Submicron-scale spatial compression of light beam through two-stage photonic crystals spot-size converter

Photonic crystals spot-size converter that achieved the controlling of the spot-size through two-stage conversions was proposed. The pre-conversion depended on the efficient coupling between the high quality factor resonator and photonic crystal waveguide. Nearly unity transmission efficiency of the pre-conversion can be achieved through optimizing the radii of the rods located surrounding the resonator. Nanowire waveguide with width of 0.14 μm at a distance 1.05 μm from the resonator was introduced to realize the second stage conversion. Through two-stage conversions, the light beam width was converted to 0.16 μm. The transmission efficiency and conversion ratio reached to 94.6% and 14.875 respectively in theory.