Ultra-high sensitivity in a photonic crystal superprism due to the curvature singularity of a dispersion surface

Three Dimensionally Interconnected Silicon Nanomembranes for Optical Phased Array (OPA) and Optical True Time Delay (TTD) Applications

“…Thus, the total device length, including the input/output access waveguides, is 13.94μm. Ultracompact directional coupler based PSs with similar dimensions have been reported [9] [10]. As discussed before, the fabrication tolerance remains an issue for short directional couplers with small gap sizes.…”

“…This is due to the presence of the multimode region of the MMI, which is 60µm wide and 563.4µm long and has a much lower loss compared to the much narrower input waveguide. We have previously demonstrated a 1x12 MMI on crystalline silicon with comparable performance [10].…”

“…1(a), to provide continuous phase tuning needed for beam steering. Independent phase shiftersenable us to reset with modulo 2π phase shifts (2mπ+Δθ n = Δθ n , where m is a positive integer and Δθ n is the phase shift of the n th element) [10]. The following passive s-bend phase shifters [ Figure 1(b)] compensate for the quadratic MMI beam splitter output phase profile [11] and change the separation of the uniform MMI outputs to that of the non-uniform array.…”

“…Vertical integration of multiple layers of active and passive components can resolve the problem of limited real estate on a single layer [9]. So far, an extra polysilicon layer on top of the crystalline silicon layer has been used for CMOS microelectronics and photonics integration [10,11]. This scheme may also be used for three-dimensional (3D) photonics integration.…”

“…This scheme may also be used for three-dimensional (3D) photonics integration. However, the optical losses in polysilicon waveguides are dominated by scattering and absorption at the grain boundaries [10], which increase significantly when the waveguide width shrinks to below 200nm [12]. Techniques such as high temperature annealing, special hydrogen plasma passivation steps, and patterning waveguides before the solid-phase crystallization (SPC) of deposited amorphous silicon were shown to reduce the propagation loss [12,13].…”