bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Waveguides in Lithium Tantalate by Vapor Diffusion Below Curie Temperature
Authors: Yoon D.W. , Eknoyan O. , Jung H.S.
Published: February 2023

For integrated optics applications, LiTaO3 offers an attractive alternative to the more commonly used LiNbO3.1 This stems from its higher optical damage threshold level, and smaller birefringence. However no extensive use has been made of this material because of its relatively high optical loss and its low Curie temperature (Tc ~ 510 – 690°C depending on composition). The latter causes domain inversion and makes repoling of crystals a necessity for producing electrooptical devices when waveguides are formed by diffusion at a temperature higher than Tc. Attempts to fabricate waveguides below the Curie temperature have been reported. These include ion exchange,2,3 and electrodiffusion.4 However in the ion exchange method, an index increase is observed only for the extraordinary mode, while in the field assisted diffusion the limitation is prompted by strong absorption peaks and surface damage.
Ferroelectric Microdomains In Lithium Niobate Optical Modulators
Authors: Pendergrass L.L. , Jungerman R.J.
Published: February 2023

Degradation of lithium niobate integrated optical device performance due to the reversal of ferroelectric micro-domains in localized regions has been described in Ref. 1. However, it has been assumed that these reversals can take place only at extremely high temperatures (near the Curie point) or with very high applied electric fields. Indeed, it has been shown theoretically (Ref. 2) that for pure lithium niobate at room temperature, an electric field of about 3 × 10 9 V/m applied along the crystalline c axis would be necessary to cause domain reversal. Titanium diffusion at elevated temperatures was identified in Ref. 1 as the cause of these reversals and usage of -Z-cut substrates rather than +Z-cut substrates was proposed to reduce their occurrence.
LiNbO3 blazed grating fabricated by reactive ion-beam etching
Authors: Ogata S. , Hosokawa H. , Yamashita T.
Published: February 2023

A guided-wave acousto-optic device will certainly serve important functions such as deflection, modulation and switching of laser light beams in future optical communication and processing systems. We had experimentally demonstrated, for the first time, a high-performance guided-wave acousto-optic light beam deflector by employing blazed grating couplers as shown in Fig.11. In order to realize their high coupling efficiency, the blazed grating couplers had been developed by the reactive ion-beam etching(RIBE) technique using holographically produced photoresist gratings as masks2.
High Efficiency Surface-Emitting Distributed Bragg Reflector Laser Array
Authors: Kojima Keisuke , Kameya Masaaki , Noda Susumu , Kyuma Kazuo
Published: February 2023

There has been considerable interest in surface-emitting laser diodes, because they are potentially very important for one- and two-dimensional monolithic laser arrays. There are several approaches to achieve surface-emitting lasers, such as (a) vertical resonator cavity [1], (b) 45° mirror [2], (c) parabolic mirror [3], and (d) grating-coupler [4-7]. Among them, grating-coupled lasers have the advantages of a narrow beam divergence and a dynamic single mode operation. However, the quantum efficiencies of grating-coupled lasers have been low. The maximum differential quantum efficiencies reported so far were 8% in distributed feedback (DFB) lasers [6] and 9% in distributed Bragg reflector (DBR) lasers [7]. In this paper, we report a three-stripe surface-emitting multiquantum well (MQW) DBR laser array with a very high differential quantum efficiency of 37% and a high output power of 500mW.
Corrugation Structure Based Semiconductor Optical Guided-Wave Devices
Authors: Murata S. , Mito I.
Published: February 2023

Corrugation structure based semiconductor opical guided-wave devices are very attracive for optical integration circuits. The corrugated waveguide has many desirable functions, such as wavelength selection and distributed optical feedback. DFB/DBR lasers are most successful devices applied this structure. In integrated optical devices based on DFB/DBR lasers, new functions and higher performance will be realized, which can not be realized in solitary lasers. In this paper, we discuss recent progress on wavelength tunable DBR lasers, narrow linewidth DFB lasers and tunable wavelength filters.
High Power High Speed Single Mode Sipbh-DFB Lasers at 1.3 Micron Wavelength
Authors: Koren U. , Koch T.L. , Corvini P.J. , Miller B.I. , Eisenstein G. , Tucker R.S. , Su Y.K. , Capik R.J.
Published: February 2023

The semi-insulating blocked planar buried heterostructure (SIPBH) laser has been described previously [1,2]. It combines a liquid phase epitaxial (LPE) or a metal organic vapor phase deposition (MOCVD) growth for the InGaAsP/InP double heterostructure (DH) base wafer followed by a regrowth by MOCVD for the blocking and cap layers. The characteristics of the laser include large modulation bandwidth and high output power [2]. Since the active layer is planar in this device, it is suitable for the fabrication of gratings that are required for single longitudinal mode operation. In this paper we describe the fabrication and performance of a first order grating distributed feedback (DFB) laser based on the SIPBH structure operating at 1.3 micron wavelength. High power wide bandwidth DFB lasers operating at 1.5 micron have been recently reported [3]. These lasers, however, required etching of a very narrow contact mesa (about 5 micron wide) to reduce the parasitic capacitance. In the present work wider contact mesas of about 50 micron width could be used because of the inherently low capacitance of the MOCVD grown Fe doped semi-insulating (SI) InP blocking layers.
Monolithically Integrated Transverse Junction Stripe Lasers with Rib Waveguides in GaAs/AlGaAs
Authors: Vawter G. Allen , Merz James L. , Coldren Larry A.
Published: February 2023

Complete integration of optical laser sources and waveguides with electronics on a single semiconductor wafer has been a long sought after and elusive goal. Future development of optoelectronic integrated circuits (OEICs) hinges on the development of monolithically integrated laser/waveguide systems with low threshold currents and high injection efficiency into the passive waveguide. This paper reports progress in developing just such a high efficiency Transverse Junction Stripe1 (TJS) laser source integrated with an external passive waveguide suitable for optical interconnection applications. Threshold current as low as 60 mA and injection efficiencies as high as 40% are reported.
Integrated Semiconductor Ring Laser Structures
Authors: Jezierski A F , Laybourn P J R
Published: February 2023

Monolithic integration of semiconductor optical devices requires the development of laser sources with feedback mechanisms other than cleaved cavities and with little influence of the output termination on the lasing action. We have been looking into both circular and polygonal ring resonant waveguide structures to be used as laser cavities, where the need for high quality mirrors is eliminated [1,2]. A variety of ring configurations, between 10 and 100μm in diameter have been succesfully formed in GaAs/GaAlAs material, coupled to the output stripe waveguides either directionally or via a Y–junction. Both ring and output waveguides needed pumping. A rib waveguide configuration was chosen to maximise light confinement and minimize bending loss at small cavity circumferences [3,4] (fig.1). Some of the structures use stress– and carrier confinement on the inner side of the ring.
Efficient Degenerate Four-Wave Mixing in a Single Mode Waveguide
Authors: Gabel A. , DeLong K. , Seaton C. , Stegeman G.
Published: February 2023

Degenerate four-wave mixing (DFWM) in bulk media has proven useful over the years for phase conjugation and material characterization [1]. It has also been demonstrated in waveguide geometries, principally fibers [2]. There has been one experiment reported in planar wave guides, but the conjugate reflectivity was only 10-9 since the nonlinear medium CS2 was used as the waveguide cladding [3]. Higher efficiencies are clearly desireable, especially since degenerate four-wave mixing in waveguide geometries is useful for signal processing operations such as signal convolution, time inversion, and time compression [4]. In this paper we report the first measurements of degenerate four-wave mixing in semiconductor-doped glass waveguides made by Na+-K+ ion exchange. Efficiencies approaching 10% have been obtained with picosecond pulses.
Microwave Bandpass Modulators in Lithium Niobate
Authors: Betts Gary E.
Published: February 2023

Microwave bandpass modulators made using Mach-Zehnder interferometers in lithium niobate with periodic phase reversal electrodes have been developed for operation at 1.3 μm. These modulators are most useful in applications requiring electrooptic modulation at a single frequency or in a range of frequencies with less than an octave bandwidth. The performance of two experimental devices, with center frequencies of 10 and 21 GHz, will be described and compared with theory. The response of the 21-GHz modulator is higher at that frequency than the response of any baseband modulator in LiNbO3.
Wideband Guided-Light Beam Deflection and RF Spectral Analysis Using Magnetostatic Forward Volume Waves*
Authors: Tsai C. S. , Young D.
Published: February 2023

Magnetooptic (MO) interactions between guided-optical waves and magnetostatic waves (MSW) in Yttrium Iron Garnet-Gadolinium Gallium Garnet (YIG-GGG) waveguides has become a subject of increasing interest in recent years. Similar to the guided-wave acoustooptic (AO) interaction in which the surface acoustic wave (SAW) induces a moving optical grating [1], the guided-wave MO interaction results from the moving optical grating induced by the MSW. Specifically, in noncollinear coplanar geometry, as shown in Fig.1, a portion of an incident guided-light wave is Bragg diffracted and mode-converted (TE- to TM-mode and vice versa). We have recently obtained a very large bandwidth and high diffraction efficiency in such interaction geometry with magnetostatic forward volume waves (MSFVW) [2]. For example, a -3dB bandwidth of 1.03GHz centered at 6.0GHz was obtained at the optical wavelength of 1.317μm using a single microstripline transducer together with a fixed homogeneous DC magnetic field of 3500 Oe. As in the AO Bragg diffraction in which the resulting modulator is called the AO Bragg cell, the resulting MO modulator may be called the MO Bragg cell. In a continuing effort we have used the wideband MO Bragg cell to perform, for the first time, wideband light beam deflection and RF spectral analysis, and have obtained large numbers of deflected light spots and frequency channels. In this paper detailed results of both the experiments and related analysis are presented. It should be noted that a number of studies on bulk-wave MO interactions involving an unguided light wave and spin and/or magnetoelastic waves were reported [3-7] in the late 60's and early 70's. To the best of our knowledge, however, neither work on light beam deflection nor on RF spectral analysis using such bulk-wave MO interactions has been reported.
Processes for Large Scale Photonic Integrated Circuits
Authors: Koren U. , Koch T.L. , Miller B.I. , Shahar A.
Published: February 2023

The Silicon integrated circuit (IC) industry had evolved during the last 35 years by introducing and refining several important Silicon based processes (such as I2L, NMOS, CMOS etc). A process is comprised of a set of processing steps (e.g. Photolithography (Plit), etching, implantation etc.) which are executed in a precise order and under rigidly controlled conditions. The individual devices differ only by the set of Plit masks that are being used on a particular wafer. Our goal here is to develop a process, in the same sense, for large scale photonic integrated circuits (PIC's). Some of the building elements are; a. lasers. b. optical amplifiers. c. grating filters. d. passive waveguides. e. waveguide branches and passive couplers. f. directional couplers g. optical switches. h. optical modulators. i. waveguide detectors.
Formation of Planar Waveguide Lenses and Lens Arrays in GaAs Using Ion Milling*
Authors: Tsai C. S. , Vu T. Q. , Norris J. A.
Published: February 2023

Waveguide lenses are among the essential components in integrated optic modules or circuits such as spectrum analyzers,(1) correlators,(2, 3) and computers.(4, 5). Various types of waveguide lens have been fabricated in LiNbO3 and glass substrates. These lens types include Luneburg, geodesic, index refraction via TIPE or two layers construction, chirp grating, and Fresnel. The material constraints such as a very high refractive index and high brittleness, and the relatively small reduction in refractive index in Ga1-xAlxAs for a desirable fractional composition x have thus far prevented the first three lens types from being fabricated in GaAs waveguides. Although fabrication of AlGaAs graded-index waveguide lenses using laser-assisted chemical vapor deposition was proposed most recently,(6) to the best of our knowledge, no working lens has been reported. However, the positive or negative index-changes required in both the chirp grating and Fresnel lenses may be produced through either deposition of a higher-index cladding material, or reduction of the waveguide thickness via etching or ion milling. As a high-quality higher-index cladding material for GaAs is yet to be grown, we have chosen the later technique through ion milling to fabricate the negative-index change lenses. Most recently, we have successfully applied this lens fabrication technique to fabricate lenses of high-efficiency and diffraction limited characteristics in LiNbO3.(7) In a continuing effort we have successfully produced single lenses and lens arrays of the types including analog Fresnel, chirp grating, and a hybrid combination of the two in GaAs waveguides, and have obtained equally encouraging results. In this paper, design, fabrication, and measured performances of single microlenses and microlens arrays of the aforementioned types are presented.
Light-by-Light Modulation in Silicon-on-Insulator Waveguides
Authors: Soref Richard A. , Lorenzo Joseph P.
Published: February 2023

We have constructed silicon-on-insulator (SOI) channel waveguides, and have obtained intensity modulation of multimode 1.3 μm light propagating in those guides using 800 nm light. From a theoretical standpoint1, single-mode SOI guides with submicron height are attractive because of their low propagation losses. However, in these early experiments, we chose to use larger, multimode guides that are easier to work with.
Direct Measurement of Refractive Index Profiles of Ti:LINBO3 Planar and Stripe Waveguides by Reflectivity Profiling
Authors: Steffen J. , Neyer A. , Voges E.
Published: February 2023

The reflectivity measurement of angular polished surfaces of Ti:LiNbO3 waveguides is utilized to determine directly the refractive index profiles of planar and stripe waveguides with an accuracy of Δn/n = 10-4 and a local resolution of <0.1 μm in depth and <1 μm in width.
Pigtailed Integrated Optical Gyro-Circuits Meeting Military Requirements
Authors: Regener Rolf A.
Published: February 2023

Pigtailed integrated optical circuits have been used in fiber gyros and tested under environmental conditions. A breakthrough has been achieved in the reliability of the fiber-to-waveguide attachment.
Improved Acoustically-Tunable Optical Filter on x-cut LiNbO3
Authors: Heffner B.L. , Smith D.A. , Baran J.E. , Cheung K. , Yi-Yan A.
Published: February 2023

We demonstrate a narrowband (≈ lnm) LiNbO3 acoustically-tunable optical filter with a tuning range adequate to span the 1.3 to 1.55-μm wavelength range, exploiting the considerable advantages of an unconventional x-cut design.
Low Loss Ion Implanted Ag Waveguides in Glass
Authors: Ashley Paul R. , Thomas Darrel K.
Published: February 2023

Silver ion exchanged optical waveguides have become of increasing interest in recent years. Continuing research in this area has led to improvements in optical performance along with many variations on the fabrication technique.1,2 Most of these techniques which yield low loss guides use a molten liquid source of silver. Reported here are the first ion implanted Ag waveguides in soda-lime glass. The ion implantation minimizes contamination from source material and allows considerable control over the placement of silver in the substrate, thus making reproducible characteristics easier to obtain. Subsequent thermal diffusion under bias was used to complete the ion exchange process and redistribute the silver. Since the implant creates an initial depletion of Ag at the surface, buried guides were possible.
Compound Bragg Reflection Filters Made by a High Resolution Deep Ultraviolet Stepper
Authors: Henry C. H. , Shani Y. , Kistler R. C. , Jewell T. E. , Pol V. , Olsson N. A. , Kazarinov R. F. , Orlowsky K. J.
Published: February 2023

Optical filters are required for a variety of applications in optical communications such as wavelength division multiplexing and rejection of unwanted spontaneous emission in optical amplification. A good filter should have high throughput, a flat pass band and a high degree of rejection of unwanted wavelengths. Bragg filters having thousands of lines are capable of meeting these needs. In general, it is necessary to vary the period of these lines and to be able to form such filters at different places on the integrated optical circuit (IOC) chip.
Monolithically Integrated 1.5 μm DFB Laser with Y-Branching Waveguide and a Monitoring Photodetector
Authors: Liou K.-Y. , Koren U. , Chandrasekhar S. , Koch T. L. , Shahar A. , Burrus C. A. , Gnall R. P.
Published: February 2023

Photonic integrated circuits (PIC), consisting of active and passive optical components fabricated on a single III-V semiconductor substrate, are important for lightwave technologies in the future. We describe in this paper the monolithic integration of a 1.5-μm distributed feedback (DFB) laser, a passive Y-branching waveguide, and a monitoring p-i-n detector, grown entirely by MOCVD.
Physics and Applications of Quantum Wells in Optics
Authors: Miller D. A. B.
Published: February 2023

Quantum wells are made from alternating thin (e.g. 100 Å) layers of two different semiconductors. These dimensions are so small that physical mechanisms can be engineered on a quantum-mechanical level, either to improve existing physical effects or to create new ones. The topic of the physics of layered semiconductor structures is one of intense current research interest in solid state physics. In optics, we see the consequences in linear and nonlinear optical properties and in electrooptical effects. (For recent reviews, see e.g. Refs. 1-5). Many of these effects are seen under rather practical conditions (e.g. room temperature), and are compatible with laser diode sources and with semiconductor electronics in wavelengths, in power and voltage levels, and in materials and fabrication. Although the quantum well materials are sophisticated structures, an impressive fabrication technology already exists through molecular beam epitaxy and other related semiconductor growth techniques. As a result, many interesting optical devices have been proposed and demonstrated.
Beam Propagation Method Analysis of the Digital Switch
Authors: Thylén L , Svensson P , Burns W K
Published: February 2023

The ”digital switch” 1,2, see also ref 3, has attracted considerable attention recently due to its digital response versus applied voltage and due to its comparative insensitivity to wavelength. This switch does not rely on interference or coupling between normal modes in the two moded structure which constitutes a basic switch, but rather on adiabatic propagation of the normal modes through the structure (cf ref 4). This feature accounts for the insensitivity to wavelength. However, an important question relates to the voltage requirements of this switch and the shape of its transfer characteristics, i e the extent to which it can be employed as an ordinary switch characterized by a voltage length product, as is the case for a directional coupler, such that shorter switches with the same crosstalk performance are achieved by increasing the drive voltage proportionally. In this paper we use the beam propagation method (BPM)5,6 to analyze the switching characteristics of a digital switch, implemented in Ti : LiNbO3, with the channel crossing angle as a parameter. The analysis is carried out for Z-cut LiNbO
3
switches; comparisons are made to published experimental data as well as to directional coupler switches. Possible optimizations are discussed.
Single Polarization Components and Applications
Authors: Suchoski Paul G. , Findakly Talal K.
Published: February 2023

Single-polarization fiber optic and integrated optic devices are required for phase-sensitive optical systems such as fiber optic gyroscopes and coherent communications. Recently, there has been significant improvement in the performance of polarization-maintaining fiber [1], polarizing fiber [2], and polarization-preserving fiber components including polarizers [3] and couplers [4]. These components are becoming commercially available. Development of single-polarization integrated optic devices and circuits has progressed much more slowly and only recently have high-quality proton-exchanged LiNbO3 and LiTaO3 integrated optic devices been reported [5-10].
High Optical Power Performance of High-Quality LiTaO3 Integrated Optical Waveguide Devices
Authors: Findakly T. , Farina J. , Suchoski P. , Leonberger F.
Published: February 2023

LiNbO3 has been extensively used for integrated optic applications primarily due to properties which lend themselves to high electro-optic efficiency and simplicity of low loss guided circuit fabrication. The Ti-diffusion technique has been the dominant technology in LiNbO3 [1]. Certain deficiencies in that technology along with emerging new requirements on device specifications led to the introduction of the proton-exchange method [2], and later to the annealed-proton-exchange method [3] which has, in certain respects yielded greatly improved overall waveguide properties for single polarization applications [4,5,16].
The Recent Development of Microoptics in Japan
Authors: Nishizawa Koichi
Published: February 2023

Great progress in optical fiber communications and optical sensing systems have been made, associated with the development of the new class of optical components like microoptic components.
Thermal aberration analysis of a laser-diode-pumped Nd:YAG laser
Authors: Kubota Shigeo , Oka Michio , Kaneda Yushi , Masuda Hisashi
Published: February 2023

A recently developed powerful GaAlAs laser diode has excellent spectral match to absorption band of NdzYAG crystal (808nm) and can provide end-pumping configuration where pump beam well overlaps with transverse resonator modes of YAG laser. These properties allow to build an efficient diode-pumped NdzYAG laser.1 We have stabilized an intra-cavity frequency-doubled NdzYAG laser with a KTiOPO4 (KTP) doubler using a quarter wave plate to decouple the polarization mode interaction inside the cavity.2 With this technique, the green (532nm) laser can be used in a readout system of a tripled density optical disk.3
Integrated Free-Space Optics
Authors: Jahns Jürgen
Published: February 2023

Free-space optical components and systems can be fabricated using planar techniques such as pattern generation using an electron-beam writer, photolithography, reactive ion etching and thin film deposition. This allows to integrate several optical components such as lenses and beamsplitters on one side of a single substrate [1]; see Fig. 1. The substrate material can be quartz glass or silicon, for example. The light propagates inside the substrate (or alternatively between two reflective substrates) along a zigzag path, thereby hitting the components (see figure below). Using this approach, it is possible to build optical imaging systems for two-dimensional inputs and outputs. Fig. 2 shows an experimental result for an integrated 4-f imaging system.
Systematic Approach to Axial Gradient Lens Design
Authors: Wang David Y. H. , Moore Duncan T.
Published: February 2023

Unlike conventional lens design, a comparatively limited accumulation of prior works exist for gradient-index (GRIN) lens design. Presently, the best GRIN solution is often discovered only after the lens designer replaces each and every homogeneous element in the optical system with GRIN elements, and in turn evaluates each configuration. Since it is considerably more time consuming to raytrace a GRIN optical system, the total design time could be reduced if the lens designer ia able to locate suitable starting GRIN solutions without resorting entirely to the trial and error method. Based on the simplified third order GRIN aberration formulas recently proposed by the authors [1], this paper introduces a systematic approach with specific design rules for locating potential axial GRIN lens solutions that reduce a given third order aberration, when they are added to an existing homogeneous lens system.
Thermal Compensation of Infrared Achromatic Objectives with Three Optical Materials
Authors: Rayces Juan L. , Lebich Lan
Published: February 2023

It is well-known that pairs of glasses (or other optical materials) for the design of thermally compensated achromatic objectives can be selected from a "γV-vs-V" plot: V is the Abbe number and γ is the thermal glass constant. Each point on the plot represents a particular glass. If the slope of a line defined by a pair of points is equal to the coefficient of thermal expansion (CTE) of the metal structure that supports the focal surface, then the image of a distant point remains sharply in focus through a homogeneous change in temperature.
Towards Global Optimization with Adaptive Simulated Annealing
Authors: Forbes Greg , Jones Andrew
Published: February 2023

The problem of global optimization is generally intractable. Of course, the lack of a guarantee that the global minimum can be found need not proscribe a search — in many practical problems, it is not unreasonable to expect to find some good local minima. Most optimization algorithms used for lens design simply seek a local minimum in the neighbourhood of some specified starting point by continuing downhill until some flat terrain is found. In essence, the tough component of this stage in the design problem becomes finding a good starting point for such a blinkered algorithm to polish up. With the continuing, remarkable advances in computer power, a more ambitious, automated search of the configuration space is becoming a realistic option.
Nonlinearity and Lens Design
Authors: Tatian Berge
Published: February 2023

The core of the problem of lens design as a mathematical discipline is that of numerical optimization with the major difficulty being the basic nonlinearity of the variables used. The struggle with this nonlinearity can be divided into two parts. One is the part played by the designer, such as in choosing a favorable starting point, and generally acting in the role of what may be best described as the parent of a talented but unruly child, the child being the automatic part of the design team. This talk will be mainly concerned with the latter, namely the algorithmic procedure used in the design process, which is the second part of the two referred to above. Almost from the beginning of computerized lens design, the procedure of choice has been some variant of Newton’s method iteration, and progress has consisted mainly of refinements to this basic procedure, the most important being the addition of the ridge-regression procedure, otherwise known as damping, to cope with the ill-conditioning which is also a characteristic of this problem. One should also mention here that a large factor in the progress being made is due to the vastly improved hardware that keeps becoming available.
Computing Illumination Bundle Focusing by Lens Systems
Authors: Forkner John F.
Published: February 2023

Lens systems for electro-optical applications are often required to focus bundles of illumination, or energy, rather than form images as in traditional optical design. The standard procedures for analizing and designing image-forming optics are not well adapted to tracing illumination bundles through systems, and can even lead to false results. In a previous paper1 the author showed that the Gaussian beam propagation equations can be modified to compute illumination bundle profiles throughout an optical system, even in the case of large incoherent bundles. Computing illumination distributions was called energy raytracing to differentiate from image raytracing. An unusual consequence of these equations is that an energy waist placed at one focal length from a lens is also imaged at one focal length on the opposite side rather than at infinity as for a point source.
Using Hybrid Refractive-Diffractive Elements in Infra-Red Petzval Objectives
Authors: Wood A. P.
Published: February 2023

Optical elements in which the power is shared appropriately between a refractive and a diffractive component offer several significant advantages over conventional lenses. For example, these hybrid lenses can be used in place of the usual achromatic doublet, offering a similar level of performance with approximately half the quantity of material [1]. Such elements are particualrly attractive in infra-red systems where the material forms a significant proportion of overall cost, and mass is often a crucial consideration. Moreover, it is possible to manufacture structures which exhibit useful diffraction efficiencies at infra-red frequencies [2-4]. The paper discusses the design of infra-red systems which include hybrid components in the form of singlet lenses with a blazed zone plate on one surface.
Design Selection using Neural Networks
Authors: Weller Scott W.
Published: February 2023

Neural Networks are not programmed - they are trained. While not appropriate for numeric applications, neural networks perform well in domains rife with "fuzzy knowledge", that is, knowledge not easily encapsulated.
Design of Array Systems Using Shared Symmetry
Authors: Miao C. H.
Published: February 2023

The design of multiple aperture array systems intended to cover a relatively wide field of view requires the appropriate combination of individual telescopes feeding a central collecting telescope system. In addition, specific aberration correction and scaling relations between the individual telescopes and the collecting telescope must be maintained. Of necessity there are at lease two optical axes that must be considered in such designs, with rotated symmetries dependent upon the position of each telescope in the array, practical systems should contain a minimum number of components in order to maintain high transmission, leading to the desirable sharing of components between the symmetries of the telescopes and such array designs, and examines the implications of adding aspheric correctors attached to the collector symmetry to the individual components of the telescope array. Two design approaches, one using collecting Mersenne telescopes and a second using four mirror telescopes are compared, the effect of changing primary mirror relative aperture and system length upon the symmetry and order of aberrations arising from the use of eccentric aspheric is explained, and some of the subtle limitations of correcting techniques applicable to adding decentered aspheric to optical design programs as special surfaces are discussed.
Concentric and confocal systems for adaptation as spectrographs
Authors: Mertz Lawrence N.
Published: February 2023

Two sufficient conditions for good unit-magnification imagery are that the optical system be concentric and retroreflecting. These conditions are satisfied by both the Dyson1 and the Offner2 systems. Schmidt corrector plates as shown in figure 1 are seen to extend the field as we note that the Offner system is a Schmidt telescope with image and pupil planes interchanged. Moving the corrector’s neutral zone outward leads to whispering gallery systems as shown in figure 2, where again the Schmidt plates can widen the annular field. In analogy with the successful inclusion of a diffraction grating in the Dyson system3, it is speculated that holographic gratings could also be used on the mirrors marked G in the systems of figure 2 to obtain stigmatic flat field spectrogaphs. Figure 3 shows a folded version of figure 2A. Figure 4 shows how to evolve an ellipsoidal confocal aplanatic system to a Czerny-Turner system along the style of an Offner spectrograph.
Photochemical and thermal effects in the UV laser ablation of low-density materials
Authors: Hargis P. J.
Published: February 2023

The recent development of techniques to fabricate microcellular polystyrene1 and TPX2 foams with densities between 0.01 and 0.20 g/cm3 has led to the investigation of their use in applications as diverse as artificial skin and blood vessels, inertial-confinement fusion targets, laboratory x-ray laser media, filters, catalytic substrates, and model porous media. The successful development of many of these applications requires machined shapes with features comparable to the 1 -20-μm cell size of the foam. Results that we have obtained on the interaction of 248- and 266-nm laser radiation with these new low-density materials show that ultraviolet laser ablation is an attractive technique for obtaining the required feature sizes. The morphology and chemical composition of the ablated surface are determined by the incident lase fluence and by the ultraviolet absorption spectrum of the foam. Photochemical and thermal effects were apparent in SEM, ESCA, laser Raman, and RBS measurements as well as in time-resolved optical emission spectra of the plume above the ablated surface. The results we have obtained on the ablation properties of well-characterized polystyrene and TPX foams can be directly applied to the biological materials they simulate.
High-resolution IR spectroscopy of ethylene dimers
Authors: Watts R. O. , Baldwin K. G. H.
Published: February 2023

A differentially pumped free-jet expansion, together with a waveguide CO2 laser, has been used to measure the infrared predissociation spectrum of ethylene clusters near 950 cm-1. The CO2 laser has a pressure broadened tuning range of 240 MHz. We observe sharp transitions in association with many of the laser lines which activate the monomer C2H2 molecules in their v7 mode. By varying the concentration of C2H4 in a carrier gas, by changing the carrier gas, and by using both bolometric and mass spectrometric detection systems, we are able to confirm the findings of Snels et al.1 that there is fine structure in the ethylene dimer predissociation spectrum near 950 cm-1. The linewidths of all the observed features lie in the 15-20-MHz range, giving a lower limit on the pre-dissociation lifetime of ~ 10ns.
Quasiperiodic and chaotic motions in intense field multiphoton processes
Authors: Chu Shih-I
Published: February 2023

The question of the behavior of quantum systems in time-dependent fields whose classical counterparts exhibit chaotic behavior is addressed. For any nondissipative bounded quantum system under the influence of polychromatic (i.e., quasiperiodic) fields, it is proved by means of the many-mode Floquet theory1 that the autocorrelation function will recur infinitely often in the course of time, indicating no strict quantum stochasticity is possible.2 In particular, for an N-level quantum system undergoing multiphoton transitions, its dynamic behavior is described by the quasiperiodic motion of an (N2 – 1)-dimensional coherence vector S in accord with the SU(N) dynamic symmetries. On the other hand, for any dissipative quantum system, SU(N) symmetries are broken, and chaotic behavior is observed as the coherence vector Sevolves from an initially (N2 – 1)-dimensional space to a lower-dimensional space. The recurrence and chaotic phenomena are illustrated for two- and three-level quantum systems driven by intense bichromatic laser fields.2
Laser-pumped laser experiments with single crystal Na3Ga2Li3F12:Cr
Authors: Caird J. A. , Staver P. R. , Shinn M. D.
Published: February 2023

A crystal of Na3Li3Ga2F12:Cr 4.5-mm thick was pumped with a krypton-ion laser operating at 647 nm. The sample was pumped longitudinally in a nearly concentric cavity and exhibited free lasing at 791 nm. With a birefringent element in the cavity, the material tuned continuously from 741 to 841 nm. A slope efficiency of 14.5% was measured with 4.5% output coupling. Experiments using a modified Findlay-Clay1 technique indicated relatively low resonator loss levels of the order of 0.5% for wavelengths ranging from 780 to 820 nm. However, the measured gain was several times smaller than might be expected. At 790 nm the measured round-trip resonator gain per unit absorbed pump power was 3.5% W-1. This was nearly a factor of 3 lower than the gain estimated using the cross section for stimulated emission based on the (assumed) purely radiative room temperature fluorescence lifetime of 330 μs. Possible causes for the gain reduction include nonradiative losses and excited state absorption.
Efficient harmonic generation of CO2 laser radiation in thallium arsenic selenide
Authors: Feldman B. J. , Zielke D. , Auyeung R.
Published: February 2023

The material TAS is a ternary chalcogenide salt with space group symmetry R3m, transparent between 1.3 and 17μm. Its large nonlinear optic coefficient and high damage threshold make TAS a promising candidate for nonlinear frequency conversion processes throughout the infrared.1 Recently, large, good quality crystals of TAS have been grown, cut, polished, and coated for CO2 laser second harmonic conversion by Westinghouse Research Laboratory. At NRL, a 2.5-cm diam 6-cm long crystal was pumped by a Lumonics 822 H P CO2 laser operating on the 9-μm P(20) transition with energy of 350 mJ in a 100 ns FWHM pulse. In type I doubling conditions, we have observed up to 25% total energy conversion to the second harmonic at 1 J/cm2 with no apparent crystal damage. Additionally, in a second similar TAS crystal we have observed both type I and type II sum frequency generation to the third harmonic with an overall total energy conversion of 1.5%. Progress toward a TAS-based OPO in the 8-12-μm range is also reported. (12min)
Remeasurement of the Rydberg constant by a crossed-beam laser
Authors: Zhao Ping , Lichten W. L. , Layer H. P. , Bergquist J. C.
Published: February 2023

We report a remeasurement of the Rydberg constant, to a precision better than one part in 109, via a single photon determination of the Balmer-α wavelength in both hydrogen and deuterium. The new value reflects the redefinition of the meter, a reexamination of corrections and improvements of the experimental apparatus. These changes include a National Bureau of Standards laser (3He-20Ne, 127l2), which is accurate to 1.6 parts in 1010, an improved dye laser, flatter mirrors, elimination of nonlinearities in pressure scanning, digital recording, a longer etalon (100 cm), and a reexamination of systematic effects and corrections. The result for the Rydberg constant is R = 109 737.315 68(8) cm, where c = 299 792 458 m/s by definition. This result is not in significant disagreement with the preceding measurement by Amin et al.1 but significantly disagrees with the measurement by Hildum et al.2 Another experiment to measure the Balmer-β transition is now under way. We report the progress of this experiment.
Applications of ultraviolet resonance Raman spectroscopy in molecular spectroscopy
Authors: Kelly P. B. , Li Shijian , Chadwick Richard , Strahan Gary , Hudson Bruce
Published: February 2023

Raman spectra obtained in conditions of resonance with electronic excitations are often dominated by transitions that are very weak in the normal off-resonance spectrum. These enhanced bands can be used to determine the symmetry of the resonant excited electronic state if this state gives rise to a forbidden transition. In this case the most strongly enhanced bands correspond to binary combinations and overtones of the vibronic promoting modes active in the transition. The use of this method to determine the symmetry of excited states of butadiene and benzene is presented.1,2 The most strongly enhanced vibrations associated with resonance with allowed electronic transitions are those that have large projections along the geometry change associated with excitation. Recent results for a series of substituted ethylene species are presented. Resonance with excitations that have both allowed and induced vibronic character gives rise to characteristic fundamental transitions of the promoting modes. The case of substituted benzene molecules is discussed.
Techniques for far-ultraviolet resonance Raman spectroscopy
Authors: Kelly Peter B. , Hudson Bruce
Published: February 2023

Resonance Raman spectroscopy performed in the 150-300-nm spectral region provides several unique opportunities in molecular spectroscopy and biophysics.1,2 The performance of such experiments in the far-UV region requires optimization of laser technology, nonlinear optical devices, collection efficiency, spectral dispersion, and detection. The construction of a UV resonance Raman spectrometer designed to operate to 150 nm is described. This spectrometer is based on a Q-switched Nd:YAG laser, harmonic generating crystals, and stimulated Raman scattering in hydrogen gas. Reflective optics with backscattering collection are used to focus the Raman scattered light onto the slits of a nitrogen or helium filled vacuum monochromator. The detector is a solar blind photomultiplier with a MgF2 window. The performance of this spectrometer is described.
Charge transfer in helium in a laser field: effect of rotation on the plane of polarization
Authors: Ganguly Susmita , Dastidar K. Rai , Dastidar T. K. Rai
Published: February 2023

In our earlier studies1,2 of laser-assisted He+ −He charge transfer collision, we chose the laser light to be linearly polarized along the beam trajectory. In this work we demonstrate the effect of varying the angle β between the beam trajectory and the polarization vector. As in Ref. 2, we consider the multiple-photon exchange with the laser field (typical bandwidth ~1 Å) until saturation. Typical results for charge transfer probability (P
s
) after saturation are shown at two different β, together with P0, the field-free values. A significant dephasing occurs in the P
s
curve as the angle β is changed from 0° to 45°. The consequent change in cross section relative to the field-free case drops from −34% to ≲ 1%.
Picosecond reorientational dynamics in polymer solutions
Authors: Quitevis E. L. , Casey K. G. , Sinor T. W.
Published: February 2023

The reorientational dynamics of two oxazine dyes, cresyl violet and oxazine 1, have been studied in dilute and semidilute solutions of poly(ethylene oxide) in methanol. The approach to this study is to use a synchronously pumped dye laser to do picosecond visible pump-probe measurements of transient absorption recovery.
Role of the temporal, spectral shape, detuning, dispersion, and diffraction on the self-induced-transparency phenomenon and in the concomitant different-wavelength coherent pulse copropagation in a three-level system
Authors: Mattar F. P. , Robinson E. J. , Delettrez J. , Babuel-Peyrissac J. P. , Bardin C.
Published: February 2023

The transition probabilities are calculated for 2-and 3-level atoms in an optically thick medium. The analysis is carried out in the frequency instead of the temporal domain. The response depends on whether the pulse shape is conserved when transformed into the momentum space. The propagation effects have been treated by McCall et al.1 and by Konopnicki et al.
2
in the plane-wave regime and were extended to include diffraction.3
Application of semiconductor diode lasers to probe photodissociation dynamics
Authors: Haugen H. K. , Hess W. P. , Leone S. R.
Published: February 2023

In the present study on the photodissociation of alkyl iodides, we utilize a recently developed technique1 of laser gain-vs-absorption spectroscopy to obtain accurate quantum yields. The laser gain-vs-absorption approach, which is a two-laser pulse-and-probe technique, obtains quantum yields from a single time-resolved transient. The initial population inversion following photolysis and the total absorption after complete quenching of the excited state species are measured on a short (~10-μs) time scale. Due to the nature of the internal normalization of the measurement, most experimental parameters cancel, and very accurate results can be obtained. In this work, gain-vs-absorption measurements are per formed with a room temperature InGaAsP diode probe laser. Quantum yields determined at 266 nm for n-C3F7I, i-C3F7I, and CH3I are 102 ± 4%, 102 ± 7%, and 73 ± 4%, respectively. The results are in good agreement with the majority of earlier works, except for recent photoacoustic measurements which gave much lower values.2
Velocity modulation IR laser spectroscopy of simple anions and cations
Authors: Saykally Richard J.
Published: February 2023

Velocity modulation infrared laser spectroscopy is used to measure gas phase vibration spectra of simple cations (HCO+, HNN+,

NH

4
+

, H3O+, H2F+, CF+, CCl+, H3CO+, HCS+) and anions (OH−,

NH

2
−

) using color center and diode lasers.1–3 From these spectra, accurate structures and potential function data are obtained on these molecules.
Effects of fluctuating laser fields and saturation on CARS spectra
Authors: Farrow Roger L.
Published: February 2023

Experiments have demonstrated that non-Gaussian fluctuation statistics of the electric field within a laser pulse can affect the spectral shapes and intensities of CARS measurements.1 These effects, attributed to the statistical properties of the second harmonic field of the particular Nd:YAG laser used, can influence diagnostic measurements analyzed from the data. A qualitative model that treats the second harmonic field as the square of a Gaussian field will be compared to observations. (This non-Gaussian model is equivalent to assuming a Gaussian output field from the Nd:YAG laser that is frequency doubled with low conversion efficiency.2) Despite the simplicity of the approach, the calculations exhibit all the non-Gaussian effects observed in the experiments.
Fluctuation-induced resonances
Authors: Prior Yehiam , Stern Peter
Published: February 2023

Recently1 a detailed analysis was given for the role played by laser phase fluctuations in NL optics. In that work, the existence of new extra resonances induced by stochastic fluctuations was predicted, based on a derivation starting from the phase diffusion model. In this work we present the results of numerical simulations of laser phase fluctuations. The optical Bloch equations are solved numerically for a phase fluctuating laser. A model of a piecewise constant phase jumping at random between all values is treated, and other models are discussed. Molecular collisions are simulated and compared to phase fluctuations. The collisions give rise to the pressure-induced extra resonance (PIER4), while the phase jumps give rise to stochastic fluctuations-induced extra resonance (SFIER). These simulations show clearly that phase fluctuations may be analogous to real collisions and may cause extra resonances, and indeed, the SFIER4 resonance has recently been observed experimentally.2