Narrow-bandwidth tunable bandstop filters with circularly cylindrical self-suspended silicon gratings

A circularly cylindrical self-suspended silicon grating (SSG) is proposed, and its reflectance spectrum is investigated by the rigorous coupled-wave method (RCWM). For TM incident polarization, when the grating period is tuned, numerical results by the RCWM reveal that the circularly cylindrical SSG possesses a tunable narrow reflectance bandwidth property in the optical telecommunication wavelength region. It is also demonstrated that both TM incident polarization and the circular grating cross section are easier to bring narrow reflectance bandwidth, compared with TE incident polarization and square grating cross section. Via a micro-electromechanical systems actuator, the proposed circularly cylindrical SSG is expected to serve as a narrow-bandwidth tunable bandstop filter in micro-optical telecommunication systems.