Negative refraction based on the superprism effect in a micromachined flexible photonic crystal

We report data on a new nanophotonic device based on a 2-D slab silicon photonic crystal (PC) matrix composed of a periodic array of high index silicon pillars embedded within a flexible low index polyimide matrix. To our knowledge, for the first time, negative refraction based on the superprism effect is reported in a 2-D silicon-based photonic crystal device. This work has a huge potential in various applications employed within silicon-based photonic crystal systems such as super-lenses, tunable filters, and optical switches. The device, designed for 1.54 mu m infrared light, is composed of a triangular array of silicon pillars of diameter 400 nm with a lattice spacing of 616 nm embedded in a thin 400 nm thick polyimide matrix. Small changes in the incoming angle of light can produce large changes in the direction of the outgoing light near zero stress. Silicon pillars are formed by RIE etching and polyimide is then spun on, baked and etched to form the PC device. The PC matrix is then released from the oxide with a WE etch. Samples with incident angles in the range of 0 degrees-8 degrees have been tested. Strong negative refraction on the order of 50 degrees is seen in the PC with the incident angle of 8 degrees. This is in close agreement with the simulated results and clearly demonstrates the effectiveness of the photonic crystal device.