A method of monitoring the temperature of the photoconductive antenna

Photoconductive antenna (PCA), as the most widely used emitter (or detector) in Terahertz time-domain spectroscopy (TDS) system, virtually acts as a semiconductor switch, whose electrical conductivity controlled by pump light. At the same time, the heat caused by the pump light and the electrical bias will be stacked in a tiny area. Inevitably, the thermal effects, which may reduce the performance of PCA and the operational lifetime of device, need to be considered, especially for that generated by a compact package fiber-pigtailed photoconductive antenna. Nonetheless, there still lacks of relevant reports about real-time temperature monitoring for PCA. This paper proposes a method to obtain the temperature information by observing the temperature dependent frequency drifting of radiation spectroscopy. In other words, it converts the temperature information via analyzing the radiation spectrum of the conventional TDS system. In this work, we simulate a design of meta-atom-loaded PCA with indium antimonide (InSb). As a kind of temperature-dependent permittivity of the semiconductor, InSb is stuffed into the gap of split-ring resonator (SRR). When the temperature increases from 300K to 380 K, the resonance frequency shifts from 0.582THz to 0.678THz (a shift more than 16%), calculated by the commercial software-CST. The significant blue shift is caused by the SRR loading temperature sensitive materials, well analyzed by the LC resonant circuit model. Then, one can clearly obtain the actual antenna temperature from the radiation spectrum through the relationship between temperature and resonance frequency. Always, this simply method could be applied to shift the peak frequency of spectrum for various applications.