RAYTUM PHOTONICS LLC — Department of Energy SBIR Phase I: 12a

Description

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-