Absorption monitoring and optical damage protection for micromechanical optics

Summary form only given. It is critically important to understand the absorption characteristics of micromachined optical devices. Etch-released microstructures generally have extremely poor thermal conductance and are unable to handle high powers without thermal damage or warping. This problem is compounded in tunable structures whose optical characteristics are dynamic because their maximum acceptable intensity is dependent on actuation conditions. Unfortunately, it is extremely difficult to extract absorption from reflectivity and transmission experiments since the contributions of the device and layers around it (such as the substrate) are often indistinguishable. In this paper, an absorption monitoring method is described using the micromachined optic as a thermal probe of its own absorption. The method requires no changes to the device design and is demonstrated by measuring the absorption of a diffractive microbeam dynamically during actuation and light source spectral changes.