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High-power Ti:sapphire laser at 820 nm for scanning ground-based water-vapor differential absorption lidar

: Wagner, G.; Behrendt, A.; Wulfmeyer, V.; Späth, F.; Schiller, M.


Applied optics 52 (2013), No.11, pp.2454-2469
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Journal Article
Fraunhofer IOSB ()
DIAL; differential absorption lidar; remote sensing and sensors; laser

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 6.75Wwith 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 about 2.4 km.