Open Cell Ring Down Spectrometer to Measure Atmospheric Visible and Infrared Ambient Light Extinction

Directed Energy systems have a variety of applications in the US Navy, but are affected by particles in the atmosphere; therefore, accurate measurements of particle-induced light extinction are critical to the development and deployment of DE systems. However, no commercial instruments exist capable of measuring ambient extinction at DE-relevant wavelengths. Here we propose an accurate, robust system for measuring ambient light extinction at multiple, DE-relevant wavelengths with high dynamic range. We propose a hybrid instrument that combines open-path cavity ring down spectroscopy (OP-CRDS) and open-path integrated cavity output spectroscopy (OP-ICOS), to measure extinction due to ambient aerosol in a free-flowing air stream. Initial proof-of-concept work focuses on extending the dynamic range of our existing single-wavelength system as required for US Navy applications, with continuing development efforts extending the concept to additional wavelengths on the same platform. We will improve the dynamic range by a) improving the laser, laser control, and detection system of the CRD system and b) implementing ICOS in the same optical cavity. After introducing these improvements, we will thoroughly characterize and test the measurement system using calibration gas standards, laboratory-generated aerosol, and environmental and vibration testing that will simulate anticipated conditions in maritime/littoral environments.