Atmospheric Concentration Retrieval Using a Quantum Cascade Laser

Atmospheric Concentration Retrieval Using a Quantum Cascade Laser System and Mid-Infrared Technologies Jensen Cheong, Stuyvesant High School Student MIRTHE Laboratory, Department of Electrical Engineering, City College of New York, NY 10031 Introduction Ozone (O 3) and Ammonia (NH 3) are air pollutants which pose a threat to human beings. They are some of the main causes for lung cancer and respiratory damage. In order to prevent future illnesses we first need to understand what is in our atmosphere and in what quantities they come in. As the world is rapidly industrializing, more pollutants are being released into the air. Quantum Cascade Lasers is a technology of the late 20 th century and is promising in its role in remote sensing. Along with mid-infrared technologies, this experiment aims to accurately retrieve the atmospheric concentration of gases as a first step in humans race to understand our environment. • Semi-conductor laser. • Concentration is based on transmission. Why Mid-Infrared • Once the electron loses energy it quickly is collected and undergoes the process again. • We use Beer’s Law with the Absorption to find concentration. • 1045 cm-1 frequency and tuning range up to 5 cm-1 corresponds to the absorption coefficients of O 3 and NH 3 (9. 7µm and 9. 55 µm respectively). Newtonian Telescope Experimental Setup QCL Telescope Gas • O 3 and NH 3 have stronger absorption lines at the mid-infrared region as opposed to the near-infrared region. • Less light extinction- the scattering of light due to molecules and aerosols. • Electrons “jump” energy levels and emit photons of light in the process. • Absorption is the negative natural log of transmission. Motivation To develop a system using a quantum cascade laser, telescope, and detector to retrieve the atmospheric concentration of gases such as ozone and ammonia which pose a threat to human beings. Quantum Cascade Laser Retrieval Method 3 TE IR deter module Detector Carbon Fiber Board • The QCL will be fired into the telescope where the beam will pass through the trace gas and the detector at the end will collect the light. Right angle mirrors Lens F E Primary mirror • Performs accurately in severe weather or foggy conditions. D Expected Results The concentration will match the result from theoretical setup involving GENSPECT and HITRAN. A Anodized Aluminum Rails B C 10. 5” 8. 5” Secondary mirror The concentration should also fit Beer’s Law. 36” Data retrieved will also include Ozone concentrations as well as Ammonia Concentrations. Ultra-light Aluminum Bread Board Base • This telescope used a primary concave mirror and a secondary convex mirror. Sample data to the right. • Portable. • Cassegrain Version of Telescope. Conclusion Sponsors: National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC) NASA Goddard Institute for Space Studies (GISS) NASA New York City Research Initiative (NYCRI) Mid-Infrared Technologies for Health and Environment (MIRTHE) NOAA-CREST Contributors: Jensen Cheong, Stuyvesant High School Student Fred Moshary, Principal Investigator, Dept. of Electrical Engineering CCNY Paul Corrigan Paolo Castillo, Graduate Student, Dept. of Electrical Engineering CCNY Applications • Our data concludes that the Quantum Cascade Laser System and Mid-Infrared Technologies accurately measured the atmospheric concentration of gases. • Our technique can be adopted and developed into high powered systems which can measure atmospheric concentration of ozone and ammonia over a large amount of area. • We can also conclude that the system is ready to be developed through further research and engineering to be used to larger fields. • We can modify this technique to fit other gases in our atmosphere which may be sensitive to the mininfrared spectrum. • Patterns in air quality and pollution may lead us to conclusions and prevention techniques in health and the environment. • This telescope is also mounted with irises and a laser on the top for alignment purposes. References • Lwin, Maung T. Evaluation of Quantum Cascade Laser Open-path Systems. Thesis. City College of New York, 2008. Print. • Castillo, Paolo. The Development of Quantum Cascade Laser System for Simultaneous Ozone-Ammonia Retrievals. Web. • Unknown. Performance Modeling and Validation of a Chirped Pulse Quantun Cascade Laser for Open-Path Ambient Gas Monitoring. Print