20 kaSTRACT (Continue on reverie aide II neceaaary and Identify by block number) Coherent optical adaptive«techniques (COAX), have been studied by by analysis, and by computer simulation. The experiments have utiliz experiment, ized a 21channel, visible-wavelength, multidither COAT system, while the computer simulations have dealt with both multidither (outgoing-wave) and phase-conjugate (return-wave) systems. Thermal blooming and turbulence distortions and complextarget effects (speckle-modulations) have been studied. This report summarizes N DD,^N RM 73l473 EDITION OF 1 NOV 65 IS OBSOLETE UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE fWien D«(« Entered) n '} y^y^V) i jn UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGECWion Data Eniarad) X-A: 20. Abstract (continued) $ the status of the 21-channel DARPA/RADC, visible-wavelength, multidither COAT experimental model and associated hardware and its use in the experimental measurements on this contract» .^ompj^r simulation studies of propagation distortion compensation and complex taft^t (speckle) effects are also described RecommenjiatiQas-,ACejnade for future work. ecommenjiaüQas ■MExperimenta Experimental observations with the 21-channel COAT system show that blooming distortions occurring in the first 30% of the focused propagation path can be compensated, leading to roughly a factor of 1.5 increase in peak focused-beam \vKKtf]gnff»,_) Depending on the experimental geometry, however, correction factors /from 1.0 to 4.0 have been observed. Both experimental and computer simulation results have shown that turbulence compensation performance is not degraded by the presence of thermal blooming, even though little blooming compensation may occur. Experimentally, the addition of tracking and focus controls to 18-channe planar-array, COAT phase control had no effect for blooming distortions, but produced some correction for an artificially-generated turbulence alone. The 18-channel phase controls could remove essentially 100,. of the turbulence distortions in most cases where there was no significant wavefront tilt error. omputer simulation of phase-coi,jugate (return-wave) COAT systems has shown almost no blooming compensation. \ In addition, there is some evidence that a return-wave COAT system may redupe the focal-plane irradiance if the blooming distortions become too stronj Experimental measurements of COAT operation with equal transmitter and receiver apertures and semidiffuse, extended-glint scotchlight surfaces have failed to produce any degradation in tht system convergence level, eve^ though significant spurious modulations within the dither band were observed in the COAT receiver.BfExperimental and computer simulation results have shown, however that it is possible to reduce the COAT system convergence level if spurious, multiplicative receiver noise signals are strong enough. Such signals can be produced in a COAT^receiver when the speckle pattern return (the target Signatur^) moves by the COAT receiver. A simple analytical model has been developed tha...

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The kinetics oflaser and furnace-induced solid phase epitaxial crystallization of As-impla~ted amorphous layers (-0.16,um) on Si (100) substrates was studied using a time-resolved optIcal reflectivity technique. Epitaxial rates from 10-10 to 0.2 cm/sec were measured over a temperature range from 750 to 1550 OK at two different As concentrations, -2 X 101~ cm -3 and -4 X 10 19 cm -3. Temperatures achieved during cw-Iaser heating were calculated usmg ~ threedimensional steady-state thermal analysis. The crystal growth rates are accurately descnbed by the Arrhenius equation v = voe -Ea 1kT , with Ea dependent on the dopant c~ncentratio.n! E = 2.62 and 2.52 eV for the lower and the higher concentrations, respectively. AddItIonally, the rate measurements at high temperatures imply that the melt temperature of amorphous Si is greater than 1550 oK.

justified as long as the Larmor frequency (and the rf field frequency) is small compared to the gap.To summarize, we have shown that a transverse rf field will induce transitions between the modes of a collective-mode multiplet in 3 He-£ and that these transitions will lead to modifications in the zero-sound propagation which can be in some cases very important. We believe that this kind of experiment should provide a very powerful tool in the detailed study of the collective modes, and therefore in the knowledge of the Cooper pair structure in 3 He-B.Finally, we note that, in order to exhibit the simplest physical picture, we have deliberately omitted some complicating features. First the equations 11 ruling the coupling between zero sound and the squashing mode are actually more complicated than Eq. (7). We have also neglected the dispersion of the various modes of a multiplet which gives rise to an additional splitting at q * 0. This will in general produce unequal spacing between the levels. In some cases this will be negligible (high static magnetic field, strong damping). But this problem can also be overcome by the use of two (or more) radio-frequency fields. There is also the possibility of exciting more than one mode by the sound wave and conversely of detecting the rf-excited mode by its associated sound wave. In all these cases we expect quantitative changes, but the basic phys-PACS numbers: 64.70.Dv, 61.40.Df It has recently been suggested 1 * 2 that the melting temperature of amorphous silicon is considerably lower than that of the crystalline material. On the basis of the assumptions that the free energy of the amorphous state is higher than that of the crystal near the melting point and that there is a first-order transition between the amorphous and ical picture should remain the same.We are very grateful to W. P. Halperin for inspiring discussions and thank E. Varoquaux for useful information.

Direct measurement of solid phase epitaxial crystallization during cw laser annealing of ion-implanted silicon is reported. The measurement technique utilizes optical interference effects between reflected light from the sample surface and from the epitaxial growth plane to time-resolve the growth process with high spatial resolution. Laser-induced solid phase epitaxial growth was monitored for two values of incident laser power; corresponding epitaxial growth rates and calculated surface temperatures are given.