Terahertz Quasi-Time Domain Spectroscopy using a 808nm multimode diode laser

Ivan Cedrick Malaluan Verona (National Institute of Physics, University of the Philippines Diliman, Philippines)
Alexander De los Reyes (National Institute of Physics, University of the Philippines Diliman, Philippines)
Hannah Bardolaza (National Institute of Physics, University of the Philippines Diliman, Philippines)
Elmer Estacio (National Institute of Physics, University of the Philippines Diliman, Philippines)

Journal of Physics and Its Applications
Vol 5, No 2 (2023): May 2023

We report on a terahertz quasi-time domain spectroscopy (QTDS) system based on a low-cost continuous wave multimode diode laser. Commercially available low-temperature grown gallium arsenide (LT-GaAs) based photoconductive antennas (PCAs) with spiral and dipole configurations were used as emitter and detector, respectively. Terahertz pulses spaced at approximately 55 ps with a bandwidth of 400 GHz were obtained. Parametric measurements of the terahertz peak-to-peak intensity were performed by varying the injection current and temperature while maintaining incident laser power. The highest peak-to-peak intensity was obtained at 170mA injection current and 20° C temperature settings. The change in the THz peak-to-peak intensity is attributed to the mode hopping characteristics of the device which in turn, is dependent on injection current and temperature.