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A continuously tunable far-IR Raman laser has been used to measure the responsivity and the spectral response of uncoated LiTaO(3) pyroelectric detectors between 230 and 530 microm. A striking feature of the spectral response curves is a periodic sequence of maxima and minima, with a modulation factor of >/=75%. Calculations based on the theory of an absorbing Fabry-Perot etalon indicate that these variations correspond to interference fringes produced by multiple reflections at the surfaces of the LiTaO(3) crystal.

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Abstract.-The formation and propagation of laser supported detonation (LSD) waves and thermal coupling for HF laser irradiated solid targets have been investigated as a function of target material, irradiance and ambient pressure. High speed photography has been employed to study the plasma dynamics and the thresholds for plasmotron and LSD wave production obtained. For the 300nsec duration CFWHM) pulses and l-2mm diameter focal spots used, the LSD thresholds for aluminium, stainless steel and platinum targets were measured to be 0,(2-3) x 10 8 W.cm -2 . Above the LSD threshold the initial expansion velocity showed good agreement with the I 1 ' 3 irradiance dependence predicted by theory. Additional data on the interaction for platinum were obtained using thermocouples to measure the thermal coupling to the target as a function of spot size, irradiance and ambient pressure. A maximum thermal coupling coefficient of 14-18% was measured at an irradiance level slightly below the LSD wave ignition threshold.

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