, for other materials a hardening can occur. This hardening can be weak and due to a simple grain refinement, as is the case for the 1050A aluminum. This hardening is significant when treating the Ti6A14V titanium and even more so for the 35NCD16 steel which goes from 250HV to almost 1000HV, which is impossible to obtain with classic thermal processes. In the case of 35NCD16 steel samples, the gain in the corrosion resistance is due to change in the structure and due to a galvanic coupling between the irradiated and the non irradiated zones.
Nonlinear Dynamics in InGaAs/InP Quantum-Well Waveguides
Authors: Coriasso C. , Cacciatore C. , Campi D. , Stano A. , Rigo C. , Faustmi L. , Leo G.
Published: February 2023

Optical nonlinearities, induced by carrier photogeneration, in multiple-quantum well structures attract much attention due to both potential applications and fundamental reasons In particular, the quantum wells based on III-V semiconductors are relevant to the realization of optically-controlled waveguiding devices for telecommunication applications, operating at wavelengths longer than the absorption threshold. The knowledge of the nonlinear optical properties in that spectral region is far from being complete and we will address here some critical issues of the dynamical nonlinear behaviors related to the underlying microscopical properties.
Corona-Wind Electro-Reagent Spectroscopy
Authors: Johnson Mark
Published: February 2023

Ultraviolet (UV) spectroscopy is an attractive detection technique for organics and other species in environmental water samples because of its potential for contactless measurement, and because of the low absorption of pure water. However, the low absolute absorptions of ppm-concentrations are difficult to resolve in the presence of high absorptions from a wide variety of benign species, such as the nitrate ion. Hence selectivity is the real problem.
Novel Aligned Composite Thin-Films For Second Harmonic Generation
Authors: Hameed-Muhammed M. S. , Seddon K. R.
Published: February 2023

A complete and fully computerised Temperature-Gradient Zone-Melting (TGZM) device was designed and built, in order to produce novel aligned NLO crystals as composite thin-films. This apparatus consists of two aluminium blocks (hot and cold) separated by glass-ceramic thermally insulating layer (1 mm thickness). The hot block was connected to a heater and was computer-controlled via temperature controller using special software assembled for this purpose. On the other hand the cooling system (cold side) was made of circulating water. Crystal growth from melt can be performed by melting NLO powdered compound on a glass slide and then drawn to the cold side via glass-ceramic sample holder using a computer-controlled motor with similar software mentioned earlier.
Low voltage high contrast n-i-p-i based waveguide modulator
Authors: Windisch R. , Kneissl M. , Kiesel P. , Döhler G.H.
Published: February 2023

We have investigated an electroabsorptive n-i-p-i waveguide modulator based on the Franz-Keldysh effect (FKE) especially designed to operate with very low voltages. This is particularly interesting for high speed modulation and applications requiring integration with CMOS technology. The modulator operates at photon energies below the bandgap, and therefore the on-state absorption losses are very low. By applying a voltage between selective contacts to the n-t-p-i structure, the internal field can be changed within a wide range Due to the FKE an increase of the electric field leads to an increase of the absorption coefficient below the bandgap As the interaction length in a waveguide modulator is in the order of several hundred microns, absorption changes of a few 100cm−1 are sufficient to achieve contrast ratios of several orders of magnitude. In addition, the absorption changes due to the FKE extend over a broad wavelength range, which gives a good stability against thermal wavelength detuning and is also important for multiwavelength operation.
Metal-semiconductor-metal-modulator structures based on electroabsorption in low temperature grown (Al)GaAs
Authors: Tautz S. , Dankowski S.U. , Ruff M. , Streb D. , Kiesel P. , Kneissl M. , Keil U.D. , Döhler G. H.
Published: February 2023

GaAs and AlGaAs grown by molecular beam epitaxy at low substrate temperatures of about 200°C (LT-(Al)GaAs) are known to posses attractive electrical and optica] properties. After annealing at higher temperatures (~ 600°C) these materials exhibit a high specific resistance up to 107Ωcm for LT-GaAs and up to 1012Ωcm for LT-AlGaAs. This results in high breakdown fields (5 105 Vcm−1) which are very appealing for fast modulator and detector structures, especially in combination with ultra short photoexcited carrier lifetimes in the sub-picosecond range.
On The Diffraction of Non-Paraxial Light Beams
Authors: Kozlov Sergey A. , Simovski Constantin R.
Published: February 2023

In the theoretical analysis of the light modes in optical resonators and laser beam propagation in a homogeneous medium the low-angle diffraction approximation is usually applied (see, for example, Kogelnic H.,Li T., Laser Beams and Resonators, Appl. Optics, 1966, v. 5, No. 10, p. 1550-1567). However, there exist some problems in which this approach is not valid, for example, ones concerning sharply focused wave beams, because they are not paraxial.
Bose-Einstein Condensation
Authors: Walraven J.T.M. , Waals Van der
Published: February 2023

As was shown by Einstein in 1924, Bose-Einstein statistics gives rise to a phase transition in which a macroscopic part of a gaseous state condenses into a phase with ground state properties, offering a unique view on the behavior of matter at zero temperature. From the very start the nature of Bose-Einstein condensation (BEC) has provoked statements concerning its relation with respect to superconductivity in electron gases (Einstein 1925) and the superfluidity of liquid helium (London 1938), but this connection is not easily grasped experimentally. Remarkably, although the concept of BEC appears routinely in very different contexts, ranging from excitons in semiconductors to nuclear matter, it had never been observed in its pure form, i.e., in a gaseous phase, until in 1995 BEC in ultracold Rb vapor was reported by Cornell and Wieman. Bose-Einstein condensation is probably the most exciting phenomenon currently under experimental investigation in ultracold atomic gases. In the tutorial the physics will be addressed which is at the roots of the current interest of BEC in atomic gases.
Compact Nd:YAG optical amplifier for intersatellite coherent communication
Authors: Graf Th. , Roth U. , Balmer J. E. , Weber H. P.
Published: February 2023

Free-space coherent communications systems require high efficiencies, output powers of about 1 W or more, and a phase modulation bandwidth of at least 1 GHz. Furthermore, spaceborne applications should exhibit exceptional ruggedness while maintaining a small package and simple thermal management. We present three different variants of a novel diode laser-pumped Nd:YAG amplifier that was designed to amplify the phase modulated beam of intersatellite optical links. The amplification, saturation, and noise properties as well as the thermally induced distortions are discussed.
Novel unambiguous interferometric technique for surface inspection
Authors: Lesso J. P. , Duncan A.J. , Sibbett W. , Padgett M. J.
Published: February 2023

We describe a new interferometric technique using polarisation measurements which eliminates the need to count fringes, giving an unambiguous measurement of surface height. Applicable to the whole image, the height of each pixel element is determined independently without the need for scanning optical components. The technique is based on analysis of the polarisation state of the light reflected from the surface following its interference with an orthogonally polarised reference beam. We have demonstrated its viability by imaging the surface of a processed silicon wafer, identifying the heights of various layers even though separated by many optical wavelengths.
Holography with crystals grown from aqueous solution
Authors: Rupp R. A. , Woike Th. , Fally M. , Imlau M. , Haussühl E. , Fink M. , Tillmanns E.
Published: February 2023

While there is already an overwhelming amount of literature on photorefractive oxide crystals, only few reports have been written on photorefractive crystals grown from aqueous solution. Recently, we reported on the nitroprusside Na2[Fe(CN)5NO]H2O which exhibits remarkable photorefractive properties in the red and near-infrared spectral range: The light-induced refractive-index changes attain values up to 1 × 10−3(633 nm) and 5×10−4(1047 nm). Such high refractive-index changes are however, like in LiNbO3 connected with strong holographic scattering. Because holographic gratings can also be written with orthogonal polarisation, also anisotropic holographic scattering phenomena can be observed.
2 µm Ho: YLF active mirror laser
Authors: Nikitichev A.A. , Kornev A.F. , Stupnikov V.K.
Published: February 2023

The use of quasi-two-level laser medium in active mirror configuration seems to be the prospective approach to realisation of the high-power solid-state lasers. This approach was successfully applied to realisation of the diode pumped Yb:YAG laser. The low Stokes shift, thin active layer and longitudinal with respect to laser radiation thermal gradient provide the high specific generation power (3 kW/cm2) with high quality of radiation.
Measurement and Virtual Elimination of Acoustically Induced Penalty in the Nonlinear Optical Loop Mirror
Authors: Olsson Bengt-Erik , Boyle Adrian , Andrekson Peter A.
Published: February 2023

One major problem when using the nonlinear optical loop mirror (NOLM) as an all-optical switch is that it is very sensitive to acoustic disturbances which affect the biasing condition due to changes in the propagation constant in the loop fibre. Since the two counter­propagating waves, in general, never are in the same physical location inside the fibre, they will experience different acoustical sound pressure and thus different refractive indices. This random change in refractive index gives rise to noise at the output of the NOLM which may seriously degrade the performance of the NOLM. This acoustic sensitivity becomes much stronger for long loop fibres and will in many cases limit the use of the device. This problem can, however, be virtually eliminated by spooling the fibre so the two counter-propagating signals always appear at about the same physical place along the fibre. Different winding geometries have previously been investigated to stabilize optical gyroscopes [1]. Here we demonstrate a winding technique where the fibre is folded and winded onto a drum starting with a bend from the middle and ending with both fibre ends on the outside of the drum.
Potassium Niobate and Lithium Niobate OPO's for Atmospheric Remote Sensing
Authors: Milton M J T , Wang J , Gardiner T D , Rytz D
Published: February 2023

Lithium Niobate has been the material of choice for OPO's used to generate mid infrared (2.5 to 4 μm) for atmospheric remote sensing by DIAL [1]. Such systems are capable of measuring a wide range of gaseous hydrocarbon species in the atmosphere. To a large extent the use of lithium niobate in theses OPO's has been a result of its widespread availability in large sizes and with good optical quality. Potassium niobate has always been a potential alternative which has the possible benefit of operating at longer wavelengths. Until recently, it has not been readily available in sizes or with the optical quality required for pulsed laser pumping. However, recent improvements in the growth and treatment of potassium niobate have made it a more realistic alternative.
Detection of airborne asbestos fibres using magnetic alignment and light scattering
Authors: Ulanowski Z. , Kaye P. H. , Hirst E.
Published: February 2023

The detection of respirable asbestos fibres in the ambient environment has grown in importance as the health risks associated with this material have become more fully understood. However, to date there is no satisfactory method of identifying airborne asbestos in-situ.
Remote Laser-Induced Breakdown Spectroscopy Using a Novel Single-fibre Arrangement
Authors: Beddows D.C.S. , Kondo H. , Morris G.W. , Telle H.H.
Published: February 2023

Increasingly Laser-induced Breakdown Spectroscopy (LIBS) is being exploited in qualitative and quantitative analysis of solid samples. While the technique has been around for a number of years the recent, rapid development in laser and detector technology have made it possible to implement the technique for use in real-time and remote analysis. In general, LIBS has been implemented by using pulses from a Nd:YAG laser for micro plasma generation, with the laser radiation transmitted in free air, and by collecting the plasma emission via an optical fibre.
Compact Photorefractive Sensors and Systems
Authors: Anderson D.
Published: February 2023

Summary not available.
Laser welding of magnetic materials
Authors: Seat Han C. , Watson Ian A.
Published: February 2023

Industrial sectors with interest in welding magnetic materials include the aerospace, electrical and defence industries [1]. The effects of CO2 laser welding and high temperatures (i.e. above the Curie temperature) on the magnetism of ferromagnetic materials were investigated. A 1.2 kW MFKP CO2 laser was used to weld the magnetic material at a constant power of 1 kW in the CW mode, for different welding translation velocities. Figure 1 shows a schematic of the magnetic field measurement system. This consisted of two orthogonal translation tables and an RS miniature Hall effect Sensor (HES), attached to an outlying platform from the larger translation table. The x-y motion was controlled via a microprocessor so that the HES was translated over the entire surface of the welded magnets (2 Alcomax magnets: 8% Al, 11.5% Ni, 21% Co, 4% Cu, Fe). The signal from the HES was signal conditioned and fed into a data acquisition card located in the PC. The magnetic field strength over the laser weld and surface of the specimen was measured before welding, immediately after welding and 3 days after welding. Figure 2 shows the spatial differences in the magnetic properties of the sample immediately after welding and Figure 3 the corresponding data 3 days after welding. The magnetisation of the weld pool and HAZ was reduced immediately after welding; 3 days later, during which the samples were isolated, magnetism recovered over the specimen except in the weld zone where it had been damaged and stayed unrecovered. A high translation velocity maximised the remagnetisation process and reduced the demagnetised zone and HAZ.
Guiding Effects in Nd:YVO4 Microchip Lasers
Authors: Kemp A. J. , Conroy R. S. , Friel G. J. , Sinclair B. D.
Published: February 2023

Microchip laser are monolithic devices typically consisting of a sub-millimetre thick slice of solid state gain material, which is polished to give plane parallel surfaces on to which dielectric mirrors are directly coated. These lasers are longitudinally pumped by a laser diode. Such devices are highly-efficient and compact lasers which produce beams of high spatial and spectral quality [1].
Single-mode diode-pumped micro-crystal laser continuously tuneable over 200 GHz in the visible spectral region
Authors: Kopylow Chr. v. , Hennecke M. , Pfeifer E. , Fuchs W , Bechstein K.-H.
Published: February 2023

Tuneable single-frequency lasers are decisive components of absolute distance interferometers for high-precision distance measuring without any ambiguity. Due to the noise they create, tuneable VIS diode lasers with an external resonator are no longer applied for measuring distances up to 100 m with acceptable measuring intervals of a few seconds. Therefore a tuneable single frequency VIS microcrystal laser, continuously tuneable over 200 GHz, was developed and tested as part of an interferometer. Nd-doped laser crystals were used for the laser and, by doubling the intracavity frequency with a KTP, a wavelength of 532 nm was reached The semi-monolithical arrangement was pumped longitudinally with a laser diode. In order to achieve a stable Single Longitudinal Mode Operation with Nd:YVO4- and Nd:LSB (NdxLa1-xSc3(BO3)4) crystals in a compact design, an Intracavity Solid State Etalon was implemented for the frequency selection This was achieved with an etalon with a Free Spectral Range of 1000 GHz and a reflectivity of 30 % for an Nd:YVO4 crystal with a thickness of 0,2 mm, that is, for an Nd:LSB crystal with a thickness of 0,3 mm at a reflectivity of 40 %. The selectivity was chosen in such a way that, due to the inertia of the homogeneously expanded medium, tuneable frequency regions of 60 GHz were shown with a stationary etalon only by changing the resonator length (see fig. 1). Scan rates of > 100 Hz were achieved in the interferometer set up by means of a sinus-formed external drive. The instantaneous frequency of the interference signal, identical with the instantaneous change of the laser frequency, follows the drive signal without delay (see fig. 2). This is of great importance for the driver electronics of the measuring system mentioned above. In order to achieve a tuneable frequency region of > 200 GHz, it was necessary to vary the etalon as well. It was the first time that a continuous variation over 240 GHz, i. e. covering half of the linewidth of the Nd:YVO4 crystal, were proved for a diode-pumped solid state laser. The tuning range was only limited by the mechanical resonator driver In principle it should be possible to vary over an even larger region using an Nd:LSB crystal with a greater linewidth that is with frequency doubling nearly 2000 GHz.
A Comparison of Deflective Q-Switches
Authors: Conroy R S , Kemp A , Friel G , Sinclair B D , Ley J
Published: February 2023

The use of electro-optic deflectors in high speed scanning systems is common place. Although suggested more than a decade ago, their use as active Q-switches has not previously been demonstrated [1], Two forms of deflector exist: one based on a prism of active material whose refractive angle varies with refractive index, and the other on shaped deflectors which give a linear refractive index gradient across the beam path [2].