The first single element 2-D acoustooptic (2DAO) laser beam deflector using a tellurium crystal was designed and fabricated for laser wavelength applications from 5 to 20 microm. The giant values of the figure of merit M associated with these two AO interactions equal to 285,000 x 10(-15) s(3)/kg, are between 2 and 3 orders of magnitude higher than germanium, the next best AO material for 10.6 microm. This latter value indicates that acoustic power densities inside the crystal of the order of 0.1 W/mm(2) are sufficient to diffract 100% of the incident light. The experimental data confirm the predicted 13 degrees /25 MHz deflection slope. The theoretical amplitude and frequency modulation characteristics of the 2DAO deflector are also evaluated.

We report the determination of the magnitude and sign of the unknown photoelastic coefficients of tellurium, p(65), p(56),and p(44), as well as all of the unknown signs of the previously determined photoelastic coefficients.

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latter function would describe the output if the average value of the input signal had been found first and then the logarithmic compression had been performed.For both Rayleigh and Maxwell amplitude distributions, the analytic relationship between the operations of l ) taking the logarithm of the average value [In (2)], =2) taking the average of the logarithm of the instantaneous value [In (x)], has been determined, and the results are illustrated in Fig. 3. The analysis presented here shows that these two operations cannot be permuted.However, for sufficiently large values of average signal compared to the system lower limit, the results of the two operations differ by a constant factor which depends on the statistics of the input signal. These difference constants are 1.45 and 0.88 dB for Rayleigh and Maxwell amplitude distributions, respectively. It can be seen from Fig. 3 that these constant differences prevail whenever the input average signal f is at least a factor of approximately ten greater than the input lower bound XO, or, equivalently, whenever the average output is more than approximately 20 dB above the output lower bound.The mean square value, rather than the average value, of random signals of the type considered here is often considered to be the most important characteristic measure of the signal because it represents signal power. When the amplitude probability density function is specified, these two measures are uniquely related, and the analysis of signal "compression" could have been couched in terms of the rms value with equal facility. In particular, for the Rayleigh and Maxwell amplitude distributions, the rms values are 1.06 and 0.72 dB above the average values, respectively. It is unnecessary to actually repeat the analysis using rms values, since these factors can be applied directly to the final results derived here in terms of the average values. Thus, in the largesignal limit, the true rms values are 2.51 and 1.60 dB above the average output values, for the Rayleigh and Maxwell distributions, respectively. Abstract-An optical homodyne technique is utilized to measure subangstrom dynamic mechanical deformations. For measurement in the frequency domain, where synchronous detection is used both the omplitude and phose of the mechanical signal con b e measured with a high sensitivity; displacements less than 10-*A0 were measured with normal environment acoustic noise. Measurement in the time domain is also feasible with reduced sensitivity. ~NTRODUCTIONOptical probing is, thus far, the most sensitive technique used in the study of small mechanical deformations. Already, optical heterodyne methods have been used to this end with considerable sucess.1s2 This letter shows that a relatively simple homodyne technique can be used not only to resolve mechanical vibrations of magnitudes several orders below one angstrom, but also to measure their phase. THEORY Fig. 1 shows the basic elements of the experimental setup. A light wave, of frequency f o , is divided equally at the beam splitter ...

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