Low reflectivity triangular groove surface relief gratings for lnP/ln(0.53)Ga(0.47)As/lnP photodetectors

Less than 0.035% reflected optical power from an InP/InGaAs/InP photodetector structure was achieved at wavelengths of 1300 nm and 1550 nm for a 24-microm diameter spot size of unpolarized light. A triangular groove surface relief grating and an antireflection overcoating were used to achieve this performance level. The grating was fabricated in the InP top layer by a novel process based on an ion mill technique. This approach may be used to improve the optical return loss of high speed optical receivers. The reflected power measurements were made using a system of N.A. = 0.05 with an objective lens whose optical axis was normal to the grating.