INJECTION-SEEDED OPTICAL PARAMETRIC OSCILLATOR FOR AIRBORNE WATER-VAPOR DIAL

Any detailed understanding of the role of water vapour in the global c limate system requires precise measurements in the atmosphere with hig h temporal and spatial resolution. A technique that is appropriate to deliver these data is airborne differential absorption lidar (DIAL) ap plied in the near-infrared spectral range. In order to accurately dete rmine atmospheric water vapour concentrations by means of the DIAL tec hnique tunability and spectral properties of the lidar transmitter are very important. It is demonstrated that the spectral and energy requi rements are achieved using optical parametric oscillators (OPOs) that are line-narrowed by the technique of injection seeding with radiation from dye lasers or from laser diodes. When the OPO is unseeded its sp ectral width is broad enough to suffer only negligible absorption from the H2O absorption lines. Therefore, the unseeded OPO radiation can b e used for off-line measurement, which simplifies the DIAL set-up sign ificantly. In addition, the laser diodes were employed to measure line parameters of a selected H2O absorption line in the near-IR. Their pr ecise determination is important in order to make accurate DIAL measur ements.