High‐efficiency TEM00 continuous‐wave (Al,Ga)As epitaxial surface‐emitting lasers and effect of half‐wave periodic gain

We report room‐temperature, continuous‐wave (cw), photopumped operation of (Al,Ga)As surface‐emitting lasers grown by molecular beam epitaxy. These monolithic semiconductor lasers comprise two multilayer semiconductor mirrors surrounding a layered active region. In the active region, GaAs quantum wells are spaced with half‐wave periodicity to center on standing‐wave maxima of the cavity optical field. By comparing threshold data for different lasers grown with and without half‐wave periodicity, we observe the first experimental evidence for reduced cw lasing threshold (as low as 2×104 W/cm2 ) with periodic gain in an epitaxial surface‐emitting laser. Up to 50 mW with high efficiency (35% total, 80% differential) and narrow spectral linewidth (2 A) have been measured. A very high quality beam with low divergence (2.5°) and circular TEM00 profile has been observed. All of these observations represent significant advances for surface‐emitting laser technology.