We report on 790-nm diode-pumped continuous-wave and passively Q-switched Tm:CYA lasers. For continuous-wave laser operation, a maximum output power of 7.62 W is achieved with slope efficiency of 50.9%. Passive Q-switching of the Tm:CYA crystal is also obtained with a maximum average output power of 1.32 W using a Cr:ZnSe saturable absorber. The shortest pulse width is about 42.6 ns with a pulse energy of 60.2 $\mu \text{J}$ and a pulse peak power of 1.41 kW. These results represent the best laser performances of continuous-wave and passively Q-switched Tm:CYA lasers, to date. The 1.94- $\mu \text{m}$ Tm:CYA lasers provide better laser sources for shallow absorption of biological tissue.

High-Power CW and Q-Switched Tm:CaYAlO4 Lasers at $1.94~\mu \text{m}$ for Shallow Water Absorption

A single-frequency Ho:YAG laser with bow-tie architecture injected by different polarized seeders

1. ABSTRACT In this work we report on design and testing of an HgCdTe Avalanche Photodiode (APD) detector assembly for lidar applications in the Short Wavelength Infrared Region (SWIR : 1,5 - 2 µm). This detector consists in a set of diodes set in parallel -making a 200 µm large sensitive area- and connected to a custom high gain TransImpedance Amplifier (TIA). A commercial four stages Peltier cooler is used to reach an operating temperature of 185K. Crucial performances for lidar use are investigated : linearity, dynamic range, spatial homogeneity, noise and resistance to intense illumination.

/pdf/performances-of-a-hgcdte-apd-based-detector-with-electric-349u0zv7h0.pdf

Performances of a HGCDTE APD Based Detector with Electric Cooling for 2-μm DIAL/IPDA Applications

We report on recent advances at ONERA on fiber-based laser and lidar systems, in the perspective of future space-borne monitoring of greenhouse gas, especially CO2 and CH4. We first present an advancement status of research activities on high-peak-power single-frequency fiber lasers at 2.05 μm and 1.58 μm for CO2 monitoring, and at 1.64 μm for CH4, as well as perspectives for future amplification and frequency-stabilization of these lasers. The second parts deals with activities led on electro-optic dual comb spectroscopy (EO-DCS), which could be a potential future alternative technique to conventional space-borne IPDA lidars (Integrated Path Differential Absorption). We report on an EO-DCS experiment performed in pulsed regime, using an Er-Yb-doped amplifier delivering up to 92 μJ, 2μs pulses at 10 kHz repetition rate. An absorption line of HCN is sampled simultaneously by a 13-teeth frequency comb, and its transmission is measured with a good agreement with respect to the expectation.

/pdf/recent-advances-on-fiber-based-laser-and-lidar-systems-for-18g962hlor.pdf

Recent advances on fiber-based laser and Lidar systems for future space-borne monitoring of greenhouse gas

Single-longitudinal-mode Ho:YLF unidirectional ring laser with single anti-misalignment corner cube retroflector

Recent developments on Ho :YLF transmitter for DIAL application and first range-resolved measurements of atmospheric CO2 are presented. Applications include 3-D anthropogenic site monitoring, spaceborne lidar mission and direct flux measurements. Article not available.

2-µm High Power Multiple-frequency Single Mode Q-switched Ho:YLF Laser for DIAL Applications

We are developing a DIfferential Absorption Lidar (DIAL) for CO2 remote sensing using coherent detection, based on a pulsed hybrid laser emitter at 2.05 μm. In the 2 μm region, the R30 CO2 absorption line has been identified as one of the most promising for space-borne DIAL instrument to provide precise sounding of the atmospheric boundary layer where CO2 sources and sinks are located. In this paper, we present the Tm-doped all-fiber part of the emitter and we demonstrate its ability to measure the CO2 Volume Mixing Ratio (VMR) in the atmosphere. The lidar setup is presented, including the telescope, the heterodyne detection system and a spectral reference system used to infer the absolute frequency of the laser and the ON-line/OFF-line energy difference. We investigate an Integrated-Path-DIAL measurement on a range of 426 m. Results compare well with an in-situ reference sensor (Picarro probe), and the estimate statistics show good agreement with theoretical error calculations. This lidar demonstrator has been called HELENA (Hybrid Emitter Lidar for ENvironmetal Applications). Once completed, it will feature an hybrid emitter combining a semiconductor laser, a high-power Tm-doped fiber amplifier stage, and a final Ho:YLF crystal single-pass amplification stage. This combination aims at benefitting of the versatility, compactness and alignment easiness of a fiber amplifier on one hand, and of the high-peak power attainable with a solid-state amplifier on the other hand. It could allow overcoming the traditional Brillouin limit met in fiber amplifiers, without sacrificing much in compactness and robustness.

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11852/118521W/2-%c2%b5m-hybrid-laser-emitter-for-future-carbon-dioxide-space/10.1117/12.2599328.pdf

Fabien Gilbert

Papers

2-µm High Power Multiple-frequency Single Mode Q-switched Ho:YLF Laser for DIAL Applications

2-µm hybrid laser emitter for future carbon dioxide space-borne lidar measurement