bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear waves guided by non-Kerrlike media
Authors: Stegeman George I. , Ariyasu J. , Seaton C. T. , Moloney J. V.
Published: February 2023

Both the effective index and field distributions become power-dependent when waves are guided by a thin film bounded on one or both sides by media with an intensity-dependent refractive index.1,2 Novel applications to all-optical devices3 have been predicted including upper and lower threshold devices3 and waveguides with multiple power-dependent branches between which switching can occur. These were based on solutions to the nonlinear wave equation for Kerrlike nonlinearities.
Integrated optical couplers with circular waveguides
Authors: Schlaak H. F. , Brandenburg A. , Sulz G.
Published: February 2023

Integrated optical directional couplers with parallel waveguides1 have large device lengths due to the guide separation regions. Curved/straight waveguide transitions cause excess loss. In this paper we present passive couplers with circular waveguides. We investigate the following structures shown in Fig. 1: an asymmetric coupler consisting of a curved and a straight guide (a); a symmetric coupler with two oppositely curved guides (b) with the coupling distance d0 (center to center) at z = 0. In contrast to parallel guides the phase fronts of both guides are tilted with respect to each other. Thus mode coupling occurs along curved phase planes with the effective distance d(z).2
Unstable resonator semiconductor laser array
Authors: Salzman Joseph , Yariv Amnion
Published: February 2023

Laser cavities of the unstable resonator (UR) type have the potential for increasing the mode volume of a laser oscillator while maintaining high discrimination between transverse modes.1 This property makes UR geometries very attractive for semiconductor lasers since it allows an increase in the lateral dimension of the laser while maintaining single-lateral-mode operation and eliminating filamentation.
Nonblocking 4 × 4 switch array with sixteen X-switches in Ti:LiNbO3
Authors: Neyer A. , Mevenkamp W. , Kretzschmann B.
Published: February 2023

Integrated optical switch arrays in Ti:LiNbO3 are promising devices for broadband signal switching especially for optical video-network systems. The most studied electrooptic switch applied in switch arrays is the directional coupler.1 To eliminate the bends and, therefore, the bending losses, in directional coupler-type networks, we have developed the X-switch by letting straight waveguides intersect.2 Further advantages of X-switch-type networks are the greater packing density3 and the easier tuning of the switches, since instead of a reverse delta beta electrode configuration a simple two-electrode configuration is used.
Strictly nonblocking 8 × 8 integratedoptic switch matrix in Ti:LiNbO3
Authors: Granestrand P. , Thylen L. , Stoltz B. , Bergvall K. , Doldissen W. , Heidrich H. , Hoffmann D.
Published: February 2023

Optical switch matrices are important devices in communication systems due to their frequency and code transparency. Several such matrices have been demonstrated, most of them, however, exhibiting different levels of blocking. For many systems applications a strictly nonblocking matrix (i.e., one where established signal paths do not need rearrangement when a connection between unoccupied ports is established) is preferable. The busbar structure, shown in an 8 × 8 version in Fig. 1, fulfills this requirement. Any of the eight upper (lower) inputs can reach any of the eight upper (lower) outputs by switching the appropriate cross-point.
Self-alignment technique for fiber attachment to guided wave devices
Authors: Murphy Edmond J. , Rice Trudie C.
Published: February 2023

Before the potential for large scale use of guided wave devices can be realized, low-loss and lowcost methods for fiber attachment must be developed. Several years ago, this problem was addressed by the flip-chip approach1 in which the waveguide substrate was placed on a silicon chip and aligned to fiber holding grooves. The flip-chip method has given way in recent years to the end-face-coupled method2–4 in which an array of fibers in a silicon chip is butt-joined to the guided wave device. This latter method has been demonstrated for large arrays with excess losses approaching the theoretical minimum.2 Unfortunately, this method requires the time-consuming and tedious alignment of six degrees of freedom.
Design and implementation of highspeed InGaAsP constricted-mesa lasers
Authors: Bowers J. E. , Hemenway B. R. , Bridges T. J. , Burkhardt E. G. , Wilt D. P.
Published: February 2023

High-speed semiconductor lasers are of interest for high-bit-rate digital and analog communication systems. We have investigated theoretically and experimentally the effects of parasitics, cavity length, transverse structure, temperature, and duty cycle on the bandwidth of InGaAsP lasers. As a result of this investigation, we have increased the bandwidth of cw semiconductor lasers from the 8–15-GHz range1–4 to a record cw bandwidth of 26.5 GHz in a constricted-mesa laser at −60°C.
Frequency chirping of external modulation and its reduction
Authors: Koyama F. , Iga K.
Published: February 2023

Dynamic frequency shift or frequency chirping limits the transmission bandwidth of a single-mode fiber system, even if we employ a directly modulated dynamic-single-mode (DSM) laser.1 An external modulation technique is considered for the purpose of eliminating this problem, and some high-speed optical modulators such as those using an enhanced electroabsorption in a quantum well are being studied.2 However, possible phase modulation followed by external intensity modulation must be investigated to discuss no chirping modulation.
Optimization of electric field profiles in semiconductor electrooptic devices
Authors: Ritchie S. , Adams M. J. , Robertson M. J.
Published: February 2023

III–V semiconductors allow considerable flexibility in the design of electrooptic waveguide devices because of the ability to control the profiles of optical and applied electric fields independently. Doping variations, including p – n junctions, are used to control the profile of the electric field, while changes in composition are used to provide the appropriate refractive-index profiles that determine the optical mode shape and position. A figure of merit for many electrooptic devices is the change in propagation constant with voltage (δ/β/V). For a slab waveguide δ/β/V = F × G with where ψ(x) is the optical field, and E(x) is the applied electric field. F can be considered as an overlap factor and is independent of wavelength and material properties.
Narrowband InGaAsP/InP Waveguide Grating-Folded Directional Coupler Multiplexer/Demultiplexer
Authors: Alferness R. C. , Buhl L. L. , Martyak M. J. R. , Divino M. D. , Joyner C. H. , Dentai A. G.
Published: February 2023

Narrowband (<10Å) optical multiplexer/demultiplexers are important components for densely spaced wavelength division multiplexed systems. Waveguide grating reflectors provide an excellent basis for such devices.1,2 This contradirectional interaction provides narrowband response even for relatively short interaction lengths (< 1 mm). However, the wavelength dependent Bragg reflection within a waveguide is, by itself, not sufficient to act as a multiplexer/demultiplexer component. Spatial, not just directional, separation, of the filtered light is also required. Two techniques to efficiently provide such spatial separation in grating-based devices have been suggested. One approach, which employs a grating to achieve phase matched contradirectional coupling between mismatched waveguides has been achieved, with relatively low efficiency, in fiber couplers3 and with vertical couplers based on ARROW waveguides.4 Another possibility, well-known in the microwave domain, combines the bandpass reflectors on both output arms of a broadband 3 dB splitter.5,6 Here we report the first demonstration of this optical waveguide grating-folded coupler to achieve narrowband, spatially isolated wavelength demultiplexing. This approach has the advantage of not placing severe demands upon either the waveguides or grating.
Electro-refraction in Semiconductor Waveguide Structures
Authors: Steijn K.W. , Leavitt R.P. , Little J.W.
Published: February 2023

A variety of mechanisms in semiconductor systems may contribute to the development of an electro-optic effect in waveguide structures,1 including the bulk linear electro-optic effect, free-carrier effects, and band-edge effects. The inclusion of quantum wells in the active region may also introduce contributions via the quantum-confined Stark effect2 (QCSE) and a new effect recently predicted3 in a system of asymmetric coupled quantum wells. In this paper, we report the investigation of these mechanisms in GaAs-GaAIAs single-mode planar waveguides in the low-loss region below the bandgap.
Analysis of Intersecting Waveguides: Novel Physical Effects Explained and Explored
Authors: McCaughan L.
Published: February 2023

We have developed a theoretical approach, more rigorous than the two-mode dispersion approach currently used, to describe the interaction between single-mode intersecting optical waveguides.1 Each waveguide is considered to be an extended scattering element for the light in the other guide. Unlike parallel waveguide geometries, the coupling between guided and radiation modes (as well as guided-guide mode coupling) must also be considered. Also in contrast to parallel waveguides, the initial and final optical states (i.e., z = ± ∞) are unambiguously defined for direct comparison to experiment.
New Formulations of the Beam Propagation Method: Application to Rib Waveguides
Authors: Yevick David , Hermansson Björn
Published: February 2023

In this presentation, we demonstrate that the beam propagation method (BPM) may be successfully applied to both the calculation of the modal electric field distributions and propagation constants associated with strongly guided structures such as rib waveguides and the analysis of electric field propagation in longitudinally varying rib waveguide structures. We further present several modifications of the method which reduce processing time to acceptable levels.
All-optical Switching and Codirectional Mode Conversion in Nonlinear Gratings
Authors: Trillo S. , Wabnitz S.
Published: February 2023

Coherent interaction of guided modes in materials exhibiting an intensity dependent refractive index offers the potential for power or phase controlled all-optical switching. During the last few years a relative large number of such nonlinear devices have been proposed and implemented. Promising switching schemes may utilize nonlinear directional couplers1, polarization conversion (arising from spatial instability) in fibers2, distributed feedback gratings3, soliton switches4, etc...
A New Technique for Analysing Planar Optical Waveguides
Authors: Kendall P.O. , Adams M.J. , McIlroy P. , Ritchie S. , Robertson M.J.
Published: February 2023

The increasing use of optical techniques for telecommunications, sensing and signal processing has generated much interest in the analysis of electro-magnetic radiation in open dielectric waveguide structures. Many opto-e1ectronic devices are planar, with rectangular refractive index distributions produced by the deposition of successive layers of different composition. The analysis of light propagation in such structures is much harder than, for example, optical fibres because of the lack of symmetry, the rectangular profiles and, in some cases, the large changes in refractive index.
1.5μm Tunable Wavelength Filter with Wide Tuning Range and High Constant Gain Using Phase Controllable DFB LD
Authors: Numai T. , Murata S. , Mito I.
Published: February 2023

A tunable wavelength filter with constant transmissivity (gain) and bandwidth is a key device for wavelength division multiplexing networks. Such a filter has recently been demonstrated with a multi-electrode DFB LD[1]. This filter is biased at just below the threshold current in operation. It has two current injection sections, and the transmission wavelength and gain are controlled by changing the two currents. Since each current causes simultaneous change of the wavelength and the gain, it is difficult to obtain a large transmission wavelength tuning range maintainig a large gain. Thus, tuning range has been restricted to 20.6GHz. We demonstrate here a wide range tunable wavelength filter which uses a phase controllable distributed feedback laser diode(PC DFB LD). We call this filter a PC DFB LD filter. In this filter, the gain and the wavelength are controlled almost separately. Therefore, tuning range as wide as 43GHz has been achieved. This wavelength tuning range is the widest of any semiconductor tunable wavelength filter, to our knowledge. In the wavelength tuning operation, 27dB gain and 5GHz bandwidth have been maintained.
Reduced-Confinement GaAlAs Tapered Waveguide Antenna
Authors: Bossi D. E. , Goodhue W. D. , Redikert R. H.
Published: February 2023

We describe the fabrication and operation of a novel GaAlAs "tapered" waveguide antenna for use at GaAs laser wavelengths (λo=0.86 μm). This antenna is tapered in the sense that the confinement of the guided mode is reduced near the sample endface both by physically reducing the waveguide dimension and, more importantly, by reducing the refractive index difference between the waveguide film and cladding along the length of the guide. In preliminary measurements this antenna is shown to produce a ~60% increase in the near-field effective mode width at the cleaved endface of a single-mode GaAlAs slab waveguide, resulting in a ~40% reduction in the far-field output beam divergence.
Properties of Focusing Grating Coupler Fabricated by Electron-Beam Lithography
Authors: Hori Yoshikazu , Sogawa Fumihiro , Yamamoto Hiroaki , Serizawa Hiroyuki
Published: February 2023

Focusing grating coupler (FGC), which has a function of coupling the planer guided wave and the spherical free space wave, will play a key role in optical integrated circuit devices. FGC is realized by forming a specific grating corrugation with chirp and bend structure on a waveguide. For fabricating FGC corrugation, either holographic exposure method(1) or electron beam lithography(2) have been employed. Since exactly tuneed wavelength laser source and non-spherical wave-front adjuster are required depending on the guided wave parameters, an aberration free FGC is difficult to achieve by holographic techniques. Computer-controlled electron beam writing technique seems to be more promising, because the appropriate electron-beam trace on the substrate is basically achievable for each waveguide by adjusting the writing guided wave parameters such as refractive index of the waveguide and the wavelength of light source. In fact, FGC (1x1mm2, f=2mm) with spot size of 1.3 times of the diffraction limited one has been realized by T. Suhara et. al.(2)
An Optical Modulator/Switch Using The Reflection From A Translated Depletion Edge
Authors: Huang T.C. , Lee K.W. , Hausken T. , Dagli N. , Coldren L.A. , Myers D.
Published: February 2023

Optical modulators/switches with high speeds, high extinction ratios and small device sizes are fundamentally important in optical communications and optical signal processing systems[1],[2]. In recent years, people have made switches by using free carrier injection[3],[4]. Unfortunately, using forward biased carrier injection the switch speed is limited since the carrier lifetime is long, and the current spreading will smear the index change to give a poor reflection. In order to overcome these problems, it is necessary to pursue some new kinds of switches. Some work has been presented that shows switching operation in a reverse biased GalnAsP/InP multiple quantum well optical switch which has a p-n junction in the intersection region by a regrowth technique[5]. In this paper we propose an optical modulator/switch which uses the concept of reflection from a depletion edge that can be translated across the waveguide. We also describe initial calculated and experimental results.
High Speed Optical Analogue to Digital Convertors using GaAs/AlGaAs Waveguide Technology
Authors: Walker R. G. , Carter A. C.
Published: February 2023

With the advent of the MOVRE and MBE epitaxial growth techniques for III-V semiconductors it has become possible to grow large areas of material of ever improving quality. This has stimulated considerable interest in the use of such materials for guided-wave optical devices over recent years, with the prospect of monolithic integration with lasers, detectors and electronics (ie. integrated optoelectronics).
Low-Loss Near Adiabatic Single-Mode Passive Waveguide Tapers
Authors: Zhenguang H. , Srivastava R. , Ramaswamy R. V.
Published: February 2023

In integrated optical devices, the constituent waveguides invariably undergo bends and curvature, causing excess radiation losses. To utilize the maximum "real estate", the packing density of the components on a single substrate can be increased by decreasing the bending radii. This will increase the bending losses substantially if the mode size is not decreased. On the other hand, efficient fiber-guide coupling requires mode sizes In the range of 7-10μm for 1.3μm operating wavelength. The solution lies in tapered structures [1] Although fiber compatible waveguides in BK7 with fiber-guide thruput losses below 1 dB in a 20 mm long device have been reported[2] by K+ - Na+ ion exchange, the maximum index change is limited to 0.009[3] which does not permit small mode sizes at 1.3μm wavelength. Therefore the K+ - Na+ exchange does not allow fabrication of useful tapers. Recently Mahapatra and Connors[4] reported thermal tapering of Ag+ - Na+ exchanged channel guides in soda-lime glass where a total thruput loss of 2.2 dB in a 7mm long device was achieved at a wavelength of 0.8μm with an excess loss of 0.4 dB in the 3 mm taper. This large excess loss appears to be caused by the nonadiabatic transition and the large thruput loss appears to be associated with the high silver concentration in the glass.
An Interdigitated M-S-M Waveguide Photodetector
Authors: Soole J.B.D. , Schumacher H. , Esagui R. , Koza M.A. , Bhat R.
Published: February 2023

Waveguide-integrated photodetectors provide the natural detection scheme following the on-chip processing of optical signals in semiconductor guides because they eliminate problems of alignment and the consequent tolerances and constraints on packaging. Both "end-fire" 1,2 and "leaky" 3-5 waveguide/detector configurations have been proposed and demonstrated. In the first, light is directed straight into the detector from the end of the guide, and in the second the optical field of the propagating mode leaks into the detector absorption region which lies adjacent to the guide. While end-fire structures have the potential for the ultimate highest speeds, they require regrowth of either the guide or detector which therefore lengthens and complicates the fabrication process. By contrast, "leaky" detectors may be formed from the same grown layer as the guide by sequential etching.
Determination of the Extent of Reaction in Proton-Exchanged Lithium Niobate Optical Waveguides
Authors: Loni A. , De La Rue R.M. , Foad M.A. , Winfield J.M.
Published: February 2023

Proton-exchange is a relatively low temperature process for fabricating optical waveguides in LiNbO3(1) and, only recently, has been shown to produce low loss waveguiding material with a restored electrooptic effect(2,3). The technique involves(4,5) an ion exchange reaction between Li+ in the substrate and H+ from an acidic source, most commonly benzoic acid, resulting in the formation of Li(1−x)HxNbO3.
Diffractive Doublet Corrected On-axis at Two Wavelengths
Authors: Farn Michael W. , Goodman Joseph W.
Published: February 2023

Due to the wave nature of diffraction, purely diffractive systems have been plagued by large chromatic and off-axis aberrations. Accordingly, there has not been much work in purely diffractive wideband imaging systems. In this paper, we present a method for the design and subsequent optimization of diffractive doublets for wideband, on-axis imaging. The method can most easily be explained with reference to Kato’s recent work[1], although the present work was arrived at independently.
The Calculation of Wave Aberrations in Optical Systems with Holographic Optical Elements
Authors: Yanrong Yuan
Published: February 2023

This paper presents a ray-tracing method for calculating the wave aberrations of an optical system including ordinary optical elements and holographic optical elements.
Examples of the Topographies of the Wavefront Variance Merit Function at Different Aberration Orders
Authors: Johnston Steve C.
Published: February 2023

The study of the behavior of wavefront aberration coefficients with respect to optical system parameters has long been successfully employed to gain insight into the properties of optical systems. However, for many optical systems it is more appropriate to examine the wavefront aberrations collectively rather than individually.
Binary Optics in Lens Design
Authors: Kathman A. D. , Pitalo S. K.
Published: February 2023

Properly applying binary optical elements (BOEs) in a lens system requires that the designer fully understand the features and limitations of these devices. Already in existence are a number of conventional lens designs which have been refitted with BOEs to achieve reduced number of elements, reduced weight, or greatly improved performance.[1,2] To illustrate the use of diffractive elements in an imaging system, a classic Schmidt camera is fitted with a binary optic correction plate. Use of this well-known design should serve to highlight features of the BOE and suggest future applications for this technology.
Tissue diagnostics using laser-induced fluorescence techniques
Authors: Andersson S. , Montan S. , Svanberg S. , Ankerst J. , Kjellen E. , Svanberg K.
Published: February 2023

The fluorescence emission from tissue subject to UV light excitation can be utilized for diagnostic purposes. The discrimination between tumors and normal tissue is of particular interest. The natural tissue fluorescence can be used but improved results are obtained using the agent hematoporphyrin derivative that is selectively retained in tumors. We have used laser-induced fluorescence for point measurements1 as well as for multicolor imaging2 of different kinds of rat tissue. For optimized characterization it is important to utilize the full spectral information and to form dimensionless contrast functions of measured spectral intensities. The importance of selecting the proper excitation wavelength is emphasized. The development of clinical instrumentation for point measurements and imaging is discussed.
Experimental determination of the spin-rotation coupling in Na-Xe molecules
Authors: Hou M. , Feng B. , Zhang J. , She Y. , Mi Z. , CHEN T.
Published: February 2023

A theory for calculating the spin–rotation coupling coefficient in alkali-metal–noble-gas van der Waals molecules was recently presented.1 It assumes the spin–rotation interaction in alkali-metal–noble-gas molecules to be mainly due to the spin–orbit interaction of the alkali-metal valence electron within the core of the noble gas, and predicts that the spin–rotation constant γ should depend on the spin–orbit interaction in the noble gas and be almost independent of the spin–orbit interaction of the alkali-metal atom. Experimentally, only a few of the possible pairs of the different alkali-metal atoms with different noble-gas atoms have been investigated. By measuring the sodium spin relaxation rate as a function of the helium buffer-gas pressure and the width of the sodium magnetic slowing-down curve, we report in this paper our experimentally determined value of the spin–rotation interaction constant in Na–Xe molecules γ = (1.1 ± 0.3)MHz. The measured value is nearly the same as was measured in K–Xe, Rb–Xe, and Cs–Xe.1 This result shows a reasonable agreement with the theoretical prediction.
Fine structure of the second harmonic time-resolved spectrum in laser plasmas
Authors: Gu Min , Tan Weihan , Lin Zunqi , Bi Wuji , Yu Wenyan , Deng Ximing
Published: February 2023

The time-resolved and integrated spectra of the backscattering second harmonic emission were presented in previous papers.1,2 Reported here are the time-resolved spectrum of both high temporal resolution (~10 ps) and spectral resolution (~6 Å) 2ω0 harmonic taken at 90° to the laser axis. It has been found that the intensity of the primary and the secondary peaks of the second harmonic emission is not a continuous distribution but composed of many fine and bright fringes with the interval ~1.5–3 Å in relation to atomic weight. On the basis of this observation we considered theoretically the influence of the standing electromagnetic wave and the ponderomotive force on the plasma dispersion relation and gave a unified description of the ion-acoustic frequency ω
i
, for the linear conversion and the parametric decay. The results we obtained are basically consistent with the experiments. Another important point is that the second harmonic emission for P polarization lasts for a longer time than that for S polarization, which means that a certain threshold exists to produce the linear conversion by the laser self-focusing filamentation.
Spectroscopic investigation of ag-metal clusters
Authors: Froben F. W. , Moller K. , Schulze W. , Winter B.
Published: February 2023

The investigation of silver clusters prepared by the gas-aggregation technique or laser vaporization using mass and fluorescence spectroscopy provides some new information about the influence of the experimental parameters for the cluster size distribution.1 The observation of time-resolved emission spectra in the case of laser vaporization allows us to distinguish between different size species. This, together with mass spectroscopy and fluorescence spectroscopy, using the gas aggregation technique is useful for better understanding of how the cluster grows dynamics. The questions of fragmentation, double ionization, and Coulomb explosion are discussed as well as the influence of charged particles for the resulting size distribution. In addition to the investigations on naked metal clusters some results on molecules adsorbed on clusters are reported.2
Steady-state light pulses in stimulated backward scattering
Authors: Ghosh Roy D. N. , Rao D. V. G. L. N.
Published: February 2023

Characteristics of backward, stimulated light pulses are analyzed in the limit where rate equation approximation breaks down, and fluctuation dynamics (oscillator displacements for Raman and phonon amplitudes for Brillouin) must beconsidered. In this limit, the scattered photon flux N
s
is N
s
= a(dN
l
/dt), (d/dt + γ
f
)A
f
= bN
l
/Af,(d/dt + γ
l
) = dN
l
/Af, where f,/referto fluctuations and pump, respectively; A
f
the fluctuation intensity, and constants a, b, and d depend on the medium characteristics. An analytical solution to this set of equations has been given by Maier et al.1 in the limit γ
f
→0 and γ
l
= 0. With these restrictions removed, analytical solution is difficult. Here, we are considering an analytical solution by reducing the set of equations to that of the cubic Schrodinger equation with real amplitude and by using Backlund transform. Preliminary calculations show that the solitary wave solutions are possible (a purely soliton solution is not admissible2 in the form of hyperbolic secant square).
Morphology-dependent resonances associated with stimulated processes in microspheres
Authors: Hill Steven C. , Benner Robert E.
Published: February 2023

The density of morphology dependent resonances (MDRs) of microspheres is much larger than the density observed in typical resonance spectra. It is large enough to be consistent with observations1 of multiorder Stokes emission in the stimulated Raman scattering from microspheres. The question of whether MDRs having extremely large cavity Q (> 1010 if the spheres are lossless) contribute to the optical feedback in real spheres is discussed. Only the low-order very narrow linewidth MDRs have angle-averaged intensities that are consistent with photographs2 of the light emission from lasing spheres. Although the integrated area under the scattered field coefficients tends to zero as the cavity Q increases, the area under the internal field coefficients (which are proportional to the intensities of stimulated processes) gradually increases as the cavity Q increases. Hence it would appear that the very high Q MDRs provide the optical feedback for stimulated processes in microspheres. When a sphere is illuminated with a high intensity laser beam a nonuniform refractive index may be induced which may so perturb or couple the low-order MDRs that it may not be appropriate to ascribe the optical feedback to the MDRs of homogeneous spheres.
Near-field light scattering by parallel glass fibers
Authors: Benincasa D. S. , Tsuei T.-G. , Barber Peter W.
Published: February 2023

Single glass fibers whose diameter-to-wavelength ratio is large, for example, d/λ = 50, strongly focus normally incident laser light to give greatly enhanced intensities both within and in the near field of the fiber, even when the fiber is not at resonance. Calculated results show the dependence of the enhancement on the diameter-to-wavelength ratio and on the fiber index of refraction. Measured results confirm the calculated spatial distribution of the intensity. Even greater enhancements are observed for spherical particles. The near-field intensity for a single fiber is greatly modified when a second fiber is moved into its near field. Calculations of the near-field intensities for two coupled fibers have been made using the addition theorem and the iterative approach of Olaofe.1 The results provide insight into the coupling mechanism, especially the dependence of the coupling on the fiber separation and on the orientation of the two fibers relative to the incident wave. Measured results for a glass fiber in front of a mirror confirm the major features of the calculated results.
Prevention of sideband-induced detrapping in tapered-undulator free-electron lasers
Authors: Quimby David C.
Published: February 2023

The sideband instability of free-electron laser (FEL) oscillators has recently been observed1 in the Los Alamos experiments. This result underscores the expected need for sideband suppression in tapered-undulator oscillators. While the instability is predicted to actually enhance the power output of untapered systems, it is a possible threat to the potential high extraction of tapered systems. Simulations2 predict that the instability will lead to detrapping in FELs with relatively long, highly tapered undulators in which trapped electrons undergo multiple synchrotron oscillations while traversing the undulator. Sideband growth is associated with loss of extraction by one-half or more. Means for sideband suppression using multilayer dielectric mirror coatings are investigated. The objective is to identify filter functions which give adequate sideband suppression. It is found that the introduction of wavelength selectivity can suppress the instability, with recovery of full extraction.
Secondary Color Correction with a Three-Parameter Index Model Incorporated in a Lens Design Program
Authors: Burke Elliot
Published: February 2023

A method is presented to optimize glass for correction of chromatic aberration in lens design. The dispersion uses nd, νd, Pg,F as coefficients. Accuracy of the is demonstrated to be adequate for moderate focal length lenses. Design strategies are discussed.
Extensions of the Linear Model for Tolerance Computation
Authors: Crawford Charles
Published: February 2023

In order to estimate the effect of manufacturing errors on image quality we construct a mathematical/statistical model for MTF-based aberrations. This model uses data from an optical design program to predict the changes in aberrations, such as the decreased MTF at best focus, the shift of focus, etc., caused by manufacturing errors such as tilt or decentration of elements and groups. The model can be used to predict the yield, that is, the expected number of manufactured samples for which the quality measures fall within acceptable limits. Starting with tolerances and estimates of the fraction of samples for which the tolerances are satisfied, the model will predict the fraction of samples for which a particular quality measure will fall within given limits.
Ultrahigh Performance Close-Focusing Large-Ratio Zoom Lens for the Visible Waveband
Authors: Neil Iain A. , Kreitzer Mel
Published: February 2023

The specification, design and fabrication of a close focusing, large ratio, visible zoom lens which rivals the performance of fixed focal length lenses is described.
Computed and Measured Illumination Beam-Waist Phenomena
Authors: Forkner John F. , Rykowski Ron
Published: February 2023

Computer generated beam maps are shown for three applications having very different physical dimensions. The large scale application is a theater spotlight. At an intermediate scale, beam maps used to study the transmission characteristics of a fiber coupling optical system are also shown. At the smallest scale, the waist map and beam cross-sections are shown for a study of the depth-of-focus characteristics around the image of a fiber-optic imaging bundle.
Optical Design of i-Line Stepper for Microlithography
Authors: Lin Dajian , Lee Zhan , Zhou Chongxi
Published: February 2023

Double telecentric configuration of an optical projection lens with alignment through lens wafer-to-reticle and uniform illumination pinciple of optical system for micro­lithography are discribed in the paper. To meet requirement of optical transfer function (OTF) for i-line lithography, the relation between photolithographic resolution (R) and numerical aperture (NA) is discussed. As an example, we have designed a new double telecentric projection lens with NA=0.42, magnification M=-l/5, image field size 15mmx15mm (21.2mm diametre) and conjugate distance 602mm.

Optical design program ZEMAX-XE is used to calculate image qualities of the i-line lens. The calculating results indicate wavefront aberrations < λ/4 and MTF >0.55 across the entire field when spatial frequency is 715 c/mn and wavelength is 365+/-3mn. This means the photolithographic resolution of 0.7um could be realized. The illumination uniformizer called the integrator consists of an array of 81 small square lens elements. The illumination non-uniformity of+/-2% could be realized by using our simulation program OPTENG to calculate light intensity distribution on tire illuminated image plane.
Optical Design and Implementation of A Multi-functional Miniature Interferometer
Authors: Lee C.K. , Wu Giin-Yuan , Wu Wen-Jong , Lee Chin-Fa , Lin Chan-Ching , Lin Yen-Jen
Published: February 2023

With the ever more stringent demands of today’s ultra-high performance machinery such as optical/magnetic disk drives, digital video disk drives, etc., metrology tools that can meet a significant portion of these high performance devices are increasing in demand. The high accuracy and wide bandwidth characteristics of an interferometer make it a natural choice to meet such needs. However, it has been identified that a new breed of interferometer must be developed before interferometers can be adopted to measure ultra-high precision high-performance machinery with ease. The ideal features identified include: (1) no special treatments to measurement surfaces required, (2) absolute/differential vibration detection possible, (3) ability to accommodate samples with significantly different reflectivity, (4) nanometer resolutions, and (5) mega-hertz bandwidth[1].
Aberration correction and desensitization of an inverse triplet objective lens
Authors: Betensky Ellis
Published: February 2023

Many objective lenses designed for very high volume production now typically contain aspherical surfaces. One such example is an aspherized version of the traditional Cooke triplet. While these aspherical designs are better than their antecedents, the basic design limitations, astigmatism and manufacturing sensitivities, remain. An inverse triplet having a negative, positive, negative configuration and aspherical surfaces has no all-spherical counterpart, but instead depends on the aspheres to correct the primary aberrations. If a sufficient number of surfaces are aspherical, there are more degrees of freedom than required for aberration correction, so the lens can be optimized to reduce the manufacturing sensitivities by reducing the amount of aberration correction contribution by an individual element.
Evolution of ring field systems in microlithography
Authors: Williamson David M.
Published: February 2023

"No sooner than we achieve a goal, we move the goalposts to create a new, more difficult one"1 Offner’s ring-field all-reflecting triplet was the first successful projection system used in microlithography. It evolved over several generations, increasing NA and field size, reducing the feature sizes printed from 3 down to 1 micron. Because of its relative simplicity it became the dominant optical design used in microlithography until the early 1980’s, when the demise of optical lithography was predicted.
Integrated Optical Polarizer
Authors: Mahlein H.F.
Published: February 2023

In the following a polarizer will be described whose dielectric multilayer is not incorporated as a discontinuity in the planar waveguide as in /1/ but is deposited as a superstrate. A polarizer in the form of a dielectric multilayer and a glass plate (refractive index nG) is deposited as a superstrate on a planar waveguide (refractive index nF, film thickness tF) which is deposited in turn on a substrate (refractive index nS) (Fig. 1). The sides of the polarizer are normal to the direction of propagation. The dielectric multilayer has a periodic structure with a basic period composed of two layers with different refractive indices (refractive indices nH and nL, thicknesses tH and tL). If the refractive indices are suitably chosen the multilayer will transform the waveguide into a leaky waveguide. The light which is consequently coupled into the dielectric multilayer will be very diversely affected at the interfaces between the layers of the multilayer as a function of the direction of polarization due to the satisfaction of the Brewster-angle condition and to interference effects. In consequence, TM modes will be transmitted and refracted out through the glass plate at the side, whereas TE modes will be reflected back into the waveguide. Thus TE modes will be dominant in the light which continues to propagate behind the polarizer. The advantages of this polarizer are that it can be deposited at practically any point of an integrated optical system, that the desired modes are not attenuated by absorption and that no birefringent materials are used.
Stripe Waveguides and Coupling Modulators of Lithium Niobate-Tantalate*
Authors: Phillips W. , Hammer J. M.
Published: February 2023

One of the most interesting and useful features of metal-diffused wave guides is the relative ease with which three-dimensional waveguide structures can be fabricated by forming patterns on the metal before diffusion. We have used this feature to construct lithium niobate-tantalate stripe guide directional couplers and have made preliminary observations of electro-optic coupling modulators employing this configuration.
Junction Lasers Prepared By Molecular Beam Epitaxy Operating Continuously (CW) At A Temperature As High As 100°C
Authors: Cho A. Y. , Dixon R. W. , Casey H. C. , Hartman R. L.
Published: February 2023

Within the last year, the study of epitaxial growth of GaAs-AlxGa1-xAs heterostructures by molecular beam epitaxy (MBE) provided a dramatic improvement in the performance of the lasers. This work included an effort to understand MBE doping profiles resulting from various dopants,1 an investigation of photoluminescence of MBE layers doped with different dopants,2 and the effect on luminescent intensities for GaAs layers grown on MBE AlxGaq1-xAs layers. It was concluded that MBE Sn-doped GaAs layers grown on AlxGa1-xAs layers have photoluminescent efficiencies equal to or slightly greater than those grown by the liquid-phase epitaxial (LPE) method, while the p-type MBE layers are more than an order of magnitude less than for LPE layers. In GaAs-AlxGa1-xAs double-heterostructure (DH) lasers, the active layer can be either p-or n-type because the excess carriers required for the recombination may be obtained by injection from either heterojunction. Therefore Sn-doped n-type active layers were used for the MBE DH lasers.
Terminal Equipment for Optical Fiber Lines
Authors: Goell J. E.
Published: February 2023

The terminal equipment that will be used in early transmission systems employing optical fiber lines will be similar to terminal equipment now used in transmission systems employing electrical lines, except for transducers at the line - terminal interfaces. Functions such as amplification and regeneration will be achieved by conventional electronic means. This paper describes the configuration and projected performance of terminals that are expected to be used in early optical fiber transmission systems.
GaAs Double Heterostructure Lasers Fabricated by Wet Chemical Etching
Authors: Merz J. L. , Logan R. A.
Published: February 2023

In the search for an efficient optical source compatible with the monolithic fabrication of integrated optical devices, much attention has been given to the use of gratings to produce the required feedback, instead of the cleaved edges of the discrete double heterostructure (DH) laser, Recently, Hurwitz et al.(1) reported on an alternative approch, utilizing etched mirrors to provide feedback; output from the Fabry-Perot resonator was coupled directly into a thick (12μm) waveguide. We have examined numerous masking and etching procedures and crystal orientations to produce laser mirrors by wet chemical etching. In these experiments, the devices were evaluated by measuring the output radiation from the etched mirrors directly into air; differential quantum efficiencies (ηd) as high as 18% have been achieved (ηd ≃ 10% is routine) as well as room temperature threshold current densities (Jt) as low as 4.2 kA/cm2. This represents a significant improvement over earlier published results.(1)
Differential speckle interferometry : test on atmospheric dispersion*
Authors: Aime C. , Kadiri S. , Martin F. , Petrov R. , Ricort G.
Published: February 2023

J.M.Beckers1 has suggested a new technique, called "differential speckle interferometry" which consists by measuring the angular displacement between two sets of speckles corresponding to micro-displacements of features in an astronomical object. This method has a wide range of astronomical applications such as stellar rotation and spectroscopic binaries. We report here the first results of an experiment which consist by letting the atmospheric dispersion produce an angular micro-displacement between two sets of speckles and measure it by means of a cross-spectrum analysis2.
Image Reconstruction from Speckle Interferograms, Speckle Spectroscopy and the Deconvolution of Space Telescope Data
Authors: Weigelt Gerd
Published: February 2023

The turbulent atmosphere of the earth restricts the resolution of large ground-based telescopes to about 1 arc second. Much higher resolution can be obtained by various speckle methods 1-11. These methods yield exactly diffraction-limited resolution, for example 0.03 arc second in the case of a 3.6m telescope and for λ = 500nm. Many of these speckle methods can also be used to improve the resolution of large space telescopes if the resolution is limited by telescope aberrations. In the following text three examples of high-resolution speckle imaging are shown.
Sensor-Array Image-Plane Processing for Improved Information Efficiency
Authors: Samms R. W. , Fales C. L. , Huck F. O. , Park S. K.
Published: February 2023

Because the spatial response of optical apertures can never be negative, the associated spatial frequency response decreases gradually with frequency, generally without a finite cut-off (except for lens diffraction). These responses tend to blur small spatial detail and insufficiently bandlimit the radiance field prior to sampling by sensor-array mechanisms.1,2 Some of these limitations of optical apertures can be overcome with image-plane processing, as suggested by Fig. 1. In this paper we assess the spatial responses that can be shaped by using image-plane signal processing for high-pass filtering, and lens diffraction, lens transmittance shading, and defocus blur for low-pass filtering. The signal processing electronics permit the spatial response of the imaging system to be adjusted either by a human operator, or as it is in human vision, by the intensity of the radiance field. The advantages of image-plane processing over conventional image data acquisition and subsequent digital processing are improved spatial response for edge enhancement, increased dynamic range, and reduced data transmission.
Forward-stimulated Brillouin scattering at 514.5 nm in dual-mode single-core fiber
Authors: Culverhouse D. , Russell P. St. J. , Farahi F.
Published: February 2023

There has been a recent growth of interest in dual-moded (DM) optical fibers for a variety of nonlinear switching and modulation schemes.1-3We report here what we believe to be the first observation of forward-stimulated Brillouin scatter (FSBS) between the LP01and LP11modes of a dual-mode (DM) fiber. Unlike normal SBS, forwhich the threshold power depends inversely on the laser linewidth, FSBS is easily observable with multimode light. This is because the pump (L) and Brillouin (B) waves propagate along exactly the same optical path and hence can maintain mutual coherence over kilometer lengths of fiber. Conservation of momentum in both cases is given bykL01= kB11+K(Ω) andkL11= kB01−K(Ω), wherekLij= ωnij/c, kBij=(ω−Ω)nij/c, andK(Ω) = Ω/|va| = 2π/Λ, wherevaand Λ are the acoustic phase velocity and wavelength; the other parameters have their usual meanings. In FSBS the direction of the phonon wave depends on whether the frequency downconversion is LP01→ LP11or vice versa (Fig. 1). In the DM fiber used, conventional SBS at 5145 nm yielded a shift of 32.4 GHz, which, because Λ = 0.176μm gives a phonon velocityva= 5702 m/s, in close agreement withvext= 5760 for silica. An Ar+laser running single-mode at 5145 nm was used to deliver light to 500 m of DM fiber (Fig. 2). To verify true single-frequency operation, part of the laser output was split off and monitored directly at a photodiode and confocal Fabry-Perot. A shutter system allowed for independent monitoring of the light emerging from the fiber. After careful adjustment of the launching conditions, the frequency spectrum in Fig. 3 was obtained at the photodiode. A clear frequency component is apparent at 16.6 MHz; no such signal was present in the laser output. In FSBS intermodal beating excites a flexural wave with A equal to the beat periodLb, which couples the LP01and LP11modes by microbending. For our fiber parameters,Lb= 0.17 mm at 5145 m/s. At Ω/2π= 16.6 MHz, a fiber diameterd= 125μm and a shear velocityvt=3764 m/s, Ωd/4πvt=0.274, corresponding4to a flexural wave velocityvaf≈ 0.5vext= 2880 m/s. The product ofLband Ω/2πgives an independent estimate ofvaf= 2822 m/s; the excellent agreement confirms that FSBS is taking place. For single-frequency excitation, the Brillouin gains are of the same order for SBS5and FSBS; the ~105× smaller modal overlap in FSBS is compensated for by an ~105× smaller spontaneous acoustic absorption per acoustic wave length. The measured thresholds were ~45 mW/μm2for SBS and ~5 mW/μm2for FSBS.
Modeling of directional-coupler wavelength demultiplexers in graded-index waveguides using normal modes
Authors: Cheng Hsing C. , Ramaswamy Ramu V. , Srivastava Ramakant
Published: February 2023

The guided-wave wavelength-division demultiplexers have potential applications in optical communication systems and sensors. They have been realized by using grating,1directional coupler (DC),2resonator,3or Y-junction devices.4In this paper we report the modeling of a DC for dual-wavelength demultiplexing in graded-index ion-exchanged channel waveguides in glass using normal-mode analysis.