Experimental results will be shown in which an external acoustic-optic modulator is used with a high power single frequency cw argon laser operated at 488 nm and 514.5 nm to produce 150 - 300 MHz tunability on a 1.6 GHz carrier signal. Amplitude modulation with a visibility of 1 is demonstrated at 3.4 W488 nm and 5 W514 nm. Each of these wavelengths is tunable over 150 MHz or 300 MHz depending on the transducer. The crystal in each case is TeO₂. At least 95% of the available laser power is modulated with a contrast of 100%, having a single-sideband power of -12 dBm with no measurable harmonics to less than -60 dBm. Thermal tests are discussed in which theory is compared to experimental data to investigate damage mechanisms. Two AOMs were tested until damage occurred at powers in excess of 6 Watts. Interferograms and sheargrams were used to measure phase changes as a function of heat load. Finally, a beam combining method will be explained in which recombined first and zero order beams from a single AOM are phased together to produce two collinear beams with output modulated power equal to the input power, except for small losses due to absorption.

The MBI develops a facility at BESSY II dedicated to pump- probe techniques combining synchrotron and laser radiation. The synchronization of laser and synchrotron pulses will allow time resolved experiments on the picosecond time scale at this. The features of the facility, the optical parameters of the synchrotron beamline, the synchronization technique and pulse stretching considerations will be outlined. Current developments will be reported.

One possibility for communicating from an airplane above water surface to submarinein sea involves the use of laser-generated sound. In previous work, optical breakdown laser-acoustic pulses in fresh water have been studied and in intense sound source has been excited. In this paper, five kinds of salt water having salinities 1.3%, 2.6%, 3.9%, 5.2% and 6.5% (max salinity of seawater near 4.0%), have been broken down to generate underwater acoustic pulse signals by Q-switched YAG- Nd laser with different pulse energies. After detail analyzing both in time domain and frequency domain, the fact that the salinity of water does not have much influence on laser- acoustic pulse signal would be found. Also, some slight but interesting differences due to different salinity are introduced.

One possibility for communicating from an airplane above water surface to submarine in sea involves the use of laser- generated sound. In this paper, we introduce the way to generate strong optical breakdown acoustic signal in a limited large volume of water but enough to do basic work in air- submarine communication realm. The optical breakdown mechanism of strong Nd:YAG laser pulse with water generates acoustic signals in water having pulse widths about 25 microseconds and a frequency spectrum peak about 58 kHz. And, its sound source level (SSL) of 196 dB for low frequencies less than 58 kHz is sufficient to be detected at far distant deep in water. This makes a stride for pursuing the feasibility of laser-acoust air-submarine communication.

Acousto-optic devices (AOD) which are intended for information transmission may be described by such parameter as information losses. This parameter determines the difference between information quantities in the input and output of the device. In order to estimate information losses in any AOD beforehand, it is necessary to find the sources of these losses in different links of the signal transmission and transformation in AOD. The comparison of AOD of different kinds have been performed from the point of view of information transmission possibilities. It has been found that the main sources of information losses are connected with the noise and limited information transmission possibilities of the devices. Proceeding from this conclusion, the basic ways to avoid the information losses in AOD have been listed.

Abstract not available.

A large amount of data are usually transmitted, stored and processed by big digital systems in satellite remote sensing applications. To alleviate this situation, an on-board data processing system can be of significant help if it allows only the useful information data be transmitted to the ground station. To this end, a new architecture of a LiNbO₃ integrated optic pre-processor is proposed in this paper. Its operation is based on the holographic substraction between two incident waves and depends on the relative phase shift. In such a way on-board identification and classification of data are allowed. The proposed device is formed by channel-planar composite waveguides to increase the number of parallel channels. Channel waveguides, which can be excited through a microlens array, allow to obtain the best performance of the electro-optic modulators, each of them is placed on a single channel waveguide, in terms of low losses and high modulation efficiency.

Miniaturized ring laser-based gyroscopes show some significant advantages with respect to the optical fiber gyros such as higher reliability, reduced volume and weight. A semiconductor ring laser has been designed with the potential to be fully integrated in a single chip. This device is formed by a circular strip-loaded waveguide having a width of 2 micrometer and diameter of 3 mm. Its configuration is a heterostructure with separate confinement with a single quantum well in GaAs/AlGaAs, emitting at 860 nm. We have determined the following performance: (1) free spectral range: 7.4 GHz; (2) longitudinal spacing between the spectral lines: 0.18 angstrom; (3) merit factor Q: 510000; (4) finesse: 10.9; (5) resonator efficiency: 70%, when interaction length is greater or equal than 450 micrometer; (6) total efficiency: 7.5%; (7) threshold current: 22 mA. This device can be used in miniaturized gyroscopes which are able to detect rotation speed greater than 0.01 rad/s with a sensitivity of 0.01 degree.

Abstract not available.

Perspectives of using the acousto-optical devices for making the on-board spread spectrum signal processing fault-tolerance facilities are shown in this article. It is revealed that building the correlator for spread spectrum signal processing by using the acousto-optical elementary base raises more than in three times its fault-tolerance in contrast with the similar device realized by using LSI circuits.

A dependence processing is described in this report. In this case for optimization each component the characteristics of the other components are taken into account, that allows rationally to use all available possibilities on suppression of interference.

We present the theoretical investigation, including design criteria, of a new optical beam former for phased-array active antennas. The device is formed by a Z-cut LiNbO₃ channel- planar composite waveguide, an array of interferometric modulators and a linear microlens array. The basic element of the new architecture is the array of Mach-Zehnder Ti:liNbO₃ intensity modulators having asymmetric coplanar-strip traveling-wave electrodes in which a relatively thick SiO₂ buffer layer is utilized to reduce the phase velocity mismatch between the microwaves and optical waves. A comparison with other optical and electronic architectures already proposed shows a number of significant advantages. In particular, our device can be used in multichannel optical computing systems as well as in optical communication and RF signal processing systems allowing to overcome severe frequency limitations typical of devices reported in literature since it can work at frequencies greater than 30 GHz. So the very large transmission rate typical of the optical fiber communication systems may be conveniently exploited.

the peculiarities of collinear acousto-optical diffraction of Gaussian optical beams by an acoustic pulse of finite dimensions with an arbitrary temporal envelope is theoretically investigated. The system of two first order equations that couples the amplitudes of transmitted and diffracted light beams and of acoustic pulse which are propagating in the same direction is deduced. The filter transmission curves during the collinear diffraction by acoustic pulses with temporal envelopes described by Gaussian and sinc(x) functions were calculated. The dependence of acousto-optical cell transmission bandwidth on both pulse and crystal length variation was studied.

If an acousto-optic spectrum analyzer (AOSA) operates in a low-frequency range, the lowest frequencies of the spectrum to be analyzed may produce higher orders of diffraction. This creates the frequency bandwidth limitation of one octave for such a device. The present paper is devoted to some methods allowing to avoid this limitations. Such methods as data decoding using the inverse part of the device transmission function, higher order suppression by means of employing the Bragg cell with specific form of its frequency characteristic, and prolongation of Bragg diffraction frequency area to the lower frequencies using some peculiarities of anisotropic Bragg diffraction. Some experimental results illustrating the discussed method have been demonstrated.

A study of acousto-optic deflection addressing switch of 1 X N is reported in this paper. The switch device that we have developed consists of a pair of optical waveguide geoidesic lenses, a titled chirped electrode transducer and a Ti:LiNbO₃ waveguide on a piece of LiNbO₃ substrate in order to achieve the optical deflection addressing function. A single mode fiber and an array of single mode fiber (N) are coupled with the two endfaces of device respectively. The device is a multiplex channel switch. The device working wavelength is 1.55 micrometer. The waveguide geodesic lenses are designed by an optimum analytical method. The non- spherical concave lenses spherical aberrationless in the apertures of beam. That is fabricated in single point diamond turning method. The titled chirped electrode transducer bandwide was designed 200 MHZ. The experiment at 0.633 micrometer He-Ne light source show that the results coincide with the theoretical design. The insertion losses of the device is 8 dB about and the channel's crosstalk is better than -20 dB. Switch has a broad range of applications. Currently, the most promising applications are in the fields of lightwave communications and optical signal processing.

The Fresnel zone plate antenna is an example of an optical analogy that has been transferred to microwave/millimeter wavelength use. The latter case has seen extensive research and application, and in the past dozen years more than seventy relevant papers have been published on a worldwide basis. These studies have dealt with either lens or reflector designs, and have quantified many parameters, such as gain, antenna patterns, efficiency, bandwidth, and structural options. The most recent designs have dealt with high efficiency or dual band configurations. This report will summarize the many advances of the past few years, and will provide some parametric design tradeoffs.

The dual MMW/IR mode for the testing of the modern missile seekers is required. The dual band test system calls for a combining element that can bring both MMW and IR beams to the same seeker head. Optical Holographic technique was used to overcome the fabrication problems associated with the manufacturing of a large size (MMW/IR) beam combiner that should be transparent to MMW while reflecting IR beam. In our previous investigation we designed and produced a surface relief holographic optical element (HOE) that satisfied the beam combiner requirements. Since the uniform metal coating of any meaningful thickness would reflect most of MMW radiation the HOE was partially metalized, so that it became transparent for TM polarized MMW, while maintaining excellent reflectance of IR. To correct the losses in the TE polarized MMW, the lines were 'cut' through the metal coating in the direction perpendicular to the groove structure, creating discontinuities in the metallic coating in both directions. The minimal size of the beam combiner required to perform dual band function with the minimal MMW distortion was calculated.

A three-dimensional metallodielectric photonic crystal (MDPC) that utilizes planar metal scattering elements in a dielectric medium has been studied in the microwave regime, both experimentally and theoretically. The metal elements are circular copper patches defined on thin dielectric sheets, which are alternately stacked with thicker polyethylene sheets to form a (111)-oriented face-centered-cubic lattice. A photonic stop band has been measured from this 'flat-atom' MDPC at 8.2 GHz with a rejection level of 18 dB per lattice period and a width of 50% of the center frequency. The photonic stop band persists over a broad range of angles. Finite-Difference Time-Domain calculations show excellent agreement with measured stop band characteristics, including a similar angular dependence and insensitivity to interplane registration. Variation of the stop-band characteristics with thickness of the dielectric layers has also been explored experimentally. Flat-atom MDPC results are compared with measurements made on 'spherical-atom' MDPC structures.

This paper addresses the similarity of microwave/millimeter wave frequency selective surfaces (FSS) to optical filters. Specifically, the design approaches of the 4-band FSSs developed for NASA's CASSINI high gain antenna are described in detail. Representative RF test results are given to demonstrate the validity of these designs. These design approaches are very general and can be applied to multiband optical filters.

This paper describes the design of infrared filters using methods drawn from microwave and millimeter wave filters. Special note is made of approximations made in the infrared design, and ways to improve upon these approximations. Results from the design, manufacture and test of linear wedge filters built using microlithographic techniques and used in spectral imaging applications will be presented.

Diffractive elements have several distinct advantages over conventional refractive elements. They are lighter and more compact and can be manufactured easily and quickly. These elements are usually used as optical elements, but they can also be used in other regions of the spectrum. An example of a diffractive element which is used for millimeter waves is a grating coupler (GC), which couples a guided wave out of a waveguide into free space. In most applications, the preferred direction of the output wave is normal to the waveguide plane. Unfortunately, as the imaging properties of diffractive elements depend strongly upon the wavelength of the readout wave, it is difficult to use GCs when the input source of the system is polychromatic or when it suffers from wavelength variations. In this paper, we present a method to design a double grating coupler (DGC), which couples a polychromatic wave out of a waveguide with only negligible angular dispersion. The aim of the design is to construct two grating functions in such a way that the chromatic dispersions of the two gratings will mutually compensate each other. In order to achieve this, we use an iterative method, whereby the main ides is to design a double grating which deflects two different wavelengths, with no dispersion, resulting in negligible dispersion within the band.

It is considered and offered the waveguide band elimination filter with the working mode H₁₀ that can be used in millimeter waves devices such as up, down-converters, mixer, etc. For example, if the millimeter wave up-converter operates with two input signals which have frequencies f₁, f₂ and the output signal has frequency f₃ equals f₁ + f₂(f₂ very much less than f₁), we need in small level of the signal with the frequency f₁ at the up- converter output. The filter consist of the rectangular metallic waveguide supporting mode H₁₀ in which it is inserted the periodic dielectric structure (the Bragg structure). The structure cross-section is the same as the cross-section of the waveguide. The characteristics of the filter was calculated by using analogy in electromagnetic the waveguide propagation and optical the wave propagation in the medium with the specific refractive index vector N. This conception can be applied for party-filled waveguide in the case when the Brillouin decomposition of the waveguide waves into plane waves is correct and the transformation of the incident (propagating) mode into other the mode types is absent. In this work were calculated the spectrum energy transmittance T(f) in the filter stop band using formulae and the wavelength (lambda) $0) (or frequency f₀ equals c/(lambda) ₀, c is speed of light) in the center of this band using the characteristic equation obtained in the result of theoretical consideration. Dielectric structure of the filter is made in the form of the polystyrene plates's assemblage with the air gaps. Plates (the quantity n equals 10) have thickness t approximately equals 0.223 (lambda) ₀ and the air gaps (the quantity m equals 9) have thickness l approximately equals 0.878 (lambda) ₀. In the result of calculation we have following parameters of the filter: f₀ approximately equals 32.93 GHz, (Delta) f equals f_b2 - f_b1 approximately equals 3.13 GHz, where f_b2, f_b are frequencies at T(t) approximately equals 0.6%, f_b2 approximately equals 34.50 GHz, f_b1 approximately equals 31.37 GHz. At the frequency f_b3 approximately equals 35.2 GHz we have height transmittance T(f_b3) approximately equals 0.99. It is also shown that an increase of the distance l between dielectric plate leads to a shift of frequency f₀ to the side of low frequencies. There is an optimum distance l in which at the frequencies f less than f_b3 the filter has low transmittance and at the frequencies f greater than f_b3 the one has high transmittance. The described approach can be used for calculation and more complex multilayer the waveguide structures and can be applied at treatments different of the EHF devices.

A compact antenna test range (CATR) has a great potential for testing electrically large antennas. However, the application of conventional reflector type CATRs becomes increasingly difficult, though not impossible, above 100 GHz due to the tight surface accuracy requirements for the reflectors. A CATR based on a planar hologram has been studied to overcome the problems incurred by the use of reflectors with insufficient surface accuracy. This paper summarizes the recent results obtained for a hologram CATR at Helsinki University of Technology.

Dielectric planar waveguides have been proven to be useful for MMW devices such as fixed beam or beam-steering antennas. Previously we developed several antennas comprising planar dielectric and semiconductor waveguides. To form the beam inside the planar waveguide we used a feed based on tunnel coupling between the dielectric rod waveguide and the planar waveguide. In this paper we are presenting a simple analysis for this coupling and comparing it with the experiment.

Communication systems based on low-earth-orbit (LEO) satellites have generated a requirement for high-performance phased array antennas with exceptional gain, sidelobe levels, and axial ratio over broad scan angles and 360 degree azimuth coverage. One approach to mitigating the effects of scan dependence is to cover the planar array with a hemispherical lens, or dome, which implements passive or active phase correction of the scanned beam. The phase correction over the dome surface may be represented as the function (Delta) (Phi) ((theta) , (phi) ), with (theta) and (phi) the polar and azimuth angles in a coordinate system having z-axis normal to the array. The purpose of this study was to determine the performance improvement achievable with such an ideal lens. Three cases were considered: a conventional lens with fixed optimum phase correction, an active lens with scan-dependent phase correction a function of polar angle only, and an active lens with phase correction a function of polar and azimuthal angles. In all cases, the planar array distribution had a fixed radial Taylor amplitude distribution and a phase taper consisting of a linear beam-pointing term and a non-linear focusing term.

Electronically scanned phased array antennas have been in use for many years for such applications as search and surveillance, tracking, and remote sensing. They offer fast beam switching and multi-beam operation, but are subject to scan blindness due to the effects of mutual coupling between elements. Scan blindness is an undesirable decrease in array gain at specific frequencies and angles. The blindness comes about when the array structure is capable of supporting a forced surface wave model. A novel substrate will be investigated which may eliminate scan blindness by cutting off these surface wave modes. Researchers have been investigating the properties of a periodic dielectric structure exhibiting a photonic bandgap since 1987. This photonic bandgap structure prevents electromagnetic propagation in any direction (in two dimensions for the 2D structure). The geometries examined have been two and three-dimensionally periodic with lattice structures typically being triangular or rectangular. The investigation of the photonic bandgap structures had been confined to theory until about 1994 when researchers constructed and characterized the properties of a finite 2D structure. Recently, researchers have suggested using the photonic bandgap structure as a substrate. This paper investigates the use of a photonic bandgap substrate, PBGS, to reject the surface wave and eliminate scan blindness. To support the theory, experimental data will be presented comparing the scan performance of an array on a PBGS and an array on a conventional homogeneous substrate.

Possibilities of the first-order diffraction tomography in the case of using of millimeter electromagnetic waves for object sounding (quasioptical tomography) is studied. Experimental images obtained using antennas and waveguiding lines of different types and radiation frequency f approximately equals 33 divided by 38 GHz and f approximately equals 135 divided by 136.5 GHz are represented. Volumetric dielectric objects and plane-parallel ferrite (or dielectric) plates distributed in free space or in homogeneous dielectric medium have been taken as objects under investigation. It is shown that in the frequency band under consideration, the images of investigated objects with characteristic dimension A approximately equals 2(lambda) divided by 7(lambda) may be obtained by first-order diffraction tomography method (Born, Rytov or high frequency approximation of the first-order for scattered electromagnetic field).

In this paper we explore the ISMP (Isomorphic Singular Manifold Projection) technique's capability for classification. The ISMP decomposes an image into a surface sculpture or manifolds represented by polynomials and a texture image. A Bayesian neural network with Hybrid Monte Carlo learning is used to classify the texture image features. The preliminary results are encouraging and the ISMP is promising as a new texture classification scheme.