Electronically Scannable Semiconductor Laser Device

Abstract

An electronically scannable electron-beam-pumped semicon-ductor laser device is described which provides laser emission from more than 1000 X 1000 randomly addressable spots. The device consists of a permanently sealed electron beam tube about 50 cm long. Attached to the inside of the face-plate is a 30 um thick cadmium sulfide single crystal wafer with typical lateral dimensions of 28 mm X 28 mm, which serves as the active laser element. Using a 50 ns pulsed elec-tron beam current of up to 2 mA, with an accelerating poten-tial of about 50 keV, laser emission is produced in a direction essentially coaxial with the pumping electron beam. A laser spot diameter of 25 um can be achieved with these devices. The emitted radiation is typically confined to a symmetric cone with a half angle less than 0.1 rad. The laser tube is capable of operation at room temperature or, for greater power output, may be conveniently cooled with conventional refrigeration to about -50°C. At this temperature, peak power outputs in excess of 5 watts have been produced from CdS at 515 nm wavelength. In preliminary tests, laser tubes have been operated at repetition rates up to 400 kHz for more than 2000 hours without significant decrease in laser emission. Applications of such devices include display, COM/CIM, and optically addressed holographic memories.