ULTRAFAST PULSED MODE EFFECTS ON THE PERFORMANCE OF GRATING-ASSISTED OUTPUT COUPLERS OF FINITE EXTENT

The performance of grating-assisted output couplers of finite extent e xcited by finite ultrafast pulsed modes is characterized numerically b y the finite-difference time-domain method. The results for pulsed exc itations with extremely long pulse envelopes are compared with those t hat contain only a few optical cycles for gratings that are both long and short compared with the equivalent pulse length. We demonstrate th at the shortest length of either the grating or the pulse dictates the far-field performance of the grating-assisted output couplers. (C) 19 98 Optical Society of America.