PhD students' seminar: Qin LIU

PhD students' seminar given by Qin LIU from the Lasers group, on 16 June 2022 at 1.15pm in the auditorium of the Institut d'Optique in Palaiseau, on the topic: "New generation of atmospheric lidars based on coherent combination of semiconductor amplifiers".

Abstract: "The spatial and temporal distribution of water vapor in the lower troposphere governs dynamical processes associated with important weather phenomena and climate change. The current existing radiosondes and passive remote sensing techniques fail to provide continuous mapping of water vapor distributions with the required spatial resolution. In this context, airborne diode-laser-based differential absorption lidar (DIAL) appears as a promising solution to deliver a low-cost, automated, range-resolved, and continuous water vapor profile measurement. Diode lasers are compact and inexpensive devices, available on a wide spectral range, and can deliver a high spectral purity laser line; however, they are limited in output powers. The power limitation can be overcome by beam combining technologies such as the coherent beam combination (CBC). CBC technique is based on the constructive interference of coherent beams with a controlled phase relationship. It increases the laser brightness while preserving its spectral purity.

In this seminar, we will describe our development towards a compact diode laser source for airborne water vapor DIAL based on coherent combination of two pulse-pumped tapered semiconductor optical amplifiers with pulse duration 1 µs and repetition rate 10 kHz. The amplifiers are seeded by a DBR diode laser at 828 nm in a master oscillator power amplifier configuration. The combined output pulse energy is 6.5 µJ."