May 16, 2025

Researchers from Germany have developed a high-speed pyroelectric receiver using a LiTaO3 pyroelectric detector as a cryogen-free solution for terahertz (THz) absorption spectroscopy measurements. This receiver can record spectra at frequencies up to 281 Hz without introducing artifacts into the observed spectral absorption profile. By operating at room temperature, the compact system provides a practical and efficient alternative to cryogenically cooled detectors, making it a reliable platform for THz spectroscopy, offering robust performance without the need for complex cooling infrastructure.

Cryogenic cooling has long been the standard in high sensitivity detection systems, particularly in applications requiring the measurement of low-energy signals, such as terahertz (THz) spectroscopy.  However, cryogenic systems are complex, expensive, and require continuous maintenance, including replenishing cooling agents. Cryogen-free detectors offer a more practical, compact, and cost-effective solution, eliminating the need for cumbersome cooling systems.

To optimize the performance and testing of the high-speed LiTaO3 pyroelectric receiver, researchers integrated the innovative capabilities of Wavelength Electronics’ QCL1000 OEM driver. Given the significant impact of temperature and noise on the pyroelectric receiver’s performance, ultra-low noise current drivers were required. Wavelength Electronics’ QCL1000 OEM driver operates with a low noise floor, maintaining an output current RMS noise of less than 0.7 μA at operating frequencies up to 100 kHz. This level of noise reduction is vital for accurately capturing the rapid spectral features without introducing artifacts, thereby ensuring a clean spectral absorption profile.

Continuous ramping of the laser current was required for fast measurements with high spectral resolution. Because the spectral resolution of the system is given by the laser linewidth, the laser drive must maintain a narrow linewidth from the QCL. The QCL1000 OEM driver achieved this with a narrow linewidth of 2 x 10-4 cm-1, approximately 6 MHz. With a typical stability of around 10 ppm, the QCL1000 OEM driver ensures optimal operating conditions for both the THz QCL and the pyroelectric receiver, significantly enhancing measurement capabilities. This integration has proven instrumental in achieving high-speed data acquisition rates of up to 281 Hz without compromising the integrity of the recorded spectra.

The complete case study is available as CS-LD13.

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