Rotating Circular Micro-Platform with Integrated Waveguides and Latching Arm for Reconfigurable Integrated Optics

Abstract

This work presents a laterally rotating micromachined platform integrated under optical waveguides to control the in-plane propagation direction of light within a die to select one of multiple outputs. The platform is designed to exhibit low constant optical losses throughout the motion range and is actuated electrostatically using an optimized circular comb drive. An angular motion of ±9.5° using 180 V is demonstrated. To minimize the optical losses between the moving and fixed parts, a gap-closing mechanism is implemented to reduce the initial air gap to submicron values. A latch structure is implemented to hold the platform in place with a resolution of 0.25° over the entire motion range. The platform was integrated with silicon nitride waveguides to create a crossbar switch and preliminary optical measurements are reported. In the bar state, the loss was measured to be 14.8 dB with the gap closed whereas in the cross state it was 12.2 dB. To the authors’ knowledge, this is the first optical switch based on a rotating microelectromechanical device with integrated silicon nitride waveguides reported to date.

State of the Art and Perspectives on Silicon Photonic Switches

“…Unlike the MEMS-actuated switches in Figure 4a,b, these devices operate with a low-voltage comb electrostatic actuator. Recently, Briere et al reported a MEMS-actuated switches based on the laterally rotating comb actuators (Figure 4e,f) [67]. The light turns on when the fixed port is aligned with one of the rotational ports.…”

Translational MEMS Platform for Planar Optical Switching Fabrics

“…Previous devices developed by our research group relied upon a rotational MEMS platform for planar optical switching using SiN waveguides surrounded by a SiO 2 cladding [42]. The device uses 5° of its total 9.5° of rotation on each side to form a crossbar switch requiring 113 V to actuate and having a 1.3 mm by 1 mm footprint.…”

“…The longitudinal motion of the central platform is unidirectional and designed to completely close the air gap between waveguides on the substrate and the platform to achieve highly efficient butt-coupling. The design operates at a reduced actuation voltage for both switching and gap closing motions compared to that reported in [42], and the device footprint is smaller. Figure 1 shows illustrations for the translational MEMS platform as a 1 × 3 optical switch (Figure 1a) and as a 2 × 2 crossbar optical switch (Figure 1b).…”

“…Figure 1 shows illustrations for the translational MEMS platform as a 1 × 3 optical switch (Figure 1a) and as a 2 × 2 crossbar optical switch (Figure 1b). These structures are meant to include integrated SiN waveguides which are not the focus on this work but that have been demonstrated in [42,43]. A cross sectional representation of the entire optical MEMS stack envisioned is also shown in Figure 1c.…”

“…Through complex MEMS integration of soft polymer waveguides, a 2 × 2 optical switch has also been demonstrated [39]. Recent developments include planar switching done by adiabatic coupling between waveguides through vertical actuation at very low voltage [40,41], and butt coupling through in-plane rotational actuation [42].…”