Advances in MOEMS-Based External Cavity QCLs

Abstract

The combination of broadly tunable quantum cascade laser chips in an external cavity (EC-QCL) with a micro-electromechanical system (MEMS) scanner with integrated diffraction grating as wavelength-selective element allows for the development of extremely compact and robust spectroscopy systems. Resonant MOEMS grating scanners enable spectral tuning rates of hundreds of wavenumbers per millisecond and consequently broad-band spectroscopy with millisecond temporal resolution. Also non-resonant (quasistatic) MOEMS grating scanners are possible, providing scan rates of tens of Hz as well as static setting of arbitrary wavelengths, as common for mechanically driven EC lasers, while keeping the small MOEMS footprint, ruggedness, and low power consumption. Here, we give a progress report on the latest developments on MOEMS-based EC-QCLs made by Fraunhofer IAF and IPMS. We will highlight two of our latest developments: A non-resonant MOEMS EC-QCL version that allows arbitrary scan frequencies up to few ten Hertz, as well as static operation. Furthermore, we present the application of a resonantly driven cw-MOEMS-EC-QCL with cavity-length control to enable fast high-resolution spectroscopy over a spectral range of >100 cm -1 , offering new possibilities for spectroscopy on complex gas mixtures.

Multiplexed dual-core QCL-based sensor for real-time standoff-spectroscopy in crime scene investigations

“…The system presented here is based on our early works [6][7][8][9][10][11] and optimized for forensic trace identification. The basic principle is shown in Figure 1a.…”