#Measuring invisible light waves via electro-optic cavities

Researchers have developed a novel experimental platform to measure the electric fields of light trapped between two mirrors with a sub-cycle precision.

These electro-optic Fabry-Pérot resonators will allow for precise control and observation of light-matter interactions, particularly in the terahertz (THz) spectral range. The study is published in the journal Light: Science & Applications.

The researchers are from the Department of Physical Chemistry at the Fritz Haber Institute of the Max Planck Society and the Institute of Radiation Physics at Helmholtz Center Dresden-Rossendorf.

By developing a tunable hybrid-cavity design, and measuring and modeling its complex sets of allowed modes, the physicists can switch between nodes and maxima of the light waves exactly at the location of interest. The study opens new avenues for exploring quantum electrodynamics and ultrafast control of material properties.

In a significant advancement in the field of cavity electrodynamics, the team has introduced a novel method to measure electric fields inside cavities. By utilizing electro-optic Fabry-Pérot resonators, they have achieved sub-cycle timescale measurements, allowing for insight into light and matter, exactly where their interaction takes place.

Cavity electrodynamics explores how materials placed between mirrors interact with light, altering both their properties and dynamic behavior. This study focuses on the terahertz (THz) spectral range, where low-energy excitations dictate the fundamental material properties. The ability to measure novel states, which simultaneously behave like light and matter excitations, within the cavity will provide a clearer understanding of these interactions.

The researchers have also developed a hybrid cavity design, incorporating a tunable air gap with a split detector crystal within the cavity. This new design allows for precise control over internal reflections, leading to selective interference patterns on-demand. These observations are supported by mathematical models, providing a key to decode the complicated cavity dispersion and a deeper understanding of the underlying physics.

This research lays the groundwork for future studies in cavity light-matter interactions, offering potential applications for quantum computing, material science, and beyond. Michael S. Spencer, first author of the study noted, “Our work opens new possibilities for exploring and steering the fundamental interactions between light and matter, providing a unique toolset for future scientific discoveries.”

Prof. Dr. Sebastian Maehrlein, the leader of the research group, summarizes, “Our EOCs provide a highly-accurate field-resolved view, inspiring novel pathways for cavity quantum electrodynamics in experiment and theory.”