High-sensitivity infrared heterodyne radiometer using a tunable-diode-laser local oscillator

Area of Science:

• Spectroscopy
• Radiometry
• Laser Technology

Background:

• Blackbody heterodyne radiometry is crucial for atmospheric and astronomical observations.
• Previous systems often relied on less tunable or less efficient local oscillators.

Purpose of the Study:

• To evaluate the performance of a widely tunable lead tin selenide (PbSnSe) diode laser as a local oscillator (LO) in a blackbody heterodyne radiometer.
• To achieve improved signal-to-noise ratio (SNR) for high-resolution absorption spectroscopy.

Main Methods:

• Utilized a PbSnSe diode laser as the LO in a blackbody heterodyne radiometer setup.
• Employed a closed-cycle cryogenic cooler for the diode laser.
• Tuned the diode laser to obtain absorption spectra of ethylene at 10.6 micrometers.

Main Results:

• Achieved SNR performance an order of magnitude better than previously reported diode laser systems.
• The system's performance was within a factor of 2.5 of a carbon dioxide (CO2) laser LO.
• Demonstrated performance within a factor of 6 of an ideal radiometer.
• Obtained high-resolution ethylene absorption spectra with a 0.4-second post-detection integration time.

Conclusions:

• Widely tunable PbSnSe diode lasers represent a significant advancement for blackbody heterodyne radiometry.
• This technology offers a viable and high-performing alternative for sensitive spectroscopic measurements.
• The system demonstrates potential for various applications requiring precise spectral analysis.