Talbot effect observed over space-time for the first time
Talbot effect observed over space-time for the first time lead image
The Talbot effect describes a periodic structure in an optical field that disappears and reemerges at specific spatial intervals despite diffraction. It is used in applications ranging from structured illumination in fluorescence microscopy to phase-locking of laser arrays. An analogous temporal Talbot effect has also been theorized and observed, and since been employed in applications such as treating noise and distortion in single-mode optical fibers.
Although well studied as separate phenomena, the spatial and temporal Talbot effect have not been studied simultaneously. Hall et al. used an optical setup to observe the co-evolution of diffraction and dispersion in space-time.
The experimental setup synthesized a “V-wave,” which is a pulsed optical beam with a spectral structure whose spatial frequency is linearly proportional to the temporal frequency. This setup ensures the V-wave experiences dispersion in free space, with intrinsically identical diffraction and dispersion lengths, which allows the effect to proceed in lockstep in space and time.
As a spatio-temporal periodic structure is introduced, the group observed the pattern to disappear and reappear over space due to diffraction, and over time due to dispersion.
The tested methodology can help enable studies of other spatial-temporal phenomena in non-linear media, such as the study of acoustics or rogue waves.
“This work highlights the non-intuitive consequences of shaping optical fields simultaneously in both space and time, rather than manipulating space and time separately,” said author Ayman Abouraddy. “For the first time, diffraction and dispersion in an optical field become two faces of the same coin, which may lead to fascinating new possibilities for nonlinear optics and optical signal processing.”
Source: “The space-time Talbot effect,” by Layton A. Hall, Murat Yessenov, Sergey A. Ponomarenko, and Ayman F. Abouraddy, APL Photonics (2021). The article can be accessed at http://doi.org/10.1063/5.0045310 .
