Abstract: An acoustic optical light modulator comprising a hexahedral ultrasonic wave media having a bottom and two sides perpendicular to the bottom, an ultrasonic wave generator attached to the bottom and controlled by a high frequency oscillator connected thereto and a laser source radiating a laser beam incident upon and reflected on a plane of the ultrasonic waves formed in the media, characterized in that the two sides of the media are provided with symmetrical grooves of V-shaped section in the middle portion of the each side thereof, the lower inclined surfaces of the grooves being formed with anti-reflective films, and the remaining surface portions of the sides including the upper inclined surface of the grooves and the bottom is coated with heat absorbing films which absorb light and heat.