Self-collimating photonic-crystal wave plates

We present theoretical results of quarter- and half-wave plates based on two-dimensional photonic crystal that has a polarization-independent self-collimating effect. The designed low-order wave plates have achromatic characteristic with high phase accuracy of +/-0.01pi in the normalized frequency range 0.273-0.281alpha/lambda, which is about 45 nm in the telecommunication band (around 1550 nm). Profiting from the self-collimating guiding mechanism, the wave plates (even the relative high-order ones) have low beam divergence and transmission loss. In addition, on the basis of the formed birefringence effect, a method for designing high-order wave plates is proposed. The wave plates presented in this Letter have potential applications in future photonic integrated circuits.