Frequency tunable THz silicon laser
The exploration of the Terahertz (THz) portion of the electromagnetic spectrum is to a large extent hindered by the lack of coherent radiation sources with tunable frequency. Researchers at the German Aerospace Center (DLR) in cooperation with other institutions have now developed a frequency tunable silicon THz laser.
The laser mechanism is based on intracenter transitions from antimony donors embedded in a silicon crystal. Population inversion is achieved by optical pumping with infrared radiation from a free electron laser. Stimulated Stokes emission has been observed. The emission frequency is tunable and covers the range from 4.6 THz to 5.8 THz. The laser process occurs due to a resonant coupling of the 1s(E) and 1s(A1) donor states via the g-TA phonon, which conserves momentum and energy within a single impurity center.
Further research focuses on electrical excitation of the silicon laser in order to develop a compact source.
Reference :
Stimulated Terahertz Stokes Emission of Silicon Crystals Doped with Antimony Donors
S. G. Pavlov, H.-W. Hübers, J. N. Hovenier, T. O. Klaassen, D. A. Carder, P. J. Phillips, B. Redlich, H. Riemann, R. Kh. Zhukavin, and V. N. Shastin, Phys. Rev. Lett. 96, 037404 (2006).