Low-temperature THz time domain waveguide spectrometer with butt-coupled emitter and detector crystal

Area of Science:

• Terahertz (THz) spectroscopy
• Condensed matter physics
• Spectroscopic instrumentation

Background:

• Traditional THz time-domain spectroscopy (THz-TDS) often requires complex setups with THz-transparent windows and external optics.
• Integrating THz components within a cryostat simplifies experiments and minimizes signal loss.
• Cryogenic measurements are crucial for understanding temperature-dependent material properties.

Purpose of the Study:

• To demonstrate a compact, high-resolution THz time-domain waveguide spectrometer operable within a cryostat.
• To enable THz emission and absorption measurements entirely inside a cryogenic environment.
• To investigate the temperature dependence of THz spectral features, specifically the absorption of 1,2-dicyanobenzene.

Main Methods:

• Development of a THz spectrometer with a photo-Dember emitter and ZnTe electro-optic detector integrated onto a parallel copper-plate waveguide.
• Operation entirely within a cryostat, eliminating the need for THz-transparent windows or external mirrors.
• Utilizing asynchronous optical sampling for high-resolution spectral acquisition from 0.2 to 2.0 THz.
• Measuring THz emission and absorption spectra of 1,2-dicyanobenzene film as a function of temperature.

Main Results:

• Successful demonstration of a compact, cryostat-integrated THz time-domain waveguide spectrometer.
• Acquisition of high-resolution THz spectra (0.2–2.0 THz) within the cryogenic environment.
• Observation of temperature-dependent THz emission from the photo-Dember emitter.
• Measurement of the absorption spectrum of 1,2-dicyanobenzene, showing a blue shift of an absorption peak around 750 GHz with increasing temperature.

Conclusions:

• The developed compact THz spectrometer allows for efficient, high-resolution spectroscopic measurements inside a cryostat.
• The system eliminates the need for complex external THz optics and electrical feed-throughs.
• The observed blue shift in the 1,2-dicyanobenzene absorption spectrum with increasing temperature provides insights into its cryogenic properties.