Abstract
Acousto-optic (AO) interaction in the terahertz range was investigated with the use of monolithic ultrasound transducers of various widths. Sulfur hexafluoride (SF) liquefied at a temperature of about 23 °C and a pressure of 25 bar was used as a medium for AO interaction. The angular and frequency bandwidths of effective AO interaction, as well as the diffraction efficiency per 1 W of the driving electric power, were determined. For the first time, a correct comparison of the AO diffraction efficiency in SF with the use of ultrasound transducers with different widths was carried out. In the experiments performed, the highest energy efficiency of the AO modulator was achieved with a transducer with a width of 12 mm.
Highlights
Acousto-optic (AO) interaction is an effective tool for modulation of laser beam intensity with a time response of about 1 μs [1,2]
The main concept is to use an acoustic wave to form a phase diffraction grating in a medium
By coding the electrical signal applied to the ultrasound transducer, one can modulate the intensity of the diffracted radiation
Summary
Acousto-optic (AO) interaction is an effective tool for modulation of laser beam intensity with a time response of about 1 μs [1,2]. The main concept is to use an acoustic wave to form a phase diffraction grating in a medium. Due to the photo-elastic effect, the refractive index variation is proportional to the amplitude of the acoustic wave. By coding the electrical signal applied to the ultrasound transducer, one can modulate the intensity of the diffracted radiation. The best medium for AO interaction in the terahertz (THz) range is liquefied sulfur hexafluoride (SF6 ) [3,4]. In AO modulators, the Bragg regime was used and there were only two diffraction orders with wave vectors ~k0 and ~k1
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