Description
From fast optical acceleration in laser cooling to time-domain phase-matching control in the study of superradiance [1], precise control of strong optical dipoles may enable a series of new opportunities in experimental atomic physics. Technically, however, control with ultrafast pulses is prone to complications from multi-level dynamics, while the control bandwidth with regular light modulators is too narrow to overcome nanosecond level spontaneous emission. The picosecond scale is the ideal choice for non-perturbative quantum control of strong optical transitions.
Based on direct reciprocal-space-to-time pulse shaping method [2], we have developed a composite acousto-optic modulator (AOM) picosecond pulse‑array synthesizer (PPAS), which converts the output of a mode‑locked laser into an array of pulses with precisely programmable amplitude and phase. With a set of technical refinements, this synthesizer now operates reliably with up to N=5 sub‑pulses, and the total efficiency reaches the 1/N limit. One direct application of the synthesizer is the generation of universal composite pulse with high dipole control fidelity [3]. By sending the optimally phased N = 5 pulse array to an 85Rb vapor, population of ground state atoms are nearly completely transferred to the D1 excited state within 100 ps pulse duration. By carefully analyzing the probe transmission, we find the inversion efficiency reaches ∼ 99%, despite ±60% laser intensity variations. Equipped with PPAS, we are also investigating collective emission by the atomic sample to the waveguide by controlling the atomic dipole through the evanescent field at the nanofiber interface [4].
