Applied Physics

THz in Practice ...

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Science  03 Feb 2006:
Vol. 311, Issue 5761, pp. 579
DOI: 10.1126/science.311.5761.579b

Terahertz (THz) radiation penetrates cloth and plastic to a degree that scales inversely with the frequency. Solid-state laser sources, such as quantum cascade lasers, have been fabricated with energy-level separations tuned for emission toward the high end of the THz regime. However, efforts to lower the frequency, and thereby improve penetration, have been hindered by scattering problems and by reduced out-coupling efficiency as the energy-level spacing approaches the emission linewidth.

Worral et al. demonstrate a superlattice quantum cascade laser that emits 2-THz continuous wave radiation at an operating temperature of 47 K. They accessed this low-frequency region in part by precise modulation of the aluminum doping level in the GaAs/AlGaAs lasing medium. The result suggests that the emission frequency might be reduced further by careful control of the fabrication and design process. — ISO

Opt. Exp. 14, 171 (2006).

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