Terahertz lasers could soon have their moment. Emitting radiation that sits somewhere between microwaves and infrared light along the electromagnetic spectrum, terahertz lasers have been the focus of intense study due to their ability to penetrate common packaging materials such as plastics, fabrics, and cardboard and be used for identification and detection of various chemicals and biomolecular species, and even for imaging of some types of biological tissue without causing damage.
Fulfilling terahertz lasers’ potential for use hinges on improving their intensity and brightness, achieved by enhancing power output and beam quality.
Sushil Kumar, associate professor in Lehigh University’s Department of Electrical and Computer Engineering, and his research team are working at the forefront of terahertz semiconductor ‘quantum-cascade’ laser (QCL) technology. In 2018, Kumar, who is also affiliated with Lehigh’s Center for Photonics and Nanoelectronics (CPN) reported on a simple yet effective technique to enhance the power output of single-mode lasers based on a new type of “distributed-feedback” mechanism.
The results were published in the journal Nature Communications and received a lot of attention as a major advance in terahertz QCL technology. The work was performed by graduate students, including Yuan Jin, supervised by Kumar and in collaboration with Sandia National Laboratories.
Now, Kumar, Jin and John L. Reno of Sandia are reporting another terahertz technology breakthrough: they have developed a new phase-locking technique for plasmonic lasers and, through its use, achieved a record-high power output for terahertz lasers. Their laser produced the highest radiative efficiency for any single-wavelength semiconductor quantum cascade laser. These results are explained in a paper, “Phase-locked terahertz plasmonic laser array with 2 W output power in a single spectral mode” published in Optica.
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