Incorporation of erbium ions into thin-film lithium niobate integrated photonics

TL;DR

This paper demonstrates the integration of erbium ions into thin-film lithium niobate photonic devices, achieving high optical quality and strong ion-cavity coupling, advancing quantum photonics applications.

Contribution

It introduces a scalable method for incorporating erbium ions into lithium niobate photonics with preserved optical quality and demonstrated Purcell enhancement.

Findings

Optical quality factors near a million after annealing

Erbium ions exhibit linewidths and lifetimes comparable to bulk crystals

Purcell factor of approximately 3.8 indicating strong ion-cavity coupling

Abstract

As an active material with favorable linear and nonlinear optical properties, thin-film lithium niobate has demonstrated its potential in integrated photonics. Integration with rare-earth ions, which are promising candidates for quantum memories and transducers, will enrich the system with new applications in quantum information processing. Here, we investigate the optical properties at 1.5 micron wavelengths of rare-earth ions (Er$^{3+}$) implanted in thin-film lithium niobate waveguides and micro-ring resonators. Optical quality factors near a million after post annealing show that ion implantation damage can be successfully repaired. The transition linewidth and fluorescence lifetime of erbium ions are characterized, revealing values comparable to bulk-doped crystals. The ion-cavity coupling is observed through a Purcell enhanced fluorescence, from which a Purcell factor of ~3.8 is extracted. This platform is compatible with top-down lithography processes and leads to a scalable path for controlling spin-photon interfaces in photonic circuits.