Large-angle beam splitter with sensitive adjustable power ratio based on superprism effect

A large-angle beam splitter (BS) with adjustable power ratio based on the superprism effect in a two-dimensional photonic crystal (PC) slab is proposed. The finite-difference time-domain results show that by appropriately truncating the PC termination, two split beams with a large separation angle can be achieved over a relative bandwidth of 13.7%. The power ratio of the two split beams can be sensitively adjusted by slightly changing the incident angle or insensitively adjusted by changing the position of the light source, while there are almost no changes in their propagation directions. Further calculations reveal that the cylinder radius of PC has wide tolerance for the BS, which is favourable for practical fabrication. As an example, we proposed a sensitive double-throw optical switch with working wavelength range from 1432 to 1644 nm based on the proposed structure.