The Extreme-range Tunable Filter

Designed by Kirat Singh and Alan Streater

We have developed a tunable filter that tunes over extremely wide ranges, in some cases spanning over two octaves.  The tuning setting corresponds to the translational position of the filter relative to the beam, e.g. in mm. The filters have the physical form of a cube beamsplitter. There are no absorptive materials, so the filters work in reflection as notch filters too. All graphs show the same curve on different scales.

This example design tunes continuously from about 322 nm to 1069 nm, covering most of the range for a Silicon-based detector. Other tuning ranges are possible. The basic design is especially attractive for infrared applications because it uses a thin film structure that is thinner than traditional bandpass filters. This example maintains a constant width of 100 cm-1 (wave numbers), but other versions can maintain a constant width in wavelength, or the width can vary with wavelength in any other way. Extra blocking could be added to longer wavelengths when the peak is tuned to shorter wavelengths.




Enter tuning translational position, from 0 to 80 mm

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