Development and characterization of an acousto-optic modulator

Abstract

An acousto-optic modulator (AOM) has been developed and characterized. The system was evaluated by feeding radio frequency (RF) signal on the AOM crystal (fused silica crystal) to generate acoustic wave. The AOM then was illuminated by He-Ne laser at its Bragg angle and the modulated beam was characterized by using a beam profiler, a power meter, and an oscilloscope. The observation result showed that the modulated beam was diffracted into zero and first order. The Bragg angle linearly increases in the range of 0.127° to 0.256° as the RF signal increase from 30 MHz to 65 MHz. The diffraction efficiency per RF drive power was found to be maximum at 50 MHz. The output power for the zero order diffraction was decreased, while the first order diffraction was increased with the increases in the RF drive power. The average power transmittance coefficient of the AOM for modulated beam is about 72.8 % and the power loss is about 0.1dB/cm at 50 MHz RF signal input. The modulated beam signal was obtained in periodical waveform having pulse width of 48.5 µs, with amplitude of 5.32 V and rise time of 18.7 µs. The pulse width and the amplitude of the modulated signal was found to increase with increases in the input RF pulses width and RF drive power, respectively.