Continuous-wave Doppler cooling of hydrogen atoms with two-photon transitions

Yb Fiber Amplifier at 972.5 nm with Frequency Quadrupling to 243.1 nm

“…With the recent trapping of anti-hydrogen in its ground state, a larger beam would also prove beneficial in mitigating the difficulties created by the low number of trapped anti-hydrogen atoms available [12,13]. However, we are mainly motivated to develop a power scalable 243 nm laser in order to explore proposals to laser cool atomic hydrogen using the 1S-2S transition [14][15][16].…”

Doppler cooling to the recoil limit by means of sharp atomic transitions with controlled quenching

“…In the limit of low velocities, the transition amplitude for each of the four processes is the same. One thus expects the DF transitions to increase the equilibrium temperature by a factor of two, which is verified both numerically and analytically [9]. Note that the analysis of the one-photon process can be deduced straightforwardly from the results below by setting the Doppler-free term to zero.…”

“…The recent progress on the generation of CW, VUV, laser radiation, in the context of metrological studies of the 1S − 2S transition [8], allows one to realistically envisage the two-photon Doppler cooling of hydrogen in the continuous wave regime on the very sharp 1S − 2S transition (the lifetime of the 2S state is 0.2 s), as we suggested in a previous work [9].…”

“…However, it is possible to develop some analytical approaches following the general idea leading to the Fokker-Planck equation (FPE) for the time-evolution of the velocity distribution (see Refs. [9], [12]). Taking the continuous limit of Eq.…”

“…In order to conciliate these antagonistic characteristics of sharp transitions, we proposed in Ref. [9] to use the "quenching" of the 2S state of hydrogen to control the cycling frequency of the process and we shown that this process allowed to approach the recoil temperature where the Fokker-Planck equation breaks down. In the present work we develop a refined analysis of the Doppler process valid up to the recoil limit both for one-and two-photon Doppler cooling.…”