We present, to the best of our knowledge, design and performance data of the first diode-pumped Alexandrite ring laser in Q-switched single-longitudinal mode (SLM) operation. The laser resonator contains two Alexandrite crystals, which are pumped longitudinally by means of two laser diode-bar modules emitting at 636 nm. Single-longitudinal mode operation is achieved by seeding the laser with a diode laser operating in SLM and actively stabilizing the cavity, yielding a linewidth of < 10 MHz at the potassium resonance line at 770 nm. The pulse energy is 1 mJ at a repetition rate of 150 Hz and 0.65 mJ at 320 Hz. The beam quality of M < 1.2 in both directions remains unchanged for the different repetition rates. After characterization in the laboratory, the laser was implemented in a novel mobile lidar system and first atmospheric measurements were conducted successfully.
We present a differential absorption lidar (DIAL) laser transmitter concept designed around a Nested Cavity Optical Parametric Oscillator (NesCOPO) based Master Oscillator Power Amplifier (MOPA). The spectral bands are located around 2051 nm for CO2 probing and 1982 nm for H216O and HD16O water vapor isotopes. This laser is aimed at being integrated into an airborne lidar, intended to demonstrate future spaceborne instrument characteristics: high-energy (several tens of mJ nanosecond pulses) and high optical frequency stability (less than a few hundreds of kHz long term drift). For integration and efficiency purposes, the proposed design is oriented toward the use of state-of-the-art high aperture periodically poled nonlinear materials. This approach is supported by numerical calculations and preliminary experimental validations, showing that it is possible to achieve energies in the 40–50 mJ range, reaching the requirement levels for spaceborne Integrated Path Differential Absorption (IPDA) measurements. We also propose a frequency referencing technique based on beat note measurement of the laser signal with a self-stabilized optical frequency comb, which is expected to enable frequency measurement precisions better than a few 100 kHz over tens of seconds integration time, and will then be used to feed the cavity locking of the NesCOPO.
In this work, the design of a diode-pumped Alexandrite ring laser in Q-switched single-longitudinal-mode (SLM) operation for a spaceborne lidar mission is presented. The laser is pumped by a self-developed fiber-coupled laser diode pump device and yields a pulse energy of 1.7 mJ at a repetition rate of 500 Hz with an excellent beam quality of M 2 < 1.1. By seeding the resonator with a narrow band diode laser, SLM operation with a linewidth of approximately 10 MHz is achieved. The electrooptical efficiency of 2% is the highest achieved for all Alexandrite lasers in SLM operation and reasonable for space operation. The performance analysis as well as benchmarking with the space-qualified mounting technology points out the TRL and the remaining effort for the development of the technology. An estimation of the requirements for a spaceborne resonance lidar mission underlines the suitability of such a lidar system with a diode-pumped Alexandrite laser as the beam source.
First atmospheric measurements with a diode pumped alexandrite ring laser in a ground-based general-purpose Doppler lidar demonstrates high-resolution spectral measurements with minimum hardware requirements. Two decades of Doppler measurements by flash lamped pumped alexandrite ring laser within the worldwide only existing mobile Doppler resonance lidar have shown the capability of such scanning lidar to measure any spectrum from the troposphere to the thermosphere without a frequency reference at the wavelength of desire. An improved second-generation system with a size of 1 m 3 , including a 50 cm telescope, is currently under development for ground-based automatic observations at harsh environments, such as Antarctica. Minimizing the size, complexity, maintenance time and improving the optical setup pave the way of this technology for future space missions. As an example for a possible future space mission, we discuss a mesospheric potassium resonance Doppler lidar by extrapolating the signal from ground-based measurements.
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