High-sensitivity laser heterodyne radiometer based on balanced detection technology

A heterodyne radiometer (LHR) based on the balanced-detection method has been developed to evaluate system performance under both balanced-detection and single-channel-detection modes. Experimental results demonstrate that the balanced-detection LHR exhibits superior suppression of laser-induced noise compared to the traditional single-channel-detection LHR. The developed system achieved a noise equivalent power (NEP) of 2.53 × 10−15 W/√Hz, which is only 1.7 times of the theoretical quantum limit. To further assess system performance, measurements of atmospheric carbon dioxide (CO2) column abundance were conducted. The measurement precision of the balanced-detection LHR was determined to be approximately 0.6%, which is 5.67 times higher than that of the single-channel-detection LHR.