Power scaling in high-power optically pumped vertical cavity surface-emitting semiconductor lasers

Abstract

Vertical cavity surface-emitting semiconductor lasers (VCSELs) are potentially useful for fast optical interconnection free-space communication or remote sensing, and formation of coherent 2-D laser arrays. The use of resonant-periodicgain (RPG) media, in which a series of gain regions with half-wave optical periodicity is aligned with the antinodes of the optical standing wave in the laser cavity, provides enhanced gain along with cavity axis and at the designed lasing wavelength. The result is a considerable reduction of the laser threshold.1 Such structures should also have greatly reduced parasitic amplified spontaneous emission (ASE) in the transverse (epitaxial) plane. Here we describe the results of experiments using a pulsed (7 ns at 10 Hz) dye laser at 740 nm to pump a VCSEL structure with 20 GaAs/AlGaAs quantum wells.2 Pumped spot sizes varied from 10 μm up to 0.1 mm (limited by available pump power), and the threshold power per unit area did not vary significantly over this range, indicating negligible parasitic ASE. The slope efficiency and lasing wavelength varied due to nonuniformities in the MOCVD-grown structure. These data indicate that the compact and efficient multiwatt diode-pumped VCSELs are feasible.