Group velocity dispersion (GVD) is a fundamental optical characteristic in a medium, and is of great importance in ultrashort pulse manipulations, such as pulse compression, generation of optical solitons, and group velocity control. It has been found that, when a pulse propagates along a dispersive waveguide, one can consider the problem in a synthetic (1+1) dimensions, that is, the optical field diffracts along a time dimension when it evolves along the spatial dimension. In this work, we move a step further and show the possibility of multiple single pulse manipulations in synthetic (2+1) dimensions including the temporal diffraction and frequency conversion in a synthetic time-frequency space while a pulse propagates along the spatial dimension.

A dispersive waveguide incorporating segmented electrodes under travelling wave electrooptic modulation is considered. We show that one constructs a 2D synthetic space including the time and frequency dimensions, and pulse dynamics is studied when the spatial propagating dimension is treated as the synthetic time evolution. An effective gauge potential core is constructed in synthetic two dimensions with non-uniform distribution of modulation phases to confine light. By manipulating the effective gauge potential core in multiple ways, we show rich physics of pulse manipulations, including confined pulse propagation, fast/slow light, and pulse compression. Fundamentally different from previous works, our results link to physics in (2+1) dimensions, which points out exotic route toward manipulating pulse profile and frequency conversion process. Our work can find important applications of optical pulse engineering in various platforms, ranging from second/third-order dispersive waveguide-based systems to on-chip dispersive microresonator-based systems.

Figure. a) A pulse propagating through a waveguide with segmented electrodes for modulations. b) The system in (a) can be mapped into a synthetic (2+1) dimensions, where an effective gauge potential is constructed in the time-frequency space by non-uniform phase modulation. c) Dispersion curves for waveguide (blue line) and modulation (red line).

The research was published in “Guangzhen Li, Danying Yu, Luqi Yuan, and Xianfeng Chen, Single pulse manipulations in synthetic time-frequency space, Laser & Photonics Reviews, 2100340 (2021)”。

Link: https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100340