High power fiber laser system for polarization of 3He gas

Polarizing high intensity 3He gas is an extremely important task since polarized 3He is an effective neutron filter or target for a broad nuclear physics programs such as some conducted in the Spallation Neutron Source (SNS) in Oakridge National lab- The 3He target polarization is realized through spin exchange optical pumping (SEOP) and thus strongly relies on the power, line width, wavelength stability, and polarization of the pumping laser- Pumping potassium (K) vapor is desired by researchers since it can increase the polarization efficiency- However, it was also found that the lack of narrow linewidth pump laser at 770nm is a hurdle in achieving the theoretical expectation in the experiment- Raytum Photonics will develop state of art fiber master-oscillator power-amplifier (MOPA) combined with the frequency doubling module to provide the best and turn-key solution for the polarization of 3He gas- This system will not only increase the pumping speed of polarizing 3He , but also provide thesolution for direct circular polarization output and thus save the setup cost and lab space- It will help to achieve the objectives specified in the topic 12a to develop polarized high density gas- We will use All-fiber MOPA configuration of high-power cw 1540 nm, the state-of-artfrequencydoubling technology realized with periodically poled crystal, the latest advances in Er-doped specialty fibers, innovative fiber-amplifier design, nonlinearity mitigation by phase modulation, to provide a high power, narrow linewidth and directly circular polarization output turn-key laser system- During Phase I, Raytum Photonics will develop state of art fiber laser system with the following features: 1) power of more than 10W at 770nm, which is much highly desired by pumping 3He gas with K vapor; 2) tunable linewidth from MHz to 10s GHz, which is narrower or comparable with the linewidth of D1 absorption line of K vapor; 3) center wavelength tunable by temperature tuning of seed laser 4) circular polarization beam directly out of delivery fiber- Raytum Photonics will collaborate with SNS researchers in Oakridge National Lab to test the performance of the laser-