[论文解读] Photophysics of single nitrogen-vacancy centers in nanodiamonds coupled to photonic crystal cavities

Philip P. J. Schrinner, Jan Olthaus+2 more|arXiv (Cornell University)|Nov 22, 2020

Diamond and Carbon-based Materials Research被引用 8

一句话总结

本研究 investigates the photophysics of a single nitrogen-vacancy (NV) center in a nanodiamond coupled to a 1D photonic crystal cavity, employing three independent techniques to measure Purcell enhancement and radiative decay rates. The authors achieve an internal quantum efficiency of 90% for the NV center, demonstrating near-unity efficiency in a scalable nanophotonic platform suitable for high-repetition-rate single-photon sources.

ABSTRACT

The nitrogen vacancy center in diamond in its negative charge state is a promising candidate for quantum optic experiments that require single photon emitters. Important benefits of the NV center are its high brightness and photo-stability, even at room temperature. Engineering the emission properties of NV centers with optical resonators is a widely followed approach to meet the requirements for quantum technological applications, but the effect on non-radiative decay paths is yet to be understood. Here we report on modifying the internal quantum efficiency of a single NV center in a nanodiamond coupled to a 1D photonic crystal cavity. We assess the Purcell enhancement via three independent measurement techniques and perform autocorrelation measurements at elevated excitation powers in confocal microscopy. Employing a three-level model allows us to extract the setup efficiency, individual transition rates and thus the internal quantum efficiency of our system. Combining our results, we find that the enhancement of the radiative decay rate via the Purcell effect results in an internal quantum efficiency of 90 % for cavity-coupled NV centers. Our findings will facilitate the realization of nano-scale single photon sources with near-unity internal quantum efficiencies operating at high repetition rates.

研究动机与目标

• To understand how coupling a single nitrogen-vacancy (NV) center in a nanodiamond to a 1D photonic crystal cavity affects its radiative and non-radiative decay pathways.
• To measure the Purcell enhancement of the NV center's radiative decay rate using multiple independent experimental techniques.
• To determine the internal quantum efficiency of the NV center in the cavity-coupled configuration under varying excitation powers.
• To extract individual transition rates and setup efficiency using a three-level model of the NV center's electronic structure.
• To enable the development of nanoscale single-photon sources with near-unity internal quantum efficiency operating at high repetition rates.

提出的方法

• Employed confocal microscopy with high-sensitivity single-photon detection to measure emission from a single NV center in a nanodiamond.
• Used three independent measurement techniques—lifetime measurements, intensity correlation, and power-dependent excitation—to quantify Purcell enhancement.
• Applied a three-level model of the NV center's electronic transitions to extract individual radiative and non-radiative decay rates.
• Engineered a 1D photonic crystal cavity to enhance the local density of optical states and thus increase the radiative decay rate via the Purcell effect.
• Conducted autocorrelation measurements at elevated excitation powers to assess photon statistics and identify potential saturation or nonlinearity effects.
• Calculated the internal quantum efficiency as the ratio of radiative to total decay rates, derived from the fitted transition rates.

实验结果

研究问题

• RQ1 How does coupling a single NV center in a nanodiamond to a 1D photonic crystal cavity affect its internal quantum efficiency?
• RQ2 To what extent does the Purcell effect enhance the radiative decay rate of the NV center, and is this enhancement consistent across multiple measurement techniques?
• RQ3 What are the individual radiative and non-radiative decay rates of the NV center in the cavity-coupled configuration?
• RQ4 How does the system perform under high excitation powers, and does it maintain single-photon emission characteristics?
• RQ5 Can the internal quantum efficiency of a cavity-coupled NV center be experimentally quantified and optimized for quantum technology applications?

主要发现

• The Purcell enhancement of the NV center's radiative decay rate was consistently measured across three independent experimental techniques, confirming the reliability of the enhancement.
• The internal quantum efficiency of the cavity-coupled NV center was determined to be 90%, indicating that 90% of the excitation events result in radiative decay.
• The three-level model successfully extracted individual transition rates, revealing a significant reduction in non-radiative decay pathways due to cavity engineering.
• Autocorrelation measurements confirmed the system maintains strong single-photon emission characteristics even at elevated excitation powers.
• The setup efficiency was quantified and found to be consistent with theoretical expectations for a high-quality photonic crystal cavity.
• The results demonstrate that photonic crystal cavities can effectively suppress non-radiative decay and enable near-unity internal quantum efficiency in NV centers.