Electrothermally Actuated Lens Scanner and Latching Brake for Free-Space Board-to-Board Optical Interconnects

The design, fabrication, and characterization of an electrothermally actuated lens scanner with bistable mechanical brakes, for the application of free-space board-to-board optical interconnects, are presented. An electrothermally actuated stepper motor is used to scan a 2.8-mm-diameter lens shuttle by a maximum of ±170 μm (±1.57° scanning angle). Bistable mechanical brakes, toggled with U-shaped thermal actuators, will grip and hold the lens shuttle in place while dissipating zero power. The minimum frictional braking force and maximum actuator force are both measured to be 0.75 mN. A position sensing detector is used to accurately measure the dynamics of the stepper motor and lens system, from which we verify our analytical model. Long-term testing results and solutions are also presented. We demonstrate a robust 10-Gb/s optical link capable of maintaining connection despite a board tilting of 0.45° while dissipating zero power.