Low Birefringence and 2-D Optical Confinement of Hollow Waveguide With Distributed Bragg Reflector and High-Index-Contrast Grating

A hollow optical waveguide is proposed in which light can be confined in an air gap between a distributed Bragg reflecting (DBR) mirror and a high-index-contrast grating (HCG) mirror. Because of the combined effect of vertical (DBR) and lateral (HCG) periodicity, the proposed hollow waveguide shows a small modal birefringence on the order of 10
^-4
. In addition, a patterned HCG is shown to provide 2-D optical confinement, which is an important requirement for practical compact photonic devices. The proposed hollow waveguide is fabricated, and a low birefringence of 5 times 10
^-4
is demonstrated experimentally.