High Power Extremely Narrow Linewidth Diode Laser for Polarizing 3He Target

Polarizing high intensity 3He gas is an extremely important task since polarized 3He is an effective neutron target for a broad nuclear physics programs such as some conducted in Jefferson Lab's Continuous Electron Beam Accelerator facility. The 3He target polarization strongly relies on the power, line width, wavelength stability, and polarization of the pumping laser. Raytum Photonics will develop state of art fiber coupled diode laser system to provide the best and turn-key solution for the production of polarized 3He target. This system will not only facilitate the polarization of 3He gas, but also improve the polarization efficiency, percentage, and the cost as well. It will help to achieve the objectives specified in the topic 24e to develop polarized high density gas. We will use high power, reliable diode laser, state of the art diode laser beam shaping and fiber coupling technology, external cavity wavelength locking and tuning, close loop differential signal amplification feedback, and optical polarization management optics to provide a high power, fiber delivered, circular polarized turn-key diode laser system. During Phase I, Raytum Photonics will develop state of art fiber coupled turn-key diode laser system with the following features: 1) power of 100- 200W, which is much highly desired by 3He gas polarization; 2) very narrow linewidth of less than 0.05 nm, which is not only sufficient for polarizing high pressure 3He target but also fitting the absorption linewidth of target under normal pressure or even lower pressure used in medical application; 3) center wavelength locking with 3He target cell absorption line which can greatly release the operation pressure of routinely checking the output laser wavelength matching with absorption line and 4) circular polarization beam directly out of delivery fiber. Raytum Photonics is also poised to develop the next generation diode laser system for 3He gas polarization. First, we will make this diode laser system power scalable, so that it will be ready to provide higher power; secondly, with our proprietary diode laser beam shaping technology, we will further increase the brightness of the laser beam. This will enable us to (jointly) develop polarization maintained fiber so as to provide a simpler, more convenient solution to create circular polarized laser.