Controlled size reduction of rare earth doped nanoparticles for optical quantum technologies.

Shuping Liu,Alban Ferrier,Alexandre Fossati,Diana Serrano,Philippe Goldner,Alexandre Tallaire

doi:10.1039/c8ra07246a

Abstract

Rare earth doped nanoparticles with sub-wavelength size can be coupled to optical micro- or nano-cavities to enable efficient single ion readout and control, a key requirement for quantum processors and high-fidelity single-ion quantum memories. However, producing small nanoparticles with good dispersion and exploitable optical coherence properties, another key aspect for these applications, is highly challenging by most synthesis and nano-fabrication methods. We report here on the wet chemical etching of Eu3+:Y2O3 nanoparticles and demonstrate that a controlled size reduction down to 150 nm, well below the wavelength of interest, 580 nm, can be achieved. The etching mechanism is found to proceed by reaction with grain boundaries and isolated grains, based on obtained particles size, morphology and polycrystalline structure. Furthermore, this method allows maintaining long optical coherence lifetimes (T2): the 12.5 μs and 9.3 μs values obtained for 430 nm initial particles and 150 nm etched particles respectively, revealing a broadening of only 10 kHz after etching. These values are the longest T2 values reported for any nanoparticles, opening the way to new rare-earth based nanoscale quantum technologies.

Highlights

Trivalent rare earths (REs) doped into a host material are attractive for multiple photonics and optoelectronics applications since they can present sharp absorption and emission lines, high quantum efficiency and no photobleaching.[1,2,3,4] Recently, since the development of rare-earth doped nanoparticles, they are intensively investigated for bio-imaging,[5,6] photodynamic therapy (PDT),[6] lighting[7] and security.[8]
We have found that chemical etching can be used for etching Eu3+:Y2O3 oxide polycrystalline nanoparticles at controlled rates
The particles size can be decreased from initial large particles in the 400–500 nm range to much smaller ones (i.e. 150 nm) with a narrow distribution, good dispersion and without obvious changes on the single crystallite size

Summary

Introduction

Trivalent rare earths (REs) doped into a host material are attractive for multiple photonics and optoelectronics applications since they can present sharp absorption and emission lines, high quantum efficiency and no photobleaching.[1,2,3,4] Recently, since the development of rare-earth doped nanoparticles, they are intensively investigated for bio-imaging,[5,6] photodynamic therapy (PDT),[6] lighting[7] and security.[8]. T2 corresponds to the lifetime of the superposition, i.e. quantum states that can be created in RE ions and are of utmost importance in quantum technologies applications. Ions of interest in this eld include Yb3+,13 Eu3+,14 Er3+,15 Nd3+,16 Pr3+ 17 and Tm3+ 18 doped into crystals such as Y2SiO5,13–17 YAG18 or YVO4.19 The longest optical coherence lifetime in a solid state system, T2 1⁄4 4.4 ms, was obtained in Er3+:Y2SiO5,20 and several

Methods

Results

Conclusion