Space-time wave packets in multimode optical fibers with controlled dynamic motions and tunable group velocities.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40016205.
- Also identified by DOI 10.1038/s41467-025-56982-9 and PMC identifier 11868423.
- Licence recorded as CC BY-NC-ND.
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Abstract
Space-time wave packets (STWPs) with correlated spatial and frequency degrees of freedom exhibit time-dependent spatial interference, thereby giving rise to interesting dynamic evolution behaviors. While versatile spatiotemporal phenomena have been demonstrated in freely propagating fields, coupling spatiotemporal light into multimode fibers remains a fundamental experimental challenge. Whereas synthesizing freely propagating STWPs typically relies on a continuum of plane-wave modes, their multimode-fiber counterparts must be constructed from the discrete set of fiber modes whose propagation constants depend on fiber structures. Here, we demonstrate STWPs with axially controllable motion of the transverse profile and reconfigurable group velocity in graded-index multimode fibers. This is accomplished by introducing a linear association between frequency comb lines and corresponding fiber modes. The synthesized STWPs present dynamic rotation and translation with a 4.8-ps period. Simultaneously, the group velocity can be tuned from positive subluminal and superluminal to negative values (e.g., 0.870, 1.35, 10, and -3.3 × 10<sup>8</sup> m/s, respectively).