聚焦离子束加工的硅酸钇波导中铕离子的光学与超精细跃迁

Optical and hyperfine spectroscopic investigations on europium ions doped in yttrium orthosilicate waveguides fabricated by focused ion beam milling

量子存储是大尺度量子网络的重要组成部分,基于波导等微纳结构的可集成量子存储可以提供更好的可扩展性并实现更低的光电能耗.在众多量子存储候选介质中,^(151)Eu^(3+):Y_(2)SiO_(5)晶体具有长达6 h的自旋相干寿命和1 h的相干光存储时间,成为长寿命存储的优异候选材料.本文通过聚焦离子束在^(151)Eu^(3+):Y_(2)SiO_(5)晶体表面加工出三角形悬梁臂波导,波导截面的边长为2μm,长度为20μm,并对三角形悬梁臂波导中的^(151)Eu^(3+)离子的^(7)F_(0)-^(5)D_(0)光学跃迁以及^(7)F_(0)基态的超精细跃迁开展了研究.结果显示,在2μm尺度的悬梁臂波导中^(151)Eu^(3+)离子基本保持了和块状晶体中^(151)Eu^(3+)离子一致的跃迁展宽及相干寿命,可以支持量子存储任务的实现.该工作为实现纳米尺度的^(151)Eu^(3+)离子可集成量子存储器以及单个^(151)Eu^(3+)离子的探测打下基础.

Quantum memory is a crucial element in large-scale quantum networks.Integrated quantum memories based on micro-/-nano structures,such as waveguides,can significantly enhance the scalability and reduce the consumption of optical and electrical power.^(151)Eu^(3+):Y_(2)SiO_(5)stands out as an exceptional candidate material for quantum memory,because it possesses a spin coherence lifetime of 6 h and an optical storage lifetime of 1 h.Here we employ focused ion beam technology to fabricate a triangular nanobeam on the surface of a Y_(2)SiO_(5)crystal.The width and length of the nanobeam are 2μm and 20μm,respectively.The optical lifetime and inhomogeneous broadening of^(151)Eu^(3+)in the triangular nanobeam are measured by fluorescence spectroscopy.The optical lifetime is(1.9±0.1)ms and the optical inhomogeneous broadening is(1.58±0.05)GHz at a doping level of 0.07%for^(151)Eu^(3+).The hyperfine transition spectra are measured by using optically detected magnetic resonance and spin inhomogeneous broadening of(19±3)kHz is obtained.Furthermore,we analyze the coherence properties of optical and hyperfine transitions,respectively,via transient spectral hole burning and spin echo measurement.We obtain an optical homogeneous linewidth down to(22±3)kHz,which is still limited by the instantaneous spectral diffusion.The spin coherence lifetime under the geomagnetic field is(5.1±0.6)ms.The results demonstrate that^(151)Eu^(3+)ions embedded within the 2μm triangular nanobeam essentially retain the same optical and hyperfine transition properties as those observed in bulk crystals.Consequently,this research lays a foundation for studying the integrated quantum memories based on 151Eu3+ensembles and the detection of the single^(151)Eu^(3+)ion based on the focused ion beam technique.