Enhanced Electro-Optic Modulation Performance in Optical Buffers by Slowing Light in Optimized Photonic Crystal Slab Structures

Abstract

Slow light holds the key to advanced optical bu ering and time-domain optical signal processing technologies. Photonic crystal based optical bu ers are particularly attractive due to their nanoscale size, room temperature operation, and enhanced eld dependent nonlinear response associated with the presence of slow light. In this study, the slow light and electro-optic modulation characteristics of a line-defect Si photonic crystal slab with triangular arrangement of holes lled with an electro-optic polymer (n = 1.6) are investigated by three-dimensional plane-wave expansion and nite-di erence time-domain methods. The rst rows adjacent to the line-defect are shifted gradually in the direction of light propagation and a slow light region with a high group index below the light-line is obtained for a shifting amount between 0.22a and 0.27a. For the photonic crystal con guration with 0.22a shifted rows, under modulated voltage change, the average group index is found to be decreasing with an increase in the bandwidth. The results show that the low group velocity supports a large delay time in a small modulated voltage variation. A linear change of group index with modulated voltage is obtained and the modulation sensitivity of central wavelength is obtained as 9.45 nm/V for a delay line length of 0.5 mm. Almost the same bu er capacity and bit length are found which provides the control of delay time exibly while keeping the bu er capacity and the bit length almost unchanged.