Fluorescence enhancement of single spin color centers in silicon carbide

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Credit: Dwarf letters (2023). DOI: 10.1021/acs.nanolett.3c00568

In a study published online in Dwarf lettersThe team led by Prof. Li Chuanfeng and Dr. Xu Jinshi of the Chinese Academy of Sciences University of Science and Technology of China has made progress in enhancing the fluorescence of single silicon carbide spin defects.

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Researchers exploited surface plasmons to dramatically increase the fluorescence brightness of single-hollow silicon carbide PL6 color centers, leading to an improvement in the efficiency of spin control using the properties of coplanar waveguides. This low-cost method does not require complex micro-nano processing technology or compromise the consistency properties of the color centers.

Spin color centers in solid-state systems are crucial for quantum information processing, and the brightness of their fluorescence is a vital parameter for practical quantum applications.

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Traditionally, fluorescence enhancement of spin color centers involves coupling with solid-state micro-nanostructures, a common method encompassing various schemes such as the fabrication of solid immersion lenses, nanopillars, bulls-eye structures, microcavities of photonic crystals and fiber cavities. However, challenges such as the susceptibility of color center rotation properties to complex micro-nano manufacturing processes and the difficulty of aligning specific color centers with micro-nano structures remain.

Pioneering a new approach, the team used plasmons to enhance the fluorescence of spin centers in silicon carbide. The researchers prepared a silicon carbide thin film about 10 micrometres thick by chemical and mechanical polishing. They used ion implantation technology to create divaricate color centers near the surface in the film.

The film was flipped and adhered to a silicon wafer coated with a coplanar gold waveguide, using van der Waals forces. This placement allowed the color centers near the surface to be influenced by the surface plasmons of the gold waveguide, thereby enhancing the fluorescence of the color centers.

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With an objective lens (with a numerical aperture of 0.85) and the enhancement effect of surface plasmons, the researchers achieved a sevenfold enhancement of the brightness of a single PL6 color center. With an oil lens with a numerical aperture of 1.3, the fluorescence of the color center exceeded one million counts per second.

Furthermore, the researchers were able to precisely manipulate the distance between the near-surface color center and the coplanar waveguide by adjusting the film thickness with a reactive ion etching process, which allowed them to study the optimal range of operation. In addition to generating surface plasmons, the coplanar gold waveguide can be used to efficiently radiate microwaves, significantly improving the efficiency of spin control.

The coplanar waveguide increased the Rabi frequency of a single PL6 color center 14-fold with the same microwave power as that of conventional microwave radiation methods.

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Furthermore, researchers investigated the mechanism of fluorescence enhancement. By fitting the autocorrelation function using a three-level model and measuring the fluorescence lifetime of non-resonant excitation, they confirmed that surface plasmons enhanced the brightness of the fluorescence by increasing the radiative transition rate of the color center energy level.

They also found that as the interaction distance decreased, the quenching effect of the surface plasmons caused the brightness of the color center fluorescence to decay.

This work marks the first implementation of plasmon-enhanced fluorescence from near-surface spin color centers in silicon carbide films. Coplanar gold waveguide preparation is simple without complex enhancement facilities or alignment processes. This method also enhances the fluorescence of other spin color centers in silicon carbide, representing a significant breakthrough in the application of silicon carbide materials to the field of quantum science.

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More information:
Ji-Yang Zhou et al, Plasmon-enhanced bright single spin defects in silicon carbide membranes, Dwarf letters (2023). DOI: 10.1021/acs.nanolett.3c00568

About the magazine:
Dwarf letters

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Provided by the University of Science and Technology of China

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#Fluorescence #enhancement #single #spin #color #centers #silicon #carbide

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