Growth and characterization of mercurous halide crystals: mercurous bromide system

Abstract

Mercurous bromide single crystals were grown by the physical vapor transport method in a sealed quartz tube. Growth rates were measured for crystals growing in different orientations. Experimental data followed the equation l t = l ∞− A exp(− t/ τ), where l t is the length of the crystal at any time t, l ∞ is the final statio nary length, and A and τ are constants. Crystals growing in 〈001〉 orientation had much higher velocity than crystals growing in 〈110〉 orientation. Large crystals were grown in 〈110〉 orientation by using preoriented seeds, an orientation needed for acousto-optic devices. The optical quality of mercurous bromide crystals was evaluated by fabricating a 5 cm long crystals. The acoustic velocity measurement data showed that the value for the slow shear velocity propagating along 〈110〉 is 2.73 × 10 4 cm/s, consistent with the values reported earlier. This translates with a high value of photelastic coefficient, into a high acousto-optic diffraction efficiency; 2600 with respect to quartz. These results showed that mercurous bromide has potential as an efficient Bragg cell with a delay time greater than 200 μs in a compact package.