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Development of Terahertz Quantum-cascade Lasers

• Authors: A. Lee, Q. Qin, T.-Y. Kao, D. Burghoff, I. Chan, S. Huang, N. Han, Q. Hu, in collaboration with Dr. J. Reno at Sandia National Lab
• Sponsorship: NSF, NASA

The terahertz frequency range (1-10 THz) has long remained undeveloped, mainly due to the lack of compact, coherent radiation sources. Transitions between subbands in semiconductor quantum wells were suggested as a method to generate long wavelength radiation at customizable frequencies. However, because of difficulties in achieving population inversion between narrowly separated subbands and mode confinement at long wavelengths, THz lasers based on intersubband transitions were developed only very recently. Taking a completely novel approach, we have developed THz quantum-cascade lasers based on resonant-phonon-assisted depopulation and using metal-metal waveguides for mode confinement. The schematics of both features are illustrated in the top-left of Figure 1. Based on the combination of these two unique features, we have developed many THz QCLs with record performance, including a maximum pulsed operating temperature at 186 K (top-right), a maximum cw operating temperature at 117 K (bottom-right), and a maximum power level of ~250 mW (bottom-left).



Figure 1: Top left: Band diagram and subband wave functions of a THz quantum-cascade laser based on resonant-phonon design. Top right: Power-current (L-I) curves of a THz laser device with a maximum operating temperature of ~200 K. Bottom right: Cw power-current (L-I) curves of a THz laser device with a maximum operating temperature of ~117 K. Bottom left: Power-current (L-I) curves of a THz laser device with a maximum power level of ~250 mW.

Qing Hu

• Title: Professor
• Department: Department of Electrical Engineering and Computer Science

Collaborators

• J. L. Reno, Sandia National Lab.

Postdoctoral Associate

• Alan Lee, RLE

Graduate Students

• Qi Qin, Research Assistant, EECS
• Wilt Kao, Research Assistant, EECS
• David Burghoff, Research Assistant, EECS
• Ivan Chan, Research Assistant, EECS
• Shengxi Huang, Research Assistant, EECS
• Ningren Han, Research Assistant, EECS
• Xiaowei Cai, Research Assistant, EECS

Support Staff

• G. Brewington, Administrative Assistant

Publications

S. Kumar, C. W. I. Chan, Q. Hu, and J. L. Reno, “A 1.8 THz quantum-cascade laser operating up to 163 K; significantly above the temperature of ,” Nature Physics 7, 166-171 (2011).

Sushil Kumar, “Recent Progress in Terahertz Quantum-Cascade Lasers,” IEEE Journal of Quantum Electronics, 17, 38 (2011). (Invited)

David Burghoff, Tsung-Yu Kao, Dayan Ban, Alan Wei Min. Lee, Qing Hu, and John Reno,“A terahertz pulse emitter monolithically integrated with a quantum cascade laser,” Appl. Phys. Lett. 98, 061112 (2011).

Qi Qin, John L. Reno, and Qing Hu, “MEMS-based tunable terahertz wire-laser over 330 GHz,” Opt. Lett. 36, 692 (2011).

Qi Qin and Qing Hu, “MEMS-plunger platform for tunable terahertz wire-laser at ~ 5 K,” J. Micromechanics and Microengineering, 21, 075004 (2011).

Y. Ren, J.N. Hovenier, R. Higgins, J.R. Gao, T.M. Klapwijk, S.C. Shi, , B. Klein, T-Y. Kao, Q. Hu, and J. L. Reno, “High-resolution heterodyne spectroscopy using a tunable quantum cascade laser around 3.5 THz,” Appl. Phys. Lett. 98, 231109 (2011).

I. Bhattacharya, C. W. I. Chan, and Q. Hu, “Effects of stimulated emission on transport in terahertz quantum cascade lasers based on diagonal designs,” Appl. Phys. Lett. 100, 011108 (2012).

Alan Wei Min Lee, Tsung-Yu Kao, David Burghoff, Qing Hu, and John L. Reno, “Terahertz Tomography Using Quantum-Cascade Lasers,” Opt. Lett. 37, 217 (2012).

Sushil Kumar and Qing Hu, “Investigation of possible microcavity effect on lasing threshold of nonradiative-scattering-dominated semiconductor lasers,” Appl. Phys. Lett. 100, 041105 (2012).

Y. Ren, J. N. Hovenier, M. Cui, D. J. Hayton, J. R. Gao, T. M. Klapwijk, S. C. Shi, T-Y. Kao, Q. Hu, and J. L. Reno, “Frequency locking of single-mode 3.5-THz quantum cascade lasers using a gas cell,” Appl. Phys. Lett. 100, 041111 (2012).

S. Fathololoumi, E. Dupont, C.W.I. Chan, Z.R. Wasilewski, S.R. Laframboise, D. Ban, A. Mátyás, C. Jirauschek, Q. Hu, and H.C. Liu, “Terahertz quantum cascade lasers operating up to ~200 K with optimized oscillator strength and improved injection tunneling,” Optics Express, 20, 3866 (2012).

Miriam S. Vitiello, Rita C. Iotti, Fausto Rossi,Alessandro Tredicucci, Qing Hu, and Gaetano Scamarcio, “Non-equilibrium longitudinal and transverse optical phonons in terahertz quantum cascade lasers,” Appl. Phys. Lett. 100, 091101 (2012).

Sushil Kumar, Qi Qin, Chun W. I. Chan, Qing Hu, and John L. Reno, “High-temperature performance and broad continuous tunability of terahertz quantum-cascade lasers,” IEEE Phonoics West, San Francisco, CA, 22-27 January (2011). (Invited)

Alan Lee, Tsung-Yu Kao, David Burghoff, Q. Hu, and J. L. Reno, “THz optical coherence tomography based on quantum cascade lasers,” IRMMW-THz 2011, Houston, TX, October 3-7 (2011). (Invited keynote talk)

Q. Hu, “THz Quantum Cascade Lasers, Sensing, and Real-Time Imaging,” DTRA CB Defense THz Forum, Falls Church, Virginia, April 3 (2012). (Invited)