Enhancement of fluorescence from nitrogen-vacancy center ensemble in bulk diamond with broadband antireflection coatings

Lixia Xu,Jixing Zhang,Pengcheng Fan,Heng Yuan,Ning Zhang,Yuchen Liu,Guodong Bian,Mingxin Li

doi:10.1063/5.0018433

Lixia Xu, Jixing Zhang + Show 6 more

Open Access

https://doi.org/10.1063/5.0018433

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Journal: AIP Advances	Publication Date: Aug 1, 2020
Citations: 2	License type: cc-by

Affiliation: Beihang University, Zhejiang Lab

Abstract

The negatively charged nitrogen-vacancy (NV−) center in diamond is a promising platform for quantum sensing. However, fluorescence from the NV− centers suffers large energy loss at the diamond–air interface. Here, we propose a broadband antireflection coating to enhance the fluorescence intensity by simultaneously reducing the energy loss of the excitation laser and the fluorescence. The reflectance for normal-incidence light decreases from nearly 17% for bared diamond to below 0.33% for coated diamond in the wavelength range 500 nm–800 nm. The reflectance averaged over the fluorescence bandwidth is below 3% for angles of incidence less than 20°. The measured emitted fluorescence for the coated diamond is 1.44 times that of uncoated diamond, corresponding to nearly 20% improvement in the measurement sensitivity. The proposed method is significant for enhancing the signal-to-noise ratio of NV−-based sensors.

Highlights

In recent years, the negatively charged nitrogen-vacancy (NV−) center in diamond has emerged as a good candidate for quantum sensing because of its capacity to measure weak fields with high spatial resolution under ambient conditions.1,2 Applications already demonstrated with NV− centers include magnetometry,3–5 thermometry,6,7 electric-field sensing,8,9 and rotation sensing.10–12 Generally, the readout of the NV− spins relies on detecting the spin-state-dependent fluorescence of the NV− center.13 Enhancing the intensity of the detected fluorescence is important to improve the measurement sensitivity.14 the current fluorescence detection efficiency is low due to the high refractive index of diamond
The reflectance curve for the coated diamond surface is reduced significantly from nearly 17% for the bare diamond surface to below 0.33%, which greatly decreases the energy loss at the interface
The experiment used a high-pressure high-temperature (HPHT) bulk diamond sample, which was electron irradiated with a dose of 1 × 1018 e− cm−2 and annealed at 800 ○C for 2 h

Summary

Introduction

The negatively charged nitrogen-vacancy (NV−) center in diamond has emerged as a good candidate for quantum sensing because of its capacity to measure weak fields with high spatial resolution under ambient conditions. Applications already demonstrated with NV− centers include magnetometry, thermometry, electric-field sensing, and rotation sensing. Generally, the readout of the NV− spins relies on detecting the spin-state-dependent fluorescence of the NV− center. Enhancing the intensity of the detected fluorescence is important to improve the measurement sensitivity. the current fluorescence detection efficiency is low due to the high refractive index of diamond. The negatively charged nitrogen-vacancy (NV−) center in diamond has emerged as a good candidate for quantum sensing because of its capacity to measure weak fields with high spatial resolution under ambient conditions.. The current fluorescence detection efficiency is low due to the high refractive index of diamond. This is due, on the one hand, to the high refractive index, which leads to a high reflection coefficient (≈17% for normal-incidence light) at the diamond–air interface, causing a large loss of optical energy for the fluorescence from NV− centers. The small critical angle due to the high refractive index makes most of the fluorescence exit from the side faces of the diamond, leading to poor fluorescence collection efficiency

Methods

Results

Conclusion