Hans H. Klingenberg

Lidar research network water vapor and wind

This paper reports on a workshop which took place on April 08/09, 2002 at the University of Hohenheim, Stuttgart, Germany. During this workshop, laser and lidar experts as well as experts in atmospheric sciences came together. The goals of this workshop were to establish an interdisciplinary network on lidar research, to develop operational reference systems for water vapor and wind lidar measurements and to demonstrate the significant impact of water vapor and wind lidar systems on climate and weather research. The main result was the setup of an interdisciplinary expert network Lidar research water vapor and wind. This network is responding to large gaps in our knowledge of the global water vapor and wind distribution and shall improve weather and climate research. The network has mainly the following objectives: 1) The development of high-performance, high-power laser transmitters for wind and water vapor measurements based on novel pump laser designs, 2) research on efficient frequency conversion techniques of the high-power pump light into wavelengths required for water vapor and wind lidar systems, 3) the development of an operational reference water vapor differential absorption lidar system, also as a demonstrator for space borne missions like the Water Vapor Lidar Experiment in Space (WALES), 4) the performance of observation system simulation experiments (OSSEs) in order to demonstrate the impact of lidar data on nowcasting and short-range weather forecast, 5) the extension of the application of current and future lidar data in combination with other instruments for process studies, 6) the design of future field studies including a new generation of remote sensing systems. The network shall investigate key questions in atmospheric sciences, particularly, the role of water vapor in the Earths weather and climate system by the application of lidar systems with unprecedented accuracy, resolution and range.

Fast tuning of external-cavity diode lasers

We report on a method for characterizing the tuning capabilities of small-bandwidth external-cavity diode lasers. The step response of a piezo-driven Littman-Metcalf external-cavity diode laser and the compensation of its optoelectromechanical frequency response is investigated. When an approximately 50-V compensated Gaussian pulse is applied to the piezo element, a detuning of 13.6 GHz is observed. This modification of the laser is useful for several spectroscopical applications and as a tunable seed laser for lidar applications.

Wavelength switching in the acceptance bandwidth of a dual injection seeded optical parametric oscillator

We describe the investigation of a dual laser injection seeding and switching of an optical parametric oscillator. This option is part of a differential absorption lidar (DIAL) transmitter system for measuring environmental species at two wavelengths. For instance the realization was accomplished by using an injection seeded diode pumped Nd:YAG laser as pump for an optical parametric oscillator (OPO). The purpose of these studies was an evaluation of different injection seeding techniques and their practical applicability. The suitable wavelengths were generated by injection seeding the OPO at the signal wavelength. Experiments with one and two external cavity diode lasers were performed to generate the required two idler wavelengths for the measurement. By this method line-narrowing occurs. A spectral width of the pulsed OPO of 200 MHz was achieved. Within the seeding and switching range at these two wavelengths inter-mode mixing was observed.

Spectral purity investigation of a KTP optical parametric oscillator

We report on a singly resonant injection seeded optical parametric ring oscillator with signal pulse energy of up to 38 mJ, 50% pump depletion, spectral purity of 99.97%, and M2 of about 6.

Comparison of a non-resonant and a signal-resonant four mirror optical parametric oscillator

High energy performance of a two crystal four mirror non-resonant and signal-resonant optical parametric ring oscillator was demonstrated. The signal-resonant oscillator had idler dumping between the crystals. Differences occurred in beam profile and stability.