Characterization of the acousto-optic tunable filter for the ultraviolet and visible regions and development of an acousto-optic tunable filter based rapid scanning detector for high-performance liquid chromatography

A novel acousto-optic tunable filter (AOTF) has been developed for the ultraviolet and visible regions. This AOTF was fabricated from quartz and based on the collinear configuration. It can diffract white incident light into monochromatic ultraviolet or visible light (from 250 to 650 nm) at a diffraction efficiency of about 15% which is comparable with the efficiency of a 0.25-m monochromator. It has, however, much higher resolution than the monochromator. The resolution at 253.4 nm was found to be 0.82 Å. The filter can also rapidly scan the wavelength of the diffracted light at the speed of sound in the crystal (i.e., microseconds). These unique properties enable the filter to be used for the successful development of the first AOTF based detector for HPLC which has combined advantages of single wavelength and diode array detectors, namely it has the same sensitivity as the former and the same speed as the latter. Particularly, this detector was able to rapidly measure absorption spectra of chloro-substituted phenols as these compounds were separated from the mixture and went through the detector, and can detect them at a detection limit of 4.0 × 10−4 AU.