A research team led by Prof. GAO Xiaoming from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences developed a near-infrared laser heterodyne radiometer (LHR), that could greatly improve water vapor measurement in the atmosphere and reduce unwanted noise during measurements.

The findings were published in Sensors and Actuators B: Chemical.

The LHR is small, portable, and has high spectral resolution, making it a great candidate for use on future satellites. However, noise from its local oscillator affects its accuracy and therefore limit its usable spectral range.

To solve this problem, the researchers introduced a semiconductor optical amplifier (SOA) to reduce the noise from the local oscillator. This greatly improved the LHR's accuracy and thus expands the device's range.

By using a tunable laser as the local oscillator and operating the SOA in dynamic gain saturation, they stabilized the laser power and significantly lower the noise of the device.

"With this improvement, the LHR can better measure water vapor and its isotopes in the atmosphere, which is important for understanding climate change and the environment," said Dr. LI Jun, a member of the team.

It also helps provide valuable data for studying the Earth's water cycle and atmospheric transport, said LI.