Monolithic photonic circuits for Kerr frequency comb generation, filtering and modulation

TL;DR

This paper demonstrates a monolithic integrated photonic chip using lithium niobate that can generate, filter, and modulate Kerr frequency combs, enabling compact and efficient optical systems for various advanced applications.

Contribution

The work introduces a monolithic lithium niobate platform capable of on-chip Kerr comb generation, filtering, and modulation, combining multiple functionalities previously achieved with separate components.

Findings

Successful generation of broadband Kerr frequency combs on-chip.

Electrically programmable filtering of a single comb line.

Electro-optic modulation of the selected comb line.

Abstract

Microresonator Kerr frequency combs, which rely on third-order nonlinearity ($\chi^{(3)}$), are of great interest for a wide range of applications including optical clocks, pulse shaping, spectroscopy, telecommunications, light detection and ranging (LiDAR) and quantum information processing. Many of these applications require further spectral and temporal control of the generated frequency comb signal, which is typically accomplished using additional photonic elements with strong second-order nonlinearity ($\chi^{(2)}$). To date these functionalities have largely been implemented as discrete off-chip components due to material limitations, which come at the expense of extra system complexity and increased optical losses. Here we demonstrate the generation, filtering and electro-optic modulation of a frequency comb on a single monolithic integrated chip, using a thin-film lithium niobate (LN) photonic platform that simultaneously possesses large $\chi^{(2)}$ and $\chi^{(3)}$ nonlinearities and low optical losses. We generate broadband Kerr frequency combs using a dispersion-engineered high quality factor LN microresonator, select a single comb line using an electrically programmable add-drop filter, and modulate the intensity of the selected line. Our results pave the way towards monolithic integrated frequency comb solutions for spectroscopy data communication, ranging and quantum photonics.