Observing momentum conservation at temporal interfaces in synthetic frequency dimension.

Area of Science:

• Physics
• Optics
• Wave Phenomena

Background:

• Electromagnetic wave dynamics differ significantly at temporal interfaces (TIs) compared to spatial interfaces.
• Understanding temporal scattering relies on momentum conservation principles at TIs.

Purpose of the Study:

• To experimentally investigate temporal scattering processes of electromagnetic waves at various TIs.
• To demonstrate momentum conservation across the entire energy band during temporal scattering.
• To establish a flexible platform for realizing TIs in the optical frequency range.

Main Methods:

• Construction of synthetic temporal interfaces in the frequency dimension.
• Study of diverse temporal operation scenarios: band shifting, unfolding/folding, and 2D band variation.
• Development and application of spectral tomography to retrieve wave function distributions.

Main Results:

• Experimental demonstration of temporal scattering processes across the whole energy band.
• Validation of momentum conservation during wave scattering at different TIs.
• Successful realization of various temporal interface configurations.

Conclusions:

• The study provides a flexible experimental platform for optical frequency TIs.
• Fundamental temporal scattering processes for photons can be effectively studied using this platform.
• Momentum conservation is confirmed as a key principle in temporal wave scattering.