The beam quality of weakly index-guided edge emitting 980nm lasers is investigated via time-resolved far-field measurement technique. A synchronous detection scheme is used to directly measure lasers' far-field pattern, intensity versus divergence angle, as functions of duration and amplitude of injection current pulses. It is shown that the degradation of beam quality, characterized as multiple lateral modes and observed as beam steering of far-field pattern, highly depends on the transient condition associated with the duration of injection current pulses. The beam steering of far-field pattern is well correlated to the kink in power-versus-current curve under the same transient condition. We experimentally found that time constant for the far-field pattern to reach steady state is ~1.4 microsecond. From thermal transience modeling, we conclude that beam steering is the result of local heating, which produces a lateral temperature gradient profile at the laser waveguide region to significantly enhance the lateral index contrast.

Date Published: 19 October 2001
PDF: 4 pages
Proc. SPIE 4580, Optoelectronics, Materials, and Devices for Communications, (19 October 2001); doi: 10.1117/12.444920

Published in SPIE Proceedings Vol. 4580:
Optoelectronics, Materials, and Devices for Communications
Tien Pei Lee; Qiming Wang, Editor(s)