bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Modelling of Dynamic Response of Loss Modulated Monolithic Multisection Mode-Locked Semiconductor Lasers
Authors: Zhu B. , Summers H. D. , White I. H. , Penty R. V.
Published: February 2023

Monolithic multisection mode-locked semiconductor lasers with an integrated distributed Bragg reflector (DBR) have recently been demonstrated to generate stable picosecond pulses at high repetition rates suitable for optical communication systems. However, there has been very little theoretical work on understanding the physical mechanisms of the device and on optimisation of the absorber modulator design. This paper therefore presents numerical modelling of the loss modulated mode-locking process in these lasers. The model predicts most aspects experimentally observed within this type of device, and the results show the output waveform, optical spectrum, instantaneous frequency chirp, and stable operating range.
Single Growth Step InGaAs DBR Laser Diodes with First Order CAIBE-etched Gratings
Authors: Mikulla M. , Chazan P. , Raynor B. , Daleiden J. , Larkins E. , Schmitt A. , Tränkle G.
Published: February 2023

DBR-laser diodes are very interesting light sources due to their narrow linewidth, frequency stability and large sidermode suppression. They are suitable for monolithic integration, which makes them a very attractive light source for monolithic master oscillator power amplifier devices.
Analysis of Beam Amplification in Hyperbolically Flared Semiconductor Laser Amplifiers
Authors: Lin Ching-Fuh , Lai Jie-Wei
Published: February 2023

Recent development in high-power single mode semiconductor lasers has stimulated in the evaluation of several types of semiconductor laser amplifiers [1], [2]. Flared semiconductor laser amplifiers have demonstrated the highest output power with extremely good spatial coherence. However, the output near-field intensities have two side peaks [2], which may cause some problems. For example, they may excite higher-order modes in side-pumping solid-state lasers. Therefore, we propose a new flared structure that could significantly eliminate the two side peaks. The conventional flared amplifiers consist of a linearly tailored gain region that serves as the spherical (circular) expansion of the wave front. The expansion is not ideal because the beam mode has a nonzero beam size instead of being like a point source. The proposed hyperbolically flared structure analogizes the expansion of a Gaussian beam and therefore is better for the beam expansion.
A Novel Hybrid Coupler Based on Antiresonant Reflecting Optical Waveguides
Authors: Deng Jau-Jan , Huang Yang-Tung
Published: February 2023

The beam splitter and the beam combiner are key elements for optical communications, and the optical-waveguide hybrid coupler has been proposed for these functions by Izutsu, et al. [1]. This conventional waveguide hybrid coupler consists of symmetric and nonsymmetric Y-junctions connected directly. In each Y-junction, there are two types of normal modes, even and odd modes, traveling along the propagation direction. For the input symmetric Y-junction, the amplitudes of the field for both modes in two individual waveguides are the same; in the output nonsymmetric Y-junction, the fields of the even and odd modes are mainly confined in the wide- and narrow-arm, respectively. The input conditions will determine the outputs of the wide- and narrow-arm in the nonsymmetric Y-junction. In this presentation, we present a novel hybrid coupler structure based on antiresonant reflecting optical waveguides (ARROWs) to provide the same functions.
High Capacity Optical Code-Division-Multi-Access System Based on Double M-Sequencc Spectral Encoding
Authors: Chen Xiabo , Su Yikai
Published: February 2023

This paper describes an optical Codc-Division-Multi-Acccss system based on double m-sequence spectral encoding of noncoherent light source on a same mask. The encoding scheme dramatically increases the multiaccess capacity.
Large-Modulation Regime of the Free-Electron Laser Exploiting a Medium with Periodically Modulated Refractive Index
Authors: Artemyev A.I. , Fedorov M.V. , Mciver J.K.
Published: February 2023

The laser gain G of the free-electron lasers exploiting media with periodically modulated refractive indices is studied in the regime of a large modulation. Such a medium can be realized as a superlattice-like structure or it can be created by a series of optical breakdowns in a gas produced by a train of pulses formed by an external laser. Criterion for existing of the large-modulation regime is determined. It requires that the period of modulation should exceed the speed of light devided by the maximum plasma frequency of the modulated medium. Thus, the largemodulation regime of the FEL can be realized under even if the modulation itself is rather small.
High-average power operation of pulsed Nd:glass slab lasers
Authors: Yoshida K. , Ochi K. , Yuki R. , Takahashi M. , Kaku S.
Published: February 2023

High-average-power, highly efficient solid-state lasers are desirable, especially for application to material processing, X-ray generation and pumping source of Ti: sapphire laser. In these applications, a large host material to irradiate high energy are required. A laser glass of a large size with an optical homogeneity of ± 1× 10-6 can be easily obtained, but high-frequency operation of glass laser is limited due to the low thermal conductivity of glass. Dane1 operated the Nd :glass flashlamp-pumped zig-zag amplifier at maximum repetition frequency of 3Hz. The array Nd:glass slab laser2 could be operated at higher repetition frequency. In this paper, the optical characteristics of the array Nd:glass slab laser operated at high repetition frequency are shown.
Flashlamp-pumped Laser with a New Crystal: Neodymium-Doped Strontium-Lanthanum-Aluminate (Nd:ASL)
Authors: Boquillon J.P. , Musset O.
Published: February 2023

Strontium-Lanthanum Aluminate (ASL) is a new material related to the previously known LNA and with composition: Sri1-xNdyLax-yMgxAl12-x019. This crystal is Czochralski-grown by Crismatec in France (Patent pending). At the difference of LNA crystals, ASL can be grown both along a and c directions, the c direction being the preferred one for laser action. ASL has a magnetoplumbite structure and the compositions are chosen with 0<x<1. As Nd is a constituent ion, the crystal lattice can have a high concentration of this ion, much higher than for Nd:YAG. Co-doping with Cr ions can also be obtained.
Optoelectronic Control of Solid-State Lasers Using New High-Voltage Silicic Elements
Authors: Gorbunkov M.V. , Vorchik D.B.
Published: February 2023

Laser radiation parameters can be essentially improved by a external feedback [1]. The optoelectronic systems now in use are rather complicated and can not be applied for a multi-purpose controlling scheme. We have suggested to use new high voltage (1-10 K.V) fast (response time ~ 0.5 ns) optoelectronic cilicic elements which allow to realize a number of the original control schemes for the solid-state lasers of near IR [2]. Their high sensitivity and ability to work with high-votage directy made possible to control a introresonator Pockel’s cell by a positive as well as negative feedback without additional amplification of a signal.
ABCD matrix modeling of thermal lensing and gain guiding in diode pumped solid state lasers
Authors: Altmann Konrad , Schmitt Nikolaus
Published: February 2023

In the paraxial wave equation for a complex gaussian duct the term describing the combined effect of thermal lensing and gain guiding is given by the complex expression in the round brackets with the real and the imaginary part corresponding to thermal lensing and gain guiding, respectively. If both parts are of comparable magnitude or if the imaginary part is smaller than the real one, as found in many practical resonator configurations, the expression obtained from this equation for the spot size is dominated by the real part, the expression obtained for the phase front curvature on the other hand is dominated by the imaginary part. Therefore, in monolithic configurations with short resonators gain guiding must only be taken into account for laser materials with negligible thermal lensing i. e. with very small or negative derivative of the index of refraction with respect to temperature. This case has been analyzed in previous papers. However, in heterogeneous resonator configurations e.g. with external mirrors or other mode shaping elements the additional phase front curvature due to gain guiding may become very important even in the presence of thermal lensing. An example for this situation is shown in Fig. 1 where a short crystal is combined with an external mirror and where the distance between crystal and mirror is chosen several times larger than the crystal’s length. As one can see, in this case the splitting of the mode shape for both directions of propagation due to gain guiding can be considerable. As can be shown by parameter variation, this splitting depends very sensitive on the relative values of the resonator’s length, the mirror’s curvature, and the parabolic coefficients n2 and α2 of refractive index and gain, respectively. In the present example, for fixed values of n2 and α2 the splitting can be nearly suppressed by an appropriate choice of the mirror’s curvature. The configuration, however, remains sensitive with respect to fluctuations of pumping power and temperature distribution. An even more complicated situation arises, if a frequency doubler is present in the resonator, which induces an antiguiding effect due to a transversely varying conversion efficiency. This examples show that a parametric study of the combined effect of thermal lensing and gain guiding can be very important to find out an appropriate resonator design. For this purpose a program was developed by the use of the complex ABCD matrix formalism which offers a very fast and valuable tool to get better insight into the behavior of resonator configurations even though it allows only a parabolic approximation.
Approach to Solving the Problem of Compromise between High Speed and High Resolution of Liquid-Crystal Spatial Light Modulators
Authors: Kamanina N.V. , Vasilenko N.A.
Published: February 2023

It is well known that a compromise between high speed of spatial light modulators (SLM) and its high resolution is one of the most important problem in physics of information systems, lasers, and joint-transform correlators. This is due to the fact that on retention of high resolution the high speed of SLM cannot be obtained by selecting characteristics of SLM layers.
Possibilities of Lasers Optical Methods for Diagnostics of Morphological And Optical Parameters of Whole Blood Under Normal and Pathological State
Authors: Korolevich A. N. , Prigun N. P.
Published: February 2023

Sizes and number of blood aggregates of a person are known to change considerably under different diseases, such as atherosclerosis, dilates, et cetera. This works studies the possibility to use dynamical spectroscopy methods for determining sizes and their variations under normal and pathological states. Samples of whole blood were in vitro investigated for ills with different diagnoses and extends of cardio-vascular diseases (strong aggregation) as well as for essentially healthy donors.
In vitro and in vivo laser induced fluorescence detection of malignancies in the female reproductive system via their natural emission and Hypocrellin probing
Authors: Liu W.Q. , Makrigiannakis A. , Vasiliou A. , Papazoglou T. , Fotakis C. , Koumantakis E.
Published: February 2023

The observed variations in three spectral regions of the laser-induced surface fluorescence emission of normal and malignant samples were studied in vivo and in vitro. In the in vivo study spectra were taken during standard surgical operations for the removal of malignant tissue (Ovarian tumors, uterine tumors). In the in vitro study tissue samples were obtained during laparotomy and hysterectomy of women pelvis. In this case the samples were tested in an unfixed state within 2 hours of excision. In all cases samples were then stored in formalin. Histologic examination followed and the results were compared with the surface fluorescence measurements. The experimental apparatus is shown below as well as two typical spectra taken in vivo from a normal and a malignant tissue. The low intensity spectrum comes from the latter.
Nd and Er: Yag Lasers in Ophthalmology
Authors: Jelínková H. , Hamal K. , Kubeček V. , Procházka I. , Čech M. , Pašta J.
Published: February 2023

In the pioneering years, laser radiation in ophthalmology was used mainly for retina coagulation (ruby laser, argon laser). With the discovery of other types of lasers, radiations of different wavelengths have been tested even for different ophthalmology treatments. Ophthalmic microsurgery (secondary cataract) uses a high power laser with the shortest pulses to generate plasma breakdown for removing the secondary lens capsule tissue. From the radiation penetration curve into the eye it follows that it is possible to use the radiation of visible or near infrared region. In case of the solid state lasers, the Nd:YAG or ruby lasers are suitable for this purpose, and therefore a simple laser unit which can generate either nanosecond or picosecond pulses is needed. Our Nd:YAG laser system (1.06 µm) for ophthalmology microsurgery allows to select either a Q-switched or mode-locked regime of operation. In clinical practice this system is used mainly for eye microsurgery - for capsulotomy or iridectomy treatment. Principe of function of immediate regimes variation with the comparison of results when the eye was treated with long (ns) or short (tens of ps) pulses (in vivo) are presented.
Investigation of temperature dependence in the dark current of InAs diode detectors
Authors: Kuan C. H. , Lin Ray-Ming , Tang Shiang-Feng , Sun Tai-Ping
Published: February 2023

InAs diode detectors are good for ~3 pm wavelength detection and promising to operate at high temperature (T). In order to decrease the dark current at high T, we have studied the I-V characteristics of the PIN (SI066) and PN (S1135) diodes, and concluded the dominant current mechanics at various T. The two diodes are grown on the InAs N-type substrates. The doping densities of the PIN diode are 3×1017 cm-3 and 6.7×1016 cm-3 for P and N types respectively, and the thickness of the intrinsic layer is 0.14µm. Those of the PN diode are 1 × 1016 cm-3 and 1×1016 cm-3. The mesa shape of the diodes is a circle with a radius of 150µm.
Measurement of the flapping angle and torsional angle of a dragonfly wing using fringe projection method
Authors: Zeng Lijiang , Aoshima Kazumi , Matsumoto Hirokazu , Kawachi Keiji
Published: February 2023

The study of the flight performance of a dragonfly requires a simple method to measure the torsional angle and flapping angle of a dragonfly wing during beating motion, we developed a fringe projection method in which the flapping angle and torsional angle of a dragonfly wing can be measured during beating motion using only one high-speed camera. The measured sections can be easily recognized from the number of fringes, without having to use any diffuse marks.
Photorefractive Keratectomy with the KrCl Laser (223 nm) - a Comparative Study
Authors: Bagayev S.N. , Rezhev A.M.
Published: February 2023

In this paper we present the results of comparative analysis of the interaction of radiation excimer ArF (193 nm) and KrCl (223 nm) lasers with the tissue of the cornea of human eye.
Nonlinear Optical Properties of Fullerenes
Authors: Couris S. , Koudoumas E. , Dong F. , Leach S.
Published: February 2023

Fullerenes, with C60, as a prototype, exhibit a unique combination of attractive chemical, physical and optical properties. Increasing interest for new tailored materials with specific linear and nonlinear optical properties have made the fullerenes an attractive class of materials for photonics and optoelectronics. Their high processibility, ease of chemical modification, thermal and oxidative stability, high-laser damage threshold, optical transparency and large nonlinear optical response are some of the properties which are important for photonic applications.
Sensitivity enhancement of the nonlinear refraction measurements with the open Z-scan by digital image processing
Authors: Marcano A. , Hernández O. F. E. , Maillotte Varid H.
Published: February 2023

The Z-scan(1) method is a well known simple and sensitive technique for measuring nonlinearities in bulk materials. A typical peak-valley transmittance curve is obtained from which it is easy to measure the nonlinear refraction (and/or absorption) coefficient of the material with a good sensitivity A modification of the technique, the Eclipsing Z-scan(2) (EZ-scan), where a disk is used instead of circular aperture has been also developed. It has been shown that the latter method is more sensitive, due to the fact that the relative changes of the transmitted power are larger than in the usual Z-scan.
Nonlinear characterisation in the near infrared of PbS doped sol-gel thin films
Authors: Fick J. , Vitrant G. , Martucci A. , Guglielmi M. , Pelli S. , Righini G. C.
Published: February 2023

Thin silica-titania planar waveguides doped with lead sulphide have been prepared on fused silica substrates using the sol-gel technique. The doping was realised by separate preparation of the matrix and the colloidal sol of the dopand, and successive mixing. Sulphide particles were obtained by reaction of metal acetates with thioacetamide and control of particle size was achieved by surface capping agents. PbS-doped films with different particle size in the range 28 nm were prepared. The films were densified for 1h at 300° C in nitrogen. The particle size was estimated from XRD spectra using the Scherrer equation. The thickness of the films is typically 900 nm and their refractive index at 1.064 microns is 1.52.
Two-Dimensional Mapping of Spatial Distribution of Excited Atoms and Ions in Laser-Produced Plasmas Using Three-Color Four-Wave Mixing
Authors: Koroteev N. I. , Naumov A. N. , Sidorov-Biryukov D. A. , Zheltikov A. M.
Published: February 2023

Although coherent four-wave mixing (FWM) has been successfully applied to different objects for quite a long period of time, recent experiments demonstrated that the use of this technique for the diagnostics of plasma and excited gases requires certain modifications in the methodology and specific investigations in the theory of coherent FWM. Specifically, recent experiments have revealed a high efficiency of nonlinear optical interactions of a strong laser radiation with excited gases and plasma.
Strain effects on heterojunction phototransistor performance
Authors: Ghisoni Marco , Sjölund Ola , Larsson Anders , Wang Shumin M.
Published: February 2023

The hetcrojunction phototransistor (HPT), with its inherent gain, is an attractive component for future optical interconnection systems [1]. The use of InGaAs as the absorbing medium is driven by the desire to operate at GaAs substrate transparent wavelengths. However, a trade-off exists between an increase in the thickness of absorbing material, and the onset of lattice relaxation giving rise to defects which degrade the devices. In this work we compare three HPTs, using 12, 20 and 30 strained InGaAs quantum wells (QWs), respectively, as the absorber. We show that all have high performance, but that lattice relaxation does cause a degradation in the device characteristics. The HPTs are of an n-p-i-n configuration grown on n-type GaAs substrate, similar to those previously reported [2]. The 1µm intrinsic collector region consists of GaAs within which are buried the different sets of InGaAs QWs.
Absolute Frequency Stabilization Of Diode-Pumped Er-Yb Lasers Around 1500 Nm Wavelength
Authors: Laporta P. , Taccheo S. , Bava E. , Svelto C.
Published: February 2023

The recently developed diode-pumped Er:Yb bulk-glass laser [1], oscillating around the 1550 nm wavelength, appears to be a very interesting source for both optical communications and metrology. In fact this solid-state laser source inherently exhibits a much narrower linewidth compared to e.g. laser diodes. For both high-density wavelength division multiplexing (HDWDM) [2] and metrology, absolute stabilization of the emitted wavelength(s) is, however, required. In this work, frequency stabilization by two different techniques and at two different wavelengths (1530 and 1550 nm) will be reported.
Polarization-Dependent Amplification in Planar Waveguides
Authors: Visser T.D. , Lenstra D. , Blok H.
Published: February 2023

We model a planar waveguide with an anisotropic active layer (i.e. with permittivity ϵ. a tensor) by using a scattering approach. The anisotropy of the permittivity can e.g. arise through the presence of strained quantum wells. It is calculated how much anisotropy is needed to get. a gain that is polarisation-independent.
Q-switched erbium lasers with FTIR-shutter and etalon reflectors of high damage threshold for medical applications
Authors: Eichler H.J. , Liu B. , Sperlich O. , Kayser M.
Published: February 2023

Laser radiation around 3 µm is of great interests in medical treatments, because water is the primary absorber in many biological tissues at the longer wavelengths and the absorption maximum of water lies at 3 µm. Furthermore, short pulses with 3 µm wavelength in the nanosecond range are especially interesting because of small thermal damage to the adjacent tissues during laser surgery, e g. by ablation of cornea material.
Femtosecond optical parametric amplifiers in the mid-infrared
Authors: Petrov V. , Noack F. , Stolzenberger R.
Published: February 2023

Tunable, nearly transform limited femtosecond pulses in the mid-infrared (MIR) spectral range are of greaT interest for the study of chemical and biological systems. The most widely spread method to produce such pulses up to 10 µm is difference-frequency mixing, but even with high-power amplifiers used as pump sources only nanojoule energies could be obtained. [1] Higher energy levels are expected with a single step of parametric conversion as in the recently developed parametric generators covering the near-infrared spectral region. [2]
Noncritically phase-matched femtosecond and picosecond CsTiOAsO4 (CTA) optical parametric oscillator
Authors: Köhler B. , Dörring J. , Nebel A. , Wallenstein R.
Published: February 2023

Optical parametric oscillators (OPOs) are known to be powerful devices for the generation of tunable ultrashort light pulses. The Ti:sapphire laser pumped CTA-OPO allows noncritical phase matching in the near infrared (1.32.3 µm) and thus generates ps- or fs pulses at the two important wavelengths for optical fiber applications.
Development of a fast mid-infrared integrating optical mutichannel analyzer
Authors: Bleuse Joël , Jacquot Jean-François , Picard Robert , Bonnet-Gamard Joël , Tribolet Philippe
Published: February 2023

We developped an optical multichannel analyzer for the 2-5 µm infrared band based on a 288x4 pixels CdHgTe detector, hybridized on a CCD chip, manufactured by SOFRADIR. It is cooled with liquid nitrogen, and mounted on a 250 mm focal length Czerny-Turner monochromator.
Photonic Band Gap Materials
Authors: Pendry JB
Published: February 2023

It is now some time since Yablonovitch proposed the optical analogue of the electron band gap: periodically structured dielectrics may totally exclude light in certain frequency ranges. At the time this concept of a ‘phtonc insulator’ provoked a furore and not a little disbelieve, but the concept is now an accepted one and the attention of the community is turning to how we can exploit the electron-photon analogy to control photons with the same facility as we do electrons. We may want to build better lasers, or to exploit more effectively use of light in communication, pushing the boundary of opto-electronics more in favour of the optical component of the subject.
High power room temperature operation of a Tm:YAG laser longitudinally pumped by a 20W diode bar
Authors: Bollig C. , Clarkson W. A. , Schmundt D. , Hanna D. C.
Published: February 2023

Diode pumped Tm:YAG laser operation in the eyesafe 2µm region is of great interest due to its numerous applications in important areas such as LIDAR and medicine. However, efficient end-pumping of this transition has proved problematic due to its quasi-three-level nature which requires a pump beam of high intensity and rather small diameter. This has been difficult to achieve with high power diode bars on account of the inconvenient shape of their output beam. Generally these lasers have been operated at reduced temperature to alleviate the reabsorption associated with the quasi-three level character.
Flashlamp-pumped Nd:KGW Laser at repetition Rate up to 30 Hz with Free-lasing and Q-switched mode.
Authors: Boquillon J.P. , Musset O.
Published: February 2023

Neodymium doped Potassium-Gadolinium-Tungstate crystal KGd(WO4)2 or Nd:KGW is a rather new crystal whose structure allows high doping (3 to 8 at.%) without detrimental concentration quenching. In this way it can compete with Nd:YAG in terms of specific energy despite a poorer thermal conductivity. Only experiments at low repetition rate and low thermal charge were performed before and we present here results obtained at repetition rates up to 30 Hz and pump powers up to 1 kW in order to see the behaviour of this crystal under such conditions. We tested several Nd:KGW laser rods, the last one was furnished by Marenna Co. (Bremen, FRG) and the dimensions were 6.35 × 76 mm with a Nd3+ doping of 3% at. The end faces were flat/flat parallel and AR coated at 1.06 µm. The optical quality was very good.
High efficiency, diode pumped Nd:glass slab lasers
Authors: Faulstich A. , Baker H.J. , Pelaez-Millas D. , Chesworth A.A. , Hall D.R.
Published: February 2023

Recently, we have reported a technique for efficient face pumping of thin slab solid state lasers [1] which overcomes the low pump absorption of slabs with thickness below one millimetre, and which is an area scalable design. The thin slab concept has the advantage of high gain, reduced optical distortion by temperature gradients and high thermal fracture pump power. The configuration is attractive for Nd:glass lasers, countering the poor thermal conductivity and low gain cross-section, and reducing active material cost. In this paper we investigate the average power capabilities of thin Nd:glass slabs, for a range of of cooling techniques, to assess thermal distortion problems and to determine the feasibility of true cw operation.
Recent progress in opto-electronic semiconductor/polymer based integrated devices
Authors: Bouadma N.
Published: February 2023

With the current trend towards optical communication, and for an effective penetration of the optical technology in the public networks, there is a particular interest in fabricating low-cost active and passive devices. Over the past years, III-V semiconductor-based opto-electronic devices have been investigated intensively as individual structures and their characteristics have attained a high performance level. However, their implementation in the public networks up to the subscribers is still impeded by their high cost level. Monolithic integrated optical devices made by planar techniques are suitable for mass production and have a strong potential for lower price: with added components defined by conventional microlithography rather by assembly, additional functionality can be obtained at minimum extra cost.
Fast linear electro - optic response in an organic salt
Authors: Sprcitcr R. , Bosshard Ch. , Pan F. , Günter P.
Published: February 2023

Organic electro - optic materials based on extended π-electron systems have been proposed for fast electro - optic application due to the large electronic contribution to (he electro - optic effect and the low dielectric constant.
Periodically poled RbTiOAsO for nonlinear frequency conversion
Authors: Karlsson H. , Laurell F. , Hansson G. , Henriksson P. , Arvidsson G.
Published: February 2023

Periodic electric field poling is an important technology for the development of tailored nonlinear materials for quasi-phasematched (QPM) frequency conversion. 0.5 mm thick samples of LiNbO3, and 1 mm thick hydrothermally grown KTiOPO4 (KTP) can be poled this way. KTP is of particular interest for blue and UV light generation as it is easier to pole and has a higher damage resistance. However, high ionic conductivity has so far impeded periodic poling of flux grown KTP, which otherwise would be desired as the flux growth technique is fast and gives large, high quality crystals.
Difference-Frequency Generation and Parametric Fluorescence In Quasi-Phase-Matched Lithium Niobate Stripe Waveguides
Authors: Baldi P. , Sundheimer M. , Hadi K. El , Aschiéri P. , de Micheli M. , Ostrowsky D.B. , Delacourt D. , Webjörn J.
Published: February 2023

Optical parametric oscillators (OPO) are excellent candidates for coherent tunable sources for many applications, such as telecommunications, spectroscopy and medicine, and optical parametric amplifiers (OPA) are interesting as amplifiers without spontaneous emission noise for generating squeezed states, etc… Integrated optical waveguide version1 of such devices could provide important additional features such as electrooptic tuning. Optical parametric fluorescence (OPF) and difference-frequency generation (DFG) are powerful techniques for characterizing the nonlinear waveguides without building the high-finesse cavity necessary to achieve the oscillation.
Kinetics of pulsed metal and metal halide vapour lasers and its influence on pulse repetition rate and average power
Authors: Petrash G.G.
Published: February 2023

One of the most important advantages of pulsed metal vapour and metal halide vapour lasers is the possibility to operate at high pulse repetition rate (PRR) which is usually in the range of 5-30 kHz. The high PRR leads to high average power exceeding for large-bore lasers several hundreds W. This is the reason of considerable interest in investigation of the processes limiting attainable PRR and average power. However, these processes are still a subject of many discussions.
Stable oscillation of AlGaInP diode laser with phase-conjugate feedback
Authors: Shiratori Akira , Aitani Kimio , Obara Minoru
Published: February 2023

Phase-conjugate feedback (PCF) is an attractive method to realize a narrow linewidth, single longitudinal mode oscillation of a diode laser. Several experiments have been reported with photorefrac five BaTiO3 phase-conjugate mirrors (PCMs)1,2,3, and passive self-pumped phase conjugators (ring type conjugator1,2 or CAT conjugator3) have been employed as external PCMs in these experiments. However, frequency shift of phase-conjugate wave leads to self-scanning of the lasing frequency, resulting in the frequency-unstable oscillation.1,3 In this paper, we have achieved frequency -stable oscillation of a 635 nm AlGaInP diode laser with a new PCF using the stimulated photorefractive backscattcring(SPB) process in a photorefractive BaTiO3 crystal.
Two-frequency configuration for correlation analysis with adaptive photodetector
Authors: Korneev N. , Rodríguez P. , Stepanov S.
Published: February 2023

Adaptive photodetectors are based on the effect of non-steady-state photo-induced electromotive force. The effect consists in generation of an alternating (AC) electric current through a short-circuited photorefractive or photoconductive sample due to interaction of the instantaneous spatial distribution of photoconductivity produced by a vibrating light pattern with that of the stable diffusion-type space-charge electric field recorded by this or another light pattern. This field pattern recorded in the sample is efficiently reconstructed (i.e. produces the maximal output AC current) only under illumination by the matched (i.e. the same) light pattern that gives rise to the photoconductivity distribution. Any other (nonmatched) or shifted picture produces noncoherent signals from different areas of the device resulting in a weak noise-like output signal. Recently we suggested to use this property for correlation analysis of 2D patterns [1].
Suppression of mode-hopping in a single-frequency intracavity-frequency-doublcd Nd:YAG ring Laser.
Authors: Marlin K.I. , Clarkson W.A. , Hanna D.C.
Published: February 2023

Mode-hopping is a typical, but undesirable feature of many lasers, being particularly noticeable and troublesome in lasers designed for single-frequency operation. It occurs as the result of small changes in cavity length, or shift (eg. due to temperature change ) of the gain peak, Elimination of mode hopping can add considerable complexity to a laser, as typical counter measures include active stabilization of the resonator length to a stable reference cavity, and temperature stabilisation of the gain medium.
A Stable 80 Watts SHG Green Laser with LBO Crystal
Authors: Gu Gordon , Morrow Clifford
Published: February 2023

For many years now, researchers have been attempting to develop a new laser system with a different wavelength for a variety of applications. The frequency doubled Nd:YAG laser with 532 nm wavelength has been used in medical, industrial and scientific fields. For some applications, the intracavity Second Harmonic Generation (SHG) of Nd:YAG laser resonator is required in order to generate a very high average power of 532 nm green laser. Potassium Titanyl Phosphate (KTP) has been used as the second harmonic crystal because it has a very high effective nonlinear coefficient for Type-II phase. [1] On the other hand, KTP has some disadvantages for high power intracavity SHG applications: (1) as a result of its low laser damage threshold, the “gray track” and “burn out” of KTP crystals are common problems for this application, (2) the smaller acceptance angle limits the optical intensity on the crystal and makes the system very sensitive to misalignment, (3) the larger walk-off angle directly impacts the quality of the laser mode and limits some of the applications.
The growth of Nd doped LaSc3(BO3)4 single crystals for diode pumped microchip lasers
Authors: Chai B. , Ye Q. , Petermann K. , Huber G.
Published: February 2023

High efficiency diode pumped Nd-doped LaSc3(BO3)4 (LSB) microchip laser has been reported before. 1-4 Nd:LSB crystals offer unique properties of large absorption coefficient, broad absorption band (FWHM = 3 nm) and high Nd doping with little concentration quenching. It is ideal for diode pumped miniature lasers where high (> 15%) Nd doping is preferred.
Crystal Growth and Characterisation of Potassium Lithium Niobate (KLN) for SHG of Semiconductor Diode Lasers
Authors: Quanzhong Jiang , Gallagher H. G. , Han T. P. J. , Henderson B.
Published: February 2023

In recent years, considerable effort has been dedicated to the search for non-linear optical crystals suitable for second harmonic generation (SHG) of semiconductor diode lasers. So far, there have been a number of reports of diode pumped phase matched SHG based on potassium niobate (KNbO3) [1] and pseudo-phase matched SHG of periodic domain inverted lithium niobate (LiNbO3) [2]. However, both these materials have disadvantages. Periodically poled LiNbO3 is difficult and expensive to produce and may not be suitable for high power applications. KNbO3 has a small phase matched temperature bandwidth (~0.5°C) and exhibits phase transitions at ~ -40°C (mm2 → m3) and ~ 210°C (4mm → mm2). In consequence, the crystals may be converted to multi-domain structure by simple mechanical shock or at temperatures over 40°C [3].
Rare Earth Doped Al2O3-Thin Film Waveguides Deposited by MO-PECVD and MO-LPCVD on Silicon Substrates
Authors: Blume O. , Mahnke M. , Sander D. , Müller J.
Published: February 2023

Optical amplification with EDFAs has opened up new ways for high speed data communication. This stimulated research activities for planar rare earth doped waveguides. Complete active devices as loss-compensated 1:8 splitters can be developed on silicon substrates, when optical amplification is combined with integrated optical waveguide components, fiber alignment structures, and hybrid pump laser mounting.
Characterization of Nd:YAG epitaxial planar waveguides grown on various substrates by pulsed laser deposition method
Authors: Ezaki M. , Kumagai H. , Toyoda K. , Obara Minoru
Published: February 2023

The solid-state laser crytsal with waveguide structure has several advantages over bulk one due to the optical confinement which leads to the low-threshold and efficient oscillation. Among various solid-state laser media, neodymium doped yttrium aluminum garnet (Nd: YAG) waveguide has strong potential for application to diode-pumped waveguide lasers1,2) and is also an ideal candidate for integrated optoelectronics applications such as Q-switched microchip lasers3,4) which can be realized by monolithically combining their waveguide lasers with other optical components (e. g. Cr YAG thin film) on the same substrate. Thus, the possibility of fabricating YAG thin films with waveguide structure on various substrates will widen their applications in the fields of integrated optics.
Carrier Dynamics in 155 µm InAlGaAs Quantum Well Laser Structures
Authors: Marcinkevičius S. , Hillmer H. , Lösch R. , Olin U.
Published: February 2023

There are several effects that make InAlGaAs/InP material system advantageous over the commonly used InGaAsP/InP system for implementing 1.3 and 1.55 µm quantum well (QW) lasers. These effects are related to different band offsets and include better electron confinement, faster interwell hole transport, higher differential gain and lower gain suppression. However, due to technological difficulties, the InAlGaAs material system has been far less investigated and applied.
High Power Multichannel Waveguide Lasers
Authors: Baker H J , Hall D R
Published: February 2023

High power and efficient carbon dioxide laser operation has been achieved with diffusion cooling in compact devices using the large area slab RF discharge technique [1]. An alternative approach to laser power scaling, useful when technological constraints limit the power which may be extracted from individual laser oscillator, is to employ the array laser concept. Considerable work has been done on developing techniques for producing phaselocked operation, both with laser diode arrays and with arrays of waveguide gas lasers. Here we consider planar and 2-d laser arrays based on multiple elemental waveguide carbon dioxide laser oscillators, operating in the mutually incoherent mode. The waveguide CO2 laser is a very suitable building block for laser arrays because it produces excellent intrinsic beam quality, is scaleable in monolithic planar and stacked plane geometries, and may be conveniently excited from a single radiofrequency power generator.
Ultra-compact R.F.-discharged pulsed CO2 laser
Authors: Rossetti F. , Lobate A. , Moscatelli S. , Lapucci A.
Published: February 2023

An ultra-compact slab-type CO2 laser has been operated in a pulsed regime obtained by switching the R. F. discharge. Laser pulses with power up to 480 W have been obtained at Pulse Repetition Rates (P. R. R.) in the range 0.5 - 10 kHz. The slab discharge channel measures 320 × 60 × 2 mm and has been fed with 2.1 KW R.F. in pulses with duration ranging from 30 to 1000 μs. Static gas fills of 1:1:3 and 1:1:5 CO2, N2, He, with or without 5% Xe admixture, have been tested.
Spatial Solitary Waves in the Coupled Wave-Carrier Systems of Semiconductor Gain Media
Authors: Sun Yan , Fanning C. Geoff
Published: February 2023

The study of spatial optical solitons has become a hot topic because of its importance in scientific research and technological applications. It is interesting to investigate solitons in semiconductor gain media. Besides enjoying wide technical application, a semiconductor gain medium is near absorption resonance and its nonlinearity stems from the gain saturation and the antiguiding factor. The resulting nonlinear Schrödinger equation is more complicated than that for a Kerr-medium. Spatial solitary waves have been experimentally observed recently. Here we show analytically that spatial solitary waves exist in a semiconductor gain medium pumped just above a threshold value. Numerical simulations show that these spatial solitary waves are not perturbation stable, but can propagate long enough for practical device applications.
Studies of an Inverse Scattering Problem Solution for Mixed-Phase and Cirrus Clouds
Authors: Oshchepkov Sergey , Isaka Harumi
Published: February 2023

The determination of cloud microphysicai parameters by light scattering methods can be referred to one of the most priority procedures of the modem atmospheric optics. Such an information including phase cloud structure is interesting as itself at studying the formation of mixed phase clouds, nucleation processes, precipitation and is a primary factor to calculate radiative transfer through clouds and to design radiative models of cloud cover.
Mid-Infrared Generation by Optical Mixing Technique
Authors: Burie J. , Boucher D. , Marquette A. , Chen W.
Published: February 2023

For applications of spectroscopy and monitoring of atmospheric trace gases, laser-based continuously tunable mid-infrared source (2-20 μm) produced through parametric frequency conversion process has been rapidly developed ([1], [2], [3]).
Photoinduced Phase Distributions in a Photorefractive Bi12TiO20 Crystal
Authors: Garcia Quirino G. S. , Iturbe Castillo M. D. , Sánchez-Mondragón J. J. , Stepanov S. I.
Published: February 2023

Experimental observation of one dimensional (1D) and two dimensional (2D) bright and dark spatial soliton propagation has been reported in photorefractive media [1,2]. The experiments were performed under externally applied dc field, which clearly sets some particular direction in the plane perpendicular to the axis of soliton propagation. In this paper we present experimental results on the interferometric analysis of the photoinduced phase changes produced by a 1D dark stripe and a 2D dark circular spot intensity distributions These kind ot intensity distributions are typical for dark spatial soliton generation.
Wood’s Anomalies in Self-Diffraction
Authors: Petruskevicius R. , Kuprionis Z.
Published: February 2023

It is known that the Wood’s anomalies can be observed on "permanent” diffraction gratings under certain conditions [1,2]. These anomalies may occur both in TM and TE polarizations of incident light and can be of different types "Rayleigh”, "leaky-wave resonance” and "Bragg-angle” types of anomalies. Stimulated Wood’s anomalies [3] can develop on the surface illuminated by a single laser beam of sufficient intensity as spontaneous highly periodic surface ripples Conventionally, laser light self-diffraction on two-wave induced dynamic gratings in a thin nonlinear film is studied in the Raman-Nath approach not taking into consideration the possibility of any Wood’s anomalies [4]. We have shown that Wood’s anomalies can be observed not only on the “permanent” diffraction gratings but also on the two-wave induced dynamic gratings [5]. We consider the Wood’s anomalies of "leaky-wave resonance” type to be related to excitation of surface polaritons or guided waves in the thin slab by means of induced dynamic gratings. These anomalies occur when one or two counterpropagating off-Bragg self-diffraction orders skim along the illuminated thin slab at some angles of degenerate two incident wave mixing. These leaky-wave resonances give rise to enhancement of local field and all nonlinear processes on the surface. The self-diffraction of laser light at these resonances exhibits instabilities which were not considered previously. The goal of this report is to present results of study of these new phenomena which would be important for nonlinear optical probing of surfaces and multiwave mixing processes in thin films.
Amplification of Solitonic Pulse Trains by Semiconductor Amplifiers
Authors: Michaelis D. , Peschel U. , Etrich C. , Lederer F.
Published: February 2023

Most of conventional long-haul fibre transmission operate around λ=1.32μm. Semiconductor amplifiers are promising candidates for an all-optical signal amplification in these lines. They are commercially available and can be operated with output intensities typically up to 10mW. Assuming a free propagation through 50km of standard fibre an overall loss of 20dB has to be compensated in each amplifier. To obtain an overall transmission capacity of 10 GB/s the basic pulse duration has to be about 30ps (FWHM). To ensure a distortion free solitonic propagation and to avoid resonance radiation one has to choose a wavelength far from file zero-dispersion-point in the region of an anormalous dispersion. In the further calculations we assumed a value of D=1ps/nm/km. To determine the soliton parameters one has to average over the whole span between two amplifiers. Hence to generate solitons every pulse has to be amplified up to a peak power of 7.8mW.
Use of Polarization Lidar for Investigation of the Atmospheric Planetary Boundary Layer
Authors: Kolev I. , Kaprielov B. , Tatarov B.
Published: February 2023

The lidar studies of the polarization characteristics of natural and anthropogenic atmospheric objects have been actively pursued in recent years both in their experimental and theoretical aspects for the needs of the applied meteorology and ecology.
Effects of Light Beam Self-Action in Waveguides With Depth - Inhomogeneous Photorefraction
Authors: Shandarov V. , Shandarov S.
Published: February 2023

The inhomogeneity of photorefractive properties in electrooptic waveguides doped by special impurities may be substantial even within cross - section of light beams. It may considerably influence characteristics of photorefractive effects [1], including self - actions like spatial soliton formation attracted great attention for last years [2, 3].
Bimorph Piezoelectric Structures in Laser and Astronomic Adaptive Optics
Authors: Safrońov Andrey G.
Published: February 2023

Simplicity and low cost of a so-called “small” adaptive optics or the adaptive optics for low order correction make it more preferable for use than a traditional techniques. Adaptive bimorph mirrors appear to be the optimum wavefront corrector for such systems. The existing bimorph mirrors have some disadvantages, namely, a limited size of the aperture under control and low sensitivity.
Experimental Verification of Trailing Pulse Suppression in Actively Mode-Locked Laser Diodes by Gain Quenching
Authors: Kawaguchi Hitoshi , Igarashi Taku , Yamayoshi Yasuhiro
Published: February 2023

Actively mode-locked laser diodes (LDs) with an external mirror configuration suffer from trailing pulses which is caused by the residual reflection at an LD facet even with an antireflection coaling. When the cavity length is relatively long (~ few GHz) and the bias and RF currents are large, we also observe trailing pulses caused by an excess gain. We proposed recently a new method for obtaining high-power short optical pulses without such trailing pulses[1]. A part of the output is reflected back into the LD with an orthogonal polarization and an appropriate time delay. Trailing pulses caused both by the excess gain and the residual reflection at an LD facet are suppressed.
Third-Harmonic Generation at a High Repetition Rate in a Femtosecond Laser Produce Plasma in Air
Authors: Rebane A. , Krylov V. , Koroteev N. , Zheltikov A.
Published: February 2023

For the most part, experiments on harmonic generation in rare gases and in laser-produced plasma use multiple pulses illumination from high-power nano- and picosec­ond lasers, which allows high-order harmonics to be observed in a substantially non-perturbative regime.