Lensing and waveguiding in birefringent double-twist cylinders demonstrated using FDTD simulations.

We demonstrate that birefringent profiles of double-twist cylinders, found in some chiral nematic systems such as blue phases, can perform as polarization-selective microlenses and waveguides in the regime of negative birefringence. Specifically, we solve Maxwell's equation using the finite-difference time-domain (FDTD) method, to simulate light propagation through double-twist cylinder birefringent structures. We show that, in case of negative material birefringence, azimuthally polarized beams experience lensing which can further be extended to waveguiding in double-twist cylinders. Lensing and waveguiding efficiency are shown to be strongly dependent on the ratio between the width of the double-twist cylinder profile and the beam width. We further characterize waveguiding in terms of losses, which are investigated in case of straight as well as curved double-twist cylinders. More generally, this work is a contribution to the design and development of (soft) birefringent profiles for optical and photonic applications.