15 February 2018 High power green lasers for gamma source
Author Affiliations +
A high intensity Gamma source is required for Nuclear Spectroscopy, it will be delivered by the interaction between accelerated electron and intense laser beams. Those two interactions lasers are based on a multi-stage amplification scheme that ended with a second harmonics generation to deliver 200 mJ, 5 ps pulses at 515 nm and 100 Hz.

A t-Pulse oscillator with slow and fast feedback loop implemented inside the oscillator cavity allows the possibility of synchronization to an optical reference. A temporal jitter of 120 fs rms is achieved, integrated from 10 Hz to 10 MHz.

Then a regenerative amplifier, based on Yb:YAG technology, pumped by fiber-coupled QCW laser diodes, delivers pulses up to 30 mJ. The 1 nm bandwidth was compressed to 1.5 ps with a good spatial quality: M2 of 1.1. This amplifier is integrated in a compact sealed housing (750 x 500 x 150 mm), which allows a pulse-pulse stability of 0.1 % rms, and a long-term stability of 1,9 % over 100 hours (with +/-1°C environment).

The main amplification stage uses a cryocooled Yb:YAG crystal in an active mirror configuration. The crystal is cooled at 130 K via a compact and low-vibration cryocooler, avoiding any additional phase noise contribution, 340 mJ in a six pass scheme was achieved, with 0.9 of Strehl ratio. The trade off to the gain of a cryogenic amplifier is the bandwidth reduction, however the 1030 nm pulse was compressed to 4.4 ps. As for the regenerative amplifier a long-term stability of 1.9 % over 30 hours was achieved in an environment with +/-1°C temperature fluctuations

The compression and Second Harmonics Generation Stages have allowed the conversion of 150 mJ of uncompressed infrared beam into 60 mJ at 515 nm.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Magali Durand, Magali Durand, Pierre Sevillano, Pierre Sevillano, Olivier Alexaline, Olivier Alexaline, Damien Sangla, Damien Sangla, Alexis Casanova, Alexis Casanova, Adrien Aubourg, Adrien Aubourg, Abdelhak Saci, Abdelhak Saci, Antoine Courjaud, Antoine Courjaud, } "High power green lasers for gamma source", Proc. SPIE 10511, Solid State Lasers XXVII: Technology and Devices, 105111B (15 February 2018); doi: 10.1117/12.2289670; https://doi.org/10.1117/12.2289670


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