# Direct optical excitation of an NV center via a nanofiber Bragg-cavity: A theoretical simulation

## TL;DR

This paper presents a theoretical simulation demonstrating that nanofiber Bragg cavities can significantly reduce background light during the optical excitation of NV centers in nanodiamonds, enhancing quantum application performance.

## Contribution

It introduces a nanofiber Bragg cavity design to suppress background light in NV center excitation, improving upon traditional methods.

## Key findings

- Optical excitation intensity can be reduced by about 10 times using a nanofiber.
- Using a nanofiber Bragg cavity with 240 grating periods can reduce excitation intensity by approximately 100 times.
- Background light suppression inside nanofibers is significantly improved with the proposed NFBC design.

## Abstract

Direct optical excitation of a nitrogen-vacancy (NV) center in nanodiamond by light via a nanofiber is of interest for all-fiber-integrated quantum applications. However, the background light induced by the excitation light via the nanofiber is problematic as it has the same optical wavelength as the emission light from the NV center. In this letter, we propose using a nanofiber Bragg cavity to address this problem. We numerically simulate and estimate the electric field of a nanodiamond induced by excitation light applied from an objective lens on a confocal microscope system, a nanofiber, and nanofiber Bragg-cavities (NFBCs). We estimate that by using a nanofiber, the optical excitation intensity can be decreased by roughly a factor of 10 compared to using an objective lens, while for an NFBC with a grating number of 240 (120 for one side) on a nanofiber the optical excitation intensity can be significantly decreased by roughly a factor of 100. Therefore, it is expected that the background light inside a nanofiber can be significantly suppressed.

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Source: https://tomesphere.com/paper/1906.05707