The monitoring of the Volatile Organic Compounds (VOCs) in the atmosphere is of great significance for reducing chemical pollution, warning of fires, and improving air quality. Among the VOCs, 1,3-butadiene is essential to monitor as a carcinogenic environmental pollutant. The space-based detection of 1,3-butadiene was made possible by recently development of infrared detection satellites and advances in spectroscopic techniques. In this work, based on the demand for space-based infrared detection of 1,3-butadiene, a modeling method of Earth background radiance characteristics coupled with remote sensing data and physical model is proposed, which can effectively simulate the Earth background radiance field distribution under any atmospheric conditions. Specifically, infrared spectral radiance of 1,3-butadiene was simulated from absorption cross-section data. Further, combined with the radiative transfer model and atmospheric profiles of satellite sensor data, such as temperature, pressure, and H2O and O3 mixing ratio, the atmospheric transmittance and atmospheric background radiance are simulated. Finally, infrared space-based detection of 1,3-butadiene is simulated by coupling Earth background radiance and the detectability is analyzed and discussed by using signal-to-clutter ratio (SCR). The results show that 1,3-butadiene has an absorption effect in space-based infrared detection. The detectability of the narrow band 9.8–10.0 μm and 10.9–11.1 μm is better than that of the wide band 9.0–12.0 μm, and 10.9–11.1 μm is a better detection band for 1,3-butadiene than other bands. This paper provides a method for the space-based infrared detection of 1,3-butadiene. It also provides a reference for selecting the appropriate band for the detector.
An experimental scheme based on interferometry is designed to measure the orbital angular momentum spectrum of vortex beam perturbed by turbulence. The orbital angular momentum spectrum of vortex beam can be calculated by using four light intensity images. The laser beam is modulated by a spatial light modulator to obtain a vortex beam, and then passes through another spatial light modulator loaded with a turbulent phase perturbation hologram to interfere with the reference beam. The orbital angular momentum spectrum of the vortex beam can be obtained by making use of two interference patterns and the intensity patterns of the vortex beam and the reference beam. The results show that the experimental scheme can measure the orbital angular momentum spectrum of the vortex beam affected by turbulence.
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