Tunable Polarization Insensitive CMOS Compatible Graphene/Si Guided Mode Resonance Active Filter

Guided mode resonance filter (GMRF) has recently attracted much attention due to its simple structure and high spectral filtering capability [1]. GMRF design relies on a subwavelength grating placed over a high index optical guided medium, where the spectral filtering occurs due to interference between the diffracted light and leaky waveguide modes at resonance condition [1]. The resonance can be tuned by altering the geometrical and material parameters, for instance, grating period, filling factor, duty cycle, waveguide thickness and refractive index [1]. However, there is a challenge to dynamically control the GMRF spectral response by active tuning of the resonance wavelength. In this study we present a new design of CMOS compatible, polarization-insensitive graphene/Si tunable guided-mode resonance filter with a high extinction ratio, where the resonance is tuned by modulation of graphene doping. Graphene is a 2D semimetal with appealing electrical, mechanical and optical properties, and it provides an active tuning of optical loss and effective refractive index by capacitive effect using electrostatic doping [2]. Our designs show a polarization-insensitive operation of electrically controlled reflection, high extinction ratio (ER) (>11 dB) and high (> 12dB) spectral tunability, which is important for applications such as wavelength division multiplexing, laser devices, add/drop filters and more [3] , [4].