Mirror-induced reflection in the frequency domain

TL;DR

This paper introduces and demonstrates the concept of frequency domain mirrors using electro-optic modulation and micro-resonators, enabling control of light in the frequency domain for advanced photonic applications.

Contribution

It presents the theoretical and experimental development of frequency domain mirrors, including tunable and trapped states, expanding the capabilities of optical control in the frequency dimension.

Findings

Demonstrated frequency mirrors using lithium niobate micro-resonators.

Showed interference effects of Bloch waves in synthetic frequency crystals.

Created tunable and trapped states with potential applications in photonics.

Abstract

Mirrors are ubiquitous in optics and are used to control the propagation of optical signals in space. Here we propose and demonstrate frequency domain mirrors that provide reflections of the optical energy in a frequency synthetic dimension, using electro-optic modulation. First, we theoretically explore the concept of frequency mirrors with the investigation of propagation loss, and reflectivity in the frequency domain. Next, we explore the mirror formed through polarization mode-splitting in a thin-film lithium niobate micro-resonator. By exciting the Bloch waves of the synthetic frequency crystal with different wave vectors, we show various states formed by the interference between forward propagating and reflected waves. Finally, we expand on this idea, and generate tunable frequency mirrors as well as demonstrate trapped states formed by these mirrors using coupled lithium niobate micro-resonators. The ability to control the flow of light in the frequency domain could enable a wide range of applications, including the study of random walks, boson sampling, frequency comb sources, optical computation, and topological photonics. Furthermore, demonstration of optical elements such as cavities, lasers, and photonic crystals in the frequency domain, may be possible.