title: High-power Ti:sapphire laser at 820 nm for scanning ground-based water-vapor differential absorption lidar.
abstract: The Ti:sapphire (TISA) laser transmitter of the mobile, three-dimensional-scanning water-vapor differential absorption lidar (DIAL) of the University of Hohenheim is described in detail. The dynamically-stable, unidirectional ring resonator contains a single Brewster-cut TISA crystal, which is pumped from both sides with 250 Hz using a diode-pumped frequency-doubled Nd:YAG laser. The resonator is injection seeded and actively frequency-stabilized using a phase-sensitive technique. The TISA laser is operating near 820 nm, which is optimum for ground-based water-vapor DIAL measurements. An average output power of up to 6.75 W with a beam quality factor of M2<2 is reached. The pointing stability is <13 μrad (rms), the depolarization <1%. The overall optical-optical conversion efficiency is up to 19%. The pulse length is 40 ns with a pulse linewidth of <157 MHz. The short- and long-term frequency stabilities are 10 MHz (rms). A spectral purity of 99.9% was determined by pointing to a stratus cloud in low-elevation scanning mode with a cloud bottom height of ≈2.4 km.
authors.affiliation: Institute of Physics and Meteorology (IPM), University of Hohenheim (UHOH), Stuttgart 70599, Germany. Gerd.Wagner@uni-hohenheim.de
authors.forename: Gerd
authors.initials: G
authors.lastname: Wagner
authors.forename: Andreas
authors.initials: A
authors.lastname: Behrendt
authors.forename: Volker
authors.initials: V
authors.lastname: Wulfmeyer
authors.forename: Florian
authors.initials: F
authors.lastname: Späth
authors.forename: Max
authors.initials: M
authors.lastname: Schiller