| Abstrakt: |
We have prepared good-quality crystals of a large number of sulfosalt-type chalcogenide crystals. These include Tl3AsSe3, Tl3AsS4, Tl3PSe4, Tl3VS4, TlGaSe2, TlGaS2, and TlInSe2. The optical band edges range from 0.55 to 1.23 μm, and the transparency region typically extends to about 15 μm. The refractive indices range from 2.5 to 3.4. The acoustic velocities were determined for each crystal for the three acoustic modes along the principal axes, and fitted to the empirical Lindemann formula relating velocity, melting temperature, and molecular weight. These materials exhibit some of the lowest velocities recorded; a shear wave velocity of only 5 × 104 cm/sec was measured for Tl3PSe4, which is the lowest to be found in the literature for any solid or liquid, away from critical points. The optoacoustic figure of merit, M2, was measured relative to fused quartz. The highest relative figure of merit, 1370, was measured in Tl3PSe4. One of these new crystals, Tl3AsSe3, has a noncentric structure and is optically nonlinear. Its symmetry class, 3 m, is one for which the P41 photoelastic tensor component is theoretically nonzero, so that this crystal may be useful for collinear acoustooptic filters. [This research was sponsored in part by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Materials Laboratory, LP, under Contract No. F33615-72-C-1976.] [ABSTRACT FROM AUTHOR] |
