[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Atmospheric CO <sub/>2</sub> -Detection Via Scheimpflug DIAL Employing a Simple Fiber Amplifier

摘要： The ever-increasing worldwide environmental awareness has prompted much effort to minimize humanity’s ecological footprint. This has led to increased demands for reliable technologies for assessing the current situation as well as the efficiency of new policies and interventions. In particular, CO2-monitoring has attracted lots of attention as CO2 is the greenhouse gas that is emitted in the largest quantities. Differential absorption light detection and ranging (DIAL) is a well-established method for measuring the atmospheric CO2-concentration. Conventional implementations of this method rely on tunable pulsed laser sources whose back-scattering at different distances are compared for different wavelengths, corresponding to being on and off the CO2-resonances, to calculate the concentration along the measured path. Integrating these types of laser sources with DIAL systems have proven to be complicated and often suffer from instabilities. Therefore, a continuous-wave DIAL (CW-DIAL) scheme was recently proposed that relates signals at different distances to different points on a detector by using a Scheimpflug configuration. This technique relies on a rapidly tunable, narrow-linewidth source to resolve individual CO2-absorption lines, making distributed feedback laser diodes (DFB) ideal. However, they lack the necessary power levels for ranging over relevant distances, usually in the km-range. We therefore designed a fiber amplifier, based on an 11 m Er-/Yb-doped fiber, to boost the power level to about 1.3 W. The output was then expanded by a telescope and the back-scattered signal was collected by a second telescope, as schematically illustrated in Fig. 1 (a). The wavelengths could be tuned about 3 nm with a 35 dB signal-to-noise ratio, as shown in Fig. 1 (b), by adjusting the driving current to the DFB, while keeping a linewidth of about 3 MHz –well below the CO2-linewidth around 1 GHz at normal pressure. The system was used to measure the atmospheric CO2-concentration above the city of Lund, Sweden, over a 15 hour period. Using the backscattered data from 48 different wavelengths over the R14, R16 and R18 absorption peaks, the range-resolved concentration, illustrated in Fig. 1 (c) with a 500 m bin discretization, could be retrieved. The large increase in the error at the final concentration bin is related to the nonlinear range mapping onto the detector, i.e. fewer pixels for greater distances. Regardless, these results show that our simple fiber source already fulfills the necessary requirements for field application of CW-DIAL.