Selective excitation of the TE01 mode in hollow-glass waveguide using a subwavelength grating

In this work we demonstrate, for the first time to our knowledge, a novel subwavelength optical element for the elective excitation of the TEO1 mode inside a 300-mu m bore diameter hollow-glass waveguide (HGW) in order to reduce the transmission loss. The device consists of form birefringent gratings, where each section is oriented in a different direction so as to convert a linearly polarized input light to a rotating polarized one matching the TEO1 mode. Using this polarization converting element, we measured a 1.65-dB decrease in the transmission loss in the HGW at a wavelength of 1.55 mu m.