A research team led by associate Prof. XU Zhenyu from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has proposed a new method to detect atmospheric greenhouse gas column with high-resolution laser heterodyne spectroscopy.
The method, which was published in Optics Letter and highlighted as an Editor's Pick, addresses the challenge of the increase of the collected effective radiation power limited by the restricted solid angle as described by optical antenna theory.
Laser heterodyne spectrometer (LHS) has been used as a complementary tool for ground-based Fourier transform spectrometer in greenhouse gas column measurement in recent years due to its high spectral resolution, small size and easy integration. However, for laser heterodyne spectroscopy, the signal-to-noise ratio (SNR) of the heterodyne signal cannot be improved by increasing the size of the optical receiver because the optical antenna theory limits the effectively collected solar radiation power.
The novel method proposed in this study improves LHS's SNR by utilizing a semiconductor optical amplifier (SOA) to resolve the issue with limited SNR induced by optical antenna theory.
The results of the study show that the developed SOA-assisted LHS has greatly improved the greenhouse column measurement accuracy and weak light signal detection capability compared with the conventional LHS.
This work has enhanced the performance of LHS, showing great potential for remote sensing of atmospheric greenhouse gases.
"Our work has greatly improved the accuracy of measurements of SNR and CO2 column abundance, it will be extended to mid-infrared LHR for high-resolution sensitive detection of atmospheric column or vertical profiles of more gas components," said DENG Hao, first author of the study.
The research was funded by the National Natural Science Foundation of China, the National Key Research and Development Program and other projects.
Schematic diagram of the developed SOA-assisted LHS. (Image by XU Zhenyu)
Atmospheric CO2 heterodyne signals obtained by SOA-assisted LHS and traditional LHS, respectively. (Image by XU Zhenyu)
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