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

摘要

Slow light holds the key to advanced optical buffering and time-domain optical signal processing technologies. Photonic crystal based optical buffers are particularly attractive due to their nanoscale size, room temperature operation, and enhanced field 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 filled with an electro-optic polymer (n = 1.6) are investigated by three-dimensional plane-wave expansion and finite-difference time-domain methods. The first 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 configuration 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 buffer capacity and bit length are found which provides the control of delay time flexibly while keeping the buffer capacity and the bit length almost unchanged.