The acousto-optic Frequency Shifter (AOFS) with RF driver is used to modify the frequency of the optical beam. Due to the Doppler shift, the frequency shift of 1st order diffracted light (variation quantity of wavelength) equals to the frequency of acoustic (wavelength) after the AO frequency shifters. If the incident direction of acoustic wave and optical wave are the same, the laser frequency shifts will be the positive value, anyway if the incident direction are opposite, the value of the laser frequency shifts will be the negative value. Applications such as interference-based optical techniques require a high extinction ratio between the diffracted and undiffracted beam; This can be achieved with a high-quality optical finish to minimize optical scatter. CASTECH offers standard products with frequency shifts of 73 MHz In addition, CASTECH provides the services of customize for center frequency and the value of frequency shifts.