Electrically tunable hot-silicon terahertz attenuator.

We have developed a continuously tunable, broadband terahertz attenuator with a transmission tuning range greater than 10³. Attenuation tuning is achieved electrically, by simply changing the DC voltage applied to a heating wire attached to a bulk silicon wafer, which controls its temperature between room temperature and ~550 K, with the corresponding free-carrier density adjusted between ~1011 cm-3 and ~ 1017cm-3 . This "hot-silicon"-based terahertz attenuator works most effectively at 450-550 K (corresponding to a DC voltage variation of only ~7 V) and completely shields terahertz radiation above 550 K in a frequency range of 0.1-2.5 THz. Both intrinsic and doped silicon wafers were tested and demonstrated to work well as a continuously tunable attenuator. All behaviors can be understood quantitatively via the free-carrier Drude model taking into account thermally activated intrinsic carriers. [ABSTRACT FROM AUTHOR]