bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourier-optic modeling of radiation profiles with application to waveguide coupling, beam shaping, optical switching, and all-optical logic devices
Authors: Falter Brian , Gauthier Robert
Published: February 2023

Fourier optics and plane wave propagation are used to obtain the radiation profile, U(x,y,z>0), generated from an original source, U(x,y,z=0).
Simple beam-splitter model of two-beam coupling in photorefractive materials
Authors: Rowan D. Jeffrey , Yarrison-Rice Jan M. , Rice Perry R.
Published: February 2023

The key to the beam splitter model is that the sinusoidally varying index grating can be approximated using an approximation of a series of simple interfaces between differing indices of refraction as encountered in a beam splitter.
A color difference formula based on color discrimination ellipsoid parameters
Authors: Cui Chengwu , Hovis Jeff
Published: February 2023

Frequently in industry, color difference formula are applied only to limited regions of the CIELAB color space. By treating the individual discrimination ellipsoids as subspaces, a general equation for specifying color differences is derived in terms of the ellipsoid dimensions.
Computer-generated near-field holograms
Authors: Jendral Andreas , Bräuer Ralf , Bryngdahl Olof
Published: February 2023

A method is presented to calculate computer-generated holograms which permit reconstructions of three-dimensional objects located in and around the hologram plane. An angular spectrum technique based on scalar diffraction theory is used.
Effect of the autocorrelation function on electronic holography methods for imaging through scattering media
Authors: Shih Marian P.
Published: February 2023

Past work on the electronic holography gating method for imaging through biological tissue has used illumination by short coherence length light: some researchers have used ultrashort femtosecond laser pulses, while others have used a wavelength-tunable CW dye laser. For the purposes of holography, these two temporally incoherent light sources were demonstrated to be fully equivalent as long as their coherence functions are identical.
Can we find a partner who shares our vision?
Authors: Brown Thomas B.
Published: February 2023

Should you launch your products? Can you find someone who shares your vision?
Integrating absorption-cavity measurements: wherein lies the truth?
Authors: Kennedy C. , Pope R. , Weidemann A.
Published: February 2023

The measurement of volume absorption coefficient for oceanic waters is made intrinsically difficult due to interference and interaction with scatterers in the media and low transmission loss over short pathlengths.
Pulsed coherent effects in atomic sodium
Authors: Wilkinson Steven R. , Smith Arlee V.
Published: February 2023

We show that gain in a noninverted medium of atomic sodium exists in the transient regime.
Spatially multiplexed composite filters for optical pattern recognition
Authors: Abushagur Mustafa A.G.
Published: February 2023

A new class of composite filters is proposed. This class of filters can be used in optical correlator based recognition systems.
Two-port photorefractive correlator
Authors: Khoury Jehad , Cronin-Golomb Mark , Kane Jonathan S. , Woods Charles L.
Published: February 2023

Real time correlation has become of interest in the areas of pattern recognition and optical signaling processing.
Coherence between elastic and inelastic scattering of light from an atom
Authors: Bali S. , Narducci F. A.
Published: February 2023

We are in the process of investigating non-classical effects in the interference between fluorescence from a single atom and a coherent, classical reference beam, when the elastic portion of the fluorescence is used as the classical reference.
Treatment of spatial propagation and localized states in quantum optics
Authors: Ho Seng-Tiong
Published: February 2023

In this paper, we show that a localized photon annihilation operators

b
^

can be constructed to treat spatial propagation and atom-field interaction problem in quantum optics, where

b
^

can be expressed as an integral over the +z or −z propagating part of the vector potential operator.
Production and detection of pulsed images from reflection holograms
Authors: Hill Kent B. , Purchase Kenneth G. , Brady David J.
Published: February 2023

Optical pulses with terahertz modulation can be produced by reflecting ultrashort pulses from reflection holograms with high spatial bandwidths.
Fiber-optic Fabry–Perot strain sensor using an optical-frequency comb-interrogation technique
Authors: Marrone M.J. , Kersey A. D.
Published: February 2023

Interferometric fiber sensing techniques are typically used for applications requiring very high sensitivity to weak perturbing fields, such as acoustic, magnetic and electric fields. There has also been interest, however, in the use of interferometric configurations for the measurement of quasi-static parameters, e.g. temperature and strain. In general, the ambiguous form of the cosine squared transfer function of an interferometric sensor negates the determination of the measurand value on initialization of the sensor. This can be overcome using various forms of signal processing which typically involve multi-wavelength operation, or source spectral modulation. In this paper we describe a fiber Fabry–Perot sensor for the measurement of strain which utilizes a mode of operation based on matching the spectral characteristics of a strongly frequency-modulated source to the frequency dependence of the Fabry–Perot resonator (or other form of resonant cavity, e.g., ring resonator). This matching allows the precise determination of the free-spectral range of the cavity, and thus the optical length of the cavity. Strain induced changes in cavity length are then reflected in a shift in the laser modulation frequency required to achieve matching of the laser and sensor resonance spectral characteristics. The principle of operation of the technique, and results obtained using a 20 m fiber Fabry Perot cavity will be reported.
Zeroth-order waveplates in dichromated gelatin
Authors: Campbell Gene , Kostuk Raymond K.
Published: February 2023

For diffraction gratings having a spatial frequency above a certain threshold, all diffracted orders but the zeroth orders are evanescent. The condition for zeroth order diffraction is simple if the incident beam is normal to the hologram surface. Such gratings exhibit form birefringence, and waveplates of arbitrary phase retardation can be made by properly adjusting the birefringence and grating thickness. The effects of grating period, permittivity modulation profile, and other parameters are theoretically investigated using rigorous coupled wave theory to determine the conditions for maximum phase retardation. Experimental results for zeroth order gratings recorded in dichromated gelatin are presented, and deviations from theory are explored. Finally, a comparison is made to the results obtained by other researchers using surface relief gratings.
Kilo-electron-volt spectroscopy of high-Z plasmas produced by subpicosecond laser pulses
Authors: Côté C. Y. , Kieffer J. C. , Chaker M. , Pelletier J. F. , Beaudoin Y. , Peyrusse O.
Published: February 2023

High Z targets have been irradiated with a high contrast 500 fs laser pulse (0.53 μm wavelength) at around 1017 W/cm2. Experiments have been realized with the INRS Table Top Terawatt laser. The absence of prepulse allows us to produce hot ultra-dense plasmas which are very interesting for the development of ultrafast X-ray sources. L and M shell spectra of respectively Ge and Ta targets which have been recorded with a Von Hamos spectrometer, will be presented and analyzed. The effects of the laser plasma density gradient scale length and of the laser intensity on the high Z source brightness and duration will be discussed.
Precision frequency-tunable nonlinear conversion by using diode lasers for a diode-laser-based optical-frequency sweep generator
Authors: Wang Weizhi , Ohtsu Motioichi
Published: February 2023

We have performed frequency-tunable sum-and difference-frequency generation in the green and the infrared region by using only diode lasers. Frequency links between the generated light and the atomic absorption line are also investigated.
Is laser removal of graffiti practical?
Authors: Liu Katherine X. , Garmire Elsa , Fathe Laurie
Published: February 2023

We have studied laser stripping paint off concrete, bricks, and other materials for the application of graffiti removal. A universal graph representing the characteristic of the graffiti removal rate as a function of the laser beam intensity, will be presented, based on our experimental measurements over an intensity range of 7 orders of magnitude. We will also present our study of the paint removal rate at different pulse widths. A characteristic pulse width corresponding to the material response time of the paint and substrate has been defined. We have experimentally observed differences in graffiti removal rate at a pulse width longer than and shorter than the characteristic pulse width. The graffiti removal rate has also been studied in terms of the thermal conductivity and surface reflectivity of the substrates. In addition, we will show our results of graffiti removal from freeway signs using lasers with different wavelengths and pulse widths. Finally, we will discuss the surface quality of laser stripping compared to that of the conventional methods, and an analysis of costs and benefits using lasers to remove graffiti.
Stability of 3-D solitary waves in a saturable self-focusing medium
Authors: Atai Javid , Chen Yijiang
Published: February 2023

In recent year self-trapped beams have been the subject of extensive investigation due to their potential applications in computing, switching and integrated optics.
Polydiacetylenes: excellent candidates as nonlinear optical materials
Authors: Abdeldayem Hossin , Paley M. S. , Frazier Donald O. , McManus S. P.
Published: February 2023

A material is considered a good candidate for nonlinear optical applications if it shows a reasonable nonlinearity at low laser energy, large second or third nonlinear coefficients, and expresses fast responses to short pulses.
Wavelength-multiplexed holographic lens array for a memory-distribution network
Authors: Catanzaro Brian E. , Ma Jian , Fainman Shaya , Lee Sing H.
Published: February 2023

In many parallel computing architectures, processing elements have a great need for simultaneous access to various addresses of page-oriented memory.
Spot-array generation using a 2-D acousto-optic deflector
Authors: Paparao Palacharla , Boothroyd Simon A. , Robertson William M. , Chrostowski Jacek
Published: February 2023

Spot array generation is essential for optical computing architectures based on free-space interconnections. Acousto-optic (AO) deflectors are potentially attractive for reconfigurable array generation or interconnection because of their large space bandwidth product and switching times of a few microseconds. In this paper, we describe the procedure and present experimental results of using a large aperture integrated two-dimensional (2-D) AO deflector to generate reconfigurable 2-D spot arrays. The generation of 2-D spot arrays is achieved by driving each of two orthogonally mounted AO deflectors with a high-frequency carrier that is phase modulated with an electronic equivalent of a holographic phase grating. The carrier deflects the incident beam by the Bragg angle, while the modulating signal gives rise to the spot pattern. The 2-D AO spot array is realized as the outer-product of two 1-D spot arrays. 1-D phase grating structures were calculated using several nonlinear optimization techniques including a genetic algorithm and the Gerchberg-Saxton algorithm. In our experiments, the AO device was used for realizing both discrete (e.g., binary, 4-level) and continuous phase gratings. The continuous phase profiles give higher diffraction efficiency. Practical limitations encountered in the generation of 13x13,21x21 and 50x50 spot arrays are discussed.
How to use an autocollimator
Authors: Bailey Sam T.
Published: February 2023

Summary not available.
Fundamental chromaticity diagram with physiologically significant axes: report of the activities of CIE committee TC 1-36
Authors: Vienot Françoise
Published: February 2023

CIE Committee TC 1-36 has as its objective the establishment of a chromaticity diagram which includes coordinates corresponding to physiologically significant axes.
Stabilized laser for hole burning and hole burning for stabilized lasers
Authors: Manson N. B. , Sellars M. , Fisk P. T. H. , Meltzer R. S.
Published: February 2023

A commercial high resolution laser (Coherent 699-21) has been modified by the inclusion of a fast phase modulator to give an improved stability.
New static and dynamic simulator for ridge-waveguide MQW DFB lasers
Authors: Hong J. , Huang W. P. , Makino T.
Published: February 2023

Ridge waveguide MQW DFB lasers are important sources in lightwave communication systems. In order to improve the system performance, both the static and dynamic responses of the MQW DFB lasers need to be carefully investigated.
Matrix analysis of dual-state waveguide arrays and Fabry-Perot étalons
Authors: Yeh Pochi , Gu Claire , Botez Dan
Published: February 2023

Waveguide arrays and Fabry-Perot etalons play important roles in the generation of diffraction-limited optical power output in semiconductor lasers, spectrum analyzers, laser cavities and modulators.
New 3-D vector soliton solutions of Maxwell’s equations and of short-wave amplitude equations with Kerr’s nonlinearity
Authors: Kovachev L. M. , Donev St. , Rusev R.
Published: February 2023

A new class of exact 3-D vector soliton solutions of Maxwell’s equations and of short-wave amplitude equations for the electric field in a nonlinear Kerr media are obtained.
Diode-pumped grazing-incidence slab laser
Authors: Bernard J. E. , Lokhnygin V. D. , Alcock A. J.
Published: February 2023

We have recently reported1 the operation of an efficient Nd:YV04 slab laser which was transversely pumped by a 200 μs long pulse from a single quasi-CW diode laser bar.
Q-switched, side-pumped Nd:YAG laser
Authors: Dawes Judith M. , Dekker Peter , Cai Ying , Knowles David S. , Piper James A.
Published: February 2023

The use of a prism to collect the diode light in a side-pumped laser geometry offers the advantages of a robust mechanical construction and a uniform gain crossection in the laser rod which is mounted in the prism.
Time-dependent temperature in laser block crystals: impact of selective cooling
Authors: Farrukh Usamah O. , Barnes Norman P.
Published: February 2023

Laser crystal blocks are sometimes multi-pulsed by a laser source at one of the faces of the block.
Quality factor of real beams: measurement problems and practical solutions
Authors: Bélanger P. A. , Champagne Y. , Pare C.
Published: February 2023

The recent introduction of the beam quality factor1 can be thought of as a major forward step towards the assessment of the spatial quality of general optical beams with a sole numerical parameter.
Star couplers with gain that use fewer fiber amplifiers
Authors: Chi Sien , Chen Yung-Kuang
Published: February 2023

A passive N× N star coupler plays a central role in the architecture of many high-throughput multiple-access optical WDM networks.
High-power erbium-doped fiber amplifier using a single tapered-diode pump
Authors: Hemenway B. R. , Livas J. C. , Walpole J. N. , Wang C. A. , Missaggia L. J.
Published: February 2023

We report a single-stage EDFA, which uses a high power InGaAs diode laser,1 with a tapered gain region and operating near 980 nm, and achieves 114 mW (+20.6 dBm) at 1532 nm.
Image-scanning ellipsometry for the measurement of thin-film thickness profiles
Authors: Liu An-Hong , Wayner Peter C. , Plawsky Joel L.
Published: February 2023

A novel technique to measure the two-dimensional thickness profile of a nonuniform, thin, film from several nm up to several μm, in a steady or transient state has been developed and tested. Image Scanning Ellipsometry (ISE) is a full-field, imaging technique that can study every point on a surface simultaneously with high spatial resolution and thickness sensitivity; it can measure and map a 2-D film thickness profile.
Optical switching and limiting in a Si/SiGe distributed-feedback structure
Authors: Fernando C. , Janz S. , Normandin R. , Wight J. S. , Baribeau J. M.
Published: February 2023

Optical switching using distributed feedback (DFB) structures has been demonstrated by several authors using a wide variety of materials.1 The use of SiGe has been hindered by difficulty in growing defect free material. However, the development of SiGe optical structures will enable traditional Si electronics to be integrated with these novel SiGe components to make silicon based optoelectronic integrated circuits (OEIC).
Wide-bandwidth terahertz system based on a GaAs-on-silicon receiver
Authors: Pedersen J. Engholm , Keidling S. Rud , Sorensen C. B. , Lindelof P. E.
Published: February 2023

Freely propagating, subpicosecond electromagnetic pulses with a bandwidth extending well into the far-infrared can be generated and detected using photoconducting switches. Several applications in spectroscopy have already been reported. However, all systems used have suffered from bandwidth limitations imposed by the receiver.
Passive-mode-locking threshold in lasers
Authors: Khanin Ya. I.
Published: February 2023

Fundamental generality between different methods of nonlinear influence on the lasing process allows to transfer some theoretical results from one model to another without additional calculations.
Thin films
Authors: Macleod H. Angus
Published: February 2023

How do antireflection coatings, laser mirrors, cold mirrors, narrow band filters and dichroic beam splitters work? What are their limitations? Simple but accurate techniques for understanding coatings are covered.
Liquid-crystal-on-silicon smart pixel device for the optoelectronic implementation of ART-1 neural networks
Authors: Bar-Tana I. , Sharpe J. , Johnson K. M. , Caudell T. P.
Published: February 2023

Direct electronic implementations of neural networks have proven difficult to scale to large dimensionality due to the high degree of interconnectivity between neurons.
Optoelectronic winner-take-all VLSI shunting neural network for use with a multi-channel associative memory
Authors: Kane Jonathan S. , Kincaid Thomas G.
Published: February 2023

Shunting networks have been of interest to the signal processing community in part because they provide a biological inspired method for handling inputs with a large dynamic range.
Inverse-scattering methods applied to the design of nonlinear optical components
Authors: Lin F. C. , Fiddy M. A.
Published: February 2023

There is considerable interest in the design of optical interconnect elements that can efficiently redirect incident light to new one or more different locations; also of interest is that the optical components which accomplishes this be efficient and can be controlled in some way.
Storing and accessing binary phase-only filters (BPOF’s) used in correlation systems employing frame grabbers
Authors: Hanson A. C. , Crowe W. M. , Buzzard R. , Jones D.
Published: February 2023

For optical correlation systems with video-addressed Spatial Light Modulator (SLM) filter devices, one of the problems has been the number of filters which can be recalled and used in real-time.
Degenerate parametric amplifier with a nonclassical pump
Authors: Hillery Mark , Yu Daoqi , Bergou Janos
Published: February 2023

The degenerate parametric amplifier is usually studied within the context of the parametric approximation.
Continued-wave stimulated Rayleigh-wing scattering and four-wave parametric oscillation in carbon disulfide microdroplets
Authors: Campillo A. J. , Lin H.-B.
Published: February 2023

Micrometer droplets are naturally occurring high Q optical cavities and can provide feedback for coherent nonlinear processes such as stimulated Raman1,2 and Brillouin3 scattering when pumped by intense laser sources.
X-ray-diffraction, Raman, and photo-luminescence spectroscopic characterization of CVD diamond films
Authors: Wang H. , Leventouri Th. , Medina F. D. , Moreno M. A. , Landstrass M. I.
Published: February 2023

Diamond films have received much attention as promising materials due to their unique combination of desirable electrical, optical and mechanical properties.
Solution dynamics and cavity QED in liquid microdroplets
Authors: Barnes Michael D. , Whitten William B. , Ramsey J. Michael
Published: February 2023

The Morphology Dependent Resonances (MDR’s) associated with micron-sized droplets create unique experimental opportunities to investigate cavity-QED effects such as enhancement and inhibition of spontaneous emission rates.
High-speed/high-bus system with optical analog of electrical high-impedance state
Authors: Jannson Tomasz , Katsman Vladimir , Jannson Joanna
Published: February 2023

Future generation, high throughput data processing applications, such as nuclear data acquisition, the determination of bi-molecular structures using synchrotron rotation, superconducting supercollider (SSC) research, aircraft data acquisition, and weather prediction will require systems capable of handling this increase in throughput.
Enhanced self-phase modulation in tapered fibers
Authors: Dumais Patrick , Villeneuve Alain , Gonthier François , Wigley Peter , Lacroix Suzanne , Stegeman George , Bures Jacques
Published: February 2023

The effective area and the dispersion of the fundamental mode of an optical fiber are affected by fiber tapering.
Comparison of free-space, single-mode-fiber and multimode-fiber mixing schemes
Authors: Jacob Donald K. , Mark Martin B. , Duncan Bradley D.
Published: February 2023

Given shot noise limited detection, the optimal carrier to noise ratio (CNR) of a heterodyne ladar system is reduced by the mixing and coupling efficiencies of the receiver.
Microlasers and microdisk lasers
Authors: McCall S. L.
Published: February 2023

The buried heterostruction laser is the basic design for many important semiconductor laser applications.
Mode-locked, Cr4+ solid-state lasers
Authors: Nathel Howard , Sennaroglu Alphan , Pollock Clifford R.
Published: February 2023

Recent advances in mode-locked solid-state lasers have resulted in pulses as short as 11 fs in the 800 nm region from To:sapphire oscillators [1].
Antiresonant Fabry-Perot saturable absorber (A-FPSA): an all-solid-state reliable, passive-mode-locking technique
Authors: Keller Ursula , Brovelli Luigi R.
Published: February 2023

Using an intracavity A-FPSA we have previously demonstrated self-starting passive modelocked Nd:YLF and Nd:YAG lasers for picosecond pulse generation [1, 2], and a Nd:glass laser for femtosecond pulse generation [3] at a wavelength of 1.06 µm.
Polarization discrimination in ion-exchanged-KTP waveguides achieved by using a dielectric overlayer film
Authors: Lau S. D. , Risk W. P. , Kurdi B. N.
Published: February 2023

Frequency doubling using a periodically-poled nonlinear waveguide element as part of an extended-cavity GaAlAs laser is a promising approach for a compact, frequency-stable blue light source.
Phase-preserving optical invariant system,
Authors: Lin Jian , Bedi J. , Lin T. W.
Published: February 2023

Conventional optical correlators are known to be very sensitive to distortions, such as rotation and scaling.
Fourier-Fraunhofer-holographic-transform spectrometer
Authors: Berlinghieri Joel C. , Droste R. E. , Hilleke R. O. , Saunders M. , Watts J. F.
Published: February 2023

We have constructed an improved Fourier transform spectrometer, using two, common path, orthogonally oriented, ring interferometers.1,2 This field widened device uses a two-dimensional CCD detector to record a channeled, Fourier–Fraunhofer hologram which is produced from laterally sheared images of the light source. A numerical Fourier transform of this interferogram produces a high resolution spectrum. There is no need to limit the extent of the spectrum since the aliasing problem associated with broad band, high resolution spectra has been unraveled without the use of narrow band filters. The second orthogonally oriented ring interferometer sorts the normally overlapping orders formed when the interference pattern is undersampled. Spectra taken in the visible wavelength region using this dual interferometer will be shown.
Optical realization of a recurrent neural network
Authors: Liang Minhua
Published: February 2023

Recurrent neural network is a theoretical model for lateral inhibition which is a common phenomena in biological systems.
Asymmetric optical Y-junctions and switching of weak beams by using bright-spatial- soliton collisions
Authors: Torres-Cisneros G. E. , Sánchez-Mondragón J. J. , Vysloukh V. A.
Published: February 2023

Spatial-soliton based optical Y-junctions can be formed by high-order dark soliton formation [1] or using the interaction characteristic exhibited by two neighboring bright-solitons [2]. Here we show that a collision between two bright spatial-soliton acts as an asymmetric optical Y-junction and, in specific cases, as an optical switch for the weak beams they guide. We demonstrate that the inputs probe beam energies can be split into the two emerging soliton channels in a controlled way, by properly adjusting the angle at which the two solitons cross, the relative phase of the colliding solitons or the wavelength of the probe beam. Therein, without modifying the soliton junction itself [2], the switching of the probe beam into a single soliton based optical channel can be actively controlled. We present a physical description of such a behavior based on the diffraction of the incident probe beams by a diffraction grating formed by the profile of the spatial-soli ton collision.
Holographic 4×4 star coupler with a ring topology
Authors: Simova E. , Yun G. , Kavehrad M.
Published: February 2023

Star couplers are fanin-fanout elements splitting each input beam into a number of output beams. Holography has been widely recognized as a high-potential method for realization of free space optical interconnects.
Coupling characteristics of a two-core fiber loop
Authors: Drolet D. , Vallée R.
Published: February 2023

We present the experimental results obtained with a two-core fiber used as a tunable directional coupler. A slight difference between the propagation constants is overcome by the optical path difference produced by a fiber loop.
Determination of all bound modes of a general multilayer planar waveguide by integration of an initial-value problem
Authors: Li Lifeng
Published: February 2023

Multilayer planar waveguides have become increasingly important in modern integrated optic devices. Numerous numerical methods have been devised to address the fundamental issue in multilayer waveguide design and analysis, that is, the determination of the bound modes.
Realization of holographic associative memory in a single BaTiO3, crystal
Authors: Ohishi Yuji , Ohashi Hirotada , Akiyama Mamoru
Published: February 2023

Holographic associative memories (HAM) is one of various applications of photorefractive crystals to optical processing, which has drawn great interest and has been widely studied during these years.
Brillouin-enhanced four-wave mixing in CS2 for a frequency-recovered phase-conjugation mirror of an iodine laser
Authors: Choi Byoung , Jo Min Sik , Kang Eung Cheol , Nam Chang Hee
Published: February 2023

The Brillouin-enhanced four-wave mixing (BEFWM) has been investigated using CS2 as a nonlinear medium to develope a phase conjugation mirror for an iodine laser.
Analysis of lateral-mode behaviour of a broad-area diode laser coupled to an external cavity
Authors: Mailhot S. , McCarthy N.
Published: February 2023

Broad-Area (BA) diode lasers have always presented poor spatial mode pattern because of the filamentation problems associated with gain irregularities.
Comparison of adult threshold elevation curves of the red-green channel with those of an 11-year-old boy by oblique masking
Authors: Pandey Rita , Vimal Ram L. P.
Published: February 2023

We have reported (ARVO ’92, ’93) that adult chromatic threshold elevation (TE) curves [TE vs. mask spatial frequency (SF)] were broad.
New type of dye laser used for a femtosecond squeezed state
Authors: Wang Ching-Yue , Dai Jian-Ming , Zhang Ruo-Bing
Published: February 2023

Femtosecond squeezed-soliton can be generated in a self-phase modulation-controlled passive mode-locked dye laser.1 This new kind of mode-locked dye laser was operated in our group. It is based on an anti-resonant ring colliding-pulse mode-locked dye laser with four intracavity prisms and two anti-resonant ring interferometers as two end reflectors of the cavity, which includes a Kerr nonlinear glass plate (SF57) in one anti-resonant ring, a saturable absorber (DODCI) jet in another and a gain (Rh6G) two jet between two curved reflecting mirrors in the middle of the cavity. The stability for the cavity is analyzed. It is found that when the average of all folded angles is between 6°and 8°, the stability regions are large enough for mode-locked operation and the stability regions vanish when the average is beyond 12°. In experiment, the laser is pumped with about 3.5W from an all-lines argon-ion laser. Very stable pulse trains with pulse width of 160 fs at 620 nm is obtained, and the spectral bandwidth is measured to be 2.8 nm. As a result, a femtosecond squeezed state with several dB noise reduction should be produced.
Analog edge-enhancement scheme with simultaneous background suppression
Authors: Munroe James L.
Published: February 2023

It is an axiom of Fourier optics that a lens is a spatial filter operating on the object spectrum. The spatial filter function is given by the Optical Transfer Function (OTF). For incoherent illumination, the OTF can be written as the autocorrelation of the original pupil function. For the ideal case of aberration free imagery, this autocorrelation relationship simplifies the calculation of the OTF to a simple area calculation. Inherent in this area calculation is the ability to mask the pupil to optimize the OTF.
Bispectrum and Knox-Thompson phase variances at low spatial frequencies
Authors: Meng Julian , Aitken George J. M.
Published: February 2023

The bispectrum (triple correlation) and Knox Thompson (KT) algorithms are capable of achieving nearly diffraction limited astronomical imaging when applied to large numbers of short-exposure speckle images. Previous comparisons of these algorithms have shown that at low signal levels the spectral noise at spatial frequencies above the atmospheric cut-off are essentially the same for the bispectrum and KT in the near-axis region. However, we have discovered a previously unreported difference in the behavior of their atmospherically-induced phase variances that dominate at high signal levels. The bispectrum phase variance decreases to zero while the KT phase variance remains almost constant. At high signal levels these differences are important and can result in images obtained from the bispectrum having as much as an order of magnitude lower error than those obtained from KT crossspectra. We have studied the phenomenon by simulations and by calculation of the bispectrum variances at low spatial frequencies with an extension of the method Von der Luhe1 used to determine the variance of the KT crossspectra.
Pyramid coding of halftone images
Authors: Fan Zhigang
Published: February 2023

The paper presents a pyramid coding technique for compression of halftone images. The image is divided into disjoint blocks. Each block is represented by a tree structured pyramid whose leaves are “uniform” areas defined to contain only the bit patterns that are possibly generated by single grey levels. The algorithm shows a high compression ratio in the experiments. The progressive transmission based on the algorithm allows an approximate image to be built up at a very low bit rate, and the details to be added gradually, which is useful for picture-browsing.
Coherence properties of optical parametric oscillators
Authors: Singh Surendra , Vyas Reeta
Published: February 2023

Most treatments of noise characteristics of optical parametric oscillators (OPOs) have been based on linearization of the equations of motion. This approach, valid far below and far above threshold, breaks down in the threshold region as it ignores the nonlinearity of interaction. We present a treatment that takes into account both the nonlinearity and the quantum mechanical nature of noise in these oscillators. Analytical expressions for the steady-state amplitude distribution functions are derived. Both the degenerate and the nondegenerate OPOs are considered. These steady-state distributions are used to study the coherence properties of the OPOs in the threshold region. These studies bridge the noise characteristics of the OPOs below and above threshold. Results are compared with classical oscillators and differences and similarities are discussed. Special attention is given to quantum mechanical features that survive even as the oscillator amplitude grows and reaches macroscopic proportions.
Input-output analysis of a linearly driven cavity with arbitrary out-coupling
Authors: Prasad Sudhakar , Fischer Dorothee
Published: February 2023

High-Q cavities play a central role in quantum optics for the generation and study of novel quantum mechanical states of light like squeezed states. It is however not widely recognized that even low-Q cavities can produce such states. For example, a degenerate optical parametric oscillator (DOPO) with one nearly perfect mirror can produce perfectly squeezed output light regardless of the second mirror transmission, provided the DOPO is at oscillation threshold. Moreover, the squeezing bandwidth increases with increasing transmission of the second mirror.
Control of mode-index modulation of a TIPE grating by multistep proton exchange
Authors: Bao Yufei , Verber C. M. , Weng Yuanning
Published: February 2023

TIPE gratings intended for integrated optical tapped delay lines have been fabricated in z-cut lithium niobate planar waveguides. The effective mode index modulation of TIPE gratings was enhanced by multi-step proton exchange process. In the first step, the ThLiNbO3 waveguide covered with grating mask was emerged in pure benzoic acid for 6 minutes. Next, the waveguide without grating mask was proton exchanged under the same condition for 4 minutes. This process was done several times until the desired diffraction efficiency was obtained. At the wavelength of 0.63 micron, the diffraction efficienct of a 2 micron period 1 mm X1 mm TIPE rating was about 40% after the first step proton exchange, and was increased to over 80% after the second step proton exchange of 4 minutes. The diffract on efficiency at 1.06 micron wavelength was increased from about 2% to about 80% after 20 minute planar proton exchange. Multiple step proton exchange is an easy, practical, and effective approach to control the diffraction efficiency of TIPE waveguide gratings.
Solid-state diffusion mechanism for integrated optical waveguide fabrication
Authors: Kapila Dixit , Plawsky Joel L.
Published: February 2023

Solid-state, electric field assisted, film diffusion (Ag+ - Na+) in glass substrates has been investigated for the fabrication of passive, integrated, optical waveguides. A new corrosion based mechanism is proposed that couples the oxidation of silver metal to silver oxide by the glass substrate, and the subsequent diffusion of silver ions within the silver oxide layer into the glass substrate. At high electric fields and/or high temperatures, the growth rate of the interfacial, silver oxide film limits the formation of mobile silver ions and constrains the diffusion of silver into the glass. This new mechanism is able to correctly predict the dopant distribution profile under those conditions and also under conditions where a constant surface concentration approximation is appropriate (infinite oxide film). It also explains the characteristics of the experimentally observed current versus time curve during the field assisted, diffusion process. The formation of silver oxide at the interface was confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis. This new mechanism provides a foundation for tighter control of refractive index profiles in glass or crystal substrates.
Demonstration of high-accuracy 3D imaging using a Si optical phased array with a tunable radiator
Authors: Yoon Jinhyeong , Yoon Hyeonho , Kim Jae-Yong , Kim Junhyeong , Kang Geumbong , Kwon Nam-Hyun , Kurt Hamza , Park Hyo-Hoon
Published: February 2023

Precise imaging in three-dimension (3D) is an essential technique for solid-state light detection and ranging (LiDAR). Among various solid-state LiDAR technologies, silicon (Si) optical phased array (OPA)-based LiDAR has the significant advantage of robust 3D imaging due to its high scanning speed, low power consumption, and compactness. Numerous techniques employing a Si OPA have utilized two-dimensional arrays or wavelength tuning for longitudinal scanning but the operation of those systems is restricted by additional requirements. Here, we demonstrate high-accuracy 3D imaging using a Si OPA with a tunable radiator. As we adapted a time-of-flight approach for distance measurement, we have developed an optical pulse modulator that allows a ranging accuracy of less than 2 cm. The implemented Si OPA is composed of an input grating coupler, multimode interferometers, electro-optic p-i-n phase shifters, and thermo-optic n-i-n tunable radiators. With this system, it is possible to attain a wide beam steering range of 45° in a transversal angle with a 0.7° divergence angle, and 10° in a longitudinal angle with a 0.6° divergence angle can be achieved using Si OPA. The character toy model was successfully imaged in three dimensions with a range resolution of 2 cm using the Si OPA. The further improvement of each component of the Si OPA will allow even more accurate 3D imaging over a longer distance.
Benefits of cascaded nonlinear dynamics in hybrid fibers for low-noise supercontinuum generation
Authors: Hänzi Pascal , Sierro Benoît , Liu Zhixin , Romano Valerio , Rampur Anupamaa , Heidt Alexander M.
Published: February 2023

The recent development of fiber supercontinuum (SC) sources with ultra-low noise levels has been instrumental in advancing the state-of-the-art in a wide range of research topics. However, simultaneously satisfying the application demands of maximizing spectral bandwidth and minimizing noise is a major challenge that so far has been addressed with compromise, found by fine-tuning the characteristics of a single nonlinear fiber transforming the injected laser pulses into a broadband SC. In this work, we investigate a hybrid approach that splits the nonlinear dynamics into two discrete fibers optimized for nonlinear temporal compression and spectral broadening, respectively. This introduces new design degrees of freedom, making it possible to select the best fiber for each stage of the SC generation process. With experiments and simulations we study the benefits of this hybrid approach for three common and commercially available highly nonlinear fiber (HNLF) designs, focusing on flatness, bandwidth and relative intensity noise of the generated SC. In our results, hybrid all-normal dispersion (ANDi) HNLF stand out as they combine the broad spectral bandwidths associated with soliton dynamics with extremely low noise and smooth spectra known from normal dispersion nonlinearities. Hybrid ANDi HNLF are a simple and low-cost route for implementing ultra-low noise SC sources and scaling their repetition rate for various applications such as biophotonic imaging, coherent optical communications, or ultrafast photonics.
Enhancing chiroptical responses in the nanoparticle system by manipulating the far-field and near-field couplings
Authors: Zhao Qian , Zhang Houjiao , Zhou Zhang-Kai , Wang Xue-Hua
Published: February 2023

Employing nanostructure to generate large chiroptical response has been cultivated as an emerging field, for its great potentials in integrated optics, biochemistry detections, etc. However, the lack of intuitive approaches for analytically describing the chiroptical nanoparticles has discouraged researchers from effectively designing advanced chiroptical structures. In this work, we take the twisted nanorod dimer system as a basic example to provide an analytical approach from the perspective of mode coupling, including far-field coupling and near-field coupling of nanoparticles. Using this approach, we can calculate the expression of circular dichroism (CD) in the twisted nanorod dimer system, which can establish the analytical relationship between the chiroptical response and the basic parameters of this system. Our results show that the CD response can be engineered by modulating the structure parameters, and a high CD response of ∼ 0.78 under the guidance of this approach has been achieved.
Polymer tapered pillar grown directly from an SMF core enables high efficiency optical coupling with a silicon photonics chip
Authors: Kamiura Yoshiki , Kurisawa Taiga , Fujikawa Chiemi , Mikami Osamu
Published: February 2023

Silicon photonics technology has attracted considerable attention
because of the growing need for high-bit-rate optical
interconnections. The low coupling efficiency resulting from the
difference in spot size between silicon photonic chips and single-mode
fibers remains a challenging issue. This study demonstrated a new, to
the best of our knowledge, fabrication method for a tapered-pillar
coupling device using a UV-curable resin on a single-mode optical
fiber (SMF) facet. The proposed method can fabricate tapered pillars
by irradiating only the side of the SMF with UV light; therefore,
high-precision alignment against the SMF core end face is
automatically achieved. The fabricated tapered pillar with resin
cladding has a spot size of 4.46 µm and a maximum coupling
efficiency of −0.28 dB with a SiPh chip.
Ferroelectric photovoltaic response engineered by lattice strain derived from local metal-ion dipoles
Authors: Liu Yaping , Zhao Yueshun , Liu Rui , Zhang Jiayi , Zhao Shifeng
Published: February 2023

An unfavorable inverse relationship between polarization, bandgap, and leakage always limits the ferroelectric photovoltaic performances. This work proposes a strategy of lattice strain engineering different from traditional lattice distortion by introducing a (Mg2/3Nb1/3)3+ ion group into the B site of BiFeO3 films to construct local metal-ion dipoles. A giant remanent polarization of 98 µC/cm2, narrower bandgap of 2.56 eV, and the decreased leakage current by nearly two orders of magnitude are synchronously obtained in the BiFe0.94(Mg2/3Nb1/3)0.06O3 film by engineering the lattice strain, breaking through the inverse relationship among these three. Thereby, the open-circuit voltage and the short-circuit current of the photovoltaic effect reach as high as 1.05 V and 2.17 µA /cm2, respectively, showing an excellent photovoltaic response. This work provides an alternative strategy to enhance ferroelectric photovoltaic performances by lattice strain derived from local metal-ion dipoles.
High spatial resolution Stokes metasurface based on three-pixel technology
Authors: Cheng Bo , Xu Yun , Song Guofeng
Published: February 2023

A dynamically reconfigurable metasurface grating is proposed in this work based on the phase change material Ge2Sb2Te5 (GST). The metasurface grating keeps as the 0° polarizer that allows only x-polarized light to pass when the GST is in the crystalline state, and switches to the 90° polarizer (only y-polarized light passes through) while the GST transforms into the amorphous state. Furthermore, the circular polarization dichroism could be achieved using a double-layer metasurface consisting of this dynamic grating and a large broadband plasmonic quarter-wave plate. We can expect to achieve fully polarized detection with the ultra-high spatial resolution using only three components. In addition, we can obtain the largest bandwidth (300 nm) of the full Stokes large-image-element to date in the near infrared band by using the six-image-element technique with the crystalline phase GST.
Perceptions around COVID-19 and vaccine hesitancy: A qualitative study in Kaski district, Western Nepal
Authors: Mahato Preeti , Adhikari Bipin , Marahatta Sujan Babu , Bhusal Susagya , Kunwar Kshitij , Yadav Rajesh Kumar , Baral Sushila , Adhikari Anisha , van Teijlingen Edwin
Published: February 2023

Burgeoning morbidity and mortality due to COVID-19 pandemic including the peaks in outbreaks due to different variants have attracted global attention. Although the development and rolling out of vaccines have been impressive, low- and middle-income countries suffer from a double burden: (1) lack of adequate vaccines; and (2) low vaccine uptake (vaccine hesitancy). The main objective of this study was to explore perceptions around COVID-19 and vaccine hesitancy among urban and rural population in Western Nepal. A qualitative study was conducted in six urban wards of Pokhara municipality and four rural municipalities in Kaski district of Nepal. A semi-structured interview guide was used to interview participants who were selected purposively to explore the perceived burden of COVID-19 pandemic, roles, and contributions of vaccine. Nineteen interviews were conducted by telephone following a government recommendation to avoid face-to-face meetings. Audio-recorded interviews were thematically analysed after transcription and translation into English. COVID-19 is a major (public) health concern and affects people at an individual, societal and national level. People dreaded its health hazards and consequences and seemed to be compliant with public health measures such as maintaining social distance, wearing masks and maintaining hygiene. Vaccine was considered to be a major intervention to fight the pandemic, nonetheless, the rationale and benefits of vaccines were blemished by the perceived lack of the vaccine’s effectiveness, duration of protection, and its potential side-events. Expedited development of vaccine was embraced with suspicion that vaccine may have incurred compromise in quality. Science and rationale behind vaccine were smeared by misinformation and clearly counteracting the misinformation were deemed critical. Providing information about vaccines through government entities (who are trusted) and respected individuals may engender trust and uptake of vaccine. Fighting off misinformation of COVID-19 is critical to curb the course of pandemic. Increased attention towards monitoring and investing in legitimacy of information and offering information through trusted sources can help improve the vaccine coverage.