Optical far-field and near-field observations of the strong angular dispersion in a lithium niobate photonic crystal superprism designed for double (passive and active) demultiplexer applications

We report on a lithium niobate photonic crystal (PC) superprism device designed for double demultiplexer applications. In fact, the strong angular beam steering cannot only be reached by passively tuning the wavelength but it can also be actively controlled by the Pockels effect enhanced due to the slow light phenomenon. The performance of the passive device is demonstrated by measuring its transmission properties. Optical far field and near-field experiments, corroborated by two-dimensional finite difference time domain (2D-FDTD) calculations, exhibit an angular dispersion of 1.5 degrees/nm. A value as high as 4.3 degrees/nm is expected by improving the PC design as supported by 2D-FDTD simulation.