Design and theoretical demonstration of an on-chip metal Bragg grating switch based on two-beam interference

We propose a slot waveguide metal Bragg grating, which can continuously convert the phase difference between two beams of light into their varying reflectivity and transmittivity. Two types of switches based on two-beam interference were designed by optimizing the geometric parameters of metal gratings. Thanks to the localized surface plasmon resonance and the strong optical confinement in slot, both types of switches are very compact. The finite element method simulation result shows the grating's good performance to controlling light reflection and transmission, especially for Type II switches. The on-state reflectivity and off-state transmittivity of Type II switches are more than 75% and 88% respectively, with both the reflection and transmission switching depths more than 93%, in a 120 nm wide wavelength range centered at 1550 nm. Moreover, slot waveguide metal Bragg gratings combined with phase modulators can be used as reflectivity-adjustable reflectors, which are expected to be promising elements for on-chip laser Q-switching. The proposed slot waveguide metal Bragg grating is expected to be used for photonic integrated circuits and applications which require broadband and high-efficiency on-chip optical switching and adjustable reflections.