Non-radio-frequency signal tuned acousto-optic tunable filter.

As for the common acousto-optic tunable filter (AOTF), the optical wavelength is directly tuned by the frequency of the applied radio frequency (RF) signal. The working wavelength range of the RF controlled AOTF could be limited by the performance of the RF source, especially in the high frequency area. We have proposed a special noncollinear AOTF system, in which the central optical wavelength could be tuned continually by rotating the AOTF, rather than changing its RF. This arrangement is confirmed to be effective to broaden the work wavelength range of a traditional RF based AOTF with the high spectral resolution. Particularly, it is welcomed to the circumstance for the flexible spectral bandwidth. This work has presented not only an original way to tune the wavelength of the filtered optical signal but also a powerful supplement of the RF controlled AOTF. It can lead to a wider applications of a noncollinear AOTF in the field of spectral analysis, hyperspectral imaging, and etc.

Narrowband double-filtering hyperspectral imaging based on a single AOTF.

A method of spectral resolution improvement was presented based on the double filtering in a single AOTF. A special narrowband hyperspectral imaging system using this single-AOTF double-filtering method was established. The spectral bandwidth of double-filtered spectra was 39% narrower than that of the single-filtered optical signal experimentally. We achieved hyperspectral images of the resolution target with better image resolutions than the single-filtering images because of the improved spectral resolution after the double-filtering process.

Design of an acousto-optic tunable filter based on momentum mismatching together with the rotatory property.

Basing on the momentum mismatching together with the crystal rotatory property, we investigate the diffraction performance of an acousto-optic tunable filter (AOTF). The relationship between diffraction efficiency, momentum mismatching, incident optical wave vector, and ultrasound wave vector is analyzed. The correlation between the frequency tuning relation and the incident angle of light is demonstrated, which is usually ignored in the AOTF design. The diffracted wavelength can be decided by a particular acoustic frequency only when the incident angle of light is fixed. Theoretical and experimental analysis indicates that we can acquire a narrowband spectrum and big angular aperture with a proper incident angle.