bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-step copying technique for multiplexed volume holograms
Authors: Piazzolla Sabino , Jenkins B. Keith , Tanguay Armand R.
Published: February 2023

A novel technique for copying the index or absorption modulation of a multiplexed volume hologram (MVH) into a second volume holographic medium in a single-step exposure is presented. The technique assumes that the master MVH is angularly multiplexed, and the individual holograms are independent in that each reference beam can recall only the corresponding object beam. Independence of the individual holograms is preserved in the copy. The copying technique utilizes a set of coherent sources (one for each individual hologram) that are mutually incoherent; each source provides two reference beams, one for an individual hologram in the master MVH and one for the corresponding hologram in the copy. When all sources are activated, the set of holograms in the master MVH are recalled and are mutually incoherent. The set of object beam wavefronts are imaged in amplitude and phase onto the secondary medium, and interfere with the corresponding reference beams, pairwise. Mutual incoherence prevents the recording of crosstalk gratings between the holograms in the copy.
Monolithic optical fiber stub array
Authors: Goossen K. W. , Walker J. A.
Published: February 2023

For optical computing and optical interconnection of electronic integrated circuits it is desirable to have 2-D arrays of interconnects. By doing so one gains the tremendous advantage of optical interconnects to utilize the entire area of the chip rather than just the perimeter. For such systems free-space optics has been the primary transmission medium considered. Optical fibers are possibly a more convenient medium, but the mechanical difficulties of fabricating a 2-D array of fibers are formidable. We present a new type of optical component, a monolithic optical fiber stub array (MOFSA). It is formed out of Corning Fotoform glass, which has the property that, when exposed to ultraviolet light and thermally cycled, it becomes highly soluble in hydrofluoric (HF) acid. Thus features can be formed in the glass via photolithographic techniques. Additionally, since only exposed regions are etched, extremely high aspect ratios can be achieved. Our MOFSA is formed by masking a 1.5-mm thick Fotoform glass plate with 65-μm diameter circular dark fields on 400-μm spaced centers and exposing and heating. The sample is then placed in an agitated HF solution. The etching proceeds from both faces, and is timed to stop when there is still a 250-μm thick central plane, producing 600-μm long fibers extending from either face. The fibers are ~65-μm diameter at the base and 55-μm diameter at the tip. The fiber tips are subsequently mechanically polished (wax is first melted, flowed between the fibers and cooled to form a support). After removing the wax, we focused a 632.8-nm He-Ne laser (with an ~1-mm diameter beam) onto a fiber tip with a 10× objective and achieved 56% transmission (-2.5-dB insertion loss).
Early vision zero-crossing liquid crystal spatial light modulator
Authors: Jared David A. , Johnson Kristina M.
Published: February 2023

The design, fabrication, and performance of an optically addressed spatial light modulator (SLM) that determines the zero-crossings from a difference of Gaussians’ operation is discussed. The SLM consists of a ferroelectric liquid crystal (FLC) modulator on a CMOS VLSI chip. The SLM receives two optically input images and generates an output image.
Fabry-Perot wavemeter for shot-by-shot analysis of pulsed lasers
Authors: Hahn Jae Won , Park Seung Nam , Rhee Chunghi
Published: February 2023

A Fabry-Perot wavemeter for analyzing pulsed laser sources used in a coherent anti-Stokes Raman spectrometer is constructed with an array detector. This wavemeter allows the real-time measurement of both the wavelength and the spectral purity of the laser pulse produced at 10 Hz. The performance of the wavemeter is checked with a frequency stabilized He-Ne laser and a doubled Nd:YAG laser, which is operated in a single-longitudinal mode by injection locking with a cw laser. Measuring the spectral purity of the pulses of the doubled YAG laser, we can improve the quality of the spectroscopic data by eliminating the signal generated by the bad pulse which is not completely locked. The resolution of the wavemeter is found to be >10 MHz. Also, we have calculated the errors in determining the wave-number by processing a Fabry-Perot fringe pattern imaged on a linear array detector. The calculation is done by changing the finesse of the Fabry-Perot etalon, the number of pixels of the array detector, the magnitude of random noise, the beam waist of the input laser beam, etc.
Two-dimensional fiber optical data link using self-electrooptic effect device modulators and OEIC detectors
Authors: Novotny R. A. , Kerbis E. , Brubaker J. L. , Basavanhally N. , Freund J.
Published: February 2023

A 4 × 4 (16-channel) parallel optical data link was demonstrated that used extensible arrays of selfelectrooptic effect device (SEED) modulators1 and an array of commercially available OEIC detectors. The link consisted of a GaAs quantum well modulator array, a custom multimode fiber bundle conduit, and a multichip module receiver array. A laser diode was used for the optical power supply and was mounted on an aluminum V-plate along with the modulator array and commercially available optics for imaging the SEED output into the fiber bundle. Each modulator consisted of a single MQW diode of a symmetric SEED pair, thus the links were single rail. Sixteen SEED modulators with 10-μm round windows were used within a 16 × 8 array spaced on a 160 × 160 μm pitch. The receiver multichip module consisted of sixteen Antel AOE1003 integrated detector/amplifiers mounted in a 4 × 4 format on a 2.62-mm pitch. The system operated synchronously at 35 Mbps/channel. We show link performance (speed, crosstalk, skew, power dissipation) and describe possible uses of this system for board to board interconnection.
Quantitative measurements of O2 in laboratory flames using near infrared diode lasers
Authors: Oh Daniel B. , Stanton Alan C.
Published: February 2023

Laser based fluorescence or ion detection methods in reactive media offer advantages such as high selectivity, nonintrusiveness and rapid time response. However, calibrating these techniques for quantitative concentration measurements is often difficult. Direct absorption methods yield quantitative measurements, but poorer sensitivity has limited their use. High frequency wavelength modulation techniques improve the minimum detectable absorbance to 10-6 or better while retaining the advantages of direct absorption detection. We have applied high frequency wavelength modulation with GaAlAs diode lasers for measurements of temperature and O2 concentration in laboratory flames. For the concentration measurement, the RQ(23, 24) line in the O2 A-band is used, while the RQ(23, 24) and RQ(33, 34) line pair are utilized in temperature measurements. A single-mode optical fiber cable is used to transport the laser beam to the flame region. Atmospheric pressure premixed methane/oxygen flames at various equivalence ratios are studied in these experiments. Radiation corrected thermocouple measurements are compared with spectroscopically measured temperatures at different locations and in varying flame conditions.
Fast absorption tomography for characterization of turbulent reactive flows
Authors: Beiting Edward J.
Published: February 2023

The design and performance of a fast absorption tomography instrument is presented that is capable of acquiring 100 projections of 100 elements each in <200 ns. The instrument uses time multiplexed, fiber optic fan-beam sources that are sequentially activated in groups to greatly reduce the total number of detectors required to achieve a given resolution. An easily replicated fan-beam generator comprising a UV transmitting silica macrofiber and two microlenses produces a flat fan with a nearly ideal intensity profile. Large area, unencapsulated fast silicon photodiodes developed for this application allow close packing, thus reducing power requirements on the optical fibers and increasing the instrument sensitivity. The optical fibers limit the short wavelength operation of the instrument to 200 nm whereas the detectors limit the long wavelength operation to 1.1 μm. A single-fiber prototype was used to verify the design and establish its sensitivity. The sensitivity is limited by laser speckle noise. The fiber-optic fan-beam generator produced a high degree of interdetector correlation of the projection noise reducing the effect of this noise on the reconstruction. The noise is measured as a function of optical fiber stability and size, laser bandwidth and mode stability, and detector size.
Deposition error compensation for optical multilayer coatings. 2: experimental results—sputtering system
Authors: Sullivan Brian T. , Dobrowolski J. A.
Published: February 2023

Deposition error compensation involves the detection of either thickness or optical constant errors in a layer after its deposition and the reoptimization of the remaining layers in the system to recover the originally specified optical performance. This process allows complicated optical multilayer coatings to be deposited with high yields. The theoretical aspects of the deposition error compensation algorithm were given and simulations of an edge filter with three different deposition systems were described in a companion paper.1 In this work the error compensation program has been interfaced to a wideband optical monitor and an automated magnetron sputtering system. Multilayer coatings can be deposited automatically, with transmittance measurements being performed after each layer to determine the actual thickness deposited. A provision to reduce thickness errors is also available by first depositing 95% of each layer and then determining the layer thickness to accurately determine the rate for the remainder of the layer.
Optical properties of graded-index silicon oxynitride coatings
Authors: Al-Jumaily G. A. , Gagliardi F. J. , McColl P. , Xiong Yi-Ming , Snyder P. G. , Woollam J. A. , Mizerka L. J.
Published: February 2023

Graded-index coatings of silicon oxynitride have been deposited using ion assisted deposition. Discrete and graded-index coatings have been deposited by evaporation of silicon and bombardment with a mixture of nitrogen and oxygen ions. Optical properties of coatings have been examined using a dual beam spectrophotometer and variable angle spectroscopic ellipsometry (VASE). Results of discrete-index measurement indicates that silicon oxynitride coatings have good optical properties over the spectral range of 350–800 nm. Good agreement between results and the mixing theory have also been demonstrated over the index of refraction range between 1.5 and 2. Graded-index AR coatings have also been examined using VASE. Effects of the different models on the results have been examined.
YF4 as a low-index material in infrared BBAR coatings using ion-assisted deposition
Authors: Oh Thomas I. , Hanke Paul V.
Published: February 2023

ThF4 is one of the most important low-index materials used in the infrared BBAR coatings, but its use is restricted because of radiation safety regulations. Therefore, the replacement of ThF4 by a nonradioactive material is badly needed in the coating industry. In this work YF4 is chosen as the candidate of the low-index nonradioactive material because the refractive index (1.35 at 10.6 μm) of YF4 is the same as that of ThF4. A series of five broadband antireflection coatings on germanium and zinc selenide substrates was deposited with or without ion-assisted deposition at a substrate temperature of 200°C. Measurements of laser damage threshold for 10.6-μm 0.1-μs pulses were made on these coatings. Significant improvements have been made in increasing the durability and laser damage threshold of broadband AR coatings (YF4/Ge/YF4/Ge/YF4 and YF4/ZnSe/YF4/ZnSe/YF4) by using the ion-assisted deposition of the germanium and zinc selenide films. Coatings prepared using this technique consistently passed the environmental tests for adhesion, 24-h salt spray, and 10-day humidity tests specified by MIL-C-675 and MIL-M-13508.
Improved laser damage thresholds using ion-assisted deposition
Authors: Smith D. J. , Jin M. S. , Chrzan Z. R. , Schmid A. W. , Papernov S.
Published: February 2023

High laser damage threshold mirrors for ultraviolet light are required for the next generation of inertial fusion lasers. These lasers place greater demands on the coatings in terms of fluence levels, optic size, and stability. We have investigated the effects of ion-assisted deposition on the laser damage threshold of high reflector coatings for 351-nm 0.7-ns pulses. The coating materials used were HfO2, ZrO2, and Y2O3 for the high refractive-index layers with SiO2 and MgF2 as the low refractive-index layers. Contamination effects from the ion source grids and filaments were found to have a significant impact on the damage threshold of the thin film device. Improvements in the coating thresholds occur after either continuous or intermittent ion bombardment with the appropriate parameters and ion source configuration.
Laser-induced surface acoustic waves as a probe of material surface properties
Authors: Grygier R. K. , Coufal H. , Hess P. , Neubrand A.
Published: February 2023

Surface acoustic waves (SAWs) provide a powerful tool to probe the surface region of materials. The advent of short laser pulses has allowed the excitation of broadband SAWs on nonpiezoelectric substrates. Since SAWs penetrate only one or two wavelengths into the substrate, different depths can be probed simultaneously by pulsed experiments. In addition, modification of the surface morphology, surface contamination or thin films on the substrate surface may be detected by changes in the acoustic phase velocity or the acoustic pulse shape. In our experiments, the SAW pulses were excited with a 10-ps pulse at a wavelength of 248 nm. The bandwidth of the excited pulse was limited to 200 Hz by the width of the line focus on the surface. The SAW pulses were detected at a distance of several centimeters from the excitation by a 6-µm thick ferroelectric foil of a copolymer of polyvinylidenefluoride and trifluoroethylene pressed onto the sample with a tungsten wedge with a 1-µm diameter radius.
Experimental characterization of zone plates for x-ray microscopy
Authors: Meyer-Ilse W. , Cuttmann P. , Thime J. , Rudolph D. , Schmahl G. , Anderson E. , Batson P. , Attwood D. , Iskandor N. , Kern D.
Published: February 2023

High resolution microzone plates for x-ray microscopy with an outermost zone width down to 30 nm have been used and characterized in the Gottingen x-ray microscope (XM) at BESSY in Berlin. The microzone plates were fabricated through a collaboration between the IBM Watson Research Center and the Lawrence Berkeley Laboratory using an electron beam writing method. The condenser zone plates of the XM were fabricated at the Institute for X-Ray Physics using a holographic method. The microzone plates allow x-ray microscopy with very high resolution. The optical performance of the microscope with these microzone plates has been studied by several methods, which use a special test pattern. The experiments have been performed at x-ray wavelengths of 2.4 nm and 4.5 nm. The results are shown as modulation transfer functions, edge response functions, and line spread functions. All these methods give similar results. Although the system is not diffraction-limited, features down to 30 nm size are visible in the images.
Lens array coupling of 10-W diode bars for cw end-pumping
Authors: Tidwell S. , Seamans J. , Lowenthal D. D.
Published: February 2023

A Nd:YAG rod has been end-pumped with a single laser diode bar that delivers up to 10 W of 810-nm cw power. Coupling of the 1-cm long diode emitter to the end of the Nd:YAG rod is achieved with a combination of conventional optics (two lenses) and a twenty-element lens array. The combination of these three elements allows a pump cross-section of <0.5 mm2 to be obtained at the Nd:YAG rod end. To date, the laser has delivered near TEM00 beam quality with 3.3 W of output power at 1.064 µm, 1.0 W at 1.34 µm and up to 0.8 W at 0.532 pm using intracavity frequency doubling.
Optical transfer function of silica multicore image fibers
Authors: Tang Qingfeng , Zhao Yang
Published: February 2023

In silica multicore image fibers the coupling among the element fibers is significant. Therefore, it is necessary to develop a model that takes the coupling effect into account. We present a model valid for these image fibers. The results of this model are compared with the experimental measurement. It is shown that this model is more accurate than the model without considering the coupling among the element fibers. From the discrete assumption about the input and output space, the optical transfer function of 1-D and 2-D silica multicore image fibers is derived systematically.
Color images: a point of view
Authors: Wandell Brian A.
Published: February 2023

Most image representations and device calibrations are based on the properties of the human visual system, described in CIE standards such as XYZ or CIELAB. But during color image transmission, an image may be input by devices whose wavelength selectivity differs significantly from the human eye. If image transmission procedures ignore these differences, information can be lost or distorted during device-to-device transmission. We are exploring image representations and calibration procedures based on the physical properties of reflectance and absorbance of light. We view device calibration and communication as a physical estimation problem in which receivers estimate and communicate about the spectral properties of the input. For initially linear devices, such as CCD devices or the initial encoding by the human eye, interdevice color communication is analogous to the problem confronting observers looking at a scene from different points of view. Each observer sees a different projection of the scene, but if the observers know enough about their environment they can infer what the other observers are seeing. So too, each color device may sense the spectrum slightly differently, but if we have enough knowledge of the likely functions of wavelength interdevice communication can succeed.
Leading teams—it’s all in the set-up
Authors: Merron Keith
Published: February 2023

This discussion focuses in depth on the following elements of teamwork: A team can begin to work together when they determine their purpose. Why are they coming together? Are they together to study a process or sole a problem? A team needs a common objective(s). What are they trying to accomplish or achieve? What results or outcomes do they hope to attain? What strategies will help them attain their objectives? How will they head in the direction they want to go? The roles and responsibilities of the team members and team leader/facilitator are defined, clarified, and negotiated so each can participate and contribute. Often overlooked, the team meeting ground rules need to be determined so the team meeting process stays in control.
Holographic see-through display for image combination
Authors: Kato Masayuki , Aritake Hirokazu , Yamagishi Fumio , Nakashima Masato
Published: February 2023

We developed a holographic see-through display enabling the user to see documents through the display plane. People working at personal computers must often take their eyes away from the display to refer to documents. Too much switching back and forth tires the person and is inefficient. In the system we have developed, an image created by a small virtual display is enlarged and projected on a reflection hologram by lenses. Light, having a wavelength width of ~30 nm, is reflected toward the eyes of the person using the display. Documents are illuminated by ambient light and can be seen through the hologram. Therefore, the enlarged virtual image is superimposed on any documents put behind the reflection hologram. Our implementation differs from a conventional HUD in that the image is displayed on a reflection hologram located at the distance of distinct vision. The large thin screen displays a bright image, free of chromatic aberration, created by projection lenses. The screen has a controllable viewing area.
Effects of polishing compound chemistry on surface quality
Authors: Tesar A. A. , Fuchs B. A. , Hed P. P.
Published: February 2023

Results of the characterization of fused silica and zerodur surfaces polished by different compounds are presented. The polishing experiments used controlled parameters and pitch lap on a small planetary machine.
Multiple quantum well waveguide modulator for fiber-optic interconnects
Authors: Liu Yanming , Grove Mike , Prucnal Paul R.
Published: February 2023

It is well-known that electrical I/O bottlenecks in integrated circuits can be remedied with optical interconnects. An optical interconnect link requires a transmitter to convert intrachip electrical signals into optical signals suitable for fiber-optic interchip communication, and a receiver to reconvert optical signals at the fiber output into electrical signals on the chip. We consider an approach using an off-chip laser as an optical power supply, connected via optical fiber to an on-chip electrooptic modulator that imprints the distributed optical power with the desired information. Optical fiber carries the modulated optical signal to a receiver, which may be on a different chip or board. The signal-to-noise ratio (SNR) at the receiver output is 10logSNR = P-L(λ)+ 10log[αβ(ΔV,λ], where P is the laser output power in dBm, the optical loss L in the link is a function of wavelength λ, the parameter α is directly proportional to the detector responsivity and inversely proportional to the bit-rate and receiver noise-equivalent-power, and the modulation depth β is a function of λ as well as the voltage-swing ΔV applied to the on-chip modulator.
Novel physical phenomena in the optical spectroscopy of single molecules in a solid
Authors: Basche T. , Ambrose W. P. , Moerner W. E.
Published: February 2023

As was recently demonstrated1 using highly efficient fluorescence excitation spectroscopy with N.A. = 0.98 collection optics, single molecules of pentacene in a p-terphenyl crystal can be detected with signal-to-noise ratios (SNR) as high as 30 in a 1 -Hz bandwidth at low temperatures. As a result, it has become possible to study the electronic absorption spectra of individual impurity molecules in solids in great detail. Our measurements include precise determination of the lifetime-limited linewidth and the temperature dependence of the optical dephasing, both of which agree with earlier measurements on large assemblies of molecules. Surprisingly, it was also found that some molecules absorbing in the wing of the inhomogeneous line change their absorption frequency with time in a random fashion. This spectral jumping behavior (which was quite unexpected in the crystalline p-terphenyl matrix but reminiscent of amorphous systems) is termed spectral diffusion and is thought to be caused by an instability in the local environment of the single pentacene absorbers that is driven by phonons present at 1.5 K. The experiments revealed that the jumps in frequency space in general are not restricted to occur between a small number of accessible states. In fact, the spectral diffusion processes observed are very rich and complex and range from discontinuous jumps between several states to quasicontinuous wandering in frequency space.
Multiple sensing channels in single fiber using a fiber specklegram
Authors: Wu Shudong , Yin Shizhuo , Rajan Sumati , Yu Francis T. S.
Published: February 2023

This paper proposes incorporating multiple sensing channels in a single fiber in terms of a fiber specklegram. A fiber specklegram is a hologram formed by a speckle field from a multimode fiber and a reference beam. When the hologram is readout by the speckle field, the reconstruction of the fiber specklegram is highly sensitive to the modal phase changes of the multimode fiber. In terms of holographic multiplexing (angular or wavelength), a set of orthogonal fiber states can be recorded in the fiber specklegram and used for multiple sensing channels. The demultiplexing scheme can be either binary or harmonic, depending on the type of the signal to detect. Since the reconstruction of the fiber specklegram is essentially an output of a common path interferometer, the technique possesses both high sensitivity to the measurands and low vulnerability to the environment. A unique feature of the fiber specklegram is its multiplexing capability, which is a result of the spatial information capacity of the multimode fiber. The technique provides a simple means to construct multiple sensing channels in a single fiber with high sensitivity.
Effects of operator ordering in effective-mass Hamiltonian on transition energies in semiconductor quantum wells
Authors: Mojahedie Mohammad , Osinski Marek
Published: February 2023

It has been recognized that use of the effective mass theory for abrupt interfaces between different materials suffers from ambiguity in kinetic- energy operator ordering, caused by nonvanishing commutator of the momentum operator and the position-dependent effective mass. This leads to nonuniqueness of the Hamiltonian, which in its general form can be written as a one-parameter family of operators.1 The matching conditions for the envelope wave function and its derivative at the interfaces are also parametrized.1 Recently, Fu and Chao reported2 that experimentally observable interband transition energies are not sensitive to the effective- mass operator ordering. In this paper, we demonstrate that optical transition energies do vary substantially with ordering. Specifically, we have analyzed GaAs/AlGaAs quantum wells using the transfer matrix technique.2 We have investigated the effects of quantum well parameters, such as subband index, thicknesses of both constituent materials, and barrier height (composition) on the shifts of subband-edge energy, between the two extreme cases of operator ordering. Calculated energy levels are more sensitive to ordering for higher subbands and for decreasing well thickness. Increasing the barrier height or thickness in coupled quantum wells will also result in a larger shift of subband-edge energies. Comparison with available data allows us to choose the ordering that provides the best fit to experiment.
Scintillation of light at two colors
Authors: Churnside James H. , Lataitis Richard J.
Published: February 2023

Simultaneous measurements were made of the scintillations of red and blue light in the atmosphere. The sources were a He-Ne laser at 633 nm and a He-Cd laser at 422 nm. Several horizontal propagation paths were used, and the strength of turbulence and its inner scale were recorded during the experiments. Weak path-integrated turbulence theory predicts a very high correlation between the scintillations at these two wavelengths. We observed that the correlations were lower than this prediction in strong path-integrated turbulence. The weak turbulence theory consists of a double integral that sums contributions from each position along the path and from each turbulent wavenumber. To include the effects of strong turbulence, we assume that the effectiveness of eddies larger than the transverse coherence length of the field at each path position is reduced.
Noise deconvolution from probability density in laser atmospheric scintillation
Authors: Consortini A. , Cochetti F.
Published: February 2023

A deconvolution procedure to remove large uncorrelated noise is applied to probability density histograms of intensity fluctuations of a laser beam after propagating a 1200-m path through atmospheric turbulence. The data were collected by very small (0.04 mm2) apertures at NOAA/ERL/WPL during an experiment not requiring noise resolved measurements at small irradiance.1 Each signal histogram contains data from a 64-s total signal (laser, background and noise) measurement. Each so-called noise histogram contains data obtained in the subsequent 3.2-s with the laser screened off; it therefore includes noise and background. The noise was independent of the laser signal.1
Proposal for a VUV laser with x-ray laser resonant pumping
Authors: Shkolnikov P. L. , Kaplan A. E.
Published: February 2023

We show that lasing action in VUV domain can be obtained by pumping Sc IV ions with a Se24+ x-ray laser (XRL). This is possible because of the perfect (within the accuracy of the measurement) coincidence between the wavelength 220.28 Å of the transition from the ground level to the level 3s23p5(2P0)4d

1

P
1
0

. in Sc IV ions, as well as favorable ratios of the radiative decay rates of the lower levels. The solution of the rate equations for Sc IV using the incident XRL radiation intensity ≃ 108 W/cm2, the electron density ≃ 3 × 1016 cm–3, and the plasma temperature ≃ 35 eV yields the small-signal gain coefficients ≃13 cm–1 and ≃5 cm–1 for the VUV radiation with the wavelengths 1665.918 Å and 1584.645 Å, respectively, within 1 ns after the XRL pulse.
Collapses and revivals in the Dicke model
Authors: Chumakov S. M. , Sanchez-Mondragon J. J.
Published: February 2023

We discuss the time evolution of the atomic inversion of a system of N two-level atoms interacting with a single quantized field mode in a high-Q cavity. We present both the operator solution and analytical expressions for the corresponding revivals, and extend the well-known picture of the single-atom (JCM). The operator solution is perturbative based on the approximate dynamic symmetry of this model1; the analytical revival method was introduced recently.2
Homodyne and heterodyne statistics of squeezed light from parametric oscillators
Authors: Vyas Reeta
Published: February 2023

We discuss homodyne and heterodyne statistics when squeezed light from a parametric oscillator is mixed with coherent light from a local oscillator. We also consider the case where the fields or the intensities of the two nondegenerate beams from a parametric oscillator are combined. By using a dynamic model of these beams we discuss photon sequences underlying these beams in terms of photoelectric pulse sequences recorded by a detector. Analytic expressions for quantities directly measurable in photon counting experiments are derived, using the method developed in our earlier investigations.1
X-ray focusing using capillary arrays
Authors: Chapman H. N. , Nugent K. A. , Wilkins S. W.
Published: February 2023

In this paper, a new class of x-ray focusing devices based on reflections from the interior surfaces of an array of capillaries is presented. The capillaries may have a range of cross sections, although square capillaries are predicted to offer the best performance. We have developed a detailed theoretical model for these devices and, in the case of circular cross section capillaries (microchannel plate blanks), have compared the results with experiment. It is found that theory and experiment are in excellent agreement provided that a description of the surface roughness is incorporated into the theory. Such comparisons, over a range of x-ray wavelengths, provide a consistent estimate of the surface roughness inside the capillaries. It is anticipated that these focusing devices may find use in areas where radiation must be transferred efficiently from a small source onto a small sample.
Novel femtosecond optical solitons
Authors: Potasek M. J.
Published: February 2023

We show that the solitons described by the derivative nonlinear Schrodinger equation (DNLS)1 may propagate in nonlinear optical fibers and have properties distinct from the well-known solitons described by the nonlinear Schrodinger equation (NLS). In particular, we show that the DNLS will give rise to bright solitons in both the normal and anomalous dispersion regions which is in sharp contrast to the NLS where bright solitons form only in the anomalous dispersion region.
Six-wave mixing generated violet emission in sodium vapor
Authors: Chu Chin-Chi , Pong Bao-Jen , Fan Jin-Eong , Yih Tai-Sone
Published: February 2023

Three violet emissions at 401.6 nm, 465.7 nm, and 471.4 nm are generated in sodium vapor under 578.7-nm excitation. It is assumed to be a six-wave mixing process including a Raman-Stokes.
Microwave pulse compression technique for the excitation of a XeCl excimer laser
Authors: Klingenberg H. H. , Gekat F.
Published: February 2023

A klystron transmitter operating in the microwave L-band (1355 MHz) with a maximum power of 10 MW, an adjustable pulse duration of 500 ns to 6000 ns and a pulse repetition frequency of up to 430 Hz was used to excite a XeCl laser without preionization. The coupling structure housed a quartz discharge tube (inner and outer diameter 5.8 mm and 10.3 mm, respectively) 43.8 cm long, which was part of a resonantly charged microwave cavity. The cavity was loaded with electromagnetic energy in ~300 ns. The stored energy was extracted by a sudden switch and dumped into the discharge. This was accomplished by increasing the electron number density in the discharge tube filled with the excimer gas mixture.
Scanning Wiener fringe optical microscope
Authors: Umeda N. , Hayashi Y. , Takayanagi A. , Ohkubo T.
Published: February 2023

A lateral resolution in a conventional optical microscope is limited by the diffraction effects of light. We wanted to develop a superresolved microscope that could operate at ambient conditions because such a microscope would be useful in many fields. This paper describes a scanning Wiener fringe optical microscope (SWM). When a plane wave incidents on a sample, a Wiener fringe, which is a kind of standing wave, results in the region of the sample surface where the reflected wave overlaps with the incident beam. A light probe, which is made by sharpening an end of single-mode fiber, can detect the optical field of the Wiener fringe. The light transmitted through the fiber to a photomultiplier tube is converted to an electrical signal, which is fed to a lockin amplifier for synchronous detection. The detected signal is used to control a tip-sample spacing at the constant phase of the Wiener fringe, so that a topographic image of the sample can be obtained by accumulating a feedback signal to a computer while scanning the fiber tip over the sample.
Null test optics for large astronomical mirrors
Authors: Burge J. H.
Published: February 2023

Advances in casting and polishing technology at the Steward Observatory Mirror Laboratory enable the production of astronomical mirrors of unprecedented size and focal ratio. The null correctors required for the interferometric center-of-curvature test of such large optics must also be of unprecedented proportions. To correct for the enormous departure of the mirrors from spherical (5.7 mm from the vertex-matching sphere for 8.4-m f/1.14 Columbus telescope primary) several extreme null lens designs are considered.
Scanning interferometer to measure index heterogeneity
Authors: Bobroff Norman , Rosenbluth A. E. , Hatzakis M.
Published: February 2023

Index nonuniformity in optical glass must be characterized at a resolution exceeding the ratio of the wavelength to the total optical path in the system, if diffraction-limited performance is to be maintained. The physical relationship between index inhomogeneity and local mass density can also be used to infer the mass distribution of precision glass rotators for gyroscopes from knowledge of the index profile. The index distribution in bulk glass is measured by scanning the sample through a closely separated pair of laser beams which are then interfered. Changes in phase between the interfering beams measure the local gradient of the refractive index integrated along the beam path.
Error diffusion algorithm for joint transform correlator
Authors: Mendlovic David , Inbar (Pinhas) Hanni , Marom Emanuel
Published: February 2023

An error diffusion quantization method has been used in conjunction with computer-generated holograms. It is shown that this procedure is advantageous in the production of the power spectrum interference pattern of joint transform image correlator (JTC) configurations. The suggested error diffusion JTC permits evaluation of noisy input cases, for example, when Gaussian white noise is added to the input plane. A computer simulation comparison of correlation peak quality was carried for three cases, using several performance criterions. The analyzed cases were classical continuous JTC and nonlinearly scaled binarized JTC, quantized by either error diffusion or hard clipping.
Bifurcative optical pattern recognition
Authors: Liu Hua-Kuang
Published: February 2023

A new bifurcative optical pattern recognizer (BOPAR) for image and/or data classification using the noise fan-out phenomenon in nonlinear photorefractive crystals is described. The inhomogeneities in photorefractive crystals naturally exits consequential to the doping procedure in making the crystals photorefractive. Scattering occurs when light impinges on the inhomogeneities. The scattered light is in general random in intensity distribution and angular orientation. Therefore such scattered light is considered as annoying noise that tends to reduce the strength of the signal. In this paper, a new and exciting discovery is reported. Contrary to the conventional conviction, we found that certain portions of the fan-out noise can be made useful for achieving bifurcative optical holographic pattern recognition and data classification. The BOPAR has a neuromorphic or brainlike nature.
High-power cw deep ultraviolet generation by doubling of the argon laser frequency
Authors: Taira Yoichi
Published: February 2023

The feasibility of generating cw high power deep ultraviolet (UV) coherent radiation, using a novel nonlinear optical technique, has been confirmed by modeling and experimentation. A new intracavity frequency doubling technique used with a visible argon ion laser and a BBO crystal has been shown to have the potential to generate quite stably high power cw coherent light with a wavelength ~0.25 μm. The expected narrow-linewidth power is >1 W, which is more than thirty times larger than that presently available in the deep UV region, for a medium sized 5-W class argon laser and higher for a larger class laser. The intracavity doubling optics was designed to maximize output UV power, keeping fundamental beam intensity in the crystal well below the damage threshold for stable and efficient intracavity conversion of the fundamental radiation of visible cw lasers when an angle-phase-matched crystal is used.
Four-wave mixing line shapes in sodium
Authors: Schreiber W. M. , Chencinski N.
Published: February 2023

A recently presented treatment of four-wave mixing for fields of arbitrary strength1 is applied to the 3S–3P transitions of sodium. The line shapes associated with ordinary resonances, and with both pressure-induced and field-induced extra resonances are investigated. In sodium, the two lower levels (g,t) are very close, i.e., their separation is 0.059 cm-1. Thus decays from the upper (k,j) levels to each of the lower levels are expected to contribute significantly. Also, contributions associated with (g,t) population exchange because of the close proximity of these states are incorporated. The influence of the decay pattern and of the respective values of the decay constants is studied, especially as compared to the line shapes that would result if all decays were dominantly to the ground state. Regions of enhancement for the more complex decay pattern are found for field-induced extra resonances. The relative effects of spontaneous decay (T1) and proper dephasing (T2) on the line shapes is examined. It is found that (T2) dominates for weak field conditions but that both contribute significantly for strong field situations.
Transient beam combination with circularly polarized radiation
Authors: Dutton T. , Rentzepis P. M. , Rogovin D. , Shen T. P. , Scholl J.
Published: February 2023

We examine coherent energy transfer between two circularly polarized degenerate Gaussian laser beams whose pulsewidth is of the order of the medium response time. For this situation, energy transfer proceeds via a phase lag that arises from the finite response time of the nonlinear medium and the pulsed nature of the incident light beams. Locally, this phase lag is driven by the difference in the local intensities of the two laser beams. Previously, we studied the gain as a function of beam delay for the case of a linearly polarized probe and a circularly pump wave, with a large pump to probe intensity radio. Here, we focus on the situation where the beam intensities are equal, both beams are circularly polarized, and CS2 is the nonlinear medium. This polarization configuration allows us to examine more closely the orientational gratings formed by the two light beams as they propagate through the sample.
Approaches for high-power reliable coherent devices
Authors: Botez D.
Published: February 2023

GaAs/AlGaAs diode lasers, without active phase control, are sought as reliable sources of high coherent powers (>100 mW diffraction-limited) for applications such as space communications, second-harmonic generation, and output fan-out for optical interconnects. Conventional narrow stripe (2–4 μm width) lasers that operate single mode are generally limited to below 100-mW reliable operation, as limited by the optical power density at the laser facet. For reliable operation at higher power levels two main approaches are pursued: (1) large-aperture sources, to reduce the optical power density at the laser facet, and (2) passivation of the emitting facet, to increase the threshold for facet damage. The primary challenge has been to maintain a coherent single spatial mode at high power levels from a large aperture device. For this reason, multielement phase-locked arrays have been under development for over a decade as a means of obtaining a mode stabilized device that can operate reliably at power levels in the range 0.5–1.0 W.
Digital optical loop mirror switch
Authors: Finlayson N. , Nayar B. K. , Doran N. J.
Published: February 2023

Concatenation of nonlinear all-optical switches offers considerable potential for the synthesis of digital switching characteristics with all the advantages that digital technology affords. Nonlinear interferometric switches such as the nonlinear optical loop mirror (NOLM) generally exhibit sinusoidal cw transmittance dependence on the optical power. The effect of concatenation is to transform this sinusoidal characteristic to one that is much more square. An important consideration in device concatenation is to minimize the component count necessary to optimize the characteristics. We have fabricated an all-optical switch with a digital characteristic that uses a single NOLM1 in a double-pass configuration. In addition to economizing on components, use of a single NOLM ensures that the properties of the switch remain unchanged for the second pass. Our experiment is conducted with 100-ps pulses at a repetition rate of 76 MHz. The device is fabricated in a conventional single-mode fiber 2 km long. Switching powers of a few watts are used. A sharp on/off threshold is generated which is in good agreement with theory. Good isolation is obtained between the pulse trains circulating in the device, i.e., the device has the two ports necessary to demonstrate switching.
Acoustooptic comparison switch with polarization multiplexed analog addressing
Authors: Jenkins R. Brian , Clymer Bradley D.
Published: February 2023

Switching networks based on perfect shuffle or Banyan interconnection techniques are useful in parallel processing and telecommunications. The integral components in these networks are the comparison switches that control the routing of data through the network. An acoustooptic comparison switch has been implemented that simplifies control using analog addressing techniques and insures high-bandwidth data transmission by multiplexing the data and the address on orthogonal polarizations of light. The addresses can be easily extracted and processed apart from the data using polarizing beam splitters so that the data transfer can continue at optical data rates. The analog addresses are encoded either as the frequencies of amplitude modulation of the optical carrier or as discrete cw optical power levels. Frequency encoded addresses are compared using frequency detectors typically found in phaselocked loops and power encoded addresses can be photodetected and compared with a simple analog comparator.
Optical switch using binary phase gratings
Authors: Chiou Arthur , Motemadi Ed , Yeh Pochi , Khoshnevisan Monte
Published: February 2023

We have successfully demonstrated and characterized a novel 1x2 optical switch using a pair of identical binary phase gratings. A binary phase grating consisting of a series of parallel rectangular grooves (~0.7 μm wide and 1 μm deep, separated by 0.9 μm) was recently fabricated by etching on a thin (~1 mm) quartz plate. In general, such a grating diffracts an incident collimated beam into multiple beams (different diffraction order). In the appropriate conditions, depending on the grating spacing, wavelength, and the angle of incidence, almost all the input optical energy can be essentially confined to 0 and the -1 diffraction orders. When two such identical gratings are placed in parallel adjacent to each other, the overall diffraction efficiency depends on their relative position. In principle, when they are exactly 180° out of phase, the optical phase modulation introduced by the first element is exactly canceled out by the other leading to a zero diffraction efficiency with all the energy being directed to the 0-order output port. In other words, the incoming beam does not feel the presence of the grating-pair due to complete cancellation of the two and simply passes through with no energy diffracted into the -1 port. In practice, the cancellation may not be complete because of misalignment and/or non-uniformity. Strong diffraction occurs when the gratings are exactly in phase. By proper choice of the depth of the gratings, 100% diffraction efficiency can be achieved. The switching is accomplished by shifting one grating relative to the other by a distance of the order of half a grating period, which is typically a fraction of a micron.
Optical self-routing crossbar switching experiment using GaAs-pin/ferroelectric liquid crystal SLM
Authors: Hashimoto Masashi , Kitayama Ken-ichi
Published: February 2023

An all-optical self-routing (OSR) crossbar switch that employs tag light with wavelength-encoded address,1 is experimentally demonstrated by using a fast GaAs-pin/ferroelectric-liquid-crystal spatial light modulator (FLC-SLM) as the switching device. The switch consists of the SLM and bandpass filters in front of it. The optical packet consists of information light along with the tag light. Each bandpass filter passes both information light and only one of the tag lights with a specific wavelength. The tag light passing the filter activates a part of the SLM. Then the information light is allowed to pass through the modulated position of SLM and routed to a preassigned output port. A fast optically addressable GaAspin/FLC-SLM is developed as a switching device. It consists of pixelized GaAs p-i-n photodiode as photodetector and FLC as modulator. The FLC modulates 1.3-μm readout light with a short wavelength (0.6 ~ 0.83μm) writing beam. Rise times (10-90%) of 86 psec and fall time of 98 psec are obtained. The 2 × 2 switching experiment was successfully carried out using tag LDs of 0.67 μm and 0.78 μm. Using a current SLM and a LD light source, up to 102 × 102 OSR crossbar switching will be possible with response time ~100 psec.