Abstract
Physical vapor transport (PVT) has frequently been adopted for the synthesis of mercurous bromide (Hg2Br2) single crystals for acousto-optic modulators. However, thus far, very few in-depth studies have been conducted that elucidate the growth process of the Hg2Br2 single crystal. This paper reports an in-depth investigation regarding the crystal growth and evolution behavior of the Hg2Br2 crystal with facet growth mode. Based on the experimental and simulation results, the temperature profile conditions concerning the seed generation and seed growth could be optimized. Next, the PVT-grown Hg2Br2 crystals (divided into single crystal and quasi-single crystal regions) were characterized using various analysis techniques. The single-crystal Hg2Br2 was found to possess a more uniform strain than that of the quasi-single crystal through a comparison of the X-ray diffraction data. Meanwhile, the binding energy states and electron backscatter diffraction images of the as-synthesized Hg2Br2 crystals were similar, regardless of the crystal type. Furthermore, Raman spectroscopy and transmission electron microscopy analyses provided information on the atomic vibration mode and atomic structures of the two kinds of samples. The synergistic combination of the simulation and experimental results used to verify the growth mechanism facilitates the synthesis of high-quality Hg2Br2 crystals for potential acousto-optic tunable filter device applications.
Highlights
Acousto-optic tunable filters (AOTFs) have attracted a great deal of attention as a core module of ultra-spectral image sensing systems
We found that the formation and growth of the seed crystal based on simulation and experimental results
We found that the formation and growth of the seed could be determined by optimizing the temperature gradient between the top and bottom heaters and crystal could be determined by optimizing the temperature gradient between the top and bottom by changing the ampoule position
Summary
Acousto-optic tunable filters (AOTFs) have attracted a great deal of attention as a core module of ultra-spectral image sensing systems. They comprise piezoelectric transducers and acousto-optic modulator (AOM) single crystals combined together. AOTF devices utilize the principle of changing and decomposing the frequency of light using soundwaves. The vibration of the piezoelectric transducer changes the diffraction characteristics of the light incident on the AOM material, which in turn only diffracts light of a certain wavelength. The unique acousto-optical properties allow the AOTF to selectively obtain a diffraction signal for each wavelength by modulating the frequency applied to the AOTF apparatus. AOTF devices have potential use for a variety of applications, such as measurements of a cell monolayer, mineral exploration, environmental monitoring, process control, and the identification of toxic biological agents [1,2,3,4,5]
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