Abstract

This chapter focuses on the optical sensing applications based on TiNi films. When the TiNi film undergoes a phase transformation, both its surface roughness and reflection change, which can be used for a light valve or on–off optical switch. Different types of micromirror structures based on sputtered TiNi based films have been designed and fabricated for optical sensing applications. Based on the intrinsic two-way shape memory effect of free standing TiNi film, TiNi cantilever and membrane based mirror structures have been fabricated. Using bulk micromachining, TiNi/Si and TiNi/Si3N4 bimorph mirror structures were fabricated. As one application example, TiNi cantilevers have been used for infrared (IR) radiation detection. Upon absorption of IR radiation, TiNi cantilever arrays were heated up, leading to reverse R-phase transition and bending of the micromirrors.

Introduction

Optical MEMS, also called MOEMS (Micro-opto-electro-mechanical systems), generally refers to the optical and optoelectronic systems that include one or more micromechanical element [1, 2, 3, 4, 5]. The micromechanical elements in MOEMS are batch fabricated by micromachining techniques. They are smaller, lighter, faster and cheaper than their bulk counterparts, and can be monolithically integrated with the optical components. The digital micromirror device (DMD) from Texas Instruments, USA is a showpiece of optical MEMS [5]. It is an array of mirrors, which are independently addressable and can deflect light through a tristable range of motion (+10°, 0°, –10°), as illustrated in Fig. 19.1 [5]. A light source is directed onto the DMD while a signal is input to the device. Each individual mirror is placed in a binary mode.