Thermally induced sideband generation in silicon-on-insulator cladding modulated Bragg notch filters

We investigate and experimentally demonstrate a cladding modulated Bragg grating superstructure as a dynamically tunable and reconfigurable multi-wavelength notch filter. A non-uniform heater element was implemented to periodically modulate the effective index of the grating. The Bragg grating bandwidth is controlled by judiciously positioning loading segments away from the waveguide core, resulting in a formation of periodically spaced reflection sidebands. The thermal modulation of a periodically configured heater elements modifies the waveguide effective index, where an applied current controls the number and intensity of the secondary peaks. The device was designed to operate in TM polarization near the central wavelength of 1550 nm and was fabricated on a 220-nm silicon-on-insulator platform, using titanium-tungsten heating elements and aluminum interconnects. We experimentally demonstrate that the Bragg grating self-coupling coefficient can be effectively controlled in a range from 7 mm-1 to 110 mm-1 by thermal tuning, with a measured bandgap and sideband separation of 1 nm and 3 nm, respectively. The experimental results are in excellent agreement with simulations.& COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

We investigate the use of a cladding modulated Bragg grating superstructure as a dynamically tunable and reconfigurable multi-wavelength notch filter. By periodically modulating the effective index of the grating, we are able to control the bandwidth and create reflection sidebands. Experimental results show that the self-coupling coefficient of the Bragg grating can be effectively controlled through thermal tuning, with a measured bandgap and sideband separation of 1 nm and 3 nm, respectively.