The performance of the Space Shuttle based Starlab experiment intended to provide an on-orbit demonstration of acquisition, tracking, and pointing dynamics is analyzed. Simulation and test methods used to generate on-orbit performance estimates are presented. The Starlab Pointing Control System is based on an advanced flight computer which intermeshes analog control loops of its mirror controlling servos. Solid state multiplying digital analog converters are used to introduce digitally derived transformation relationships to the analog channels. An end-to-end scientific simulation of the system hardware and software uses mathematical models of optical tracking, including space object imagery and the beam control mirror servos. A special test set has been developed to provide a special purpose hardware system supported by an external computer for supplying an emulated interface of the Starlab actuators, sensors, and effective geometric line of sight conditions.

A high fidelity end-to-end Starlab simulation developed for the acquisition, tracking, and pointing of a cooperative booster, called Starbird, is described. The models of the four imaging sensors, their associated scenes, and the video tracker model are considered, and simulation run results are presented. Imaging sensors modeled include a wide field of view intensified charge coupled device (ICCD) camera, a narrow field of view ICCD camera, an active ICCD camera, and an infrared camera. A composite high altitude radiation model is used to describe the Starbird imagery for each of sensor's spectral bands and pixel sizes. This imagery is rotated and translated within the sensor's field of view which uses the positions of the control mirrors and the Starbird's and Space Shuttle's trajectories. The sampled imagery is then passed to the video tracker model to calculate target position. It is concluded that this simulation is capable of generating imagery corrupted by camera noise and image centroids out of the video tracker.

An optical resonator with holes on-axis for applications in a FEL oscillator was recently proposed by Pantell et al. These authors presented an analytical approach based on approximating the field inside the resonator by a truncated expansion in Gauss-Laguerre modes. The authors performed further investigation of this configuration by using a Fox and Li type code which was recently applied to the analysis of a laser resonator with internal circular aperture. This numerical approach allows one to check the range of validity of Pantell's solutions, the parameters for which they constitute the lowest-loss mode and to map the transverse profile of the mode at different planes inside the resonator.

This paper is a review of experimental and theoretical results obtained at Kurchatov Atomic Energy Institute. The paper reviews the possibility of developing high-power laser systems on a base of coupled CO2 laser arrays.

Results are reported of a time-dependent, three-dimensional code, which models phase conjugation by stimulated Brillouin scatter (SBS). The nonlinear equations for the pump, the backscattered Stokes, and the phonon fields are transformed to remove the major effects of demagnification down to each focal region. Bradley's adaptive coordinates in this code allow efficient allocation of a three-dimensional grid for the finite Fourier transform propagation algorithms. A second-order Runge-Kutta scheme integrates the counter-propagating waves spatially and the phonon field temporally. The code models a phase conjugation assembly that consists of one or more cells of a nonlinear medium, such as 40-atmospheres xenon or liquid n-hexane, in a single focus or multifoci threshold reduction configuration. Time-delay is applied to the pump and Stokes field crossing the distance between foci. The focus-to-focus distance is close to the value corresponding to the length of the resonator that generated the longitudinal laser modes in the pump, to maintain coherence over the large distances. Multiple transverse modes, having different spatial field distributions, may also be included. With both transverse and longitudinal modes, it is shown that the conjugation fidelity can be modulated to an undesirable extent. The results include time histories of the output Stokes intensity and of the conjugation fidelity. Polarization properties of the fields are also reported for test simulations, in which an approximate quarter-wave plate lies between two such SBS cells. The implications for oscillator isolation owing to undesirable polarization rotation by optical birefringent windows (analogous to the quarter-wave plate) are discussed.

In many applications it is desirable to be able to accurately predict the SBS threshold of a given laser beam. Existing physical optics computer codes which solve the problem iteratively and include pump depletion do this routinely for one dimensional cases. However, if a high spatial resolution or a large number of cases are required this approach becomes intractable for two dimensional calculations. As an alternative approach threshold scaling can be estimated with reasonable accuracy by ignoring pump depletion and integrating the intensity weighted average gain along the propagation path. This technique has been applied to several cases of interest. For one dimensional aberrations the results compare favorably with more comprehensive BRIWON code predictions and with experimental data. The effects of both beam shape and two dimensional segmented mirror aberrations have also been evaluated. The results are in reasonable agreement with experimental data. General implications for other classes of aberration have also been assessed and are reported.

To provide high-energy, high-power beams at short wavelengths for inertial-confinement-fusion experiments the authors rountinely converted the 1.053-micrometers output of the Nova, Nd:phosphate-glass, laser system to its third-harmonic wavelength. We describe performance and conversion efficiency modeling of the 3 X 3 arrays potassium-dihydrogen-phosphate crystal plates used for type II/type II phase-matched harmonic conversion of Nova 0.74-m diameter beams, and an alternate type I/type II phase-matching configuration that improves the third-harmonic conversion efficiency. These arrays provide energy conversion of up to 65% and intensity conversion to 70%.

The authors present a numerical analysis of the transient stimulated Raman scattering (SRS) process, by which pulse-compression performances are exploited. To obtain the shortest pulses by SRS, an optimization rule exists. The calculations show that it changes as the higly transient regime is met (pump pulses as short as the vibrational relaxation time or less). The results are compared with a pulse shortening experiment, in which a SRS compressor produced few picosecond long pulses ((lambda) =0.64 and (lambda) =0.79 micrometers ) with a high shortening ratio (approximately equals 25-50). In addition, these were found to be the phase-conjugated replicas of the pump.

This paper reports the measurement of electron emission due to 2.06 micrometers Q-switched laser excitation on Cs, O2 activated GaAs photocathodes with different sensitivity. The cubic dependence on fluence is consistent with three-photon excitation across the bandgap of GaAs semiconductor. The same cubic response in photoelectron emission at liquid nitrogen temperature (77K) demonstrates that the electron emission is three-photon photoemission and thermal emission is negligible. The characteristics of multiphoton photoemission is strongly determined by the sensitivity of photocathode. A formula based on three-order perturbation theory accounts quantitatively for the authors' observation.

A substantial amount of progress has been made in the past three years in understanding the small scale physics of thermal blooming, and in particular, in understanding the interaction of thermal blooming with atmospheric turbulence. The authors present a brief review of some of the theoretical aspects of small scale thermal blooming.

The image resolution of a conventional imagaing system is limited by aberrations produced by the intervening atmosphere. Nonlinear optical techniques like real-time holography can be used in a single-pass configuration to correct for the turbulent aberrations. In this paper the authors present analytical calculations using the modulation transfer function (MTF) approach and numerical simulations using the three dimensional wave optics code GLAD-386 of the resolution characteristics of nonlinear holographic and conventional imaging systems for extended and thin aberrators. The MTF approach under predicts for conventional images and over predicts for holographic images the effect of random apodization and anisoplanatism. For strong but thin aberrators, diffraction limited resolution with a large field of view (FOV) can be obtained using a holographic imaging system.

A wave-optics model has been used to describe fast focusing phenomena by a thin or thick lens. In particular, lenses with a hyperboloidal surface profile have the best focusing property for a collimated beam and have been studied using vector field analysis. It was found that the relative focal intensity decreases substantially comparing to a thin lens when the f-number becomes small.

The interaction physics of intracavity laser heated particles has been analyzed for the case of a moderate power (20 kW), high repetition rate ($OM 12 kHz) Nd:YAG laser oscillator producing low energy ($OM 10-5 J) optical pulses at (lambda) = 1.06 (mu) . The particles considered in this work are contaminants that inadvertently become attached to intracavity optical surfaces lying within the beam line of the laser during the course of assembly and test. Computer simulations were written to describe the behavior of a variety of dielectric, refractory, and metallic particles when irradiated with small diameter ($OM 10-2 cm), high intensity (108 W/cm2) intracavity laser radiation. The simulations have shown that owing to the small laser beam diameters, contaminating intracavity particles larger than 5 (mu) can affect the dynamics of Nd:YAG laser oscillation, causing mode changes, delaying the achievement of peak laser power, and reducing performance. Significant heating of the particles may occur during the relatively short ($OM 40 ns) oscillation build-up time applicable to these laser cavities. Ablation of material, melting, and vaporization of small diameter (< 10-4 cm) particles under these intracavity laser conditions is predicted. Steady-state conditions are calculated for high repetition rate operation with the result that asymptotic particle and substrate temperatures depend upon the thermal properties of the optical substrates. Operating regimes for which laser heated particle damage does not occur were determined.

Analysis of the known laser-induced evaporation (thermodestruction) model predicts the quasiperiodic oscillation of the effective absorption depth between its normal value and some minute quantity consisting of a part of the incident wavelength. This prediction explains the experimental data on the polymer laser ablation depth as well as the reflection transient drop of the laserdestructed aluminum.

By using optical interference and shadowing methods and an optical path delay set-up, the initial process of laser-induced self-focusing in H2 is studied on one Q-switched YAG laser and a series of time-resolved Mach-Zehnder interferograms and shadows are obtained. Some phenomena during the self-focusing are observed and explained. The theoretical model of moving foci is demonstrated by the experiments discussed in this paper.

The energy coupling coefficient is first measured in a 1.06 micrometers laser pulse interaction with Al target in air by using a new method. The timing of plasma absorption processes are also recorded by the techniques of time-resolved measurement. The energy coupling coefficient is within the range of 3-7% and there is not LSD wave ignition with the incident laser intensity in the order of 107-108W/cm2.

The theory of active-passive mode-locking in solid state lasers, controlled by a passive-negative feedback loop, is presented for the case of an intracavity two-photon absorbing semiconductor plate. It is shown that the combination of a GaAs plate and a pinhole acts simultaneously as power limiter and pulse compressor, ensuring optimum operation of the intracavity saturable absorber, making possible the generation of very long, flat, and stable trains of energetic, almost bandwidth limited pulses. The most recent experimental results are also presented, showing the excellent agreement with the numerical model.

In an iodine photodissociation laser the inversion population build-up (excited iodine atoms in the 52P1/2 state) is due to photodissociation of a suitable alkyliodide (usually C3F7I) by UV light from surrounding Xe flashlamps or an open discharge. Most existing systems utilize a short (10 microsecond(s) ) pumping pulse to prevent an inwardly propagating shock wave from destroying the inversion and to quench the excited iodine minimizing the adverse effect of secondary chemical processes. This advantage is at a cost of technical inconvenience such as a high discharge voltage or a need to exchange the Xe filling of the flashlamps after a certain number of shots. An alternative way is to use a long (300 microsecond(s) ) pumping pulse from sealed lamps. The pulse is then 'soft enough' so as not to release the lethal shock wave from the wall of the laser vesel, but the pumping kinetics is fairly complex as many more chemical reactions are allowed to participate in the inversion build-up. A detailed investigation of the kinetics is the subject of this paper. Three different sets of kinetic constants were used and tested against experimental results. For that purpose the third amplifier of the system PERUN at Institute of Physics in Prague was converted to an oscillator and the measured output power was compared with the theory for some typical compositions of laser mixture. Apart from a direct assessment of the kinetic constants used in the calculations the results point out that a pyrolysis must be included with a secondary photolysis of iodine molecules by visible light. This work is designed as an end-to-end enrgy modeling of the system PERUN.

This paper discusses the diffusion coefficient of minority carriers in solid state junction lasers in the presence of a longitudinal quantizing magnetic field, i.e., III-V, II-VI and IV-VI lasers. An expression of the normalized diffusion coefficient of the minority carriers under magnetic quantization, spin, and broadening of Landau levels respectively, have been formulated without approximations of band parameters. The authors used three-band Kane model and the four-band Kane model for III-V lasers, Hopfield model for II-VI lasers, and the model of Genzow et al. for IV-VI lasers respectively. It was found, taking InSb, CdS, and PbTe junction lasers as examples of III-V, II-VI, and IV-VI lasers respectively, that the diffusion coefficient oscillates with inverse magnetic field for aforementioned lasers due to SdH effect. The diffusion coefficient continuously decreases at low temperatures with increasing values of the longitudinal magnetic field in the quantum limit. Unlike the decrease of the diffusion coefficient in a transverse magnetic field due to deflections of the minority carriers, the decrease in the longitudinal magnetic field results from the lowering of the electron quasi-Fermi level with respect to the bottom of the conduction band. The numerical magnitudes of the normalized diffusion constants are greatest for the II-VI lasers and the least for the III-V lasers. The theoretical results with experimental observations reported elsewhere. In addition, the results of wide band gap junction laser materials have been obtained as special cases of generalized formulations under certain limiting conditions.

A numerical model of Q-switched solid state laser for investigation of energetical, temporal, and spatial characteristics of laser radiation is described. The possibilities of the model are demonstrated on the concrete laser example for which the experimental results are represented.

Since the inception of the Strategic Defense Initiative (SDI) there have been a multitude of comparison studies done in an attempt to evaluate the effectiveness and relative sizes of complementary, and sometimes competitive, laser weapon systems. It became more and more apparent that what the systems analyst needed was not only a fast, but a cost effective way to perform high-level trade studies. In the present investigation, a general procedure is presented for the development of PC-based algorithmic systems models for laser systems. This procedure points out all of the major issues that should be addressed in the design and development of such a model. Issues addressed include defining the problem to be modeled, defining a strategy for development, and finally, effective use of the model once developed. Being a general procedure, it will allow a systems analyst to develop a model to meet specific needs. To illustrate this method of model development, a description of the Strategic Defense Simulation - Design To (SDS-DT) model developed and used by Science Applications International Corporation (SAIC) is presented. SDS-DT is a menu-driven, fast executing, PC-based program that can be used to either calculate performance, weight, volume, and cost values for a particular design or, alternatively, to run parametrics on particular system parameters to perhaps optimize a design.

This paper describes a wave optics end-to-end laser beam train model and applies it to an outgoing wavefront sensor (OWS) adaptive optical system. The model permits evaluation of complete beam trains by passing a complex field through each optical element as it occurs in the real beam train. The model has been used to evaluate the effects of the OWS imaging the primary mirror instead of the deformable mirror (DM). The results show that the imperfect imaging of the DM by the OWS that occurs as a result of the finite propagation distance from the DM to the OWS can influence the beam quality depending on spatial frequency content of the wavefront, propagation distance, and actuator spacing.

A computer model that simulates light propagating through an optical data storage system has been developed. This paper discusses a model of laser beam that originates at a laser diode, propagates through an optical system, interacts with an optical disk, reflects back from the optical disk into the system, and propagates to data and servo detectors.

This paper reports results of a program to integrate geometrical and physical optics. Limitations to the theory, numerical considerations, and methods of optimization are discussed and the procedures illustrated by several examples.

Experimental investigations on high power CO2-laser systems have been carried out. To ensure the processing quality and to allow a fast reaction in case of an accident, a diagnostic system was developed and realized with integrating special equipment for on-line and off-line diagnostics for laser beam, gasflow, and workpiece temperature.

Computer models have been developed for the industrial CO lasers, those are oparated by transverse dc discharge in the temperature region 1 50-200 K. The 1D (dimensional) model has been developed to analyze and predict the output performance characteristics, mainly the laser power. The flow equations are coupled with the kinetic equations of the direct excitation by electron impact in discharge, V-V (vibration to vibration) and V-R/T (vibration to rotation and translation) energy transfer by collision, and spontaneous and stimulated emission. The 2D model to analyze the spatial distribution of the gas temperature and excited molecules is now under development. The flow equations, based on the control volume method for the 2D Cartesian coordinates, are described. The time integration is performed by the SIMPLEST method.

A one-to-one correspondence between the parameter spaces of propagated top-hat (plane wave, flat top) irradiance profiles and Gaussian beams has been proposed. The diffractive 'size' of the propagated top hat is estimated by calculating that of an equivalent Gaussian beam with the same Fresnel number. Given the propagation Fresnel number, one also knows the detailed intensity and phase profiles of the propagated top hat within the Gaussian envelope; a library of plots of beam profiles is provided for both rectangular and circular top hats propagated over a large spectrum of Fresnel numbers. For Fresnel numbers less than approximately 10, the Gaussian envelope is shown to enclose roughly 90 percent of the top hat's total power. The formalism thus allows one to perform the simple matrix manipulations of Gaussian beam propagation to determine the propagated top-hat beam envelope and then use the look-up tables of beam profiles to determine the detailed intensity and phase of the plane as it propagates through a paraxial optical train. The equivalent Gaussian method allows one to include lowest order diffraction effects when designing an optical system instead of relying solely on geometrical optics. For beams that are not significantly different from top hats, one can approximate their propagated profiles by using this method with a modified wavelength, lengthened to account for non-ideal beam spreading. Examples include propagation through a focus and a one-to-one imaging system, both encountered in ring resonator designs, and design and implementation of a multiwavelength imaging laser diagnostic optical train. A final example is extension to non-orthogonal optical systems using the analysis of J. A. Arnaud to propagate the Gaussian beam.

Experimental observations of micron-sized particle removal from optical surfaces by pulsed laser irradiation are reported. The laser was a Nd:YAG device operating at 1.06 micrometers . The authors observed that absorbing particles were removed from non-absorbing surfaces, but that non-absorbing particles were not. An explanation for these observations based on forces generated by rapid thermal expansion of the particles is presented. The results are compared with those of other groups studying particle removal by laser irradiation.

A linear decrease in the 'second laser threshold' is found when two lasers are optically coupled in the bad cavity limit. The coupled lasers are modeled as on-resonance, single mode, homogeneously broadened lasers. In-phase coupling does not cause lasers operating in the good cavity limit to operate chaotically and may make such lasers more stable. The authors observed that out-of-phase coupling of lasers in the good cavity limit can lead to self-pulsing and limit cycles.

The problem of diffraction limited laser beam generation in gas flow CO2 lasers of high power turned out to be rather complicated because of a number of factors that are of physical or technical nature. The ultimate solution to the beam quality problem in these lasers would be the use of phase conjugation to compensate simultaneously for the most of laser beam distortions along the optical train of the laser. The main point, in which the situation with the development of phase conjugate mirrors for CO2 lasers differs from one for lasers of visible and near infrared regions of spectrum is that the use of four-wave mixing in a nonlinear medium is the only technique of phase conjugation available in this region of wavelengths. In this paper an attempt is made to present some results of experimental investigations of four-wave mixing phase conjugation in CO2 lasers, which have been obtained at S. I . Vavi by Opt ical Inst itute , Leningrad, USSR.

The paper reports the latest results obtained in control for temporal and spatial characteristics of laser beams using stimulated scattering and wavefront conjugation technique. The method and experimental results for precise beam positioning using intracavity spatial light modulators are described.

A diode-pumped Nd:YAG laser which is part of a laser communications system was simulated. The model covers four areas: laser gain, lifetime performance, cavity-dump design, and pulse-by-pulse operation.