Double Bragg grating tunable filter

A novel concept for a very efficient tunable filter for the optical and near infrared is proposed. The filter consists of two parallel volume phase holographic Bragg gratings used in a dispersion-recombination configuration. The passband profile is determined by the first order grating efficiency curve which changes in wavelength according to the angle of incidence. The filter can be continuously tuned over ranges of wavelengths larger than 600 nm by adjusting the tilt of the gratings, while bandwidth can be selected between 0.1 and 200 nm. The conceptual design is presented, along with predicted performances. Potentially useful instruments for large volume surveys and targeted observations are explored, along with application in areas other than astronomy.