Proposal of Tunable Hollow Waveguide Distributed Bragg Reflectors

Abstract

We propose a novel tunable distributed Bragg reflector (DBR) consisting of a grating loaded slab hollow waveguide with a variable air core. A change in an air core thickness of the tunable hollow waveguide gives us a large shift of over 100 nm in Bragg wavelength due to a change of several percents in a propagation constant. In order to obtain the high reflectivity and wide tunability of the tunable hollow waveguide DBR, the optimisation of the grating depth and grating length is carried out with minimizing radiation loss and distortion of reflection spectra induced by the corrugation. The modelling result shows a possibility of wide tunability of several tens nm with maintaining a high reflectivity of more than 90% without noticeable radiation loss and distortion of reflection spectra. We expect various device applications of the proposed tunable hollow waveguide DBR, which may include tunable band-pass filters, gain equalizers and dispersion compensators.