Diode-laser-seeded optical parametric oscillator for airborne water vapor DIAL application in the upper troposphere and lower stratosphere

Abstract

Powerful narrow-band pulsed radiation was gen- erated by a diode-laser-seeded optical parametric oscillator (OPO) in the 940 nm wavelength region. With a pump energy of 180 mJ=pulse from a Q-switched Nd:YAG laser an OPO output energy as high as 40 mJ=pulse could be extracted at the signal wavelength. By injection seeding with a 4: 5m W external cavity diode laser system, the spectral width of the pulsed OPO was line-narrowed, ending up at a bandwidth of 190 MHz. The spectral purity was measured by long-path ab- sorption, yielding a value of 99:8%. Seed powers of less than 0: 1m Ware sufficient in order to obtain a value as high as 99%. The line-narrowed OPO fulfils the spectral and energy requirements for airborne water vapor DIAL measurements in the upper troposphere and lower stratosphere. The residual measurement error caused by the finite bandwidth of the OPO is of the order of 1%, only.