We experimentally demonstrate that a grating outcoupler used for complex beam shaping (spot-array generation) can produce unintentional optical feedback that severely disturbs the integrated in-plane laser that illuminates the coupler. Simulations show that these outcouplers, in contrast to conventional collimating or focusing outcouplers, tend to produce high levels of feedback in spite of the detuning used to suppress feedback. Further, this feedback is focused to high intensity in the laser gain medium. This focused light acts as a seed for the nonlinear self-focusing that causes wave-front distortion and filamentation, which degrades the beam quality.
© 2002 Optical Society of America
(050.1950) Diffraction and gratings : Diffraction gratings
(130.5990) Integrated optics : Semiconductors
(140.5960) Lasers and laser optics : Semiconductor lasers
(250.5300) Optoelectronics : Photonic integrated circuits
Peter Modh, Johan Backlund, Niklas Eriksson, Jörgen Bengtsson, Sigurgeir Kristjánsson, and Anders Larsson, "Effects of feedback from collimating, focusing, and spot-array generating outcoupler gratings in surface-emitting semiconductor lasers," Opt. Lett. 27, 574-576 (2002)