Sub-nanoseconds pulse generation at 780 nm from a continuous wave laser for ultrafast Rydberg excitation.

Rydberg atoms are remarkable candidates for realizing ultrafast quantum operations, due to their huge electronic orbitals offering dipole-dipole interaction reaching the GHz range at micrometer range distance (C₃ ~ GHz.μm³). While the standard approach to produce such states used continuous wave laser (C-W) performing excitation on the microsecond timescale, in our group we rather aim at producing Rydberg state in a sub-nanosecond timescale, only limited by the finite splitting energy levels. In a previous work, we have demonstrated ~10 ps excitation of a single Rydberg level (100 GHz separation) using pulsed laser technology [1]. Now, we want to define a two-level system in the hyperfine structure of ⁸⁷Rb (6.8 GHz) and perform hyperfine-resolved ultrafast excitation. We thus developed a novel system to generate a 780nm pulse with arbitrary duration from 100 ps to 1 ns, allowing to resolve the hyperfine structure (>100 ps) while still being much faster than the intermediate state lifetime (5P, 25 ns). This system allows to excite atoms from the ground state to the 5P state, before being excited to Rydberg level in a second step.