An acousto-optic tunable filter (AOTF) is an all solid-state robust device with no-moving parts that has been used in the
development of hyperspectral imagers from the ultraviolet to the longwave infrared. Such a device is developed by bonding
a piezoelectric transducer on a specially cut prism in a birefringent crystal. When broadband white light is incident on the
prism input facet, two orthogonally polarized diffracted beams at a wavelength with a narrowband bandpass are
transmitted. The transmitted wavelength can be tuned by varying the applied radio frequency (RF). This is what is done
in a hyperspectral imager. An AOTF can also be used with multiple RFs applied at the same time to diffract a number of
different wavelengths. This mode can be exploited to design a tunable optical notch filter where multiple RFs are applied
simultaneously such that all wavelength in a specific range can transmit except for a specific wavelength which is notched.
We designed an optical system using a TeO2 AOTF with telecentric confocal optics operating in the shortwave infrared
(SWIR) with a 16-channel RF driver where both the amplitude and frequency can be controlled independently for each
channel. We will discuss the optical system, its characterization and present results obtained.
Neelam Gupta, Neelam Gupta,
"Acousto-optic tunable filter as a notch filter", Proc. SPIE 9822, Advanced Optics for Defense Applications: UV through LWIR, 982212 (17 May 2016); doi: 10.1117/12.2224238; https://doi.org/10.1117/12.2224238