bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of ultrashort (<500 fs) wavelength tunable laser pulses by self-seeding and adiabatic soliton compression
Authors: Huhse D. , Warmuth C. , Bimberg D. , Sysoliatin A. A. , Dianov E. M.
Published: February 2023

Ultrashort, wavelength tunable laser pulses find an increasing range of quite different applications, like measurement techniques of ultrafast physical phenomena (e.g. electro-optic sampling), analysis of environmental data, and telecommunications. A simple way to generate wavelength tunable semiconductor lasers pulses having a width (FWHM) of a few picoseconds is self-seeding (SeSe) of a gain-switched Fabry-Perot (FP) laser diode and subsequent chirp compensation. This technique is particularly simple and low-cost. Neither highly sophisticated laser structures like, e.g. Tunable Twin Guide (TTG) or multi-section DBR lasers, nor anti-reflection coating of the facet, as required for mode-locking, is needed. Additional compression of SeSe pulses can be performed using nonlinear (soliton) effects in fibers. The potentially most promising method to generate ultrashort pulses of high quality is adiabatic pulse compression in dispersion decreasing fibers. In this contribution we demonstrated that it is indeed possible to generate femtosecond wavelength tunable pulses in such a way.
Ultra-Short Pulse Stabilization by Slow and Fast Nonlinear Refraction in Cw Solid-State Laser with Semiconductor Saturable Absorber
Authors: Mikhailov V. P. , Kalashnikov V. L. , Poloyko I. G.
Published: February 2023

Over the past few years the considerable progress has been achieved in the generation of the femtosecond ultrashort pulses. This progress was based on the use of fast electronic phase nonlinearity, which causes the Kerr lensing in the active medium and has response time closed to few femtosecond [1].
Use of Blue InGaN LEDs for the Setting of Light Activated Dental Composites
Authors: Girkin J. M. , Dawson M. , Carey J J , Whitters C J
Published: February 2023

Over the past two years high power, (several mW) blue LEDs have become commercially available1. Such devices have started to make their appearance in practical devices, in particular in large outdoor displays. We have investigated their potential use in the dental field, in particular their use for setting light activated materials.
Wavelength Converter/Amplifier With Fine Tunabilty
Authors: Sari H. , Ergun Y. , Sokmen I. , Balkan N. , Ali A. , Entee N. Mc , Mills S.J.
Published: February 2023

The results of the study of a novel monolithic wavelength converter / amplifier which can be timed, with the application of an external field are presented. The tuning range is Dl=300 Å about the operation wavelength, 1= 8400. The proposed device is a modified version of the HELLISH-1 (Hot Electron Light Emitting and Lasing Semiconductor Heterojunction) device1,2. It consists of a graded Ga1−xAlxAs quantum well (0< x< 0.15) placed on the n side of the depletion region, of a Ga0.7Al0.3As p-n junction, as shown in figure 1. As a result of the built-in field coupled with the grading the quantum well looks as if it were an isolated square well in zero field. Forward biasing the junction reduces the built-in field, thus the field associated with the grading becomes effective as shown in figure 2. The tuning of the operation wavelength is based on the Quantum Confined Stark Effect and is achieved during the forward biasing of the device. The wavelength as a function of the forward bias is shown in figure 3. Forward biasing the junction (electrical pumping) results in an enhanced conversion efficiency.
Novel scheme of dynamic correction using negative optical feedback
Authors: Venediktov V. Yu. , Berenberg V.A. , Bezina N.A. , Leshchev A.A. , Vasil’ev M.V.
Published: February 2023

The energy loss lacking and wide spectral band method of one-way dynamic correction for phase distortions, based on the use of the optically addressed liquid crystal spatial phase light modulator (OA LC SLM) in negative optical feedback1 is very promising Probe beam passes through the distorter and through the LC layer of SLM Then it is collinear combined with reference beam, and the resulting interference pattern controls phase retardation in LC SLM. Negative feedback dynamics results in realisation of the corrector, adding to the distorter influence Practical implementation of the method was blocked by the 2π-problem — indeterminism of phase reconstruction from intensity distribution For the extended range of distortions scale the corrector breaks into domains, and can be used only for narrow spectral band or, without breaking, for small-scale distortions. Recently2 we have solved the problem by the application of the dynamic holographic converter of distortions scale The talk describes the improved schematics of the corrector record. The distortions are probed by two collinear beams with wavelengths λ and λ′. Distorted probe beam at λ′ writes in another OA LC SLM the thin dynamic hologram, which is reconstructed by the distorted probe beam at λ. Reconstructed reference wave has residual distortions of the scale |λ − λ′|/λ′. Its interference pattern with nondistorted beam reveals much wider range of monotonous variation. OA LC SLM, controlled by such pattern can be used for wide spectral band correction for large scale (say, several or several dozen λ) distortions. System performance analysis, key technologies involved and performance simulation will be discussed in the talk.
Dye-Treated Vegetable Lasers
Authors: Taniguchi Hiroshi , Tanosaki Shinji , Devaraj B. , Inaba Humio
Published: February 2023

Experimental studies on laser action from highly scattering gain media are of current topics in the laser field; optically pumped bulk solution 1 and liquid microdroplets 2-7 of high-gain dye containing strongly scattering nanoparticles. The mechanism for lasing action is considered owing to enhanced stimulated emission through multiple light scattering in a strongly scattering and diffusive gain-medium that can provide dispersive feedback to exceed the gain over loss in a small spatial region.
Performances of the self-frequency doubling Nd:GdCOB crystal under diode-pumping
Authors: Augé F. , Mougel F. , Aka G. , Kahn-Harari A. , Vivien D. , Balembois F. , Georges P. , Brun A.
Published: February 2023

Nonlinear host crystals for Nd3+ ions allow to device compact green laser sources using self-frequency doubling if it can be efficiently pumped by a laser diode. Previous works have been done with NY AB [1] but this crystal is very difficult to grow and has an significant absorption of the SHG wavelength.
V3+:YAG - A New Infrared Passive Q-Switch
Authors: Malyarevich A M , Denisov I A , Yumashev K V , Mikhailov V P , Conroy R S , Sinclair B D
Published: February 2023

Passive Q-switching has provided a very successful, compact, means of generating short, high intensity pulses. Many bulk passive Q-switches use the Cr4+ ion, in particular Cr:YAG, which has yielded pulses of 600ps duration in combination with Nd:YAG, in a microchip geometry [1]. More recently the use of quantum wells in semiconductor devices (SESAMs) has produced ultrashort pulses: 230ps at 1342nm and 56ps at 1064nm [2]. However these SESAM devices appear to be limited to relatively low pulse energies.
Polarization properties of the diode-pumped Nd: lasers passively Q-switched with Cr4+-.saturable absorbers.
Authors: Klimov I.V. , Bartschke J. , Boiler K-J. , Tsvetkov V.B. , Shcherbakov I.A. , Wallenstein R.
Published: February 2023

Excellent output parameters of Cr4+-passively Q-switched diode pumped Nd-lasers causes strong interest to these system as laser sources for the consequent nonlinear frequency conversion through external harmonics generation or through pumping the optical parametric oscillators [1]. Mode-selection property is quite common for passive Q-switching technique and can by explained by means of strong gain difference between adjacent modes during multipass build up of the pulse. However, the polarization features of the Cr4+ :crystals-Q-switched lasers are determinated mainly by polarization anisotropy of the Cr4+-saturable absorption and it’s interaction with resonator polarization inhomogeneity.
Spot-Size Expander and Reducer Made by Local Heat Treatments
Authors: Nishimura Junji , Morishita Katsumi
Published: February 2023

Spot-size expanding and reducing fibers are required for collimating a beam from a fiber, focusing a beam onto a fiber, and matching spot-sizes between different waveguides. Several methods have been proposed to change the spot-size, including a tapered fiber, a thermally diffused expanded core fiber, a microlens fabricated directly on the end of a fiber, and a graded-index fiber tip fused to a single-mode fiber.
Backscattering-CARS on CVD Diamond
Authors: Bühler Jürgen , Prior Yehiam
Published: February 2023

Diamond Growth by Chemical Vapor Deposition has developed in the last years to the point of being commercially used in industrial applications1). Due to the superiority of many of its properties, applications of diamond films can be found in the tool industry (e.g. wear resistant coatings), semiconductor industry (e.g. heat conductive substrates) and optical industry (sturdy optical coatings). The early nucleation stages, however, are still not fully understood.
A Laser Operated Precision DC HV Voltmeter
Authors: Knaak K.-M. , Wendt K. , Kluge H. J.
Published: February 2023

The precision of HV voltmeters based on voltage dividers is limited by the systematic errors induced by nonlinear currents and resistive drift. Therefore we take a different approach by accelerating ions with the potential to be measured. The resulting fast ion beam is collinearily superposed with a diode laser beam tuned to an optical resonance of the ions. Comparison to a cesium stabilized reference laser yields the absolute laser frequency to within a MHz. Now the accelerating voltage can be determined via the dopplershift of the optical resonance. Thus collinear laser spectroscopy [1] translates the voltage measurement to an absolute determination of an optical frequency.
Q-Switching a Continuously End-Pumped Multirod Resonator.
Authors: MacDonald Michael P. , Graf Thomas , Balmer Jürg E. , Weber. Heinz P.
Published: February 2023

The variable configuration multirod resonator (VCR) is capable of producing fundamental mode output with high power at a high efficiency from a small resonator.1 It consists of three Nd:YAG rods in a folded cavity so that each rod is endpumped by a fibre coupled diode laser. This gives it good mode overlap in the pump beam and ability to overcome the problem of thermal lensing so that it can produce up to 13W cw. In order to obtain very high peak powers from the VCR, it is necessary that it be Q-switched. The VCR has stability properties that point towards a new form of Q-switching which does not require significant changes to the efficient cw set-up. It is possible, by choosing suitable dimensions and pump powers, to have the resonator stable when operating as a ring resonator but to be unstable when operating as a Fabry-Perot Resonator. In the VCR the difference between the resonator being in Fabry-Perot and ring configurations is simply the presence or otherwise of a quarter wave element.
Integrated optical interferometers for low coherence sensing applications
Authors: McLaughlin A.J. , Bonar J.R , Jubber MG. , Camacho F. , Aitchison J.S.
Published: February 2023

Fibre optic low-coherence interferometry is of great interest for industrial sensing applications In general, systems use a low-coherence source to illuminate two interferometers with matched optical path differences (OPD), greater than the source coherence length. Typically, the first interferometer is used as a sensor, for example micro-machined silicon resonant sensors [1], where a reference and modulated sensing signal are derived from the sensor head. Due to the large OPD the two signals can propagate together without interference. The second interferometer acts as a detector, where due to its matched OPD, the signals from the sensor head are brought back into coherence and interfere.
Near-field Optical Microscopy of Photonic Crystal Waveguide Structures
Authors: Phillips P.L. , Knight J.C. , Mangan B.J. , Russell P.St.J. , Charlton M.D.B. , Parker G.J.
Published: February 2023

Photonic band gap structures are a topic of very active research because of their novel physics and many potential applications. Theoretical studies of photonic crystals have revealed many interesting features: however, realisation of genuine applications has been hindered by the difficulties associated with modelling, fabricating and characterising devices. In this paper, we describe how scanning near-field optical microscopy (SNOM) enables the complete characterisation of the electromagnetic fields in 2-dimensional photonic crystal waveguide structures.
High Efficiency Diode Pumped Yb:Er:Glass Lasers
Authors: Boutchenkov V. , Kuchma I. , Levoshkin A. , Mak A. , Petrov A. , Hollemann G.
Published: February 2023

Recent years Er:glass lasers attract more attention due to their " eye-safe" radiation. The objects of special interest are Q-switched lasers with an output energy of up to 8 mJ as eye-safe emitters for laser rangefinders and lidars. One of serious imperfections of these lasers is their rather low efficiency. In this connection laser-diode pumping seems perspective. However, as far as we know, the efficiency of such lasers realised to date is still rather low and does not exceed 0.8 %. [1-4].
Site Selective Excitation and Upconversion in Er3+:KLiYF5
Authors: Smith Anita , Manson Neil B. , Silversmith Ann J. , Henderson Brian
Published: February 2023

KLiYF5 is a promising new laser host crystal. Nd3+:KLiYF5 forms the basis of a low threshold infrared laser1, and has also been characterized for its potential as an upconversion laser.2 We have measured the low temperature excitation and emission spectra of a single crystal of 1% Er3+: KLiYF5. The rare earth ions reside in two similar but optically separable sites. The similarity of the centers is obvious because of one to one correlation in the number of spectral lines, similar strengths and polarisations of transitions, and very small shifts in energy (typically less than 10cm1) between corresponding levels. Selective excitation and emission experiments have been performed using a pulsed tunable dye laser in the wavelength range 450nm to 700nm. With a combination of excitation and emission experiments, positions of all levels below 25,000cm-1 have been determined. Lifetimes relevant to the upconversion work have been measured.
Infrared to blue wavelength upconversion in Pr3+ doped LaCl3 and Be2La2O5 single crystals
Authors: Piramidowicz R. , Szczepañski P. , Woliñski W. , Malinowski M.
Published: February 2023

Trivalent praseodymium ion (Pr3+) activated crystals and glasses are interesting materials for visible and infra-red (IR) solid-state lasers. Because of the energy level structure, and suitable lifetimes of the excited states, Pr3+ systems are also attractive as short wavelength upconversion laser systems. Recently, simultaneous blue, green and orange wavelength lasing in Pr3+ doped ZBLAN fiber has been reported as a result of IR-laser-diode pumping.
The effect of oxide on the spectroscopic properties of the 1.3, 1.7, and 2.9 μm transitions in dysprosium-doped gallium-lanthanum-sulphide glass
Authors: Martins E. , Schweizer T. , Brocklesby W.S. , Hewak D.W.
Published: February 2023

Gallium-lanthanum-sulphide (GLS) chalcogenide glass doped with dysprosium (Dy3+) shows promise as 1.3 μm fibre-optic amplifier and mid-infrared laser material. GLS glass has attracted great interest due to its low phonon energy of ~ 425 cm-1, resulting in low non-radiative decay rates of rare-earth ions. Its high refractive index of 2.4 results in high radiative emission rates. Both properties improve the radiative quantum efficiencies for all transitions.
Anisotropies and intensity saturation of gray-tracking in KTiOPO4
Authors: Rousseau I. , Boulanger B. , Fève J.P. , Ménaert B. , Marnier G.
Published: February 2023

We performed a complete quantitative study of anisotropy of gray-tracking induced in flux-grown KTiOPO4 by a polarized 532 nm pulsed laser, on the basis of transmission measurements before and after irradiation. The laser has. a 10 Hz repetition rate and a 6.5 ns half-width duration at 1/e2; its polarization is orientated parallelly or orthogonally to the polar axis (z-axis) of KTP. Two kinds of experiments were realized: measurement of transmission spectra from 300 nm to 3000 nm with a spectrophotometer which we modified for crystal measurements with polarized light; measurements of transmission of a polarized HeNe probe which is superposed on the 532 nm beam.
Gain measurements of transverse stimulated Raman scattering in KDP, KD*P
Authors: Novikov V.N. , Belkov S.A. , Buiko S.A. , Voronich I.N. , Efimov D.G. , Zaretsky A.I. , Kochemasov G.G. , Kravchenko A.G. , Kulikov S.M. , Lebedev V.A. , Okutin G.P. , Rukavishnikov N.N. , Sukharev S.A.
Published: February 2023

The gain measurement method of radiation at Stimulated Raman Scattering (SRS) excitation in medium placed into transverse pump cavity /1/ has been developed and tested. On the third harmonic of iodine laser ISKRA-4 (λ=438 nm) values of gain coefficient (g) for transverse SRS (TSRS) radiation have been measured in benzene and in the frequency converter crystals (KDP, KD*P) grown following the traditional and rapid-growth technology, cut out by Type-II (9=60°). At the g measurement in crystals pumping wave was ordinary, the pumping and scattered wave vectors and the crystal optical axis were coplanar.
Geminate and Distant Radiative Recombination of Si-centers in Porous Glasses
Authors: Sokólska I. , Mugeński E. , Cywiński R.
Published: February 2023

Silicon quantum dots (SQD) are promising luminescent centers for opto- and microelectronics. Up to now only few papers have been devoted to the properties of SQD in porous glasses [e.g.1-5].
Design and characterisation of an Indium Gallium Arsenide Multiple Quantum well modulator operating with 5 Volts
Authors: Byrne Declan , Horan Paul , Hegarty John
Published: February 2023

Design and characteristaion of a Fabry-Perot InGaAs MOWpindiode modulator operating at 5 Volts is described. The modulator is optimised to give maximum reflectivity change, but still compatible with high speed and detector operation.
Optical Highways for Computing Architectural and Topological Issues
Authors: Dines Julian A. B. , Snowdon John F. , McArdle Neil
Published: February 2023

The Optical Highways [1] scheme is a design for an optical, free-space interconnect for massively parallel computers. Unlike some other optical interconnect schemes this design is not constrained to low-order networks but is a general purpose interconnect onto which almost any network topology can be mapped. For example, the Optical Highway can be configured to implement topologies such as a low-order 2-D Mesh, a multi-dimensional Hypercube, or even a high-order Crossbar. This flexibility makes the scheme appealing to parallel computer architects, especially the ability to implement large-scale, higher-order network topologies, which were previously impossible using only conventional electrical interconnects.
External-cavity diode laser using optical feedback for sensitive measurements of aerosols
Authors: Sandsten Jonas , Gustafsson Ulf
Published: February 2023

Allergy and asthma is known to increase because of indoor environment exposure to for example mould fungus spores and outdoor environment exposure to pollution and pollen. Rapid changes in working life concerning production technology and the development of materials lead to rapid introduction of new potential risks. In the working life we would like to be able to monitor and identify aerosol particles of hazardous materials such as respirable fibers in real-time.
Length Measurement by Speckle Velocimeter Using Two Self-Mixing Laser Diodes
Authors: Takasu Tatsuya , Ozdemir Shahin Kaya , Shinohara Shigenobu , Ikeda Hiroaki , Yoshida Hirofumi , Sumi Masao
Published: February 2023

Recently, we demonstrated a speckle velocimeter to measure both velocity and length of a moving plate using a self-mixing laser diode (SM-LD).(1),(2) Although the measurement error by the previous velocimeter was 1% for velocity and a few % for length, it requires advance calibration to determine a pair of constants which depend on a beam spot size and material surface to be measured.
Application of rigorous diffraction theory to scanning optical microscope problems
Authors: Morgan S.P. , Somekh M.G. , See C.W.
Published: February 2023

If a structure to be examined by a scanning optical microscope has a width less, or height greater than, a wavelength or if the microscope system has a high numerical aperture (NA) then scalar diffraction theory will break down and a more rigorous approach to the diffraction problem is required. With advances in technology producing smaller structures rigorous modelling of the microscope response becomes a necessity.
Self-Pulsation and Mode-Locking in Narrow Stripe Lasers
Authors: Dubbeldam J. L. A. , Lenstra D.
Published: February 2023

Self-sustained pulsation phenomena were first observed in degraded lasers. Narrow stripe lasers also show this self-pulsating behavior. Although rate-equation models predicting the self-pulsations exist, a more physical explanation of the self-pulsations is still lacking. Since self-sustained pulsations can also be obtained in structures with an unpumped region in the longitudinal direction of the laser, which then acts as a saturable absorber, the connection with saturable absorber mode-locking is tempting.
Ultrabroadband Parametric Amplification in the Visible
Authors: Gale G. M. , Hache F. , Cavallai M.
Published: February 2023

A general non-collinear geometric condition for broadband femtosecond parametric amplification (known as tangential phase-matching in the nanosecond regime) has recently been exploited to produce 13 fs pulses in the visible from an optica! parametric oscillator [1] and less than 11 fs from a single-stage optical parametric amplifier [2]. These results will be compared to detailed numerical simulations of the parametric process and it will be shown that pulse duration is limited by third- and higher order dispersion This opens up the possibility for the generation of significantly sub-10 fs pulses in the visible by use of mirror dispersion controlled systems.
Novel resonator design for efficient high power TEM00 mode operation of solid state lasers
Authors: Ostermeyer Martin , Hodgson Norman , Menzel Ralf
Published: February 2023

Single rod flashlamp pumped Nd:YAG lasers in fundamental mode operation provide maximum output powers of about 25 W. These systems use dynamically stable resonators to achieve total efficiencies in the sub-percent range for beam propagation factors < 1.2 [1].
LD-Pumped High Average Power Nd: YAG Laser for the Pumping of Ultra-Short Pulse CPA Laser
Authors: Maruyama Yoichiro , Tei Kazuyoku , Kato Masaaki , Niwa Yoshito , Oba Masaki , Matoba Tohru , Arisawa Takashi
Published: February 2023

We have been developing LD-pumped solid state laser to realize high average power and a compact ultra-short pulse Ti:sapphire CPA laser1,2). A Nd:YAG laser being developed consists of an oscillator, a preamplifier, and two post amplifiers and installs zigzag slab laser crystals to achieve high pulse repetition rate (PRR) as well as high pulse energy shown in Fig.1. The both ends of all the zigzag slab Nd: YAG crystals have nearly Brewster's angle. The TEM00 laser pulse (10 mJ) from the oscillator passes through the preamplifier. Then the amplified pulse (30 mJ) propagates through two post amplifiers which have angle multiplexed double-pass configuration. These post amplifiers are connected each other with three image relay telescopes in order to archive high beam quality. Then the amplified laser pulse is relayed to a LBO crystal (10 × 8 × 15 mm3) with another image relay telescope. The maximum fundamentalaverage power of 250 W was obtained at the PRR of 200 Hz. The second harmonic of 105 W was produced by introducing the fundamental laser radiation of 200 W into the LBO crystal at the PRR of 170 Hz. The pulse energy of the second harmonic was 0.62 J and the pulse duration 15 ns. The energy conversion efficiency was around 53 % and the wall-plug efficiency for the second harmonic 2.0 %.
0.9Watt 580nm solid-state laser source
Authors: Pask H.M- , Piper J.A.
Published: February 2023

Laser sources producing output in the yellow spectral region are of interest for a variety of display, remote-sensing and medical applications, including the removal of vascular lesions, for which the main requirement for the laser is strong absorption by haemoglobin, with minimal absorption by the melanin pigment in tissue. Average powers of about 0.5 to 1W are required at 580nm+/-5nm, and a high repetition-rate source is beneficial in reducing thermal damage to the surrounding tissue. A solid-state laser source would offer an attractive alternative to the laser sources currently used for these procedures, which include pulsed dye, krypton ion and copper vapour lasers.
Novel features of phase conjugation at SBS with using an ordered phase plate
Authors: Kochemasov G. G , Starikov F. A.
Published: February 2023

To reproduce the near field intensity of laser beam in the back SBS beam, it is needed to obtain the phase conjugation (PC) fidelity h≥0.95, where h= |∫∫ELEsdxdy|2/[∫∫|EL|2dxdy·∫∫|Es|2dxdy], EL and Es are the laser and Stokes field amplitudes. Such big values of h were attainable at SBS in light waveguide only [1]. However, the waveguide wall damage resistance is a challenge In the case of focused laser beam one can overcome the damage problem but at the cost of decreasing h up to ~0.3 (near SBS threshold and at the divergence θL exceeding θD = λ/a by ≥3 times). In the present talk we optimize a special arrangement of PC-mirror [2] that can give a new way of achieving nearly perfect PC with h≥0.95 in focused beams.
Single and Multi-pulse Soliton States observed in a Ti:Sapphire Laser Mode-locked by an Ion-implanted Anti-Resonant Fabry-Perot Saturable Absorber
Authors: Lederer Max , Luther-Davies Barry , Tan Hoe , Jagadish Chennupati , Akhmediev Nail N.
Published: February 2023

Solitonic mode-locking in broad band lasers such as Ti:Sapphire has led to increasingly shorter pulses in the near infrared. Absorption modulation in soliton lasers, either through the ultra-fast Kerr lens or from a saturable resonant absorber, is necessary to stabilise the soliton pulses against growth of dispersive radiation which would finally deplete the laser gain and cease mode-locking. It was pointed out [1] that the solitons are more stable than pulses created by mere absorption modulation and can be stabilised by absorber recovery times in excess of 10 times longer than the pulse width itself, depending on other parameters. This allows for the use of slower absorbers, thereby improving the lasers’ self-starting behaviour. The latter is the main detriment of the ultra-fast Kerr-lens.
Compact Spot-Size Converters Using Non-Periodic Segments for High Refractive Index Contrast Planar Waveguides
Authors: Spühler Michael M. , Offrein Bert J. , Bona Gian-Luca , Germann Roland , Emi Daniel
Published: February 2023

A compact, ~140pm long spot-size converter allows to improve the coupling efficiency between SM-fiber and high effective refractive index contrast (Δn=0.02) planar lightwave circuits by more than 2dB. It is implemented in the form of a non periodic segmented waveguide structure with irregular tapering. For the fabrication of the planar structures a simple single step lithography process is sufficient.
Precision laser beam shaping apertures
Authors: Johnson B. C.
Published: February 2023

The important role played by beam shaping (apodizing) apertures in the successful operation of high-power laser systems is a acknowledged fact.1-4 In systems such as those being developed for laser fusion experiments at LLL, the optimum whole beam spatial profile represents a sensitive tradeoff between conflicting requirements: (1) efficient energy extraction from the laser and (2) propagation through the amplifier chain with minimal beam breakup from linear (diffraction) and nonlinear effects. An additional constraint on the choice of whole beam profile is imposed by the specifications on the focal (far-field) distribution of the beam occurring at, or near, small laser fusion targets. In order to achieve a balance among these requirements, it is mandatory to utilize optical elements that can exercise precise control of the whole beam spatial intensity profile of the laser.
Applications of Stark cells to CO2 laser communication
Authors: Abrams R. L. , Asawa C. K. , Plant T. K. , Tangonan G. L.
Published: February 2023

The availability of Stark tunable molecular absorption lines coincident with CO2 laser transitions has led to several applications in laser communications. Three applications are described here: (1) frequency stabilization of a CO2 laser; (2) a technique for direct demodulation of an optical FM signal; and (3) a method for producing single sideband ir modulation at microwave frequencies.
Far infrared difference frequency generation
Authors: Barnes N. P. , Nickle R. A. , Mace P. N.
Published: February 2023

One method of laser isotope separation requires a far FIR, nearly monochromatic source of radiation having an energy per pulse on the order of tens of microjoules. An attractive method of producing this required energy is difference frequency generation using a CO and a CO2 laser as sources.1,2 The difference frequency generation could occur in a nonlinear material such as CdGeAs2 or AgGaSe2. The engineering development of the lasers and the results obtained from second harmonic generation as well as difference frequency generation experiments are described. The major emphasis in the development of the CO laser was the increase in the peak power. However, the major emphasis in the development of the CO2 laser was the attainment of consistently good spatial and temporal mode quality.
Split beam system for laser drawing of optical fibers
Authors: Saifi M. A. , Borutta R.
Published: February 2023

Development of low-loss glass-fiber optical waveguides has intensified research in the area of fiber drawing techniques. Many of these fibers are made from fused silica with suitable dopants in the core and clad region, requiring a drawing temperature of over 1900°C. As compared with a furnace or a gas torch, CO2 lasers offer an excellent alternative highly responsive heat source. However, since the output of a laser is a collimated beam, it is necessary to restructure it to provide uniform distribution around the preform circumference.
Broadband passive isolator for high-power 10-μm laser systems
Authors: Phipps C. R. , Thomas S. J. , Figueira J. F.
Published: February 2023

One critical feature in the design of very high-power multistage CO2 laser systems is provision of adequate interstage isolation. The requirements for isolation are stringent due to the large gain bandwidth of the medium and the necessity of highly saturated operation.
Computer controlled infrared parametric oscillator source
Authors: Brosnan S. , Fleming R. N. , Herbst R. L. , Byer R. L.
Published: February 2023

Previously we have reported on the LiNbO3 angle tuned parametric oscillator and its potential for computer control and operation as a coherent spectrometer.1 In this paper we report the operation of the parametric oscillator under full interactive computer control. The present system allows the user to choose the starting wavelength, scan range, scan rate, and resolution. The computer controls the stepper motors that rotate the LiNbO3 crystal and line narrowing grating. The user can also designate a data file for recording the spectral data on disk for later display on an x-y recorder. With the present system we have generated a coherent anti-Stokes spectrum2 of H2 gas at gas pressures from 1 atm to below 10 Torr. The absolute wavelength resettability of the parametric tuner determined from the spectrum was ±0.2 cm−1 at a resolution of 2 cm−1. Additional line narrowing with an etalon led to line-widths of less than 0.2 cm−1.
Holographic recording of magnified dark-field images
Authors: Gassend Max L. A. , Davis Kim I. , Boerner Wolfgang M.
Published: February 2023

Gabor has described1 the dark-field method as a means of improving the reconstructed image by eliminating the disturbance caused by the ghost image when the object is in the Fresnel region. The reconstructed image was filtered by placing an apodized dark spot at the real image of the pinhole of the reconstruction source, thus removing the rays of light undiffracted by the object.
Modulatable lasers for systems applications
Authors: Hawkins J. D. , Shull W. A. , Reynolds T. B. , Dowley M. W.
Published: February 2023

We report on the development and proving of a rugged, wide bandwidth modulatable laser of relatively low cost. Conventional laser modulation systems employ external electrooptic (EO) or acoustooptic (AO) modulators.1,2 In the He–Ne case de modulation has been used. In applications such as laser beam recording the EO and AO modulators suffer various shortcomings, the principles of which are high cost, sensitivity to alignment, and imperfect extinction. Current modulation of the He–Ne laser is power-limited, bandwidth-limited, and can result in reduced tube life.
Performance characteristics of a holographic laser beam deflector
Authors: Pole Robert V. , Werlich Harald W.
Published: February 2023

The concept of the holographic deflector has been described previously.1 This paper, in addition to reviewing the principles, describes the development of a prototype device and its performance characteristics.
Isolation of high-power multiline CO2 laser amplifier chains from the target reflection
Authors: Diels J.-C. , Bass M.
Published: February 2023

Measurements at Los Alamos Scientific Laboratories have shown1 that, when a high energy (larger than 5G) nanosecond pulse at 10.6 μm is focused into a target, 5% of the incident energy is back-scattered into the laser source. (The measurements were performed at grazing incidence.) As the reflected pulse propagates back into the amplifier chain, its intensity will increase because of (1) the residual gain of the amplifiers and (2) the converging (for the direction of the reflected pulse) optic of the chain. The latter mechanism alone is sufficient to lead to destruction of components in the optical chain since the ratio of the oscillator to the amplifier diameter is about 10−1.
Large mode-area all-solid anti-resonant fiber based on chalcogenide glass for mid-infrared transmission
Authors: He Lelu , Liang Yachen , Guan Yongnian , Gu Zhengxiang , Xia Kelun , Wang Xunsi , Dai Shixun , Shen Xiang , Liu Zijun
Published: February 2023

A large mode-area chalcogenide all-solid anti-resonant fiber has been designed and successfully prepared for the first time. The numerical results show that the high-order mode extinction ratio of the designed fiber can reach 6000, and the maximum mode-area is 1500 um2. The fiber possesses a calculated low bending loss of less than 10−2 dB/m as the bending radius is larger than 15 cm. In addition, there is a low normal dispersion of -3 ps/nm/km at 5 μm, which is beneficial for the transmission of high power mid-infrared laser. Finally, a completely structured all-solid fiber was prepared by the precision drilling and two-stage rod-in-tube methods. The fabricated fibers transmit in the mid-infrared spectral range from 4.5 to 7.5 μm with the lowest loss of 7 dB/m @ 4.8 μm. Modeling suggests that the theoretical loss of the optimized structure is consistent with that of the prepared structure in the long wavelength band.
Self-supervised phase unwrapping in fringe projection profilometry
Authors: Song Wanzhong , Gao Xiaomin , TAN CHUNQIAN , Lei Junzhe
Published: February 2023

Fast-speed and high-accuracy three-dimensional (3D) shape measurement has been the goal all along in fringe projection profilometry (FPP). The dual-frequency phase shifting (DF-PS) is one of the prominent technologies to achieve this goal. However, the period number of the high-frequency pattern of existing DF-PS approaches is usually limited by the amplified phase errors, setting a limit to measurement accuracy. Deep-learning-based phase unwrapping methods for single-camera FPP usually require labeled data for training. In this letter, a novel self-supervised phase unwrapping method for single-camera FPP systems is proposed. The trained network can retrieve the absolute fringe order from one phase map of 64-period and overperform DF-PS approaches in terms of depth accuracy. Experiments on real scenes demonstrate that the proposed method can unwrap the phase map of motion blur, isolated objects, low reflectivity, and phase discontinuity.
Perceived quality of care and choice of healthcare provider in informal settlements
Authors: Conlan Chris , Cunningham Teddy , Watson Sam , Madan Jason , Sfyridis Alexandros , Sartori Jo , Ferhatosmanoglu Hakan , Lilford Richard
Published: February 2023

When a person chooses a healthcare provider, they are trading off cost, convenience, and a latent third factor: “perceived quality”. In urban areas of lower- and middle-income countries (LMICs), including slums, individuals have a wide range of choice in healthcare provider, and we hypothesised that people do not choose the nearest and cheapest provider. This would mean that people are willing to incur additional cost to visit a provider they would perceive to be offering better healthcare. In this article, we aim to develop a method towards quantifying this notion of “perceived quality” by using a generalised access cost calculation to combine monetary and time costs relating to a visit, and then using this calculated access cost to observe facilities that have been bypassed. The data to support this analysis comes from detailed survey data in four slums, where residents were questioned on their interactions with healthcare services, and providers were surveyed by our team. We find that people tend to bypass more informal local services to access more formal providers, especially public hospitals. This implies that public hospitals, which tend to incur higher access costs, have the highest perceived quality (i.e., people are more willing to trade cost and convenience to visit these services). Our findings therefore provide evidence that can support the ‘crowding out’ hypothesis first suggested in a 2016 Lancet Series on healthcare provision in LMICs.
Regional variation in knowledge and practice regarding common zoonoses among livestock farmers of selective districts in Nepal
Authors: Bagale Kosh Bilash , Adhikari Ramesh , Acharya Devaraj
Published: February 2023

Background

The majority of Nepalese people are involved in farming. However, due to limited knowledge of zoonoses and poor preventive practices on the part of livestock farmers, vulnerabilities to zoonotic diseases are very high. The main objective of this study was to assess the regional variation in zoonoses-related knowledge and preventive practices of livestock farmers in different ecological regions of Nepal.

Material and methods

Descriptive cross-sectional quantitative research design was followed in the study. The total sample size was 380 livestock farmers from randomly selected three ecological regions of Nepal. Systematic sampling techniques were applied for data collection. Data were entered into an excel sheet and then imported into Statistical Package for Social Sciences (SPSS) software. The data were calculated using descriptive statistics. Univariate, and bivariate analyses were performed, and the result of the study was presented in the form of text and tables based on their nature.

Results

Of the studied six zoonotic diseases, most of the respondents (95.8%) knew about zoonotic bird flu; 90.7% of them, were about rabies; and 54.2% knew about swine flu. However, a few respondents knew about bovine tuberculosis, neurocysticercosis, and brucellosis. Ecologically, the highest number of respondents in Nawalpur had knowledge of rabies (95.3%), and swine flu (61.6%), whereas 98.3% of them had knowledge of avian influenza in Tanahun; and 12.5% of neurocysticercosis in Manang. Regarding zoonoses preventive practices such as regular hand washing with soap water, mask-wearing, gloves, boots, the respondents’ representation of 60.8%, 6.6%, 1.8%, and 1.3% respectively in such practices show that although these are easy and cost-effective, personal protective equipment (PPE), such preventive practices were extremely underperformed. Not only that, only 12% of respondents maintain a standard distance (>15m.) between their house and shed. Similarly, 17% still consumed meat from sick animals, and vaccination of livestock was also found poor coverage (36%) in the study.

Conclusions

Livestock farmers need to be more knowledgeable about many common zoonotic diseases, and their preventive practices still need improvement, with significant regional variation in the study. This has invited various zoonosis threats for them. Therefore, it is recommended that the interventional programs related to common zoonoses be conducted for livestock farmers to solve the problem.
Prevalence of asymptomatic malaria infection by microscopy and its determinants among residents of Ido-Ekiti, Southwestern Nigeria
Authors: Ibrahim Azeez Oyemomi , Bello Ibrahim Sebutu , Ajetunmobi Adewumi Oluwaserimi , Ayodapo Abayomi , Afolabi Babatunde Adeola , Adeniyi Makinde Adebayo
Published: February 2023

Background

Asymptomatic malaria infections have received less attention than symptomatic malaria infections in major studies. Few epidemiological studies on asymptomatic malaria infections have often focused on pregnant women and children under-five years of age as the most vulnerable groups. However, there is limitation on data regarding asymptomatic infections among the old adult populations, particularly in the study area. Therefore, this study determined the prevalence of asymptomatic malaria infection by microscopy and its determinants among residents of Ido- Ekiti, Southwestern Nigeria.

Methods

A hospital-based cross-sectional study was conducted between July and September 2021 among 232 consenting apparently healthy individuals aged 40 years and above who were recruited during a free health screening program using a standardised interviewer-administered questionnaire. The questionnaire sought information on respondents’ socio-demographics, presence and types of co-morbidity, and the prevention methods being adopted against malaria infection. Venous blood samples were collected and processed for asymptomatic infections using Giemsa-stained blood smear microscopy. Data were analysed using SPSS version 21. Multivariate logistic regression was used to identify factors associated with asymptomatic infections.

Results

Of the total 232 respondents, 19.0% (48/232) were confirmed to be infected with Plasmodium falciparum (95% confidence interval (CI): 14.1% - 24.6%). Lack of formal education (Adjusted odds ratio (AOR): 5.298, 95% (CI): 2.184-13.997), being diabetic (AOR: 4.681, 95% CI: 1.669-16.105), and not sleeping under Long Lasting Insecticide Net (LLINs) (AOR: 4.594, 95% CI: 1.194-14.091), were the determinants of asymptomatic Plasmodium falciparum infection.

Conclusion

The prevalence of asymptomatic Plasmodium falciparum was 19%. Lack of formal education, being diabetic, and not sleeping under LLINs were the determinants of asymptomatic infections.
The influence of dietary protein concentration on digestive enzyme activities, growth, and body composition in juvenile bullseye snakehead (Channa marulius)
Authors: Nazir Sadia , Khan Noor , Fatima Mahroze , Azmat Hamda , Naveed Saima , Ramzan Malik Muhammad , Asghar Muhammad , Bano Sheeza , Khizer Ayesha , Wan Alex H. L. , Davies Simon John
Published: February 2023

The bullseye snakehead (Channa marulius) is considered as an affordable and robust freshwater fish for farming in Asia. However, there is limited knowledge on the species’ full nutritional requirements to date with extensive gaps in our knowledge and particularly in precision aspects of protein requirements. Therefore, a three-month feeding trial was conducted under semi-intensive farming conditions to determine the protein requirement of bullseye snakehead using test diets containing 40 (P40), 45 (P45), 50 (P50), and 55% (P55) crude protein levels. The growth performance results revealed that the 55% dietary protein group (P55) had the highest final mean weight (14.09 g fish-1), and net weight gain (12.82 g fish-1). When compared to other dietary treatments, the final weight (R2 = 0.921), and weight gain (R2 = 0.913), displayed a linear increasing trend as dietary protein is raised. The lowest FCR was observed in 50% (1.94±0.01) and 55% (1.97±0.01) CP diet groups compared to dietary treatments. Further analysis has shown that the body protein content also significantly increased as dietary protein was raised to 55%. Although, a reverse trend was found in body lipid levels with increasing protein in the diet. The incremental dietary protein also elevated proximal intestinal protease activity but decreased amylase and lipase activity. The overall essential and non-essential amino acids levels of snakehead fillet muscle reflected an increase in dietary protein. Overall, this study has shown that the fish fed a diet with 55% crude protein attained the highest growth performance and nutrient profile of the whole fish when compared to other dietary treatments tested. It would appear we did not obtain the maximum potential for growth under the present experimental conditions due to the upper protein constraint of 55% in the diet. Further quantitative studies are suggested.
Development of a data platform for monitoring personal health records in Japan: The Sustaining Health by Integrating Next-generation Ecosystems (SHINE) Study
Authors: Fukuda Haruhisa , Murata Fumiko , Azuma Sachie , Fujimoto Masahiro , Kudo Shoma , Kobayashi Yoshiyuki , Saho Kenshi , Nakahara Kazumi , Ono Rei
Published: February 2023

Background

The Sustaining Health by Integrating Next-generation Ecosystems (SHINE) Study was developed as a data platform that incorporates personal health records (PHRs) into health-related data at the municipal level in Japan. This platform allows analyses of the associations between PHRs and future health statuses, and supports the production of evidence for developing preventive care interventions. Herein, we introduce the SHINE Study’s profile and describe its use in preliminary analyses.

Methods

The SHINE Study involves the collection of participants’ health measurements and their addition to various health-related data from the Longevity Improvement & Fair Evidence (LIFE) Study. With cooperation from municipal governments, measurements can be acquired from persons enrolled in government-led long-term care prevention classes and health checkups who consent to participate in the SHINE Study. For preliminary analyses, we collected salivary test measurements, lifelog measurements, and gait measurements; these were linked with the LIFE Study’s database. We analyzed the correlations between these measurements and the previous year’s health care expenditures.

Results

We successfully linked PHR data of 33 participants for salivary test measurements, 44 participants for lifelog measurements, and 32 participants for gait measurements. Only mean torso speed in the gait measurements was significantly correlated with health care expenditures (r = -0.387, P = 0.029).

Conclusion

The SHINE Study was developed as a data platform to collect and link PHRs with the LIFE Study’s database. The analyses undertaken with this platform are expected to contribute to the development of preventive care tools and promote health in Japan.