ABSTRACT
We present an intra-cavity frequency doubled Q-switched diode-pumped alexandrite ring-laser directly emitting in the UV at 386â nm. Using LBO as nonlinear crystal, the laser yields a pulse energy up to 3 mJ at 500â Hz with an excellent beam quality of M2 = 1.1. The pulse length is about 920â ns, allowing for very narrow bandwidth in single longitudinal mode operation. The optical-to-optical efficiency for the UV laser is > 9% and almost unchanged compared to the fundamental laser. First injection-seeding experiments show single longitudinal mode operation. The parameters of the laser are suitable for the use as an emitter in a multi-purpose atmospheric Doppler lidar system.
ABSTRACT
We present design and performance data of an energy-scaled diode-pumped Alexandrite laser in single longitudinal mode operation developed as a beam source in a mobile general-purpose Doppler lidar. A maximum pulse energy in Q-switched operation of 4.6 mJ and a maximum average power of 2.7 W were achieved for a repetition rate range from 500 to 750 Hz with excellent beam quality of M 2=1.1. Two rugged and compact demonstrator lasers were built and integrated into mobile lidar systems, where a bandwidth of approximately 3 MHz is measured. Measurements of atmospheric winds and temperatures were conducted during several field campaigns from summer 2022 to spring 2023.
ABSTRACT
We present design and performance data of two diode-pumped Alexandrite lasers developed explicitly as laser emitters in mobile potassium resonance lidar systems. The lasers yield an output power of up to 1.75 mJ at a repetition rate of 500 Hz with a beam quality of $M{{^2}} \lt {1.1}$ in both spatial directions. Reliable single longitudinal mode operation with a unrivaled narrow linewidth of 3.3 MHz at a potassium resonance line at 769.898 nm is achieved. The wavelength can be switched from pulse to pulse in a range of several gigahertz so the potassium line can be scanned. The lasers are finally integrated in highly efficient lidar systems with a power consumption of 500 W for the whole lidar system. The extremely high spectral requirements are investigated and the performance for different working points regarding repetition rates and pump durations is investigated. Several weeks of remotely controlled operation of the prototype in a field campaign were conducted without changes of the output parameters. Approximately 1000 h of reliable single longitudinal mode operation was achieved during the campaign and measurements of Doppler-Mie wind observations in the stratosphere and of the potassium layer in the mesopause were conducted simultaneously even at daytime.
ABSTRACT
We present significantly improved performance data of a diode-pumped Q-switched Alexandrite laser in single longitudinal mode operation developed as a beam source for resonance lidar systems. The average output power of the laser-operating at the potassium resonance at 770 nm with a linewidth below 10 MHz-could be increased by a factor of five to the Watt-level by means of an optimized resonator design and pump scheme. The pulse energy is 1.7 mJ with a beam quality of M2≤1.1 in both spatial directions at a repetition rate of 500 Hz.
ABSTRACT
We report on what we believe to be the first continuous daytime measurements of temperature and vertical wind with a mobile scanning iron lidar. The favorable combination of low backscatter coefficient, high number density, narrow resonance line, and strong Fraunhofer line allows nearly background-free observations during daylight. Owing to the low backscatter coefficient at 386 nm the Fe lidar can operate at a field of view of 54 microrad, which permits efficient spectral filtering with a compact double etalon.
ABSTRACT
At daytime, metal resonance lidars need narrowband spectral filtering in the receiver to measure Doppler temperatures in the mesopause region. For our K lidar equipped with a Faraday anomalous dispersion optical filter we demonstrate that the derived resonance temperatures can be shifted by 10 K because of the wavelength dependence of the filter transmission for the Rayleigh scattered light when this filter transmission is used for normalization. We show that, if all filter effects are considered correctly, temperature measurements at daytime can be as accurate as at nighttime without such filters.
ABSTRACT
We introduce a new method for temperature profile measurements in the mesopause region in the altitude range from 80 to 105 km. A frequency-doubled narrowband alexandrite laser is used to scan the iron resonance line at 386 nm. The isotopic shifts of the iron isotopes and the laser bandwidth are derived by the measurement itself. Neglecting the minor isotopes results in large temperature errors up to 28 K. We discuss the derived temperatures in comparison with results of our potassium temperature lidar. The iron lidar-derived temperatures have typically a statistical error of 0.4 K and vary by less than 10 K, which is due to the daily natural variation. The all-solid-state system, which is compact, can be containerized and deployed at remote locations.
ABSTRACT
For daytime operation a new receiver for potassium resonance temperature lidars was developed that includes a twin Faraday anomalous dispersion optical filter and a high-performance photon-counting avalanche photodiode instead of a photomultiplier. The design of a flat spectral filter shape over the lidar scan range avoids instrumental error on the temperature results. Initial temperature measurements under daylight conditions were realized.
