Laterally-coupled distributed feedback (LC-DFB) lasers offer compelling advantages over standard DFB lasers. The use of surface grating on the ridge waveguide sidewalls in LC-DFB devices avoids any epitaxial overgrowth. This provides a considerable simplification in the fabrication process, reducing cost and time of manufacturing, and ultimately increasing yield. It offers also the potential for monolithic integration with other devices; paving the way towards low-cost and mass-production of photonics integrated circuits. In this work, we report on the realization of high-order grating InGaAsP/InP multiple-quantum-well (MQW) LC-DFB lasers at 1.55 μm by means of stepper lithography and inductively-coupled reactive-ion as well as wet chemical etching. Third-order rectangular-shaped grating has been lithographically defined on the ridge waveguide sidewalls with a relatively deep etching along the laser cavity. The preliminary experimental characterization shows interesting results for as-cleaved devices tested in room temperature under CW operation. A fabricated 1500 μm-long cavity LC-DFB laser shows stable single-mode operation with a side mode suppression ratio as high as 50 dB. The tested device can emit at power as high as 9 mW, and the measured threshold current is around 80 mA at room temperature. Moreover, the measured linewidth has been found to be as narrow as 178 kHz using the delayed self-heterodyne interferometric technique.

Date Published: 24 October 2012
PDF: 6 pages
Proc. SPIE 8412, Photonics North 2012, 84121R (24 October 2012); doi: 10.1117/12.2001459

Published in SPIE Proceedings Vol. 8412:
Photonics North 2012
Jean-Claude Kieffer, Editor(s)