MEMS-Based QCL Spectrometer Aims at Hazardous Materials Detection

A new MEMS-based spectrometer that operates in the mid-infrared could form the basis of a handheld system for detecting hazardous materials.

Developed at the Fraunhofer Institute for Photonic Microsystems (IPMS), the device incorporates a 5-mm diffraction grating controlled by microelectromechanical systems (MEMS). It works with a quantum cascade laser (QCL) — under development by another Fraunhofer institute and international partners — to measure atomic absorption lines from 3 to 12 µm.

A QCL module with an integrated MEMS diffraction grating. Courtesy of Fraunhofer IPMS.

“Electrostatically driven MEMS grating mirrors are much more compact than galvanometer scanners, make almost no sound and allow for very high scanning frequencies due to their low weight,” said Fraunhofer IPMS project manager Dr. Jan Grahmann.

“In combination with miniaturized laser sources, they are ideal for integration into mobile, handy sensor systems, simple measurements on location and for integration into industrial measurement technology at production and processing facilities.”

The MEMS diffraction grating acts as the QCL’s variable frequency external resonator. It allows for the tuning of laser wavelengths with a scanning frequency of 1000 Hz, with a variable frequency range of up to 20 percent of the central wavelength.

Fraunhofer IPMS earlier developed a mobile MEMS scanning grating spectrometer for use in the near-infrared from 950 to 1900 nm.

For more information, visit www.ipms.fraunhofer.de.