bluuebunny/crossref_metadata_2025 huggingface dataset:
Picosecond gain-switched laser diode amplified in a diode-pumped laser crystal
Authors: Balembois François , Gaignet Mickaël , Georges Patrick , Brun Alain , Stelmakh Nikolaï , Lourtioz Jean Michel
Published: February 2023

There is a great interest in developping a very compact source emitting tunable picosecond pulses with a few milliwatts of average power in the UV at high repetition rate (> 10 kHz). This kind of source will be useful for the detection of molecules by time resolved fluorescence in the biomedical domain for example. To reach those specifications, a simple way is the use of a gain-switched picosecond laser diode whose pulses are amplified in diode-pumped crystals having good energy storage capabilities. The concept of injection seeding of gain-switched laser diode in amplifiers was already demonstrated [1,2]. However, to our knowledge, the previous systems operated at a fixed wavelength.
Modelling Deep Etched Optical Wavguide Step Discontinuities
Authors: Allan B.D , Avrutin E.A. , Arnold J.M. , De La Rue R.M , Marsh J.H.
Published: February 2023

Gratings are important components for optoelectronic applications such as high reflectivity mirrors in distributed Bragg reflector (DBR) lasers and as wavelength dependent filters. Most theoretical methods use the coupled mode theory which is only suitable for very shallow etched structures. As the etch depth of the structure increases, radiation becomes important, and must be included in the calculation.
Nd:YAG oscillator power amplifier using photorefractive BaTiO3:Rh internal loop and ring self-pumped phase conjugate mirrors
Authors: Huot N. , Jonathan J.M.C. , Pauliat G. , Roosen G. , Brignon A. , Huignard J.P.
Published: February 2023

Rhodium doped Barium Titanate (BaTiO3:Rh) is known for its significant response at 1.06µm: high two-wave mixing gain (23cm–1 in the cw regime and 16cm–1 in the nanosecond regime for a 45° cut sample) and low absorption (0.1cm–1). The characteristics of BaTiO3:Rh are now well reproducible, making it an attractive medium for phase conjugation and its application to the solid state compensation of thermal aberrations of pulsed laser sources at 1.06µm.
Strain and Temperature Sensitivity Measurements of Bare, Coated, and Embedded Optical Fiber Bragg Gratings
Authors: Nelien Ph. M. , Frank A. , Mauron P. , Sennhauser U.
Published: February 2023

Fiber optical Bragg grating sensors are of high interest for long term surveillance of structural elements in mechanical and 'civil engineering applications. Uncoated, acrylate and polyimide coated fiber Bragg gratings, and gratings embedded in glass fiber reinforced polymer rods (GFRP) during a continuous pultrusion process on a full-scale production machine were spectrally characterized while subjected to both strain up to 20'000 µm/m and temperature between-40 °C and 80 °C.
Novel optical fiber absorption sensor based on fluorescence lifetime encoding
Authors: Kobe Andrej , Možina Janez
Published: February 2023

Advantages of lifetime based sensors (for temperature etc.) compared to intensity sensors have been thoroughly presented in terms of intrinsicaly stable and reference-free measurements1. There is however a limited number of materials that have strong fluorescence lifetime dependence on desired physical or chemical property of the environment. Even smaller subset have properties such as long lifetime, high quantum efficiency and chemical stability that enable long term adecquate SNR with simple electronics and design. Vast majority of fiber optic sensors is intensity based, so the possibility of encoding absorption in the measured material in a time-dependent signal with all the advantages of a lifetime based sensors is highly desired.
Physics and engineering of high-power laser systems
Authors: Emmett J. L.
Published: February 2023

The Lawrence Livermore Laboratory is heavily involved in the development of high-power laser systems for applications in fusion research. For near and intermediate term applications the neodymium-glass laser was chosen as it represented the best available technology for the production of high-power pulses. However, extensive research and development have been required to optimize the laser to deliver maximum power to small diameter fusion targets. The nonlinear refractive index of the laser glass and passive optical elements profoundly influence system performance, necessitating an entirely new approach to the design of such lasers. New optical materials are also being developed which are expected to improve substantially the performance of this class of laser systems. Three major neodymium-glass laser systems are operating or under construction at LLL which have been made possible by the technology development program. These systems are given in Table I.
Design of disk laser amplifiers for laser fusion applications
Authors: Fountain W. D. , Hagen W. F. , Linford G. J.
Published: February 2023

Large laser systems for fusion research employ disk laser amplifiers at the output of each amplifier chain owing to the superior nonlinear performance of large-aperture (d > 10-cm) disk amplifiers over rod amplifiers of the same aperture. This superior performance arises from three sources:

(1) generally higher attainable gain coefficients;

(2) reduction in beam intensity inside the Brewster’s angle disks; and

(3) the air spaces between successive disks permitting diffraction to diverge small-scale self-focusing filaments.
Evaluation of new Nd glasses for fusion laser amplifiers
Authors: Weber M. J. , Trenholme J. B. , Saroyan R. A. , Layne C. B. , Linford G. J. , Jacobs R. R.
Published: February 2023

The gain coefficient of Nd glass used in amplifiers for fusion lasers affects the staging and over-all performance. Significant improvements are possible by the development of improved glass compositions. We have evaluated a large number of new glasses for amplifier applications. Predictions of gain coefficient are based upon measurements of absorption and fluorescence spectra and decay properties combined with computer calculations of flashlamp pumping. The results for several silicate and phosphate glasses are in good agreement with the actual performance in a laser cavity. Since the information required for this evaluation can be obtained from small samples of the laser material, this considerably simplifies the comparison and selection of Nd glass for use in large laser amplifiers.
Designing large aperture Pockels cells
Authors: Summers M. A. , Johnson B. C.
Published: February 2023

Electrooptical (EO) devices, such as Pockels cells, can provide effective bidirectional isolation for high-gain laser systems, such as those used for laser fusion experiments. In these systems, undesirable forward propagating radiation in the form of a precursor to the main pulse can preheat or destroy the target. Retroreflected radiation, arising from target or component surfaces, can experience sufficient amplification to destroy optical elements near the front end of the system. Protection of the target and laser from these effects is an important consideration in the design of any high-power laser irradiation system.
Extended line-of-sight optical communications
Authors: Mooradian Gregory C. , Geller Myer , Barstow Glidden J. , Davies Kirk E.
Published: February 2023

Optical communications has traditionally suffered from two major limitations: weather and line-of-sight ranges. Efforts at the Naval Electronics Laboratory Center, San Diego, California, have in the past concentrated on high-bandwidth high-availability systems, primarily 10.6-µm heterodyne transceivers. The exploitation of optical carriers to provide extended line-of-sight (ELOS) communications is currently being evaluated. Conventional rf technologies employing 2–30 MHz suffers from spectrum crowding, susceptibility to interference, lack of privacy, and a surprising low availability (50-85% worldwide to ELOS ranges). Considering this, the feasibility of a practical ELOS optical link utilizing existing components is being investigated for ranges of 30–150 miles.
3M electron beam laser
Authors: Packard J. R.
Published: February 2023

The electron beam laser is a technology in which laser emission is generated by exciting a single crystal semiconductor cavity with a high-energy electron beam. A large number of semiconductor materials have been shown capable of producing laser emission in this way. Of significance is that these materials include several II–VI semiconducting compounds from which junction laser emission has not been observed.
Acoustooptic snapshot PROM: a real-time optical signal spectrum analyzer
Authors: Sprague Robert A.
Published: February 2023

This paper describes a system that performs real-time optical processing of electrical signals. The signals of interest are recorded in a raster format on the Itek PROM (Pockels Readout Optical Modulator), a light addressed electrooptic imaging device. The PROM is then read out with laser light to perform optical Fourier transformation, achieving spectrum analysis in near real time. A technique called acoustooptic snapshot recording is used to generate the required low distortion raster at rf bandwidths.
Performance of 8.5-m imaging systems in degraded atmospheres
Authors: Biberman Lucien M.
Published: February 2023

This paper presents hourly estimates of the performance of a series of electrooptical image-forming systems based upon hourly weather records at Hannover, Federal Republic of Germany. The questions addressed include how great are the effects, how often they occur, and how long they persist.
KMSF Laser fusion systems overview
Authors: Thomas C. E.
Published: February 2023

The unique requirements of a laser fusion experimental facility have led to the development of many new optical engineering and manufacturing techniques over the past several years. This paper will discuss some of these developments in the areas of high-power Nd+ glass laser systems and target illumination systems. The success of our laser fusion program to date has also required significant engineering advances in pellet fabrication techniques and in plasma diagnostic devices, but these nonoptical developments are not included in this paper.
KMSF laser subsystems
Authors: Moncur N. K. , Guscott B. R. , Hildum J. S.
Published: February 2023

A laser amplifier, rod or disk, has a well defined aperture that limits the diameter of the beam. If one attempts to fill this entire aperture with useful energy, the interaction of the beam with the hard limiting aperture produces Fresnel diffraction rings at the edge which will propagate throughout the beam. These diffraction rings will be amplified by later amplifiers, resulting in intensity modulation detrimental to the beam propagation and even initiating self-focusing with consequent damage to optical components.
Design and performance of a low-temperature multiple-reflection absorption cell
Authors: Griggs J. E. , Henke M. D. , Aldridge J. P. , Kim K. C.
Published: February 2023

Design characteristics and performance of a low-temperature multipass White cell are described. The optical pathlength can be varied from 40 m to 2000 m, and absorption measurements can be made under controlled temperature environment between 160 K and ambient temperature. The special feature of its construction, which combines White cell optics for laser applied spectroscopy and accurate temperature control, is that it allows the study of molecular fine structure of many species of both chemical and atmospheric interest. Spectroscopic measurements under conditions in which the temperature of the absorbing species is accurately known and pressure broadening is minimized provide information on molecular fine structure, populations of excited states, line intensities, and transition probabilities.
Oxygen-17 enrichment by Ne II ion laser photopredissociation of formaldehyde
Authors: Marling John B.
Published: February 2023

High-resolution coincidence absorption spectroscopy of formaldehyde enriched in the rare isotope oxygen-17 was performed to search for coincidences with uv ion laser transitions in the noble gases. This technique has previously proved successful in proof-of-principle laser separation of deuterium.1 The existence of a fortuitous coincidence with an ion laser would greatly simplify the proof of applicability of formaldehyde photopredissociation as a means to enrichment of oxygen-17.
Experimental fiber optics communications system
Authors: Cook J. S. , Mullins J. H. , Schwartz M. I.
Published: February 2023

An experimental optical fiber (fiberguide) system has been designed by Bell Laboratories to evaluate applicability of fiberguide communications to interoffice trunking. The system employs a 1.3-cm o.d. sheathed and protected cable, containing over 100 multimode graded-index fibers, which is terminated in a mass cable splice. The cable made for the experiment was over 1 km in length. It was cut to a length of a little over 600 m, commensurate with the length of the available duct run, and successfully pulled into standard plastic underground ducts at Bell Labs, Atlanta. The fibers are of germania-doped borosilicate made by Western Electric using a modified CVD process.
Lasers for fiber optics
Authors: De Loach B. C.
Published: February 2023

The characteristics of lasers designed for use in optical fiber transmission systems will be presented. These devices have excellent optical properties that allow efficient coupling to optical fibers. Their electrooptical properties are compatible with silicon integrated circuit driver and feedback control design, and a companion paper discusses both the electrical and optical coupling problems.
Wavefront distortion sensing for control of an adaptive optics system
Authors: Fried David L.
Published: February 2023

By sensing the wavefront distortion in the propagation path, between an aperture and some distant point of interest, and using this information to control the deformation of some adaptive element in the optical train behind the aperture, it is possible to achieve nearly diffraction-limited performance in an imaging system viewing the point of interest through the aperture, or to achieve the same in a laser transmitter irradiating the point of interest through the aperture. The key to this process lies in the ability to sense accurately the wavefront distortion. Methods have been discussed in the published literature1,2 for directly sensing the random phase distortion at each point in the aperture relative to the aperture average phase. These methods have a noise sensitivity such that the error in the estimate of the wavefront distortion increases rapidly as the total aperture size, or the number of adjustment degrees of freedom encompassed by the aperture, increases. As a result, in many applications the useful aperture size of an adaptive optics system is significantly limited by SNR considerations in the wavefront distortion sensing.
A 24 × 36 flatbed laser scanner/recorder for lithographic platemaking
Authors: Oliver Donald S.
Published: February 2023

The laser possesses unique properties that can be exploited for achieving the objective of converting digital data to pressplates. It is a source of high intensity light that can be focused to a fine spot, precisely directed, and electronically modulated at high speeds. Its high intensity permits image recording on unconventional material for use as printing plates and/or lithofilm. The labor and material economies afforded to the user by an inexpensive imaging material that requires no postrecording processing have immediate economic advantages over the conventional labor intensive platemaking process. The electronic control feature permits image processing, remote transmission, electronic storage, computer output graphics, and other capabilities.
Philips MCA videodisk system
Authors: Bulthuis K. , Philips N. V. , Kenney George C.
Published: February 2023

The optical video disk system can read a disk with high resolution with no wear of or damage to player or disk. The information can be simple and buried within the bulk, safe from damage by handling. Because of the contactless reading, the system includes tracking and focus error sensing and correction.
Laser applications In microelectronics
Authors: Zaleckas Vincent J.
Published: February 2023

This paper reviews the various applications for which lasers have been employed in the microelectronics industry. The applications encompass the integrated circuit technologies, including SICs and thin and thick film HICs. General topics covered include the fabrication, inspection, and repair of masks, wafer scribing, and passive and active trimming of devices.
Laser machining of micron-dimension rectangular holes on thin film photomasks
Authors: Cohen M. G. , Kaplan R. A.
Published: February 2023

Hard surface photomasks consisting of thin opaque metallic or dielectric films on glass substrates are increasing in popularity as a result of the durability and high resolution they provide in the fabrication of semiconductor integrated circuits. Although in many cases the surfaces are reflective, sufficient absorption of optical radiation occurs to permit machining of these films via melting and/or evaporation, thus permitting modification or repair of processed masks using laser-based machines. The primary requirements of such systems are the ability to (1) machine the opaque film without affecting the substrate and (2) provide the precision and resolution dictated by the mask patterns.
CO2 laser drilling system for computer circuitry
Authors: Wrenner W. R.
Published: February 2023

The laser operates cw at a nominal power level of 150 W. The laser beam is normally interrupted by a disk that is rotating at 3600 rpm. A narrow slit in the disk creates a short pulse of 1-msec duration when a flag, activated by a high-speed stepping motor, is moved out of the beam path.
Pulsed and Doppler CO2 laser radar
Authors: Mocker Hans W. , Chow C. N.
Published: February 2023

This paper discusses the design, construction, and performance tests of a feasibility model of a CO2 laser radar suitable for the simultaneous determination of velocity and range. The highly stable Q-switched CO2 laser transmitter features an intracavity Stark cell filled with methylchloride and a grating that tunes the laser to the P(26) line of the P branch of the 0 0°1-0 2°0 band at about 9.6 μm. By adjusting the gas pressure in the Stark cell the laser emits a train of Q-switched pulses riding on top of highly stable cw oscillation. For coherent detection we require that the generation of the Q-switched pulses does not destroy the frequency stability of the cw oscillation. Heterodyne experiments have been conducted by beating the return signal against another stable laser, and the results indicate that the instabilities have been held to less than 100 kHz thus allowing a velocity resolution of better than 1 knot. The use of the Stark effect in gases requires the match of an absorption line with a CO2 laser emission line. Two gases, methylchloride and difluoroethylene, have been used to Q switch a 20-W CO2 laser.
Dual Bragg cell local oscillator generator for laser heterodyne radar systems
Authors: Huang Cheng-Chung
Published: February 2023

In a laser heterodyne radar system it is convenient to generate the necessary optical local oscillator beam by frequency translating a sample of the transmitter beam power. Of the several means for doing this, one that stands out for simplicity, stability, and efficiency is the Bragg cell. The Bragg cell generates an output beam at frequency f0 − f
a
from a transmitter beam at f0. Unfortunately, it also provides some weaker outputs at h0 + f
a
, f0, f0 − 2f
a
, etc. These first two weaker outputs can interfere with the acquisition of fine Doppler information in weak returns at zero range rate and at some other range rates.
Large scale laser display systems for commercial applications using path controlled galvanometers
Authors: Selverstone Peter , Grenda Ed
Published: February 2023

This paper describes explorations of the commercial feasibility of large-scale laser displays for advertising and other commercial purposes. Consideration is given to the required information density, raster scanning vs path control, and open vs closed loop operation of scanners.
Flow systems diagnostic technology: a review
Authors: Kamentsky Louis A.
Published: February 2023

The practice of medicine today is intimately dependent upon an increasing number and range of medical laboratory tests performed in hospitals, clinics, and doctor’s offices. Some of these are examinations that have been automated, notably in biochemistry, but most of the tests that require classification or evaluation of cells still are performed manually. This includes cytologic examinations for cancer cells, differential blood and bone marrow counts, examinations of the urinary sediment, bacteriologic examinations, chromosome karyotyping, blood typing and cross-matching, and research examinations of potential clinical application, such as tissue typing or immunofluorescence. While human judgment may always be needed to interpret, if not to carry out many of these examinations, it is likely that automated instruments can and will become ever more important laboratory aids. Some simple tests are now routinely performed by automated devices that combine blood handling and diluting technology with particle counters; but other laboratory examinations of cellular specimens will require more complex instrumentation than the simple single-parameter measurements of the kind used for cell counting. To perform these tasks, other instruments are being designed that carry out simultaneous multiparameter measurements on individual cells in an effort to distinguish different cell types.
Waveguides for delivering infrared laser power
Authors: Garmire E. , Mcmahon T. , Bass M.
Published: February 2023

Optical fibers, which transmit visible light, have made it possible to guide a beam of light to a designated target with ease and efficiency, in particular, light from laser sources. The development of the CO2 laser has provided a powerful and efficient source of ir light. Thus the need has arisen for ir waveguides that can increase the effectiveness of the CO2 laser as a light and energy source. We have fabricated waveguides for ir light that allow nearly the same ease of transporting and steering ir energy as do optical fibers. One direct application for which the CO2 laser is especially suited is the use of its high power as a cutting and welding tool as well as for surgery. Since ir beam guidance is presently accomplished with complex and awkward articulatedarm optical systems, the device we report on offers great simplification and the potential for significantly reduced system costs.
Cervical cytological (Pap) smear screening with coherent optics
Authors: Pernick B. J. , Kopp R. E. , Wohlers R. , Herold R. , Lisa J. , Mendelsohn J. , Stone H.
Published: February 2023

Coherent optical signal processing techniques for automatic screening of exfoliated cervical cytological samples were evaluated. Work centered on deriving feature measurements from the Fourier transform patterns of individual cells. The two-dimensional Fourier spectra of a large number of high resolution cell photographs were generated in an optical spatial spectrum analyzer. A special geometry solid state detector array measured the light intensity in a number of regions of the cell diffraction pattern. The optical system achieves a large sample data base with automated data collection, processing, and storage capabilities. Stringent optical component stability is needed for reliable and repeatable performance.
Aerosol sizing by laser Doppler relaxation-time measurement
Authors: Mazumder M. K. , Nichols S. N. , Overbey R. L.
Published: February 2023

Methods using laser Doppler velocimeters have been developed for measuring the dynamic relaxation time (τ
p
) of aerosol particles and droplets. For real-time measurement of aerodynamic size spectra in the range of 0.2-50.0 μm in diameter, the most promising methods employ (1) acoustic excitation, for the size range of 0.2-5.0 μm in diameter, and (2) gravity settling, for the size range of 5.0-50.0 μm in diameter. Both methods have been applied to rapid in situ measurement of the size distribution of stable and unstable aerosols. Experimental results indicate that these newly developed methods compliment the existing methods of real-time aerosol size analysis.
Microprocessor controlled sixty-four element pulsed optical receiver
Authors: Fossey Michael E. , Holmes J. Fred , Jacob R. Larry
Published: February 2023

A microprocessor controlled, sixty-four element, pulsed optical receiver system has been developed. It is used in conjunction with a double pulse ruby laser (1 J/pulse) for remotely sensing crosswind in the atmosphere by analyzing the laser energy scattered from a diffuse target.1
Use of optical fibers as instrumentation transducers
Authors: Kingsley S. A. , Davies D. E. N.
Published: February 2023

Optical fiber communication systems are currently being developed for the telemetry of instrumentation data in various applications, including the transmission through electrically noisy environments and in situations where the environmental requirements involve the use of flameproof techniques. Such telemetry systems employ instrumentation transducers to measure vibration levels, temperatures, pressures, and other parameters. A frequent disadvantage with such an approach is the need for power supplies at the transducer to convert its output into a suitable modulated optical signal. This paper draws attention to the fact that optical fibers are microphonic in the sense that when they carry coherent optical signals, the fiber can pick up acoustic energy from the air and, through a parametric interaction, cause phase modulation of the guided wave. The fiber itself can act as a transducer, e.g., as a strain gauge, and its sensitivity may be enhanced by coiling a long length of fiber over a suitable former. Alternatively, its sensitivity can be conveniently decreased by coating the fiber with an appropriate amount of absorbent material. For many applications it would obviously be more convenient to couple mechanically some form of resonant mechanical transducer to the fiber.
Sliding reference interferometer
Authors: Skolnick M. L. , Robertson H. J.
Published: February 2023

A differential phase measuring device is described that is suited for measuring, at high frame rate, the two-dimensional optical phase and intensity distributions of a high power laser beam. This device is insensitive to the fluctuations in amplitude, polarization, and wavelength that are characteristic of high power laser radiation.
Infrared transparent materials and components
Authors: Enrique Bernal G.
Published: February 2023

Infrared transparent components are critical elements of laser and electrooptical systems where they are used as environmental interface elements, as in detectors and laser windows, refractive elements, and beam combiners.
Design and application of ultrafast KD*P electrooptic modulators
Authors: Johnson B. C. , Anafi D.
Published: February 2023

Since the pioneering work by Kaminow1 and others in the early Sixties, there has been a continuing interest in obtaining broadband low power microwave light modulators for a number of applications, ranging from optical communication and data processing systems2 to active Q switching and mode-locking of lasers.3 The work reported here was prompted by the fast pulse amplitude and phase control requirements of high-power laser fusion experiments and their associated diagnostics, where it is desirable, often mandatory, to perform optical gating or temporal pulse shaping operations in the sub-100-psec range. In this paper, we consider the problem of designing and constructing ultrafast electrooptic (EO) modulator devices capable of producing optical transmission risetimes shorter than 100 psec.
Double heterostructure lead-salt lasers for high resolution gas spectroscopy
Authors: Preier H. , Riedel W. , Maier H. , Bleicher M.
Published: February 2023

Lead-salt lasers have proved powerful tools in ir-gas spectroscopy. Their wavelengths can be selected in the 4–30-μm range by choosing proper compositions of the ternary compounds: PbS1−
x
Se
x
, Pb1−
x
Sn
x
Se, or Pb1−
x
Sn
x
Te. Fine tuning is achieved by temperature variation, application of a magnetic field, or hydrostatic pressure. The major handicap against their widespread use in gas spectroscopy is their relatively low operation temperature. Until recently cw operation has been achieved only below 77 K and pulsed operation not much above 100 K. Recently Groves et al. from the Lincoln Laboratory reported on PbTe-Pb1−
x
Sn
x
Te-PbTe DH lasers prepared by liquid phase epitaxy which could be cw operated at 77 K. Detailed results on PbS-PbS1−
x
Se
x
PbS as well as preliminary results on PbSe-Pb1−
x
Sn
x
Se-PbSe DH laser structures, which were prepared by the hot-wall evaporation—a modified molecular beam—technique, will be reported.
Solid state lasers
Authors: Pressley R. J.
Published: February 2023

The term, solid state lasers, has come to mean not only the rod-lamp combination but a complete machine with some defined output in space, time, and wavelength. Examples of the most important commercial systems will be presented and their performance related back to the basic limits of their component parts, primarily the laser rod and secondarily the pump source. Finally a best case analysis will be used to predict the properties of some ideal machines.
Properties of Nd:La2Be2O5 laser crystals
Authors: Jenssen H. P. , Begley R. F. , Morris R. C.
Published: February 2023

Neodymium-doped lanthanum beryllate (La2Be2O5 or BEL) is a laser crystal that looks promising as an intermediate gain laser material. A lasing threshold comparable to Nd:YAG, higher slope efficiency, and three times higher Q-switched output energy have been obtained. The laser tests were performed on 6.3-mm diam by 76-mm log rods under identical conditions.
Practical limitations of transmission holography in particle analysis
Authors: Pitlak R. T. , Page R. , Selvin Neil P.
Published: February 2023

Pulsed holography has proved to be an extremely useful technique for detecting particle size and velocity distributions of pollutants, projectiles, aerosols, etc. The technique is particularly advantageous in that it allows entire volumes to be recorded, undisturbed, in one exposure and analyzed at a later time.
Multiple-beam apparatus for rapid large-spot laser-damage measurements
Authors: Milam D. , Murphy G.
Published: February 2023

Damage tests are necessary to guide material selection and component design and to furnish quality control during assembly of large lasers. Relatively few samples can be characterized since tests are routinely performed using oscillator/amplifier systems of low repetition rate as the laser source. The output of such lasers is only approximately predictable, and many firings may be required to evaluate a sample. Each firing must be individually monitored, resulting in masses of data which are tedious to reduce.
Position-sensitive photodetectors: key characteristics and systems implications
Authors: Klein Claude A.
Published: February 2023

The utilization of lasers for precision-guidance applications has stimulated much interest in novel photodetection devices capable of operating in conjunction with short-duration pulses typical of Q-switched YAG designators. Position-sensitive photodetectors (PSPDs), in particular, offer unique advantages in providing the capability of tracking laser-designated targets without requiring gimballing mechanisms. They exploit the lateral photoeffect to deliver electrical signals, which can be processed to extract both horizontal and vertical components of the seeker-to-target look angle.1 The lateral photocurrents, which result from the nonuniform illumination of the detector when operated in a photovoltaic mode, are collected at four electrodes suitably located at the edge of the active area. After amplification and ratiometric amplitude processing, these signals provide two de analog outputs which are linearly related to the spot position and, thus, can be exploited for tracking the target over the total field of view of the seeker.2
Advances in electrooptic TIR diffraction modulators/deflectors as industrial devices
Authors: Scibor-Rylski M. T. V.
Published: February 2023

Modulator/deflector applications in communications addressing and data processing call for simple, inexpensive, reliable, and fast devices that can be mass produced from readily available materials. The newly introduced TIR modulators using low voltages (<90 V at 0.63 μm) fit this description.
High-power nitrogen laser engineering and manufacturing
Authors: Sasnett Michael W. , Woodward Benjamin
Published: February 2023

Design principles for pulsed nitrogen lasers operating in the 100-kW-1-MW range are discussed with emphasis on manufacturing and reliability. Areas where continuing development of component parts, including high peak current switches and capacitors, appears important are discussed. Performance levels for various state-of-the-art designs are compared.
Engineering advances in environmental remote sensing
Authors: Melfi S. H. , Eckert J. A. , Pressman A. E.
Published: February 2023

Remote sensing, especially from aircraft, has provided invaluable data to assess the environmental impact of man’s activity. The primary techniques that have been successfully demonstrated include aerial photography, thermal scanning, and multi-spectral scanning. In addition, laser probing techniques have also been used recently, from airborne platforms, to monitor specific pollutants over wide geographical areas. The success of these activities has prompted increased research and development to improve the utility of this class of monitoring technique.
Active spill detection pollution monitoring system
Authors: Blanchard A. J. , Hulse W. C. , Rouse J. W. , Schell J. A.
Published: February 2023

Escalating interest in environmental monitoring and quality control has generated requirements for instruments capable of obtaining quantitative measurements of specific environmental parameters. In the field of water quality, these parameters might include stream and estuary turbidity fluctuations, the detection and surveillance of pollutant spills, etc. This paper describes laser polarimeter instrumentation capable of remotely providing quantitative measurements of water quality parameters.
CO2 laser systems for fusion studies
Authors: Reichelt W. H.
Published: February 2023

CO2 laser systems used in fusion experiments consist of a short pulse generator (≤10−9-sec pulse duration), preamplifiers, and main power amplifiers. The former are double discharge amplifiers operating with a gas mixture of He, N2, and CO2 at atmospheric pressure. The main power amplifiers are electron beam controlled systems operating at several atmospheres. The short pulse generator normally operates on a single line (P-20) but is designed to operate multiline and multiband (9-μm and 10-μm bands).
Scattering techniques to detect and record various human cell types
Authors: Salzman G. C. , Crowell J. M. , Price B. J. , Hansen K. M. , Ingram M. , Mullaney P. F.
Published: February 2023

Light-scattering techniques represent an appealing approach to the flow-system analysis and sorting of mammalian cells because they do not require fixation and staining, procedures that kill the cells and can introduce artifacts. A flow-system instrument has been developed1,2 at the Los Alamos Scientific Laboratory in which the intensity of light scattered by a cell as it passes through a focused laser beam is measured simultaneously at up to 32 angles between 0° and 21° with respect to the laser beam, and the scatter pattern is transferred to a computer for analysis.
Real-time optical matched filtering of moonlight illuminated objects
Authors: Grumet Alex
Published: February 2023

A multiple optical matched filter automatic image recognition system described earlier1 has had two additional features added. The first new feature consists of an incoherent to coherent image transducer that permits processing incoherent imagery through the optical matched filter bank. The second new feature incorporates an image intensifier that can present a moonlit scene to the transducer. The present system, therefore, permits a moonlit scene to amplitude modulate a collimated laser beam. An object in the scene can then be recognized and tracked by the automatic image recognition system.
Effects of specular roughness on the perception of color and opacity
Authors: Cai Yuyang , Kiyokawa Hiroaki , Nagai Takehiro , Haghzare Leyla , Arnison Matthew , Kim Juno
Published: February 2023

Previous studies have shown that information concerning object shape is important for the perception of translucency. This study aims to explore how the perception of semi-opaque objects is influenced by surface gloss. We varied specular roughness, specular amplitude, and the simulated direction of a light source used to illuminate a globally convex bumpy object. We found that perceived lightness and roughness increased as specular roughness was increased. Declines in perceived saturation were observed but were far smaller in magnitude with these increases in specular roughness. There were inverse correlations found between perceived gloss and perceived lightness, perceived transmittance and perceived saturation, and between perceived roughness and perceived gloss. Positive correlations were found between perceived transmittance and glossiness, and between perceived roughness and perceived lightness. These findings suggest that specular reflections influence the perception of transmittance and color attributes, and not just perceived gloss. We also performed follow-up modeling of image data to find that perceived saturation and lightness could be explained by the reliance on different image regions with greater chroma and lower lightness, respectively. We also found systematic effects of lighting direction on perceived transmittance that indicate there are complex perceptual interactions that require further consideration.
Spatial beam narrowing in Raman amplifiers made with graded-index multimode fibers: a semi-analytic approach
Authors: Agrawal Govind P.
Published: February 2023

A semi-analytic model of the amplification process is presented for Raman amplifiers made with graded-index multimode fibers. When the pump beam remains much more intense than the signal being amplified, it evolves in a self-similar fashion and recovers its initial width periodically. Using this feature, the width of the amplified signal is found to satisfy an equation whose form is similar to that of a damped harmonic oscillator. We use this equation to discuss the spatial beam narrowing occurring inside a Raman amplifier. In addition to oscillating with a period ∼1mm, the beam also narrows down during its amplification inside a graded-index fiber on a length scale ∼1m. The main advantage of our simplified approach is that it provides an analytic expression for the damping distance of width oscillations that shows clearly the role played by various physical parameters.
Spatiotemporal mode-locked fiber laser based on dual-resonance coupling long-period fiber grating
Authors: Xing Dengke , Feng Mao , Liu Congcong , He Jiangyong , Chang Kun , Li Jin , Wang Pan , Liu Yange , Wang Zhi
Published: February 2023

Spatiotemporal mode-locked (STML) fiber lasers have become an excellent platform in nonlinear optics research due to the rich nonlinear evolution process. In order to overcome modal walk-off and realize phase locking of different transverse modes, it is usually crucial to reduce the modal group delay difference in the cavity. In this paper, we use long-period fiber grating (LPFG) to compensate the large modal dispersion and differential modal gain in the cavity, realizing the spatiotemporal mode-locking in step-index fibers cavity. The LPFG inscribed in few-mode fiber could induce strong mode coupling, which has wide operation bandwidth based on dual-resonance coupling mechanism. By using dispersive Fourier transform involved intermodal interference, we show that there is a stable phase difference between the transverse modes constituting the spatiotemporal soliton. These results would be beneficial for the study of spatiotemporal mode-locked fiber lasers.
Spectral broadening scheme for suppressing SBS effects based on time-domain optimized chirp-like signals
Authors: Li Jie , Shi Mengyue , Wu Yong , Fang Zhiwei , Wang Jiajin , Mu Huan , Hu Weisheng , Yi Lilin
Published: February 2023

We propose a novel (to our knowledge) driving scheme to suppress the stimulated Brillouin scattering (SBS) effect in master oscillator power amplification (MOPA) systems based on an external high-order phase modulation. Since seed sources with the linear chirp can uniformly broaden the SBS gain spectrum with a high SBS threshold, a chirp-like signal was designed by applying further editing and processing to the piecewise parabolic signal. Compared with the traditional piecewise parabolic signal, the chirp-like signal has similar linear chirp characteristics and can reduce the driving power and sampling rate requirements, enabling more efficient spectral spreading. The SBS threshold model is constructed theoretically based on the three-wave coupling equation. The spectrum modulated by the chirp-like signal is compared with the flat-top and Gaussian spectra in terms of the SBS threshold and the bandwidth-distribution normalized threshold, and a considerable improvement is demonstrated. Meanwhile, the experimental validation is carried out in a watt-class amplifier based on the MOPA structure. At a 3 dB bandwidth of ∼10 GHz, the SBS threshold of the seed source modulated by the chirp-like signal is improved by 35% compared to the flat-top spectrum and 18% compared to the Gaussian spectrum, respectively, and the normalized threshold is also the highest among them. Our study shows that the SBS suppression effect is not only related to the power distribution of the spectrum but also can be improved by the time domain design, which provides a new idea for analyzing and improving the SBS threshold of narrow-linewidth fiber lasers.
Reversibly switching liquid crystals between three orthogonal orientation states for use in rapid-response THz phase shifters
Authors: Oh-e Masahito , Zheng Deng-Yun
Published: February 2023

Liquid crystal (LC) devices for terahertz phase shifters inevitably use a thick cell gap for the required retardation, severely delaying the LC response. To improve the response, we virtually demonstrate novel LC switching between in-plane and out-of-plane for reversible switching between three orthogonal orientation states, broadening the range of continuous phase shifts. This LC switching is realized using a pair of substrates, each with two pairs of orthogonal finger-type electrodes and one grating-type electrode for in- and out-of-plane switching. An applied voltage generates an electric field that drives each switching process between the three distinct orientation states, enabling a rapid response.
Helmholtz-resonator quartz-enhanced photoacoustic spectroscopy
Authors: Luo Huijian , Wang Chenglong , Lin Haoyang , Wu Qian , Yang Zhifei , Zhu Wenguo , Zhong Yongchun , Kan Ruifeng , Yu Jianhui , Zheng Huadan
Published: February 2023

In this work, Helmholtz-resonator quartz-enhanced photoacoustic spectroscopy (HR-QEPAS) was developed for trace gas sensing. A pair of Helmholtz resonators with high-order resonance frequency was designed and coupled with a quartz tuning fork (QTF). Detailed theoretical analysis and experimental research were carried out to optimize the HR-QEPAS performance. As a proof-of-concept experiment, the water vapor in the ambient air was detected using a 1.39 µm near-infrared laser diode. Benefiting from the acoustic filtering of the Helmholtz resonance, the noise level of QEPAS was reduced by >30%, making the QEPAS sensor immune to environmental noise. In addition, the photoacoustic signal amplitude was improved significantly by >1 order of magnitude. As a result, the detection signal-to-noise ratio was enhanced by >20 times, compared with a bare QTF.
Long-range photon-efficient 3D imaging without range ambiguity
Authors: Dai Chen , Ye Wen-Long , Yu Chao , Huang Xin , Li Zheng-Ping , Xu Feihu
Published: February 2023

Single-photon light detection and ranging (LiDAR) has broad
applications ranging from remote sensing to target recognition. In
most cases, however, the repetition period of the pulsed laser limits
the maximum distance that can be unambiguously determined. The
relative distances are normally obtained using a depth map. Here, we
propose and demonstrate a photon-efficient three-dimensional (3D)
imaging framework which permits the operation of high laser pulse
repetition rates for long-range depth imaging without range ambiguity.
Our approach uses only one laser period per pixel and borrows the
information from neighboring pixels to reconstruct the absolute depth
map of the scene. We demonstrate the absolute depth map recovery at
ranges between 2.2 km and 13.8 km using ∼1.41 signal photons per
pixel. We also show the capability to image the absolute distances of
moving targets in real time.
Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression
Authors: Qin Senlin , Wang Guoyan , Chen Lei , Geng Huijun , Zheng Yining , Xia Chao , Wu Shengru , Yao Junhu , Deng Lu
Published: February 2023

Pharmacological vitamin C (VC) is a potential natural compound for cancer treatment. However, the mechanism underlying its antitumor effects remains unclear. In this study, we found that pharmacological VC significantly inhibits the mTOR (including mTORC1 and mTORC2) pathway activation and promotes GSK3-FBXW7-mediated Rictor ubiquitination and degradation by increasing the cellular ROS. Moreover, we identified that HMOX1 is a checkpoint for pharmacological-VC-mediated mTOR inactivation, and the deletion of FBXW7 or HMOX1 suppresses the regulation of pharmacological VC on mTOR activation, cell size, cell viability, and autophagy. More importantly, it was observed that the inhibition of mTOR by pharmacological VC supplementation in vivo produces positive therapeutic responses in tumor growth, while HMOX1 deficiency rescues the inhibitory effect of pharmacological VC on tumor growth. These results demonstrate that VC influences cellular activities and tumor growth by inhibiting the mTOR pathway through Rictor and HMOX1, which may have therapeutic potential for cancer treatment.