Abstract

Widely tunable semiconductor lasers are critical components for future wavelength division multiplexed networks and switching systems. Indeed, the total capacity of such systems is presently limited by the laser tuning range. The electrical tuning range of DFB and DBR lasers is limited to less than ~15nm. This limitation results from the fact that the fractional tuning range, Δλ/λ, of the fine-pitch Bragg grating wavelength-selective reflector is simply proportional to the normalized effective index change, ΔN/N. However, we have recently demonstrated that the grating-assisted vertical coupler provides an attractive bandpass filter that can be electrically tuned over a range substantially greater than a grating reflector for the same induced refractive index change [1,2]. Indeed, very recently a tunable twin guide laser that includes a vertical coupler structure between two nearly-synchronous guides exhibited evidence of extended, but irregular tuning [3]. Here we report a novel monolithic extended cavity laser with an integrated grating-assisted vertical coupler as a tunable intracavity filter. This laser has measured tuning range of 57nm and a tuning response that depends monotonically on the filter tuning current.

© 1992 Optical Society of America