High-radiance room-temperature GaAs laser with controlled radiation in a single transverse mode

A GaAs laser for room-temperature operation is reported with high radiance and short delay times. For high radiance, the radiation of a 200-μ-wide GaAs laser diode is confined to the lowest order transverse mode. This is accomplished by operating the laser diode with an optical cavity in which the transverse mode is controlled by aperture-limiting slits. In the cavity, built of spherical lenses and plane mirrors, the mode width and height coincide with the width and height of the active region of the injection laser. The diffraction losses of the higher order transverse modes introduced by the apertures are sufficiently high to yield controlled radiation in the TEM
00
mode ; this control was not always assured in the earlier design of the GaAs laser with the external resonator [1]. For short delays of the onset of stimulated emission, GaAs lasers are used for which the transition from short to long delays occurs above room temperature. Also, the external cavity is coupled closer to the active region of the semiconductor diode than reported previously [1] to minimize losses that would increase the delay times. Test results on the radiance, room-temperature delay times, and mode structure of the GaAs laser with the optical cavity are presented and the observed spiking pattern is discussed.