Compact ultra-broadband light coupling on chip via nonadiabatic pumping

TL;DR

This paper introduces a compact, ultra-broadband light coupling method using nonadiabatic pumping in integrated photonic waveguides, achieving high efficiency over a 320 nm bandwidth with significantly reduced device size.

Contribution

The authors develop and experimentally demonstrate a nonadiabatic pumping technique for broadband light coupling in integrated photonics, enabling smaller devices with wider bandwidths.

Findings

Achieved >400 nm bandwidth in simulation and ~320 nm experimentally

Reduced coupling length to ~50 μm, about 1/10 of adiabatic methods

Constructed functional devices like beamsplitters for broadband routing

Abstract

Enlarging bandwidth capacity of the integrated photonic systems demands efficient and broadband light coupling among optical elements, which has been a vital issue in integrated photonics. Here, we have developed a compact ultra-broadband light coupling strategy based on nonadiabatic pumping in coupled optical waveguides, and experimentally demonstrated the designs in thin-film lithium niobate on insulator (LNOI) platform. We found that nonadiabatic transition would produce a decreased dispersion of the phases related to eigenstates in the waveguides. As a consequence, we realized high-efficiency directional transfer between edgestates for various wavelengths covering a 1-dB bandwidth of ~320 nm in experiment (>400 nm in simulation), with a coupling length (~50 {\mu}m) approximately 1/10 of that required in the adiabatic regime. Furthermore, we have constructed complex functional devices including beamsplitter and multiple-level cascaded networks for broadband light routing and splitting. Our work preserves significant advantages simultaneously in extending the operation bandwidth and minimizing the footprint, which demonstrates great potential for large-scale and compact photonic integration on chip.