Turn-key compact high temperature terahertz quantum cascade lasers: imaging and room temperature detection

Area of Science:

• Physics
• Electrical Engineering
• Optics

Background:

• Terahertz (THz) quantum cascade lasers (QCLs) are emerging as compact and efficient THz sources.
• Widespread applications require reliable and well-characterized THz generation systems.

Purpose of the Study:

• To provide a comprehensive analysis of THz QCL performance.
• To evaluate their suitability for various applications, including imaging.
• To assess measurement techniques and potential artifacts.

Main Methods:

• Two THz QCLs were operated in a liquid nitrogen-cooled dewar with a pulse driver.
• Characterization included current-voltage (I-V) measurements, spectral analysis, polarization, pulse duration, and repetition rate.
• Laser power was measured using a germanium photoconductor and compared with a Golay detector.
• Far-field mode profiles were analyzed.
• Imaging capabilities were demonstrated using optical elements and a test object.

Main Results:

• Detailed I-V characteristics, emission wavelengths, polarization, pulse lengths, and repetition rates were obtained.
• Laser power measurements were compared between a germanium photoconductor and a Golay detector, with potential artifacts evaluated.
• Far-field mode profiles were found to correlate with the internal laser mode structure.
• Successful imaging of optical elements and a test object was achieved.
• Video-rate, room-temperature imaging was demonstrated conceptually.

Conclusions:

• The investigated THz QCLs provide a robust and tunable THz source.
• The characterization confirms their potential for diverse applications, particularly in imaging.
• The study validates measurement techniques and highlights the feasibility of advanced THz imaging systems.