Extension of spectral region of sub-terahertz spectroscopic system with multimode laser diodes by simple configuration for photomixing technique

Abstract

The photomixing technique is applied to a sub-terahertz spectroscopic system with continuous-wave multimode laser diodes (CW-MLDs) to extend the spectral range. I employ two CW-MLDs which have equal spectral widths and slightly different central wavelengths, where sophisticated techniques such as external cavities are not required. I observe that photomixing causes generation of new spectral components of the signal in the frequency region of about 0.5–0.65 THz, while spectral components are limited below about 0.5 THz before the photomixing technique is applied. The generation of spectral components implies that the spectral range covered by the spectroscopic system is extended to higher-frequency regions.