Spectrally Tunable Infrared Detector

B.J. Potter and Yuyan Wang

B. J. Potter and Yuyan Wang are teaming up on a project to develop an infrared (IR) detector that has the capability of being tuned to specific infrared wavelengths. A detector such as this could then be integrated into an imaging system, which would allow the user to identify things by their infrared signature. Many objects and chemicals have identifiable infrared signatures that could be resolved by such an imaging system.

They are designing a bolometer based infrared detector. The standard bolometer is simply a thermally isolated plate that absorbs infrared photons. When photons are absorbed, the heating of the plate causes a measurable resistance change. The idea with this project is to filter the light that reaches the bolometer, so that only certain infrared wavelengths are selected. This will allow us to have more information about what the detector is observing, thereby allowing it to better identify chemicals and objects. One unique quality of our design is that we can filter the light on a pixel by pixel basis, as opposed to across the entire detector.

Currently B. J. and Yuyan are building and testing preliminary systems for the spetctrally tunable infrared detectors. The figures below show the results of some of the work they have been doing.

PUBLICATIONS

View the paper that B. J. and Yuyan wrote for the Transducers '05 conference.

Step-wise Tunable Microbolometer Long-Wavelength Infrared Filter

FIGURES

Figure 1

This figure shows the measured transmission of a structure we made to test the quality of infrared optical coatings that we have the ability to make. Our aim was to make an optical filter in the infrared with a small full width half maximum (FWHM) value. This structure had an FWHM of 110 nm, so it was a success.

Figure 2

A preliminary step in constructing our filter is to make a infrared mirror that has high reflectivity in the 8-12 micron wavelength range. This figure shows a comparison of our simulated mirror with experimental data measured using a Fourier transform infrared (FTIR) spectrometer.

Figure 3

Shown here is the results of our first successful tunable filter. This filter can be tuned to center around three different infrared wavelengths. The filter is tuned by moving one plate of our filter to different heights above its substrate. The movement is done electrostatically by applying a voltage between the plate and the substrate.