Design of fiber-integrated tunable thermo-optic C-band filter based on coated silicon slab

Background: Optical filters are required to have narrow band-pass filtering in the spectral C-band for applications such as signal tracking, sub-band filtering or noise suppression. These requirements lead to a variety of filters that offer thermo-optic effect for optical switching, however, some of which without proper thermal and optical efficiency. Methods: In this paper we propose a tunable thermo-optic filtering device based on a coated silicon slab resonator with an increased Q-factor to allow for an efficient thermo-optical switching in the C-band. The device can be designed either for long range wavelength tuning or for short range with increased wavelength resolution. Results: Theoretical examination of the thermal parameters affecting the filtering process is shown together with experimental results. Proper channel isolation with an extinction ratio of 20 dB is achieved with a spectral bandpass width of 0.07 nm. Conclusions: This Si slab based filter characteristics make it suitable for wavelength switching systems such as dense wavelength division multiplexing. In addition, the filter is fiber integrated in order for it to be more compatible with other optics communication devices.