Grating May Improve Spectrometers

Barbara Grant

Spectrometer manufacturers seeking to reduce the size and cost of their instruments may benefit from an innovation utilizing microelectromechanical systems technology. InterScience Inc. has developed a compound optical grating that could provide smaller, lower-cost solutions while retaining the functionality common to current grating-based instruments.

An optical grating developed by InterScience Inc. can dynamically reconfigure within a spectrometer to enable observation over visible and infrared wavelengths.

The patented silicon-based device consists of a series of gold-coated rulings suspended over a substrate; electrodes are buried underneath a selected subset of rulings. Applying voltage to the electrodes attracts the selected rulings to the substrate by electrostatic force, changing the grating geometry. As a result, the distribution of light energy between diffraction orders changes as well. "This ability to dynamically reconfigure constitutes a new degree of freedom in the grating," said Mikhail Gutin, principal scientist at InterScience. "It allows observers to examine a variety of passbands from the visible to the infrared."

The grating will expand the instrument's spectral range beyond that provided by traditional gratings, Gutin added. A spectrometer could employ one electronically reconfigurable grating in place of several conventional gratings that require mechanical insertion and removal.

The grating typically measures 0.5 × 1 cm and is fabricated by a process similar to that used to make electronic microchips. Its small size allows its resolution to be compatible with the limitations defined by existing optical systems in commercially available compact spectrometers, whose typical dimensions are 5 × 4 × 1 in., Gutin said.

InterScience developed the grating with support from NASA and other government agencies. The company is seeking technology licensees and commercialization partners to exploit the innovation's potential in spectroscopic instruments and applications.