Highly compact polarization-independent grating coupler

We propose a compact polarization-independent output grating coupler, which consists of T-shaped grooves. For only 20 periods on a silicon-on-insulator wafer with a 260 nm thick top silicon layer, the output coupling efficiencies for both the TE and the TM modes are larger than 50% in the wavelength range of 1480-1580 nm and are approximately 58% around 1550 nm. The polarization-dependent loss of the device is within 0: 05 dB in the range of 1510-1580 nm. (C) 2010 Optical Society of America