Towards Continuous-wave Laser Cooling for Anti-hydrogen

Anti-hydrogen synthesis opens new avenues for precision measurements for investigating the antimatter-matter asymmetry. The narrow line of the 1S-2S transition in hydrogen and anti-hydrogen provides an excellent test for this asymmetry. Precision hydrogen spectroscopy is typically performed in a beam configuration. This is not applicable for anti-hydrogen due to constraints in the ability to produce and contain it. Laser cooling is thus a prerequisite for precise anti-hydrogen spectroscopy in a neutral particle trap. However, the required cooling laser wavelength, Lyman-alpha (121.56 nm for 1S-2P transition), is difficult to produce coherently. A pulsed source can be used to achieve few microwatts of average power [1], but the broad linewidth limits the cooling performance. Based on [2] where 20 nanowatts of Lyman-alpha was demonstrated, we are working towards improvements to microwatt coherent Lyman-alpha generation. Some important improvements are: (1) efficient collection schemes for Lymen-alpha, and (2) implementation of a build-up cavity for 254 nm. With these improvements, we expect to achieve cooling in all three axes on the time scale of minutes. [1] G. Gabrielse et al., Opt. Lett. 43, 2905 (2018). [2] K. S. E. Eikema, J. Walz, and T. W. Hänsch, Phys. Rev. Lett. 86, 5679.