bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact spectrograph: design and implementation
Authors: Capron B. A. , Beranek M. W. , Huggins R. W.
Published: February 2023

We have designed and fabricated a compact (3 cm × 3 cm × 2 mm) spectrograph for use as a wavelength-division demultiplexer. The design is based on an alteration to the classic Rowland mounting. Using a ray-tracing model that allows us to predict the linewidth, we have optimized the spectrograph spectral resolution by cancelling the coma term in the aberrations. We fabricated gratings holographically by using photoresist to coat a convex substrate that is illuminated by converging beams. The resulting gratings achieved 20-30% efficiencies, and the linewidths agreed with our model predictions. The gratings are made on a thin substrate (several hundred microns thick) that acts like a waveguide in the nondispersive direction, which makes it for compatible with fiber optic inputs. This maximizes optical efficiency but limits the spectral resolution because of due to multimoding effects. We have also developed an algorithm for scribing the grating with a computer-controlled ruling engine, and gratings replicated from a master that is ruled according to this algorithm have linewidths comparable to holographic gratings and efficiencies greater than 50%.
N-dimensional correlation filters for pattern recognition
Authors: Gheen Gregory
Published: February 2023

N-dimensional filters generalize the notion of a filter as a vector in a signal space to a filter acting as a N-dimensional subspace in a signal space.1,2 This new approach to filtering is easily implemented in an optical correlator by time-integrating the response of a series of filters on the output detector array. The resulting response is then threshold detected to determine if a target is present. This improves target discrimination for distortion-invariant recognition and helps alleviate the disparity between the operating speed of the filter spatial light modulator and the output detector array.2 An algorithm for designing distortion-invariant N-dimensional filters is presented, and simulation results will be given.
CERAFORM® silicon carbide as an optical material
Authors: Vivaldi Alexander M. , Slomba Albert F.
Published: February 2023

The need for increasingly large, precision optical instruments presents severe impediments for space-based systems. These difficulties arise due to the limited payload size and weight than can be lofted into earth orbit by available launch vehicles. Size limitations can be overcome, at the expense of increased complexity, by dividing the aperture into multiple segments, which may be unfolded or otherwise reassembled after achieving orbit. Other problems exist in regard to weight, however. In the absence of gravity, structures may be lightweighted to an extreme degree with limits only imposed by factors such as vibration, thermal, and inertial loads. Optical surfaces, on the other hand, must be manufactured and tested to precise, absolute shapes in a one-g environment. The problem to be solved then becomes one of a trade between stiffness and weight versus deployment and manufacture. Ultimately, launch weight reduces to optimization of specific stiffness, which considers not only materials' properties but fabricability as well. Because of the favorable mechanical and thermal properties of silicon carbide, special manufacturing methods have been developed to produce mirror substrates with areal densities of 15 kg/m2 or less. This paper will discuss application of this material and precision forming process, to large lightweight optical systems, and will compare mechanical and thermal figures of merit to other material candidates. Some examples of this process as applied to prototype mirrors will also be shown.
Tilt corrector based on spring-type magnetostrictive actuators
Authors: Aksinin V. I. , Appollonov V. V. , Chetkin S. A. , Kijko V. V. , Murav’ev S. V. , Vdovin G. V.
Published: February 2023

Spring-type magnetostrictive actuator (STMA)1 and platform for adaptive tilt correction in astronomy and high-power technological lasers is discussed. STMA is one of the most promising types of macroactuators for large ground and space-based adaptive optics. By means of STMA it is possible to realize precision displacements in ranges up to 50–100 μm with an accuracy of positioning 0.1 μm and enforcement up to 1000N in a real time scale (1–10 ms). Experimentally investigated static and dynamic characteristics of STMA are discussed in comparison with that of piezoceramical actuators. Real-time two-coordinate mirror positioning system for precise optical engineering is proposed and investigated. The dynamic range of corrected tilts is up to 3°10−3 rad with sensitivity 10−6 rad and frequency range up to 40 Hz. High efficiency for correction of tilts induced by atmosphere turbulence is demonstrated.
Mirrors for optical telescopes
Authors: Miroshnikov Michael M.
Published: February 2023

There are two principal approaches to handle specific difficulties arising in design of mirrors tor space telescopes. The first, most radical one, involves the use of mirrors with active surface shape control (adaptive mirrors), whereas the second one realizes "rigid" mirror maintaining the optical surface shape within the specified tolerances for any conditions or manufacture and operation. The difficulties inherent in design of a segmented adaptive base mirror of a telescope for visible spectral region are due to very high control accuracy required in a wide dynamic range. Therefore, the problems of correction are usually tackled by means of a small auxiliary mirron conjugated to the base one. Owing to certain shortcomings of such approach, a design concept is discussed for a telescope with the segmented base mirror. Basic consideration is given to computer simulation of an adaptive optical system. The results obtained in this way make it possible to determine the requirements on accuracy of manufacture and alignment of mirror segments depending on criteria of image quality. Essential results were obtained with simulation of a system with a wavefront sensor and aposteriori image correction. In design of "rigid" mirrors, principal attention was drawn to the unique characteristics of beryllium, which ensures the required mirror weight-to-hardness ratio. In order to eliminate optical-quality processing in the technological procedures of beryllium mirror manufacturing, which evolves hardly controlled small-size dispersed particles, a technique has been developed for deposition of a glass coating layer on the beryllium. The mirrors have been built, featuring diameter of 1, with rms deviation of the optical surface from the designed shape within 0.02–0.06 mcm.
Silicon optical bench research at AT&T Bell Laboratories
Authors: Blonder G. E.
Published: February 2023

This decade will see photonics move from individual components providing simple point-to-point communications, to more complex optical circuits and applications. We will review our work on using silicon integrated circuit processing to make substrates with planar waveguides, in order to join together hybrid-mounted active and passive devices.
Phase-modulation change in barium titanate caused by the sudden shift of wave front in photorefractive holographic interferometry
Authors: Itoh Masahide , Kuroda Kazuo , Ogura Iwao
Published: February 2023

Photorefractive two-wave mixing can be regarded as a real-time holographic interferometer. By using this technique we can observe a slowly varying phase change or vibration mode. If the phase of signal beam is changed, we observe an interference pattern between the pump beam diffracted by phase grating and that of transmitted-signal beam. The pump beam and the new signal beam generate a new phase modulation in the crystal and, at the same time, erase the old phase modulation. The visibility of the interference fringes decreases with time; the time constant of the photorefractive index change in BaTiO3 is about 10 s under a 1 W/cm2 irradiation at 488 nm. The time necessary for phase modulation depends not only on the total intensity in crystal but also on the ratio of the signal beam intensity to the pump beam intensity. We experimentally investigate the temporal behavior of phase modulation in a crystal in which the phase of signal beam shifts suddenly. We analyze the response of making and erasing phase modulation in the crystal by using coupled wave equations and a simplified photorefractive material equation. We find that the large coupling coefficient of materials such as BaTiO3 brings about rapid fast generation of phase modulation.
Pattern-recognition experiments with annealed binary phase only filters
Authors: Kim Myung Soo , Guest Clark C.
Published: February 2023

Binary phase-only filters encoded by a simulated annealing algorithm are able to distinguish between similar patterns that cannot be distinguished by optical matched filters or by binary phase-only filters that are encoded by conventional methods. Binary phase-only filters encoded by the simulated annealing algorithm and by conventional methods were fabricated by means of electron-beam lithography and chemical etching. Optical pattern-recognition experiments were then performed. The filter encoded by the simulated annealing algorithm clearly distinguished between the similar patterns, but the filter encoded by conventional methods did not.
GaAs microcrystallites-doped glass: preliminary results
Authors: Picard Françis , Jerominek Hubert , Tremblay Réal
Published: February 2023

A new type of semiconductor microcrystallites-doped glass has been fabricated by ion beam sputtering of GaAs/glass composite targets. The deposition of such a material was a preliminary step toward the fabrication of semiconductor doped glass, which would demonstrate large optical nonlinearities at wavelengths compatible with the emission wavelengths of solid-state lasers and laser diodes. GaAs, which is known to exhibit large optcial nonlinearities at the wavelengths close to the material bandgap (870 nm), was then selected as the doping semiconductor. Physical properties and characteristics of the deposited thin films were studied by electron spectroscopy for chemical analysis (ESCA) and Raman spectroscopy. Results of ESCA demonstrated that concentration of the doping semiconductor is relatively high, at least on the sample surface. Identification of the Ga and As compounds present in the films were also performed using ESCA. In particular, GaAs, Ga2CO3 and AS2O3 were found on the surface of the samples while only GaAs was present in the core of the films. Raman spectroscopy studies lead to detection of the characteristic GaAs phonon peaks in the films. This demonstrates that the GaAs microcrystallites are present in the fabricated films. Finally, real and imaginary parts of the complex refractive index of the films were determined using optical ellipsometry technique.
Observation of hollow-core ARROW waveguide resonances
Authors: Côté Roger , Duguay Michel A. , Ouellette François , Lebel Paul
Published: February 2023

Antiresonant reflecting optical waveguides (ARROWs)1 have previously been implemented on silicon and InP substrates by forming optical layers of fixed thicknesses. We have built a hollow-core ARROW waveguide by holding two 1.5 µm thick plastic pellicles 20-30µm apart. The pellicles were flat and were aligned parallel to one another and to a flat glass substrate held next to one of the pellicles at a distance that could can be continuously varied from 15–500µm by means of a computer-controlled micropositionner. Light from a 1300 nm laser was injected into the air gap between the pellicules, and it excited predominantly the lowest-order modes of the ARROW waveguide. Laser power emerging from the waveguide exhibited loss resonances as the substrate was gradually moved from 15 to 500µm away.
Electronic and photonic band structure engineering of semiconductor lasers
Authors: Yablonovitch E.
Published: February 2023

In modern semiconductor lasers the electronic band structure is being artificially modified by strain and quantum confinement in order to reduce the valence band effective mass. Likewise, a photonic band structure is being consciously created, with the aim of producing a photonic band gap in which spontaneous emission is eliminated. This paper is a review of both trends, which seem to be converging into an interesting new ultra-low threshold semiconductor laser technology. If this new technology is successful, there will be microampere threshold lasers generating number-state squeezed light. Single-strained quantum-well (SSQW) lasers are rapidly becoming preferred for many applications. They overcome one of the main problems in III-V semiconductors, namely, the heavy valence band. A light hole mass reduces laser threshold requirements, minimizes intervalence band absorption, cuts down Auger recombination, and allows faster direct modulation. In spite of early fears of strained material instability, SSQW lasers are showing themselves to be more reliable than conventional GaAs lasers. At threshold, in a good-quality SSQW laser, spontaneous emission can dominate all other parasitic processes. We are now beginning to learn how to control spontaneous emission. In a three-dimensionally periodic dielectric medium it is possible to create a "photonic band gap" that is a forbidden energy gap for photons. In this energy band optical modes, spontaneous emission, and zero point fluctuations are all absent. This may be called band structure engineering for photons. The combination of all these ideas in a very small SSQW laser will lead to ultra-low microampere thresholds. More importantly, the quantum efficiency into the lasing mode can approach unity. In the absence of parasitic processes and under that conditions just described, we can look forward to the prospect of high-quality photon number-state squeezed light from these lasers.
Hemisphere projection methods for calculating illumination
Authors: Wittels Norman , Bian Burning
Published: February 2023

Understanding irradiance/illuminance is important in many fields including machine vision, image processing, and computer graphics. In this paper we present a general method for calculating the illuminance at a point due to an arbitrary spatial arrangement of uniform, diffusely-emitting sources whose surfaces comprise arbitrarily-shaped planar polygons. The calculation is based on a hemisphere projection method that had been considered suitable for obtaining qualitative, but not quantitative, understanding.1 By approximating sources as planar polygons, exact solution is achieved. This approximation is not restrictive in practice because surfaces can be tesselated into polygons that are arbitrary with respect to number and shape. The calculation handles cases that can be difficult using other methods: sources that occlude each other and points that lie on edges where sources meet. The hemisphere projection method has use in designing illumination systems for machine vision, in calculating illumination for model-based image processing algorithms such as "shape-from-shading," and in calculating radiosity form factors for computer graphic simulation of scenes with interreflection between objects. We also present the conditions under which the method can be extended to planar polygon sources with non-uniform, non-Lambertian emission.
Chamber design for Fabry-Perot interferometer containment
Authors: Goad Joseph H. , Romanczyk Kazmere C. , Engle Charles D.
Published: February 2023

This paper outlines some of the "how-to" and "how-not-to" empirical experiences en countered in the design and construction of thermal/vacuum chambers for Fabry-Perot interferometer containment. The thermal environment is controlled to provide stable interferometric data for varying ambient temperatures. The interferometer operation in a vacuum ensures that the data will not vary with changes in the optical refractive index due to ambient pressure changes. Wedged windows are used to prevent secondary reflections from interfering with the data. Our paper reviews several examples of wedged-window attachments. Because a near-zero leak-proof design cannot be maintained with O-rings, small vacuum pumps are required to obtain continuous evacuation. We will also review our experiences relating to keeping chamber ambient temperature changes from affecting the interferometric data. We have used techniques providing a thermally stable interferometric system that produces stable data over an ambient-temperature range of 1540C with variations in ambient pressure.
Angle and time-resolved studies of photon transport in random media
Authors: Yoo K. M. , Liu Feng , Alfano R. R.
Published: February 2023

The transport of photons in a random medium may be directly studied by studying the angular and temporal distribution of photons after they transverse a slab of random medium. We found that a coherent (ballistic) pulse coexists with an incoherent (diffuse) pulse when the ultrafast laser pulse transverses a slab of random medium that is less than 10 scattering mean-free-paths thick. The incoherent pulse shows large angular and temporal spreads. The temporal profile of the incoherent component can be approximated by diffusion theory if the thickness of the slab is greater than 10 transport mean-free-paths; e.g., for slab 10 mm thick. Photons are found to arrive significantly earlier than the arrival times predicted by diffusion theory when the thickness of the slab is less than 10 transport mean-free-paths. We computed the mean time of photon arrival from experimental data, and it compares favorably with the theory. Anisotropic scattering, as well as coherent interference among the multiple scattered waves, may account for the early arrival of photons.
Nonlinear-optical properties of thin films
Authors: Yeh Chao Y. , Diels J.-C. , Wang Feiling , Wu Adam
Published: February 2023

We report measurements of harmonic generation in thin films of BBO and PLZT. Sputtered thin films of BBO exhibit the largest second-harmonic conversion (SHG), with an efficiency as high as 10-6 for a thickness of only 1 μm. Interdigitated Cr-Au electrodes were deposited for measurement of field-induced SHG on PLZT samples. Second-harmonic generation was measured using a Q-switched, mode-locked picosecond pulse train from a Nd:YAG laser. No damage was observed for intensities above 20 GW/cm2. In the case of PLZT films, plots of SHG as a function of electric field, varying from −3 × 105 to 3 × 105 V/cm, exhibit a strong hysteresis, which, to our knowledge, has not been reported. The PLZT (28/0/100) shows less hysteresis than PLZT (7/0/100), indicating that the latter should be better for memory applications and the former should be better for switching applications. Comparing the efficiencies of BBO and PLZT at the highest de field of 3 × 105 V/cm; we observed a conversion for BBO that was 75 times as large as that for PLZT. Because of their high damage thresholds and large nonlinearities, these materials are ideally suited for waveguide applications.
Detection of signals in inhomogeneous backgrounds by human observers and linear discriminants
Authors: Rolland J. P. , Barrett H. H. , Seeley G. W.
Published: February 2023

Many psychophysical studies of the ability of a human observer to detect an exactly specified signal in a uniform background with Poisson noise have been reported. Most of their results can be adequately explained by an ideal-observer model, which, for this problem, reduces to a simple, linear matched filter. If, however, the background is spatially in homogeneous ("lumpy"), then the ideal observer becomes nonlinear, and its performance is usually very difficult to calculate. Because inhomogeneous backgrounds are very important in many practical applications, we have investigated the performance of human observers on this problem as a function of the amount of background in homogeneity, the blur of the imaging system, and the amount of Poisson noise in the image. We find that all of our results are well described by the assumption that the human observer behaves as the optimum linear observer (Fisher and Hotelling). A simpler linear model, the so-called nonprewhitening matched filter, predicts different behavior.
Laser processing of materials for optoelectronic devices
Authors: Podlesnik Dragan V.
Published: February 2023

This talk provides an overview of laser-assisted processing of semiconductors for integrated-optic device applications. Results also will be given from studies of laser-iduced chemical modification of semiconductor surfaces designed to alter electrical and optical properties of electronic devices.
Experiment and theory of diffraction of aluminum strip gratings
Authors: Schimert T. , Magnusson R. , Wang S. S.
Published: February 2023

A comparative theoretical and experimental study of the diffraction characteristics of aluminum strip gratings in the infrared region is presented. The gratings were made on ZnSe and ZnS substrates by means of standard photolithographic techniques and reactive-ion etching. We used a grating period of 3 m and a fill factor of approximately 0.33. The grating thicknesses varied from 2400 Å to 9500 A. Transmittance measurements were carried out in the 713 m wavelength band, in which only the forward and backward zeroth-order waves propagate. The gratings exhibit a long-wavelength bandstop, i.e., a high-pass filtering characteristic in transmission in which the transmission decreases with increasing grating thickness.
Ion-exchanged waveguides and devices
Authors: Ramaswamy Ramu
Published: February 2023

The tutorial will cover the basic waveguide theory in isotropic media, describe the binary exchange process at the glass-melt interface, and describe the diffusion process, relating it to the index profile for various cation pairs and substrates. This knowledge will be used to illustrate the design, fabrication, and experimental verification of various passive waveguide components.
Interface structure of XUV multilayer coatings
Authors: Windt David L. , Hull R. , Waskiewicz Warren K.
Published: February 2023

From cross-sectional transmission electron microscopy images of XUV multilayers, quantitative interface profiles are extracted and related to the optical properties of these coatings.
Fluorescence spectra from normal and tumor tissues of the gynecological tract
Authors: Sha W. , Liu C. H. , Tang C. C. , Lubicz S. , Alfano R. R.
Published: February 2023

We measured the fluorescence and excitation spectra from different tissues of the gynecological tract (uterus, cervix, and ovary) by means of both laser and lamp excitation. Experiments were performed by using different excitation wavelengths on fresh tissues, dried tissues, and also the interstitial medium. We found significant differences between the normal and tumor tissues. Statistics analyses show the specificity, sensitivity, and accuracy of determining malignancy by means of these spectroscopic differences. The reasons for differences in spectra profiles may be attributed to the transformation of the local distribution of the different molecular groups such as flavins, tryptophan, tyrosine, and hemoglobin. We will discuss their contribution to the fluorescence profile and the similarity between the spectra of the different tissues.
Stability in an optical amplifier
Authors: Schoonmaker D. L. , Oraevsky A. N. , Clark M. , Protscnko I. P. , Bandy D. K.
Published: February 2023

Using the Maxwell-Bloch equations for a two-level atom with longitudinal space and time, we study the effects of various traveling waves in a homogeneous and an inhomogeneous amplifier using different pumping schemes. These schemes include functional dependence such as F(z/t-v) and Gaussian structures. When pump is pulsed at different time intervals (tp), an exponential growth in the average intensity as a function of tp is seen fora given functional form of the pump. Investigations of unstable behavior are illustrated.
Generation measurement and applications of ultrashort pulses
Authors: Ting Guo , Peixia Qiu , Fucheng Lin
Published: February 2023

LBO crystal is transparent up to 165 nm, making it a very good nonlinear crystal in the UV region—better than BBO crystal. Still, it has a smaller double refraction coefficient than BBO (0.12). Thus efficient phase-matching UV frequency conversion requires one of the mixing input wavelengths to be longer than 1.2 m. From this point of view, an intense near-infrared source is needed, so we developed a system that can output 1.55μm picosecond pulses with an intensity of MW/cm2 by means of stimulated Raman scattering. The fourth harmonic was mixed with 1.55-m SRS output in LBO crystal. Being dispersed by grating, the UV output (2200 Å) can be measured easily. With the same infrared source, we can generate vacuum violet output (1850 Å) picosecond pulses by mixing with the fifth harmonic of a Nd:YAG laser.
Cavity-mode expansion for stable resonator power extraction
Authors: Erkkila John H. , Hedin Vance A.
Published: February 2023

Techniques for predicting the mode shape of stable resonators as a function of gain, such as the Fox-Li iterative method, can encounter difficulty in multitransverse-mode lasers because of the effects introduced by employing coherent combination of the individual modes. We have developed an alternative approach that assumes incoherent mode combination. The modes of the bare cavity or of a "gain-weighted" cavity are identified first. Then an iterative technique is applied to establish the mode amplitudes for self-consistent round-trip propagation in the laser. The specific characteristics of the gain media exert a strong influence on the numbers of transverse modes that lase.
Effect of changing dye flow velocity on the fluctuations of a dye laser
Authors: Bali S. , Noh J. , Fougéres A. , Cheng F. , Mandel L.
Published: February 2023

Because of the possibility of triplet state quenching, the behavior of a dye laser is expected to be affected by changes in dye flow velocity. We have investigated the effect on the intensity fluctuations of changing the jet flow velocity of a single-mode dye laser in the range 12.1 to 13.4 m/s. Both the mean light intensity and the dispersion <(ΔI)2> were obtained from photon counting measurements. At first it appears that changing the flow velocity has a significant effect on the relation between <(ΔI)2> and . However, the closer examination reveals that changing the flow velocity affects the orientation and thickness of the dye jet. After compensating for these effects we find that the relation between <(ΔI)2 >/2 and  remains unchanged over the velocity range 12.1 to 13.4 m/s.
Pump statistics and micromaser dynamics
Authors: Bergou Janos , Hillery Mark
Published: February 2023

The realization of the micromaser prompted theoretical interest in the fundamental problems of laser physics. In particular, it has been shown that the usual quantum theory of the laser can be recovered from the micromaser theory if a Poissonian average with respect to the time intervals between subsequent injections is taken. The problem of general injection statistics has not been fully resolved but, instead, has been circumvented in the following ways. Instead of the time period between successive injections, the number of injected atoms during a fixed time interval was considered as a stochastic variable and was averaged with respect to a general sub-Poissonian distribution. This led to a closed-form master equa tion, but correction terms arise when the effect of cavity damping is significant. In another approach a stroboscopic theory has been developed: The system is observed when a full cycle of pumping, firing, and decay is completed. This assumes observation of the system on a nonuniform time scale. Here we carry out the averaging over the time interval between subsequent injections with sub-Poissonian distribution, suggest a new compact master equation, and exploit some of its consequences. We show that this approach reproduces the previous ones if the cavity damping is negligible. The surprising result of our approach is that altering the pump statistics affects both the gain and the loss part of the laser dynamics.
A sign/logarithm number-system-based fast optical binary multiplier
Authors: Kim Dai Hyun , Kostrzewski Andrew , Li Yao , Eichmann George
Published: February 2023

We will present a new fast binary multiplication scheme based on the use of a nonholographic parallel optical content addressable memory (CAM). The multiplication operation is performed by means of binary logarithmic addition that uses a sign/logarithm number system. Multiplication of two binary numbers a and b begins by converting them into a sign/logarithm number system. Multiplication is accomplished by adding appropriate logarithms. A 3-stage non-holographic CAM is required to implement a sign/logarithm number multiplier. By means of a Quine-McCluskey minimization method, the number of CAM's minterms are reduced. For a 7-bit binary multiplication the first CAM, reduced from 605 to 111 minterms, converts the binary numbers to sign/logarithm numbers. To add the two logarithms, a second CAM, reduced from 2519 to 270 minterms, performs a floating-point binary-carry look-ahead addition. Finally, a third CAM with 329 instead of 891 minterms, does the conversion from sign/logarithm numbers back to binary numbers. In general, the storage capacity needed for each CAM stage depends on the range of input numbers and the calculation accuracy.
Signal-to-noise limitations on the number of channels in holographic interconnection networks
Authors: Lahrichi Adil , Johnson Kristina M. , Fredericks George , Maniloff Eris S.
Published: February 2023

Volume holograms stored in a photorefractive crystal can be used as routing templates for an optical communication switch.1,2 The holograms are recorded by using reference beams that are spatially modulated with different intensity-modulated codes. When a communication channel's optical carrier is subsequently used as the read beam for the stored holograms, a spatial light modulator (SLM) applies the desired code to program the switch to deliver the signal to a particular detector. The diffraction efficiency, beam power, system bandwidth, and the detector noise determine the signal-to-noise ratio and hence the bit error rate (BER) at the detector. Furthermore, if the system is to multiplex multiple channels, the finite SLM contrast ratio will add crosstalk noise. If values for these system parameters are chosen, the minimum diffraction efficiency (hence the maximum number of holograms that can be stored in a l cm3 holographic recording medium) as a function of the SLM contrast ratio, the particular photodetector, and system bandwidth requirements are determined.
Integrated optical clock distribution by means of a binary beam-splitter tree
Authors: Walker Susan J. , Jahns Jurgen
Published: February 2023

Synchronous distribution of optical power to an array of optical components is of inter- estforsystem applications in very-large-scale integrated (VLSI) electronics, photonic switching, and optical computing. A variety of possibilities exists for optical clock distribution, including the use of integrated waveguides, fiber optics, and free-space optics. We present a technique in which integrated free-space optics are used to distribute power from a single source. The optical signal propagates through N successive stages of 12 beamsplitters to achieve a fanout of 2N. In this study, a single glass substrate is used with gratings and lenses integrated on one side of the substrate. The optical signal travels under an angle inside the substrate from one component to the next. The complete optical system is fabricated by lithographic techniques. This approach can be extended for building a parallel optical bus with two-dimensional input signals.
Measuring losses of thin film waveguides with a two-dimensional charge-coupled device camera
Authors: Himel Marc D. , Sisk J. Patrick , Guenther Karl H.
Published: February 2023

The improved resolution, sensitivity, and uniformity of CCD cameras, and their lower cost, make them more cost-effective than scanning detector systems when used in combination with frame grabbers for computer-based measurements of waveguide attenuation. We report on the use of a high-resolution (768 493 pixels) Hamamatsu C3077 CCD camera for measuring the mode propagation losses of high-index oxide waveguides on oxidized Si wafers. The waveguides were deposited by electron-beam evaporation, reactive low-voltage ion plating, or RF sputtering. To achieve high spatial resolution, we used a fixed-aperture, fixed-focus macro lens at 1.6 reduction to image a 1.5 cm 1.0 cm area onto the CCD. The camera is interfaced with a computer by means of a Data Translation frame grabber for fast data acquisition and analysis. Using this two-dimensional camera will allow us to characterize the size and distribution of defects and to measure propagation losses. Measurements are possible over a wide range of losses from 1 dB/cm to 50 dB/cm with a spatial resolution of 50 m. Loss measurement accuracy, which is alignment dependent, will be examined.
Chromatic shifts caused by phase differences on juxtaposed flickering lights
Authors: Yamashita Y.
Published: February 2023

I measured color appearance changes that could be caused by juxtaposing flickering lights with different phases. A flickering annulus test field (inside diameter 2°, width 10 ft.) was embedded at the center of a 6.8° flickering surround field. Subjects matched the apparent color of the test field to a steady reference field, which was adjustable in chromaticity, had the same shape as the test field and was separated from the surround by 3°. These fields were displayed on color cathoderay tobes (56 Hz frame rate). One period of the flickers consisted of a sequence of eight frames. Both fields were turned Off in the first half of the period and On with a white color in the latter half, except for the fifth frame, in which only the surround was On with a certain color. Two types of shifts were observed, depending on subjects. In one type, the apparent color caused by a white or cyan fifth-frame color was brighter, had about a 488 nm dominant wavelength appearance and was similar to red or purple. In the other type the apparent color was dimmer, had about a 561 nm complementary dominant wavelength appearance, and was similar to green or yellow.
Precision optical measurement of saturated curves for high-speed centrifuge in petroleum prospecting
Authors: Ming Wang Hui
Published: February 2023

A new optical technique is employed in petroleum prospecting and exploiting departments for determining capillary pressure curves and measuring dynamic parameters of oil layers. This method is more accurate and automatic than traditional mercury intrusion and semipermeable portioned methods. In petroleum prospecting and exploiting, a high-speed centrifuge is employed to determine the oil contents of core samples. As the rotating speed of the centrifuge increases from 300 to 21000 rpm, the oil and water in the rotating core are separated gradually; the height of the separation level gives information on the percentage of oil. In our system, four rotating cores are synchronously illuminated by an xenon flash lamp that is monitored by a laser synchrosystem attached to the rotating axis of the centrifuge. The dynamically steady image is photographed by a video camera and displayed on a television monitor. I propose that the water column height can be determined by number of horizontal scan lines. To do this the video signal is processed with a binary-state pulsed strobe, and the processed data are sent to the printer. As a result, the experimental data can be analyzed by using the method of least squares.
True three-dimensional capture and illusory contours
Authors: Swift Dan , Smith Robert A. , Panish Steven
Published: February 2023

Several intriguing demonstrations with stereoscopically presented subjective contours and capture have been presented in recent years. Examples include (1) subjective squares with "Pac-men" inducing figures whose "bites" are presented in disparity, and (2) random-dot stereograms with sparse dots that capture the background. Different depth planes are present, but all perceived objects are surfaces (either flat or curved) rather than true volumetric entities.
Transient gain measurements of nonradiative dynamics in chromium doped forsterite (Cr4+:Mg2SiO4)
Authors: Seas A. , Petricevic V. , Alfano R. R.
Published: February 2023

The gain dynamics of photoexcited chromium-doped forsterite (Cr4+:Mg2SiO4) were measured by means of a pulsed excite-and-probe technique. The nonradiative relaxation time within the 3T2 vibronic state was determined by measuring the change in the induced gain of the probe pulse as a function of the pumpprobe delay. A 30 ps, 1.064 m pulse from a mode-locked Nd:YAG laser was split into two beams. The first beam provided the pump pulse to populate the 3T2 manifold. The other beam was focused in a calcite crystal to generate a 1.2 m probe pulse by means of stimulated Raman scattering. The transient gain was determined from the measured ratio of the transmitted probe intensity for unpumped and pumped cases as a function of the pumpprobe delay. The rise time (time for growth of the gain from 10% to 90%) was calculated to be 50 ps. A rate-equation analysis of population in the various states was used to extract a value for the vibrational relaxation time from the experimental data under the assumption of Gaussian pump and probe pulses. The best fit to the experimental data of gain as a function of time yields a value of 10 5 ps for the intra-3T2-state vibrational relaxation time.
Loss reduction of polymer thin-film optical waveguides
Authors: Amleshi Peerouz M. , Naylor David L.
Published: February 2023

Polymer thin films have become a major part of optical integrated circuits in the last two decades. Polymer-based optical waveguides can be easily fabricated by deposition of a polymer solution on a substrate by spin-coating. Under proper conditions, the deposited polymer films exhibit excellent optical properties. Loss quality is an important characteristic of optical waveguides, which dictates the size of the integration of the optical circuits or, in an extreme case, the applicability of the structure. A large part of the optical loss in thin-film waveguides is due to the scattering of the optical wave at the film interfaces with its substrate and cladding. The optimized processing of polymer solutions, which was mentioned earlier, results in a uniform interface at the cladding and reduces this loss. To minimize the scattering loss, other steps can be taken after the polymer film has been deposited.
Link budget analysis for fiber optic LANs and data communication
Authors: McIntosh Thomas F.
Published: February 2023

One approach to the link budget analysis of fiber optic transmission systems is to evaluate the link loss as the sum of the worst case losses for all components such as cable, connectors and splices. This total link loss is then compared to the worst case transmitter power minus the worst case receiver sensitivity to determine system power margin. Statistical budget analysis of fiber optic links provides a more precise characterization of actual system performance than worst case analysis. Statistical methods are used not only for engineering long-haul trunk and loop feeder systems, but also for LANs and other data communication applications. Statistics for the losses of cable, connectors, splices, dispersion penalty and higher order modes are combined with the statistical performance of the optical transmitter and receiver to calculate the mean and standard deviation of system margin. These parameters are, in turn, used to predict the link optical performance to a desired level of confidence. The methods of analysis are reviewed and the statistical performance of typical optical components are presented. A comparison between the statistical and worst case analysis is included, and the techniques of how to use the statistical design are illustrated by engineering a practical LAN application.
Optical properties of dielectric coatings deposited using reactive sputtering
Authors: Al-Jumaily G. A. , Gagliardi F. J. , Edlou S. M. , Raouf M. A.
Published: February 2023

Deposition of dielectric coatings by reactive sputtering is widely used in the microelectronic industry. The application of the process for the deposition of optical coatings has been very limited. In this report we outline results in our effort to apply the sputtering process for dielectric coatings. Coatings with excellent optical properties of SiO2, Al2O3, HfO2 and TiO2, were deposited using magnetron sputtering of Si, Al, Hf, and Ti, respectively with oxygen backfill. These materials cover a wide range of indices from 1.45 to 2.5. Coatings were deposited in a 60 cm box coater. The deposition system is equipped with a three inch diameter magnetron sputtering source. The system is cryogenically pumped to a base pressure of 3 × 10–7 Torr. The pressure with oxygen backfill is 5 × 10–4 Torr, while the total pressure after adding the argon is 1 × 10–3 Torr. The optical and mechanical properties of single and multilayer coatings were examined. The index of refraction of SiO2, Al2O3, and TiO2 were 1.45, 1.64, 2.0, and 2.5, respectively. Coatings were durable with good adhesion and abrasion resistance.
Analysis of Bragg diffraction imaging by means of a three-dimensional computer ray tracing algorithm
Authors: Mehrl David I.
Published: February 2023

Bragg diffraction imaging provides a convenient method of visualizing ultrasonic sound fields. The technique images the transverse sound field profile, and may be conveniently analyzed with ray tracing techniques. We first consider the case of a three-dimensional sound field illuminated by a two-dimensional light field, and then examine an alternative scheme, in which the same sound field is illuminated by a three-dimensional light field. In both cases, the diffracted light is three-dimensional in nature, so that the ray tracing must ultimately be rendered as a two-dimensional projection of the original three-dimensional construct. We discuss the development and implementation of an interactive computer program that realizes three-dimensional acousto-optic ray tracings and generates two-dimensional projections from various vantage angles. Using two slightly different vantage angles makes stereoscopic presentations possible. The ray tracings are depicted by color graphics, such that sound and diffracted/undiffracted light rays are easily distinguishable. Results clearly reveal the astigmatic nature of the image as also predicted by previous geometric analyses of the same configurations.
Testing cylindrical surfaces using a grating reference
Authors: Creath Katherine , Wyant James C.
Published: February 2023

Optical components with cylindrical surfaces are hard to test in most interferometers because a cylindrical reference wave-front needs to be produced. A grating which produces a high-quality cylindrical wave-front in the first diffracted order has been used to test cylindrical surfaces in a phase-measuring Fizeau interferometer. The test arm of the interferometer contains the grating and the test surface. A plane reference wave-front is produced by a transmission flat. The test surface is placed so that its center of curvature is at the center of curvature of the reference cylindrical wavefront. The test beam is reflected back by the test surface to the grating which then diffracts the test beam back into the interferometer. This paper describes this technique, and shows results of testing cylindrical surfaces using this technique.
Shock tube spectroscopy of astrophysical molecules using an optical multichannel analyzer
Authors: Nicholls R. W. , Shen J. Z. , Shin J. B. , Cann M. W. P.
Published: February 2023

As part of a continuing laboratory study of astrophysical spectra, bands of SiH and SiN, in the wavelength region 390–450 nm have been shock-excited in emission in silane-nitrogen mixtures under known thermodynamic conditions. Spectra from individual shocks have been recorded using an optical multichannel analyser. They have been interpreted by comparison with realistic numerical line-by-line synthetic spectra.
Phase-sensitive, time-resolved detection of ballistic phonons
Authors: Ambrose W. P. , Moerner W. E.
Published: February 2023

Time-of-flight detection of ballistic phonons in solids at low temperatures has previously employed phase insensitive detectors such as bolometers, tunnel junctions, or changes in optically excited fluorescence orabsorption. We present a phase sensitive technique for time-of-flight detection of phonons using frequency-modulation spectroscopy (FMS) of persistent spectral holes (PSH). A PSH is burned into the 607 nm color center zero phonon line of a NaF crystal at 1.5 K using a dye laser. Then, ballistic phonon pulses are generated by the absorption of Nd:YAG laser pulses in a Cr film on a NaF surface. Local measurement of the propagating stress-strain field is achieved by detecting the PSH splitting with a frequency-modulated cw dye laser beam. By examining the phonon time-of-flight signal dependence on the probe light polarization, position within the sample, and FM detection phase, an identification of the types of propagating phonons is made. Along with the ability to determine the sign of the acoustic disturbance, this experiment features a strain detection limit of 4 × 10−9 in 1500 averages at a time resolution of 50 ns.
Effects of chromatic aberration on Vernier and stereo acuities
Authors: Campbell Melanie C. W. , Simonet Pierre
Published: February 2023

Amounts of transverse chromatic aberration (TCA) and chromostereopsis were measured in normal view for nine subjects at two levels of illumination. Vernier acuities associated with the TCA measurements for a split bichromatic target were worse than those associated with measurements using monochromatic targets at both low and high illuminance. The reduction in vernier acuity can be shown to be due to chromatic aberration because the effect disappears when a Maxwellian view system is aligned with the achromatic axis of the eye. Thus for vernier alignments of bichromatic targets, chromatic aberration introduces both a bias and reduction in acuity. Chromostereopsis will introduce a bias in the depth alignment of targets of differing spectral composition. However when measurements were made of the amount of chromostereopsis for the same subjects, the associated stereoacuity was not reduced as much as expected. This result, combined with the lack of correlation between TCA and chromostereopsis for some subjects, suggests a difference in monocular and binocular processing in hyperacuity tasks.
Observation of induced IR optical anisotropy in picosecond pulse excited CdSe
Authors: Cruz J. M. R. , van Driel H. M. , Kuokstis E.
Published: February 2023

CdSe samples have been photoexcited with λ = 0.53 µm, 40 ps pulses and probed in reflection with λ = 2.8 µm pulses generated by second-order stimulated Raman scattering of λ = 1.06 µm pulses in methane. Besides the Drude like free carrier response, whose temporal characteristics are governed by plasma diffusion and recombination, the reflectivity shows features which are attributed to defects and/or impurities. These features depend on the orientation of the polarization relative to the crystal axis. A model correlating the reflectivity kinetics to the trapping of carriers in defects/impurity levels is going to be discussed.