bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous Color Contrast and Constancy
Authors: Arend Lawrence E.
Published: February 2023

The influence of surrounding colors on the appearance of a focal region is one of the oldest topics of vision research, and a wide variety of experimental paradigms has produced large quantities of data. From the beginning investigators were interested in the role of contrast in everyday color appearance. For the sake of close experimental control, most of that work involved very simple stimulus patterns. As a consequence relatively little systematic information has been available concerning the role of color contrast in patterns more closely approximating the conditions of everyday scenes. Most natural scenes involve many different chromaticies varying over the relatively small range produced by reflective surfaces under nearly white illumination. My colleagues and I have recently performed a series of experiments on contrast in complex patterns1,2.
Image Sameness: Some Experiments on Contrast in Simple Scenes
Authors: Cowan William B. , von Grünau Michael W.
Published: February 2023

Our experiments show that observers perceive the absolute luminance of areas in an image under some viewing conditions, and average luminance and contrast under other conditions. When average luminance and contrast are important sensitivity to contrast mismatches is up to 25 times as great as sensitivity to luminance mismatches.
Effects of Neutral Surrounds on Hue Estimation of Spectral Lights
Authors: Smith Vivianne C. , Pokorny Joel
Published: February 2023

The Bezold-Brücke effect (change in hue with luminance) is observed for unrelated colors by techniques such as hue naming. (Boynton & Gordon, 1965; Luria, 1967; Smith, Pokorny & Swartley, 1973). For related colors the phenomenon is seen when a hue match is made between two fields of different brightness, either by presenting the fields at different luminances (Purdy, 1931) or by setting adjacent regions at different luminances to create a darker field by induction (Wildt & Bouman, 1968; Coren & Keith, 1970). There are several studies that suggest that the Bezold-Brücke effect may not occur for related colors embedded in an equal luminance surround (Takahama, Sobagaki & Nayatani, 1978; Bartleson, 1979; Fuld & Otto, 1985). However these studies did not address the issue of the Bezold-Brücke effect specifically.
Semi-Automatic Generation of Film Compensation Tables
Authors: Rosenbaum Jan
Published: February 2023

Because of the non-linear response of photographic film to linear increases in light, the spectral quality of light output from phosphors, the extremely short duration of exposure for each pixel, and the differing gamuts of color available in film and color monitors, color compensation tables are necessary in digital film recorders to insure that film images correctly reproduce computer generated images. Compensation tables (look-up tables, or LUTs) serve as a mapping array between the digital count represented in the image desired and the digital count which is processed into the voltage applied to the CRT cathode in the film recorder.
Frequency-Doubled Diode Lasers
Authors: Kozlovsky W. J.
Published: February 2023

Single-mode infrared diode lasers produce high output powers with long lifetimes, 1,2 and nonlinear optical processes can be used to convert the output of these sources to the blue. For instance, 430–nm light can be generated by frequency doubling the output from a GaAlAs diode laser in potassium niobate. To increase the efficiency of blue generation, an external enhancement resonator can be used to increase the fundamental intensity inside the nonlinear crystal.3–8 For stable operation of such a system, a match of the output frequency of the diode laser and a resonant frequency of the external cavity must be maintained, since frequency differences will result in substantial fluctuations of the infrared power inside the resonator and thus in the blue output Passive optical feedback has been used to lock the diode laser frequency to a resonator frequency,3 with the requirement that the phase of the optical feedback be electronically controlled.7 As an alternative, we have used an electronic feedback technique to frequency lock the diode laser frequency to a resonator frequency to produce 54 mW of stable blue output.8
Harmonic Generation from 1.079 μm to 0.54 μm with 85% Efficiency
Authors: Ou Z.Y. , Pereira S.F. , Polzik E.S. , Kimble H.J.
Published: February 2023

For many years, potassium titanyl phosphate (KTP) has been a well known crystal for frequency doubling of Nd:YAG lasers (1.064 μm). The large nonlinear coefficient of KTP crystal together with the wide temperature width, large acceptance angle, and very low absorption loss make KTP a promising candidate for high conversion efficiency. One problem with the use of KTP is that phase matching at 1.064 μm is possible only by Type II angle tuning, so that walk-off of the ordinary and extraordinary beams inside the crystal limits its utility in situations involving high finesse resonators. Recently however, Garmash et al. [1] have reported that Type II 90° noncritical phase-matching is possible with an a-cut KTP at 1.079 μm, thus enhancing the possibilities for intracavity cw frequency doubling. Indeed by following this lead, we have achieved 85% nonlinear conversion efficiency for doubling of 1.079 μm radiation to 0.54 μm.
Blue Second-harmonic Generation with Low Cerenkov Angles from Ta2O5/KTiOPO4 Waveguides
Authors: Tamada Hitoshi , Isobe Chiharu , Murakami Takaaki , Saitoh Masaki
Published: February 2023

Efficient blue second-harmonic generation (SHG) with Cerenkov angles of less than 1° has been observed for a Ta2O5/KTiOPO4 channel waveguide1) In order to realize low (<1°) Cerenkov angles as well as a high SHG efficiency, it is important to adjust waveguide parameters so that the overlapping between a nonlinear polarization wave and a SH wave in the KTiOPO4 substrate becomes quite large as shown in Fig.1.
Remarks About Quasi Phase Matching in Periodically Poled LINBO3 Waveguides
Authors: Delacourt D. , Armani F. , Papuchon M.
Published: February 2023

We have analyzed how the involved modes convert via the overlap integral, the image of ferro-electric polarization into an effective periodic non-linear coefficient.
Application of Blue-Green Diode Laser Sources to Optical Recording
Authors: Carlin Donald B.
Published: February 2023

A primary motivation for the original development of optical recording
was that the technique allowed a much smaller area for the storage of
a bit of information than did the magnetic techniques of that time.
Most early data recording was by ablative effects, the formation of
"pits" in an optical media. Today, storage may be by ablation,
magneto-optic effects, or phase changes. The basic optical principles
remain the same for all recording techniques. In general, recording
laser light that has a gaussian-like spatial beam profile is expanded
to fill the optics to the

1

e
2

intensity points of the beam profile and to focus the light onto the
recording medium. The recorded spots are formed with a diameter of
approximately equal to the full-width-at-half-power (FWHP) of the
primary central lobe of the diffraction pattern on the medium.
Rare-Earth-Doped Waveguide Devices: The Potential for Compact Blue-Green Lasers
Authors: Sanford N.A. , Aust J.A. , Malone K.J. , Larson D.R. , McCollum M.J.
Published: February 2023

Rare-earth-doped channel waveguide devices have demonstrated to lase in the infrared. The possibility for upconversion visible lasing is also being explored.
Overview - Blue-Green Semiconductor LED/Laser Work in Japan
Authors: Kukimoto Hiroshi
Published: February 2023

The research in Japan on the wide-bandgap materials for short-wavelength light emitting devices based on modem growth techniques of MOVPE and MBE started in early 1980s. The first attempt to organize a cooperative research system for wide-gap semiconductors in Japan can be traced back to the year 1984, when about 20 university research groups which had already been engaged in research on wide-gap II-VI materials gathered and started to make plans for joint research. This was followed by a three-year period research project on the property control of compound semiconductors, especially of II-VI, wide-gap III-V and I-III-VI2 materials, within a priority area research program for "New Functionality Materials - Design, Preparation and Control", which started in 1987 under support of the Ministry of Education, Science and Culture. It was renewed in 1990 as an advanced project for additional three years, and since then it has been running with emphasis on atomic-scale control of crystal growth, control of localized electronic states, creation of new optical functionality, quantum structures and new properties, and control of material properties for new optical devices. Under the project, the growth of wide-gap II-VIs, especially of ZnSe and related alloys and superlattices has been very actively studied in many university laboratories.
Operation of an eightfold transversely diode-pumped Nd:YAG laser using glass plates
Authors: Wälti R. , Lüthy W. , Weber H. P. , Schwarzenbach P.
Published: February 2023

Diode lasers represent efficient (46%),1 powerful, and intense (76 W for a 1 cm long laser bar),1 narrow-band, reliable, and compact power sources for pumping solid state lasers.2 A transverse pump geometry is evaluated combining the advantage of adding a scalable number of diode lasers around and along a crystal rod with the capacity of matching the pump intensity maximum onto the axis of a fundamental solid-state laser mode. The pump arrangement uses glass plates to guide the radiation from the diode front surfaces onto the Nd:YAG crystal. The 2-cm-long and 150-μm-thick glass plates open the space for eight singly cooled 5-W laser diodes mounted circumferentially around the crystal.
Diode-pumped Nd:GdVO4 laser with high- efficient fiber-optic module
Authors: Vlasenko O. A. , Zavartsev Yu. D. , Zagumennyi A. T. , Kozlov V. A. , Pashko S. A. , Studenikin P. A. , Shcherbakov I. A.
Published: February 2023

For small and efficient diode pumped solid-state laser systems, laser diode (LD)—optical fiber coupling has several advantages—high-power density at the end of a fiber, a possibility to combine powers of different LDs, a much higher degree of freedom in designing, small size, and electrical safety of the laser head, more simple scheme for cooling of the laser crystal, a remote LDs mounting, etc.
Ablation of fused quartz by multi-wavelength irradiation of vacuum-ultraviolet Raman laser
Authors: Sugioka Koji , Wada Satoshi , Tashiro Hideo , Toyoda Koichi , Ohnuma Yoshinori , Nakamura Akira
Published: February 2023

Ablation using short wavelength lasers is one of the promising techniques for microfabrication of solid surfaces. Most of the studies have been concentrated on organic materials and polymers.1 Few works on quartz materials have been carried out, although the materials are of great use for optics and optelectronics. In the present paper, novel ablation of fused quartz is demonstrated by multiwavelength irradiation of a vacuum-ultraviolet (VUV) laser using high-order anti-Stokes stimulated Raman scattering.
Practical applications of laser cleaning for removal of surface contaminants
Authors: Park Hee K. , Grigoropoulos Costas P. , Yavas Oguz , Leung Wing P. , Poon Chie C. , Tam Andrew C.
Published: February 2023

As microelectronic fabrication technology advances, there has been an ever-increasing need to develop more effective techniques to remove submicron-sized contaminants.1 A submicron particle adheres strongly onto a surface, with a force as large as millions of times its weight. Recently, it has been demonstrated that explosive vaporization and ablation of a thin liquid film on a solid surface induced by short-pulsed laser irradiation can be efficiently used to remove submicron-sized particulates from the surface.2 It has been also demonstrated that lasers can provide an environmentally sound, cost-effective method of removing organic coatings from a variety of substrates.3 Two kinds of laser-assisted cleaning technique have been developed, i.e., "steam laser cleaning" and "dry laser cleaning."2 The first kind utilizes flash heating and subsequent rapid vaporization of a micron-thick liquid film which is deliberately deposited on the surface. It has been shown that a strong acoustic wave is generated by the explosion which is responsible for the removal of particles.4 The second utilizes ablative photodecomposition of organic substances which are adsorbed on the surface. Hence, cleaning can best be done with the combination of these two laser cleaning modes.
Broadly tunable parametric generation of ultrashort pulses
Authors: Umbrasas A. , Diels J.-C. , Jacob J. , Piskarskas A.
Published: February 2023

Negative feedback-controlled, mode-locked Nd:YAG or Nd:YLF lasers are attractive pump sources for parametric oscillators (OPO)1,2 because of their exceptional stability, and extended pulse train and the short duration of the pulses. In this work we demonstrate effective parametric compression down to 600 fs in a simple synchronously pumped linear cavity OPO using a KTP crystal. As pump source, the active-passive, mode-locked Nd:YAG laser with passive-negative feedback was used (Continuum model PY-61C-10). This laser generated stable (less than ± 0.2% pulse to pulse fluctuation) picosecond pulse trains of 600 ns (85 pulses) with energy of 4.7 mJ at a repetition rate of 10 Hz. A minimum pulse duration of 9.5–10 ps is achieved after an initial transient of 7–10 roundtrips in the laser cavity. The pulse duration increases after the first 200 ns to reach a maximum of 13–15 ps towards the end of the train. The OPO crystal is pumped through a 1-m focal distance lens by the second harmonic of this source, generated in a 6-mm-long KTP crystal. The OPO cavity, resonant for the idler only, was formed by two flat mirrors: Al-coated and dielectric output mirror (R ≈ 50% between 1.2 and 3 μm). We used a noncollinear scheme for parametric interaction, with an angle between pump beam and optical cavity axis of ≈ 3°). As nonlinear OPO element 14-mm and 6-mm-length KTP crystals cut at θ = 54° and ϕ = 0°, and θ = 90° and ϕ = 23.5°, respectively, were used.
Tunable visible ultrashort pulses by parametric generation and amplification
Authors: Watson J. , Lépine T. , Georges P. , Brun A.
Published: February 2023

Tunable high-power femtosecond pulses over the entire visible and infrared spectrum are very interesting for time-resolved spectroscopy. To achieve this high tunability, we have developed a femtosecond optical parametric amplifier (OPA)1–3 based on the highly nonlinear BBO crystal.
Effect of pump beam propagation on transient degenerate four-wave mixing in saturable Nd:YAG amplifiers
Authors: Brignon A. , Huignard J.-P.
Published: February 2023

Phase distortion correction of an optical wave propagating in laser media is a crucial problem to be taken into account in most of laser systems. For this purpose, phase conjugation through stimulated Brillouin scattering using the master oscillator-power amplification configuration has shown a very good potential to obtain high beam quality in solid-state lasers that operate at variable repetition rates. Another attractive alternative to generate the phase-conjugate wavefronts is to use a four-wave mixing (DFWM) process in the laser amplifier. In this medium, the interference between the interacting beams leads to a spatial modulation of the complex susceptibility of the medium by gain saturation (amplitude gain grating). This all-solid-state solution presents the advantage of suppressing the external nonlinear medium and would realize the required functions in the laser medium itself. Moreover, due to the amplification experienced by all the interacting beams, associated to the resonant nonlinearity of the gain saturation, high reflectivities already have been achieved in Nd:YAG amplifiers using a multipass geometry.1,2
Two-tone frequency-modulation spectroscopy for low-absorption tomographic imaging
Authors: Kauranen P. , Hertz H. M. , Svanberg S.
Published: February 2023

Non-intrusive spatially resolved measurements of gas concentrations are important in fluid flow, combustion, and heat transfer research. By combining multi-angle absorption measurements with tomographic reconstruction, quantitative and spatially resolved measurements may be performed.1 Due to the low absorbance of most gaseous species in the visible wavelength region, previous attempts in optical absorption tomography have been restricted to specially selected species in order to obtain a sufficiently high signal-to-noise ratio for the tomographic reconstruction. We combine tomography with two-tone frequency modulation spectroscopy (TTFMS), a highly sensitive absorption technique, extending the possibilities for quantitative and spatially resolved measurements to a vast number of species.2 Our TTFMS experiment uses laser modulation at 647 ± 5.2 MHz and has an absorption sensitivity of 1:106. The tomographic method is demonstrated by mapping the concentration in a section of a weakly absorbing O2 gas flow, using a GaAlAs diode laser operating around 760 nm.
Nonlinear mirror mode-locking of cw Nd lasers
Authors: Danailov M. , Cerullo G. , Magni V. , De Silvestri S. , Segala D. , Cybo-Ottone A. , Gioino M.
Published: February 2023

In the last few years there has been an increasing interest in the development of mode-locking (ML) techniques for CW solid-state lasers based on saturable absorber-like action of fast nonlinearities.1 Using additive pulse ML, nonlinear Fabry–Perot interferometer ML, and Kerrlens ML, nearly bandwidth-limited pulses have been generated with Nd: YAG and Nd:YLF in CW lamp and diode-pumped lasers.2 A very attractive technique for passive ML, which can provide high nonlinear loss modulations, is the so-called "nonlinear mirror" ML.3,4 Up to now, however, this method has only been applied to pulsed systems.
Low threshold all solid-state femtosecond Kerr lens mode-locked Cr:LiSAF laser
Authors: Lincoln J. R. , Botheroyd I. M. , Dymott M. J. P. , Ferguson A. I.
Published: February 2023

Kerr lens mode-locking (KLM) has been increasingly acknowledged as a reliable method of producing femtosecond pulses from Ti:sapphire and Cr:LiSAF laser systems.1,2 However, the previous thresholds for KLM action have been relatively high, and the production of femtosecond pulses has required large frame Ar+ or Kr+ pump lasers. To realise an all solidstate femtosecond system Cr:LiSAF has been extensively studied, since it has a significantly lower laser threshold and requires a red pump source compatible with the high power red diodes. However, the low brightness of red diodes prevents accurate mode matching of the pump beam to the Cr:LiSAF KLM laser mode, thus raising the Cr:LiSAF threshold and, to date, preventing operation of a directly diode pumped KLM Cr:LiSAF system.3
Studies on an optical memory effect in doped gel matrices
Authors: Bentivegna Florian , Canva Michael , Brun Alain , Chaput Frédéric , Boilot Jean-Pierre
Published: February 2023

Including polarizable dopants into the pores of a gel matrix can lead to an all-optical memory system.1,2 Powerful, linearly polarized optical pump pulses, provided by a femtosecond laser and focused on a doped gel, tend to align the dopants' dipolar moments in the direction of the pump polarization. This induces a strong anisotropy: inserting the sample between two crossed polarizers, whose polarization axes are at 45° to the pump polarization, allows one to probe the resulting birefringence An. In contrast to the optical Kerr effect in solutions, the anisotropy remains during long periods of time, up to several months, despite the thermal Brownian agitation. It is classically explained that the dopants are attached to the matrix through hydrogen bonds. These are broken by the pump beam and the dopants can be realigned. After each optical pulse, new bonds are formed, stabilizing the new orientations (Fig. 1). Aligning the molecules either on one of the polarizers' axes or at 45° enables switching between two states of probe light transmission—low and high. This system can be described as an erasable, rewritable, all-optical memory, potentially with a molecular resolution, yet limited by the optical diffraction.
A pulsed CO2 laser to process high damage threshold materials
Authors: Watson Ian A. , Chatwin Chris C. , McDonald Donny W. , Scott Brain F.
Published: February 2023

Pulsed CO2 lasers with suitable output characteristics can efficiently process high reflectivity and/or refractory materials. Following a combined simulation and experimental research programme on both the laser and the interaction process, a transversely excited, high PRF, CO2 laser was constructed.1,2 Fig. 1 shows the pumping circuit configuration. To enter the highly absorbing interaction regime, an incident flux intensity of 1011W m-2 is required with a pulse duration between 6–8µs and, to avoid the deleterious melt-freeze process of conventional pulse modulated CW sources, a pulse repetition frequency (PRF) of 5–10 kHz is necessary. The specific energy density of the pumping medium to generate such optical pulses is approximately 12 J 1-1atmosphere-1. Consequently, the gas discharge operates in a substantially different regime to that of TEA lasers, and instabilities due to gas shock wave effects are reduced. Conventional trigger wires were utilised to generate an auxiliary preionising discharge to form stable, uniform glow discharges in a 3-litre cavity over a range of operating conditions, i.e., gas pressure and mixture composition. Analysis of the spatio-temporal development of the electron gain indicates that owing to the low applied E/N the discharge breaks down via the Townsend mechanism. A gas circulation system convectively clears the heated gas from the discharge region. Experimental results are presented for the maximum PRFs achieved with this simple technique of preionisation both with planar-planar electrodes using different laser cavity flow shaping designs (Fig. 3) and for a prototype segmented, ballasted cathode (Fig. 4). Large, gain-switched spikes in the laser output pulse generate intensities sufficiently high to form a plasma above the workpiece. Excessive plasma growth decouples the beam from the workpiece, severely degrading the efficiency of the interaction process. Consequently, the magnitude of the gain-switched spike must be controlled. This can be achieved by optimising the design parameters of the optical resonator and the composition of the laser gas mixture.3 Results are presented that clearly demonstrate the effect of the gas composition on the spike power relative to the total power in the laser output pulse (Fig. 5).
All polarization maintaining erbium-doped fiber ring laser utilizing fiber sole filter
Authors: Sejka Milan , Edvold Bent , Piilsdottir Bera
Published: February 2023

Erbium-doped fiber lasers, with light emission around 1.55 µm, have attracted increasing interest in recent years.’ However, the output from these lasers is often affected by amplitude and frequency fluctuations. The fluctuations are mainly caused by random fluctuations of the polarization state in the laser. Wavelength fluctuations of the output signal may be stabilized by different combinations of broadband and narrow band filters.2,3 Fluctuations in the polarization state can be overcome by using all polarization maintaining (PM) fiber configurations.4
Achromatic optical interconnects using holographic optical elements
Authors: Schwider J. , Völkel R. , Junger S.
Published: February 2023

Diffractive optical elements as deflectors for optical free-space interconnects have been proposed by several authors.1,2 Unfortunately, the high flexibility of such elements is in many cases outweighed by the strong chromatic aberrations. Surface relief gratings have commonly a rather low carrier frequency (due to the limited resolution of the lithography) and, therefore, the chromatic aberrations are less severe. For volume gratings with their high carrier frequency a close cascade geometry has been proposed to reduce the chromatic aberrations.3,4 Another possibility for optical interconnects is spaceinvariant imaging of the transmitters onto the receivers? Both approaches have been demonstrated for an optical backplane (Fig. 1).
Time resolved reflectance spectroscopy on turbid media with distributed inhomogeneities
Authors: Hielscher A. H. , Liu H. , Wang L. , Tittel F. K. , Chance B. , Jacques S. L.
Published: February 2023

In most biological tissues the absorption does not result from a homogenous distribution of absorbing materials. Absorbers are often localized e.g., in blood vessels, which are randomly distributed. An understanding how this localization of absorbers influences the near infrared reflectance signal is a prerequisite for the correct interpretation of this measurements. For example time resolved reflectance measurements from the head have been used to determine the brain blood oxygenation.1 However, little attention has been paid to the fact that blood is a highly absorbing fluid (µa ~ 4-cm–1), which is localized in blood vessels, which are embedded in a very low absorbing background medium (brain µa ~ 0.1 cm–1). Furthermore, blood vessels (capillaries, veins, and arteries) have different diameters and the blood oxygenation differs from vessel type to vessel type. The question arises, how strongly do these different vessels influence the result of the reflectance measurements and thus the determination of the blood oxygenation?
Networks with quantum amplifiers
Authors: Karlsson Anders , Gillner Lars , Goobar Edgard , Björk Gunnar
Published: February 2023

As the best fibre optical systems are approaching fundamental quantum limits, the role of Heisenberg's uncertainty principle in communications has shifted from being of academic interest to becoming an (un)practical restriction.
Correlation between spectral characteristics and the value of linewidth enhancement factor in quantum-well laser diodes
Authors: Lukyanov V. N. , Shramenko M. V. , Yakubovich S. D.
Published: February 2023

Single mode semiconductor lasers are widely used in spectroscopy, coherent optical communication, interferometry, holography. Their main parameters for these applications are output power, spectral linewidth, and side mode suppression. To ensure the single mode radiation, external and integrated spectral selective elements are often used. In recent years the high-efficient single mode laser diodes (LD) with the traditional cleaved cavity were created due to the utilization of quantum well (QW) structures.
High-quality CO2 laser beam delivery using dielectric-coated metallic hollow waveguides
Authors: Somkuarnpanit S. , Su D. , Hall D. R. , Jones J. D. C.
Published: February 2023

Over the past decade, a number of different types of hollow waveguides have been used for the delivery of CO2 laser radiation.1-3 However, much of the previous work has been concentrated on beam attenuation and the power transmission characteristics of the waveguide, whereas to take full advantage of the available CO2 laser technology, i.e., a combination of high power and high beam quality, it is necessary to try to preserve beam quality in the passage of the beam through the fibre. The principal object of this paper is to investigate the transmission properties of hollow wave guides for the case when high-quality CO2 laser beams are launched efficiently at the input. In a number of important applications of carbon dioxide lasers, beam quality issues are very important, not only in terms of the achievable spot size, but also as regards the transverse intensity profile.
Influence of the cross talk in a phase-shift laser rangefinder
Authors: Bosch Th. , Lescure M.
Published: February 2023

A 1-10-m laser rangefinder has been developed (Fig, 1). The range data is obtained by measuring the phase-shift ΔΦ between the transmitted and the received sinusoidally modulated beams. The distance d is then given by the relationship: where f is the modulation frequency and c the speed of the light.
Crystal growth and laser properties of Nd-doped strontium fluorovanadate for diode pumped laser operation at 1.06 μm and 1.34 μm
Authors: Scott M. A. , Botheroyd I. M. , Gallagher H. G. , Han T. P. J. , Ferguson A. I. , Henderson B.
Published: February 2023

Due to the availability of efficient and compact laser diodes as pump sources, there has been a recent resurgence of interest in crystals having the apatite structure.1,2 In this paper we report the crystal growth, optical characterisation and laser properties of a new fluorapatite host Sr10(VO4)6F2 (SVAP) for use as a gain medium for diode pumped laser action at both 1.06 μm and 1.34 μm.
Multiple grating interactions in photorefractive optical interconnects
Authors: Andersen Peter E. , Petersen Paul M. , Buchhave Preben
Published: February 2023

Storage of interconnection patterns as holographic gratings in photorefractive crystals is a promising technique for interconnect systems.1,2 Our work has been concentrated on an angularly multiplexed scheme in Bi12SiO20 (BSO) crystals for storage of such patterns. Two important issues are addressed in this paper: (1) crosstalk as a function of the ratio β between the reference and the object beam intensities, and (2) the effect of the separation angle Δθ between the object beams on the crosstalk.
Single pulse phase conjugation by self-pumped four-wave mixing in BaTiO3
Authors: Troth R. C. , Ramos-Garcia R. , Damzen M. J.
Published: February 2023

Self-pumped phase conjugation1 can be used to generate automatically self-aligned counterpropagating pump waves for four-wave mixing in a single crystal of BaTiO3.2 Here we give a physical explanation for previously unreported features of what we term "self-pumped four-wave mixing" in a BaTiO3 crystal, by comparing experimental results obtained using a train of nanosecond pulses with a steady-state photorefractive four-wave mixing theory. From this physical explanation we have optimized a self-pumped four-wave mixing geometry to produce the phase conjugate of a single pulse.
All-optical synchronisation of a compact disk laser
Authors: Phelan Paul , Rodriques Jose H. , Salcedo Jose R.
Published: February 2023

All-optical synchronisation of self-pulsating diode lasers has recently attracted considerable attention for possible application to clock extraction, information processing, and pulse generation.1 Two-section InGaAsP self-pulsating lasers have proved attractive for synchronisation, but single-section AlGaAs self-pulsing lasers developed for compact disk (CD) systems are low-cost and easily available.2 Only electro-optic synchronisation of these lasers has been reported to date,3 and little is known about their all-optical synchronising properties. This paper reports synchronisation of selfpulsing CD lasers to a train of picosecond optical pulses.
High energy, flashlamp pumped Ti: sapphire amplifiers
Authors: Kolenda J. , Rairoux P. , Wolf J. P.
Published: February 2023

Recent successes in flashlamp pumping of Ti: sapphire1,2 opened new fields of applications to this laser material.3 Flashlamp pumped Ti: sapphire lasers providing more than 2 Joule per pulse are already commercially available.4 However, the spectral brightness of these high power oscillators is often not large enough for spectroscopic applications or for efficient frequency conversion. Investigations showed5 that the bandwidth and mode profile of the resonator are determined by the large volume of the gain medium and the small diameter of the fundamental Gaussian mode. Commercial ways to achieve large TEM00 volumes with gradient reflectivity mirrors are limited by the broad tuning range of the Ti : sapphire crystal. A commonly used solution to achieve narrow spectral bandwidth and a good mode profile is to seed the laser medium with a high purity oscillator source.
Laser operation of Tm:Ho:GdVO4
Authors: Morris P. J. , Lüthy W. , Weber H. P. , Zavartsev Yu. D. , Studenikin P. A. , Shcherbakov I. , Zagumenyi A. I.
Published: February 2023

Using vanadate as host for the thulium sensitised 2-μm holmium transition offers several advantages over YAG. As shown in Fig. 1, the vanadate absorption is considerably stronger, broader, and closer to 809 rm, the standard wavelength for high power diode lasers, than YAG. The S polarised absorption spectrum has a maximum at 979 nm of α = 19.1 cm-1 and a FWHM of 7 nm. Pump wavelength dependence is therefore reduced and crystals with lengths under 1 mm can be used. High numerical aperture pump beams can be used as the energy is deposited before the beam can diverge out of the resonator mode, severely reducing the collimation requirements of the diode coupling optics.
Experimental and numerical investigation of short pulse amplification in the 1.3µm region
Authors: Ammann H. , Hodel W. , Weber H. P.
Published: February 2023

Short pulse amplification has been widely investigated down to the sub-100 fs regime in the third telecommunications window around 1.55µm. Amplification in the important 1.3µm telecommunications band has recently attracted much attention, whereby Pr -doped fluoride fibre amplifiers (PDFAs) with gains up to 38.2 dB have been reported. However, investigation of pulse propagation in active fluoride fibres and demonstration of short pulse amplification has not been demonstrated.
Mirror tilt effects in free electron lasers with a hole coupling
Authors: Zhulin V. I.
Published: February 2023

In an ordinary laser operation a misalignment of resonator mirrors leads usually to undesirable effects and has to be avoided. But in some certain types of cavity configurations deliberate introduction of misalignment makes it possible to improve considerably the characteristics of output radiation. An example of such configurations is an optical scheme with hole coupling. We considered two options:

• the free electron laser (FEL) with the radiation output through the on-axis hole at the exit mirror;1

• the external resonator (used for pulse stacking) where the exit FEL radiation enters this resonator through the on-axis hole at the input mirror.2

These configurations were investigated with the continuous wave 3-D code developed earlier.3
Coupling of polarization and transverse modes in vertical cavity surface emitting lasers
Authors: Jansen van Doorn A. K. , van Exter M. P. , Woerdman J. P.
Published: February 2023

The need for small laser devices that produce low divergence circular beams (e.g., coupling into fibers) has initiated intense research in the field of vertical cavity surface emitting lasers (VCSELs). Actual devices turn out to operate in a single transverse TEM00-mode only close to threshold; in general they lase in several transverse modes.1-3 Ideally one expects spherically symmetrical Laguerre-Gaussian higher-order modes with degenerate frequencies. In practice one often observes non-degenerate Hermite-Gaussian modes, indicative of spatial anisotropy. We have studied the effect of this anisotropy on the polarization characteristics of a 1 × 16 array of VCSELs; more specifically we investigated the coupling between the polarization and the transverse intensity distribution. We show how the results can be understood in terms of stress-induced and modal birefringence.
Statistical properties of the spectrum of light pulses in fast pseudorandom nonreturn to zero word modulation of a single-mode semiconductor laser
Authors: Balle S. , Homar M. , Miguel M. San
Published: February 2023

Timing jitter and chirp noise are two limiting factors in the performance of long distance high-speed communications systems. We characterize their relation, implications on pattern effects, and their dependence on bias level and modulation frequency.
Precise Laser Ablation with Ultra-Short Pulses
Authors: Momma C. , Nolte S. , Chichkov B. , Tunnermann A. , von Alvensleben F.
Published: February 2023

Nowadays, short-pulse laser systems based on the chirped pulse amplification (CPA) technique are available, allowing a variation of the pulse duration from about 100 fs to several ns without changing other important beam parameters. Therefore, more detailed analysis of fundamental interaction processes of laser pulses with solids become feasible. These investigations can result in a significant improvement of the achievable precision and resolution of laser-based material processing and microstmcturing.
Spectral Behaviour of Nd-Doped Double-Clad Fibers
Authors: Reichel V. , Ertmer A. , Schröter S. , Müller H.-R. , Zellmer H.
Published: February 2023

In context with the development of silica based, Nd-doped double-clad fibers for the application in high-power fiber lasers [1] we have investigated the spectral behaviour of the emission in the three wavelength regions around 880 nm, 1064nm and 1300 nm in the nonresonant and resonant case, respectively. For these experiments we used fibers with a high NA of the outer core (0.38), a singlemode, Nd-doped core (Nd concentration approx. 1300 ppm) and a diameter of the second core of 100 to 130 μm.
Laser Deposition of Two—Dimensional Tin Oxide Patterns
Authors: Geretovszky Zs. , Kelemen L. , Szörényi T.
Published: February 2023

Close to metallic electrical conductivity, yet still high transmittance in the visible and near-IR render tin oxide films indispensable in many important applications [1]. One of the technological issues to be resolved before successful device fabrication is the efficient and controlled patterning of these films. SnOx films are physically and chemically resistant and adhere well to various substrates and so their patterning is not a straightforward matter. Here we report a novel technique for two dimensional tin oxide patterning by localized laser deposition from the traditional precursor of spray pyrolysis [2, 3 and Refs, therein].
Sub-20 fs Soliton Modelocked Lasers
Authors: Kärtner F. X. , Jung I. D. , Fluck R. , Zhang G. , Keller U.
Published: February 2023

It is well known that solitonlike pulse shaping generates pulses that are both shorter and more stable [1]. However, for modelocking of solid state lasers it has been always assumed that a window of net gain as short as the pulse itself has to be created that supports only the pulse and suppresses the growth of instabilities. We showed by soliton perturbation theory that in a passively modelocked femtosecond solid-state laser with solitonlike pulse shaping the modelocking process can be stabilized by a broadband slow saturable absorber only [2]. This opens the possibility to generate sub-10 fs pulses with semiconductor absorbers. We reach with the technique of soliton modelocking stabilized by a broadband saturable absorber a regime which was previously only possible with Kerr-Lens Modelocking but our approach is in addition self-starting.
Tunable Single-Frequency Diode-Pumped Cr:LiSAF Microchip Lasers
Authors: Knappe R. , Bitz G. , Boller K.-J. , Wallenstein R.
Published: February 2023

Monolithic microchip lasers are of interest as compact, reliable single frequency laser sources, (1) The broad gain bandwith of Cr3+ makes Cr:LiSAF an attractive material for a broadly tunable single-frequency laser source (2).
High Energy Tuneable Picosecond Travelling Wave Optical Parametric Oscillator Covering Region of 42nm÷10μm
Authors: Lukosius Jonas , Michailovaś Andrejus , Rinkevicius Andrius
Published: February 2023

A number of spectroscopic applications, eg, pump-probe spectroscopy, sum frequency spectroscopy, etc - require a source of picosecond high energy pulses, broadly-tuneable in near and mid-IR. Two solutions are known as most popular - optical parametric generation and mixing of dye laser radiation with that of Nd:YAG,– each not void of its definite drawbacks [1],[2].
SBS Phase Conjugation for Diffraction Limited Laser Beams
Authors: Eichler H.J. , Haase A. , Mehl O.
Published: February 2023

Solid-state lasers for high average output power suffer from thermal lensing. stress birefringence and other phase distortions which reduce the beam quality significantly1. Using phase conjugation based on stimulated Brillouin scattering (SBS) the beam parameter product of conventional laser systems can be decreased down to the diffraction limit. SBS cannot compensate stress birefringence and therefore different compensation schemes for Nd:YAG were developed2,3 resulting in complex setups. Therefore in contrast to multi-amplifier YAG systems with SBS4,5 we use Nd:YALO as active material to avoid the depolarization effect resulting in simple optical arrangements.
Nd:YAG Loop Laser with a Thermal Holographic Mirror
Authors: Betin Alexander A. , Matthews Steven C. , Mangir Metin S.
Published: February 2023

Employing thermal gratings recorded in slightly absorbing liquids as a mirror, in an optical scheme with a laser amplifier inside a loop, offers the possibility to build effective phase conjugate lasers, as demonstrated previously for CO2 and Nd lasers [1,2]. We present results of an experimental investigation of Nd:YAG loop laser performance for short (30ns) and long (1ms) pulses.
Self-pumped phase conjugation mirror based on Nd:YAG with reciprocal multi-loop feedback scheme
Authors: Antipov O.L. , Belyaev S.I. , Kuzhelev A.S.
Published: February 2023

The effect of self-pumped phase conjugation (SPPC) of the light beam in the inverted laser crystal (LC) with the feedback loop was investigated in recent years. The possibility of SPPC in the reciprocal loop scheme is concerned with the refractive index grating which occurs due to difference of polarizability of the Nd ions in the metastable and the ground states [1]. The high efficiency of multipass geometry in the phase conjugation systems based on the laser crystals have been demonstrated for the degenerate four-wave mixing processes [2].
Two-wavelength laser emission from a coupled semiconductor microcavity
Authors: Pellandini P. , Stanley R. P. , Houdré R. , Oestcrlc U. , Ilegems M. , Weisbuch C.
Published: February 2023

Multiwavelength laser sources are desirable for several applications such as wavelength division multiplexing, two-wavelength interferometry and frequency mixing. An optimal source would be a single diode laser capable of simultaneous coaxial emission at different wavelengths. We present here results on laser emission from an optically pumped monolithic coupled microcavity. A coupled microcavity structure (CMC) contains two optical cavities, separated by a common mirror1. Depending on the detuning between the two cavities, laser action can be achieved either simultaneously at two different wavelengths or at only one wavelength.
Performance of Multiquantum Barriers in Bulk Double Heterostructure Visible Laser Diodes as a function of Temperature
Authors: Morrison A. P. , Lambkin J. D. , van der Poel C.J. , Valster A
Published: February 2023

To investigate the validity of the claim that multiquantum barriers (MQBs) improve the performance of visible laser diodes by virtue of a virtual barrier height increase over the bulk barrier height1 three types of bulk active region double hetcrostructure Ga0.5In0.5P/(Al0.4Ga0.6)0.5In0.5P laser diodes were designed. The first was used as a reference while the remaining lasers included an optimised and non-optimised MQB structure respectively. The optimised MQB design is intended to produce a virtual barrier height increase of 75mcV while the non-optimised design is expected to be identical to the bulk reference laser The active region of each laser was adjusted to keep the total optical confinement the same for all three structures.2
Wide range tunability of short wavelength GaInP/AlGaInP DFB lasers
Authors: Gauggel H.-P. , Artmann H. , Geng C. , Scholz F. , Schweizer H.
Published: February 2023

Wavelength tunable distributed feedback (DFB) lasers in the visible emission range are of great interest for the application as single-mode light sources for optical memories [1] and for the atomic absorption spectroscopy. In both cases stable single mode emission and a wide range tunability of the lasers are required.
Beam parameter dynamics of laser radiation in cavities with variable reflectivity mirrors
Authors: Mascello A. , Perrone M.R. , Guattari G. , Palma C.
Published: February 2023

Short-pulse lasers deliver pulses that have made only a few round trips inside the cavity before leaving it definitively, before the equilibrium state of the beam parameters is reached. Hence, a good knowledge of the beam parameters dynamics inside the laser cavity is necessary to develop improvements of the overall output brilliance. In fact, the beam quality depends on the spatial coherence of the beam, which grows with the number of transits made inside the cavity and affects the beam divergence. We have developed a theoretical model1,2 giving the main beam parameters (spot size, radius of curvature and beam quality factor M2) of the intracavity radiation at each round trip, starting from the ASE radiation of low coherence and high divergence. The numerical results from this model have been compared with experimental measurements made on the laser pulse from a XeCl excimer laser, collecting data on the spot size and divergence in correspondence to each round trip1,2. The laser cavity structure has been changed for three different groups of measurements. For each group, mirrors with a Gaussian, a super-Gaussian and a phase-unifying reflectivity profile, respectively, have been used as output coupler of a plane-parallel cavity containing the XeCl laser medium. Results of the theoretical analysis and of the experimental measurements result in good accordance, indicating that the beam parameters dynamics can be understood and then controlled.
Pulse to pulse wavelength switching of a narrowband excimer laser
Authors: Müller D. , Grebner D. , Triebel W.
Published: February 2023

Tunable excimer lasers of narrow linewidth deserve special attention for various applications in lithography, spectroscopy and holography. In the field of spectroscopy Laser Induced Fluorescence (LIF) of small molecules has proved to be a valuable tool e.g. in combustion research [1]. Using narrowband excitation (≈1 cm–1) it enables the determination of 3-dimensional distributions of concentrations and temperatures. Two different excitation wavelengths are necessary for the observation of temperature fields and are also helpful for the quantitative determination of concentration profiles.
Retrieving of laser beam intensity distribution from the temperature along surface of heated thin target
Authors: Aksenov V. , Isaev Yu. , Zakharova E. , Reino V. , Tsvik R.
Published: February 2023

When studying the regularities of variations of laser beam parameters, a problem arises to measure the intensity I(ρ, t) in the beam cross section. One of the possible methods of intensity measurement is its reconstruction from the temperature field T(ρ, t) on the target surface The theory of solving of the inverse heat transfer problem and results of numerical experiment for uniform target irradiated by nonuniform laser beam was reported1 In the case of a thin thermally insulated target the following relationship was obtained, where R is the reflection coefficient; a
2
and k are the thermal diffusivity and conductivity, respectively; L is the target thickness; Δ⊥ = ∂/∂
x

2
+ ∂/∂y2 is the transverse Laplacian operator Deriving algorithms for this equation we use the difference procedure For decreasing of the effect of random errors we performed filtration of initial data. A simple and effective filter that ensures satisfactory accuracy is the convolution of initial data with a stabilizing function sinc(x) = sin (æmax x)/π x, æmax ≈ 2 cm–1