DIODE-LASER-SEEDED OPTICAL PARAMETRIC OSCILLATOR FOR AIRBORNE WATER-VAPOR DIAL APPLICATION IN THE UPPER TROPOSPHERE AND LOWER STRATOSPHERE

Powerful narrow-band pulsed radiation was generated by a diode-laser-s eeded optical parametric oscillator (OPO) in the 940 nm wavelength reg ion. 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 4.5 mW external cavity diode laser system, the spectral width of the pulsed OPO was line-nar rowed, ending up at a bandwidth of 190 MHz. The spectral purity was me asured by long-path absorption, yielding a value of 99.8%. Seed powers of less than 0.1 mW are sufficient in order to obtain a value as high as 99%. The line-narrowed OPO fulfils the spectral and energy require ments for airborne water vapor DIAL measurements in the upper troposph ere and lower stratosphere. The residual measurement error caused by t he finite bandwidth of the OPO is of the order of 1%, only.