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High-power portable terahertz laser systems

Abstract

Terahertz (THz) frequencies remain among the least utilized in the electromagnetic spectrum, largely due to the lack of powerful and compact sources. The invention of THz quantum cascade lasers (QCLs) was a major breakthrough to bridge the so-called ‘THz gap’ between semiconductor electronic and photonic sources. However, their demanding cooling requirement has confined the technology to a laboratory environment. A portable and high-power THz laser system will have a qualitative impact on applications in medical imaging, communications, quality control, security and biochemistry. Here, by adopting a design strategy that achieves a clean three-level system, we have developed THz QCLs (at ~4 THz) with a maximum operating temperature of 250 K. The high operating temperature enables portable THz systems to perform real-time imaging with a room-temperature THz camera, as well as fast spectral measurements with a room-temperature detector.

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Fig. 1: Probability density functions of subband states in a THz QCL with two quantum wells per module in the active region.
Fig. 2: Optical and electrical characterization of a device fabricated from wafer G652 with dimensions 1.23 mm × 150 μm, biased with 400-ns pulse width at 500 Hz.
Fig. 3: Measurements of a TEC-cooled THz QCL device using room-temperature pyroelectric detectors and a THz camera.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank A. Lee and W. Kao at LongWave Photonics for the loan of the NEC THz camera. This work is supported by National Aeronautics and Space Administration (NASA), the Canada First Research Excellence Fund and the Natural Sciences and Engineering Research Council of Canada (NSERC).

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Authors

Contributions

A.K. developed the simulation and optimization codes, designed and fabricated the lasers and performed the measurements. The single-stage TEC chamber was designed by A.K. and further improved by A.K.P. A.K.P. optimized the multistage TEC set-up and performed the real-time imaging with a THz camera and spectral measurements using a pyroelectric detector. C.D. performed MBE growth and optimization of growth conditions, as well as MBE related material characterization, under the supervision of Z.R.W. The project was supervised by Q.H., who was also involved in the design and formulated the design strategy of clean n-level systems for the QCL structures. A.K. and Q.H. wrote the paper with editing help from C.D. and Z.R.W. A.K.P. wrote the TEC section in the Supplementary Information. C.D. and Z.R.W. wrote the MBE growth details in the Supplementary Information.

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Correspondence to Qing Hu.

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Khalatpour, A., Paulsen, A.K., Deimert, C. et al. High-power portable terahertz laser systems. Nat. Photonics 15, 16–20 (2021). https://doi.org/10.1038/s41566-020-00707-5

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