Broadband femtosecond lasers enable efficient two-photon excitation of the ultranarrow linewidth singlet 1s2s state in helium

Shashank Kumar, Justin D. Piel, Chris H. Greene +1

We propose a broadband, femtosecond two-photon excitation scheme for efficient population transfer to the ultra-narrow linewidth $1s2s{}^1{S}_0$ metastable state in helium. Using $12…