Future Trends in Microelectronics: Up the Nano Creek

Terahertz Quantum Cascade Lasers and Real-Time T-Ray Imaging

Q. Hu, B.S. Williams, S. Kumar, A. W. M. Lee, Q. Qin

Department of Electrical Engineering and Computer ScienceMassachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.

J. L. Reno

Sandia National Labs, Albuquerque, NM 87185-1303, U.S.A.

H. C. Liu and Z. R. Wasilewski

Institute for Microstructural SciencesNational Research Council, Ottawa K1A 0R6, Canada

1.   Introduction

Terahertz (1–10 THz, ħω = 4–40 meV, and λ = 30–300 μm) frequencies are among the most underdeveloped in the electromagnetic spectrum, even though their potential applications are promising in detection of chemical and biological agents, imaging for medical and security applications, astrophysics, plasma diagnostics, end-point detection in dry etching processes, remote atmospheric sensing and monitoring, noninvasive inspection of semiconductor wafers, high-bandwidth free-space communications, and ultrahigh-speed signal processing.¹ This under-development is primarily due to the lack of coherent solid-state THz sources that can provide high radiation intensities (greater than a mW) and continuous-wave (cw) operation. This is because the THz frequency falls between two other frequency ranges in which conventional semiconductor devices have been well developed. One is the microwave and millimeter-wave frequency range, and the other is the near-infrared and optical frequency range. Semiconductor electronic devices that utilize freely moving electrons ...