Acousto-optic tunable filters: fundamentals and applications as applied to chemical analysis techniques

Acousto-optic tunable filters (AOTFs) are solid state wavelength tunable optical filters. Modern AOTFs are constructed by attaching piezoelectric transducers to an appropriate crystalline material. By driving the transducers at the appropriate frequency, a series of perturbations traverse the material. Interactions of photons with these perturbations allow the AOTF to selectively diffract a single narrow-bandpass wavelength. The wavelength may be varied by changing the applied frequency. The focus of this review is to detail chemical analysis applications of AOTFs. A brief historical background of AOTF development is presented. Mathematical and physical descriptions of AOTF behavior are summarized. Currently used materials and characteristics of these materials are described. AOTFs are compared with other wavelength selection devices including: monochromators, absorption filters, transmission filters and liquid crystal tunable filters. Atomic, molecular, fluorescence and Raman spectrometry applications, as well as the use of AOTFs, for remote and proximal imaging applications are highlighted. Lastly, the combination of AOTF and fiber optic technology to make a new device known as an integrated AOTF is considered.