Analysis and design of a high power laser interrupter for MEMS based safety and arming systems

A high power laser energy interrupter is investigated and developed. The micromachined laser interrupter is a critical component of the MEMS based safety and arming (S&A) system, which acts as a switch to selectively couple optical power between input and output fibers using direct coupling technique. The switching of high power laser energy is demonstrated by taking advantage of direct thermal actuation of cantilevered large-core multimode fibers. Models describing the combined electrothermal and thermomechanical characteristics of the thermal actuators are developed with temperature-dependent parameters. The temperature distribution of the actuator is investigated, and the influence of the actuator's geometrical parameters on its force and displacement is analyzed. Actuator displacement versus drive current is found to be in good agreement with model predictions. Switching time is 19 ms from the safety to the arming state with a maximum operational frequency of 34 Hz. Optical efficiency is predicted and a series of tests are conducted to measure transmission efficiency of the laser interrupter. The optical efficiency is found to be about 92.7% with a maximum power transfer of 2780 mW from a 3000 mW input, and the channel isolation is 57 dB.