THz optical beat-note detection with a fast superconducting hot electron bolometer operating up to 31 GHz

Area of Science:

• Superconducting devices
• Terahertz (THz) technology
• Detector physics

Background:

• Hot-electron bolometers (HEBs) are crucial for THz detection.
• Superconducting materials like niobium nitride offer potential for high-performance detectors.
• Understanding HEB performance at THz frequencies is essential for advancing scientific instrumentation.

Purpose of the Study:

• To evaluate the performance of a niobium nitride-based hot-electron bolometer (HEB) at THz frequencies.
• To characterize the voltage response and bandwidth of the HEB detector.
• To assess the sensitivity and noise equivalent power (NEP) of the HEB.

Main Methods:

• Fabrication and packaging of a niobium nitride HEB.
• Measurement of the HEB's voltage response using various THz sources.
• Characterization of the impulse response and 3 dB cutoff frequency.
• Heterodyne beating experiments with a THz quantum cascade laser frequency comb.
• Evaluation of the optical noise equivalent power (NEP) at 1 MHz.

Main Results:

• The packaged HEB operating at 7.5 K exhibits a 3 dB cutoff frequency around 2 GHz.
• Detection capabilities extend beyond 30 GHz, as demonstrated in heterodyne beating experiments.
• An optical noise equivalent power (NEP) of 0.8 pW/√Hz was measured at 1 MHz.

Conclusions:

• Superconducting niobium nitride HEBs demonstrate robust performance at THz frequencies.
• The HEB shows a broad detection bandwidth, with significant capability beyond its 3 dB cutoff.
• The measured NEP indicates high sensitivity, making the HEB suitable for various THz applications.