Tunability of space-time wave packet carrying tunable and dynamically changing OAM value
Kaiheng Zou, Xinzhou Su, Мurat Yessenov, Kai Pang, Narek Karapetyan, Maxim Karpov, Hao Song, Runzhou Zhang, Huibin Zhou, Tobias J. Kippenberg, Moshe Tur, Ayman F. Abouraddy, Alan E. Willner
Abstract
Space-time (ST) wave packets have gained much interest due to their dynamic optical properties. Such wave packets can be generated by synthesizing frequency comb lines, each having multiple complex-weighted spatial modes, to carry dynamically changing orbital angular momentum (OAM) values. Here, we investigate the tunability of such ST wave packets by varying the number of frequency comb lines and the combinations of spatial modes on each frequency. We experimentally generate and measure the wave packets with tunable OAM values from +1 to +6 or from +1 to +4 during a ∼5.2-ps period. We also investigate, in simulation, the temporal pulse width of the ST wave packet and the nonlinear variation of the OAM values. The simulation results show that: (i) a pulse width can be narrower for the ST wave packet carrying dynamically changing OAM values using more frequency lines; and (ii) the nonlinearly varying OAM value can result in different frequency chirps along the azimuthal direction at different time instants.