Coherent Optical Memory Baesd on A Laser-written On-chip Waveguide

TL;DR

This paper demonstrates a coherent on-chip optical memory using a laser-written waveguide in a rare-earth doped crystal, achieving high interference visibility and promising integration for quantum networks.

Contribution

It introduces a novel integrated optical memory on a waveguide in Eu-doped crystal, preserving optical properties and demonstrating spin-wave storage.

Findings

High interference visibility of 97% confirms coherence.

Successful demonstration of spin-wave atomic frequency comb storage.

Waveguide properties comparable to bulk crystal.

Abstract

Quantum memory is the core device for the construction of large-scale quantum networks. For scalable and convenient practical applications, integrated optical memories, especially on-chip optical memories, are crucial requirements because they can be easily integrated with other on-chip devices. Here, we report the coherent optical memory based on a type-IV waveguide fabricated on the surface of a rare-earth ion-doped crystal (i.e. $\mathrm{Eu^{3+}}$:$\mathrm{Y_2SiO_5}$). The properties of the optical transition ($\mathrm{{^7}F{_0}\rightarrow{^5}D{_0}}$) of the $\mathrm{Eu^{3+}}$ ions inside the surface waveguide are well preserved compared to those of the bulk crystal. Spin-wave atomic frequency comb storage is demonstrated inside the type-IV waveguide. The reliability of this device is confirmed by the high interference visibility of ${97\pm 1\%}$ between the retrieval pulse and the reference pulse. The developed on-chip optical memory paves the way towards integrated quantum nodes.