At the Massachusetts institute of technology (MIT) Electronics Research Laboratory (Research Laboratory of Electronics) researchers show a new terahertz (Thz) spectra of the system, can use a quantum cascade lasers (QCL) technology in just 100 microseconds (mu s) time capture some material of spectrum.

Traditional THz spectrum needs as large size suitcase strong radiation source, and has to manually adjust the frequency in different variety of measurement. By contrast, the chip based system can perform in a few milliseconds (ms) of time automatic absorption spectrum and chemical identification.

The theme of "using laser light frequency comb for Terahertz heterodyne spectroscopy" (Terahertz multiheterodyne spectroscopy using laser frequency combs) of the study is published in the latest issue of "Optica" journal, author of the paper, the authors of the MIT electrical engineering and computer science graduate student Yang Yang explained, based on the frequency of the OCL optical comb to mathematically reconstruct the absorption of the material after several measuring fingerprint, without any mechanical adjustment, can achieve rapid automation through electronic integration.

The study of the main breakthrough is that can make the QCL optical comb more average spacing, allowing it to the "gain medium" (gain medium) length decided to launch multiple frequency range radiation light source.

In order to make the laser frequency section is more uniform, MIT researchers use a strange shapes of gain medium, each side has rules and symmetrical groove, can change the refractive index of medium and the restoration of transmitting frequency distribution uniformity. They can produce to develop a single, continuous frequency optical comb new gain medium, by hundreds of gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) hierarchical composition, each with different thickness but accurate calibration.

This new building QCL has another interesting feature - with only very short pulses of THz radiation, can from the spectral characteristics of target capture and reliable. Because it's only about 1% of the time, the laser doesn't need a large number of cooling, just like any other THz sources and closer solution can be realized.