Double-slit time diffraction at optical frequencies

The double slit experiment, first carried out by [Thomas Young] in 1801 provided the first definitive proof of the dual wave-particle nature of photons. A similar experiment can be performed showing diffraction at optical frequencies by changing the reflectivity of an indium tin oxide (ITO) film, as demonstrated in an April 2024 paper (preprint). [Romain Tirole] et al. as published in Natural physics. The reflectivity of a 40 nm thick ITO film deposited on a glass surface is altered with 225 femtosecond pulses from a 230.2 THz (1300 nm) laser, creating temporal “slits.”

In this case, diffraction occurs in the temporal domain and produces frequencies in the frequency spectrum when a separate laser emits a short probing pulse. The effect can be seen most clearly in an interferogram (see detail on the right). Perhaps the most interesting finding during the experiment was how quickly and easily the reflectivity of the ITO layer could be changed. ITO is a very commonly used composite material that offers properties such as electrical conductivity and optical transparency that are extremely useful for windows, displays and touch panels.

Although practical applications for temporal diffraction in the optical or other domains are not immediately obvious, this tends to be the case [Young]The effects of the original experiment will likely not be felt until much later.

Selected image: the conventional and temporal double slit experiments with experimental setup (G). (Source: Tirole et al., Nature Physics, 2024)