Publications

In optical firing sets, laser light is used to supply power to electronics (to charge capacitors, for example), to trigger electronics (such as vacuum switches), or in some cases, initiate explosives directly. Since MEMS devices combine electronics with electro-mechanical actuators, one can integrate safe and arm logic alongside the actuators to provide all functions in a single miniature package. We propose using MEMS-activated mirrors to make or break optical paths as part of the safe and arm architecture in an optical firing set. In the safe mode, a miniature (∼1 mm diameter) mirror is oriented to prevent completion of the optical path. To arm the firing set, the MEMS mirrors are deflected into the proper orientation thereby completing the optical path required for system functionality (e.g., light from a miniature laser completes the path to an optically triggered switch). The optical properties (i.e. damage threshold, reflectivity, transmission, absorption and scatter) of the miniature mirrors are critical to this application. Since Si is a strong absorber at the wavelengths under consideration (800 to 1064 nm), high-reflectivity, high-damage-threshold, dielectric coatings must be applied to the MEMS devices. In this paper we present conceptual MEMS-activated mirror architectures for performing arming and safing functions in an optical firing set and report test data which shows that dielectric coatings applied to MEMS-mirrors can withstand the prerequisite laser pulse irradiance. The measured optical damage threshold of polysilicon membranes with high-reflectivity multilayer dielectric coatings is ∼ 4 GW/cm 2, clearly demonstrating the feasibility of using coated MEMS mirrors in firing sets.