Real-time visualization of transient terahertz waveforms emitted from a resonant tunneling diode

Visualizing the electromagnetic waveforms of device outputs is a fundamental aspect in the development of terahertz emitters and the optimization of their performance. However, such optimization processes are often challenging owing to the frequency of terahertz waves exceeding the detection bandwidth of conventional oscilloscopes, which is typically limited to below 100 GHz. In this study, we employed high-sensitivity, single-shot terahertz time-domain spectroscopy using a femtosecond laser and a reflective echelon mirror to visualize the electric field waveforms generated by terahertz devices. This approach enabled real-time observation of terahertz waveforms emitted from both an impact ionization transit-time diode and a resonant tunneling diode. Moreover, this setup allowed us to capture the transient emission of chirped, large-amplitude terahertz waves during device switching, which is likely attributed to an ultrafast transient change in the device capacitance and bias voltage. These findings underscore the importance of real-time terahertz waveform measurements for advancing terahertz technology development.