Title of Presentation: Development of Miniaturized Intra-Cavity DFG, Fiber-Optic, and Quantum Cascade Laser Systems in Conjunction with Integrated Electronics for Global Studies of Climate Forcing and Response
Primary (Corresponding) Author: Mark Witinski
Organization of Primary Author: Harvard Universtiy
Co-Authors: J. N. Demusz, M. Rivero, C. Tuozzolo and J. G. Anderson
Abstract: The 2007 National Research Council (NRC) report, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, delineates and array of challenges facing society as the global climate system passes through a period of unprecedented changes. The Decadal Survey goes further, recommending specific science missions that will concentrate NASAís tremendous technical resources on meeting these challenges. Central to completing these science missions will be the effective union of advancing laser, electro-optical, and computing technologies with emerging Uninhabited Aerial Systems (UAS), allowing for satellite validation and independent science missions of unprecedented duration and scientific capability, in effect linking NASAís orbital and sub-orbital programs to each other and to the objectives of society as a whole.
In order to harness the power of UASs for in situ atmospheric monitoring of tracers such as CO2, N2O, and CH4 as a precursor for extending detection limits to encompass sub-ppb level species, we have developed small, lightweight, single mode laser systems with co-developed integrated electronics. The laser sources are of various types including newly developed cavity-enhanced difference frequency generation (CE DFG), distributed feedback quantum cascade lasers (DFB QCLs), and new types of commercially available DFB diode lasers. All are continuous wave (cw) and thermo-electrically cooled, ensuring a high instrument duty cycle in a compact, low maintenance package. The light sources are collimated with miniature aspherical lenses and coupled into a home-built astigmatic Herriott cell for detection of the various targets using direct absorption. In parallel with the optical components, we have developed integrated electrical systems for laser control, data processing, and acquisition. A prototype instrument suite is described that illustrates the importance of parallel development of optical and electrical components in achieving an apparatus that is compact, fully automated, and highly capable scientifically. Although the emphasis here is on atmospheric tracers, we are already applying these technologies to spectroscopic measurements of other atmospheric species such as isotopes, free radicals, and reactive intermediates in order address several urgent science priorities defined by the NRC.