Fig. 4: Tunable phase shifter.
a 3-D schematic view of an in-plane actuated phase shifter. b SEM recording of the phase shifter, comprising a suspended waveguide and a comb-drive actuator to tune the modal cross-section of the waveguide by pulling away a 220 nm wide silicon beam attached to the movable shuttle60. c Characterization of the phase shifter within an unbalanced Mach Zehnder interferometer (MZI), displaying an over 2π phase shift and low insertion loss (large extinction ratio). d Extracted phase shift and e insertion loss versus voltage at a wavelength of 1550 nm. Dotted: single device, line: median for N = 10 devices, shaded region: +/−1σ. f Tunable basic unit composed of two MEMS phase shifters, one per arm of a suspended balanced MZI, here configured as an all-pass ring resonator. g Example characterization of the tunable basic unit with two MEMS phase shifters, showing versatile control over the ring filter response and a free spectral range of 0.93 nm at a wavelength of 1550 nm. h Actuation map of the corresponding filter extinction ratio and i resonance tuning at a wavelength of 1550 nm. For low values of the extinction ratio, no resonances were observed, and no resonance shift was extracted
