# Quantum Emitters in Hexagonal Boron Nitride Have Spectrally Tunable Quantum Efficiency

## TL;DR

This paper investigates the spectral dependence of quantum efficiency in hexagonal boron nitride emitters, revealing the need for wavelength matching to optimize single-photon emission and providing insights into their complex internal level structure.

## Contribution

It demonstrates the importance of excitation wavelength matching for bright emission and offers a new method to distinguish emitters based on their spectral and photon correlation properties.

## Key findings

- Quantum efficiency depends on excitation wavelength.
- Emitters exhibit complex internal level schemes.
- Method to distinguish emitters spatially and spectrally.

## Abstract

Understanding the properties of novel solid-state quantum emitters is pivotal for a variety of applications in field ranging from quantum optics to biology. Recently discovered defects in hexagonal boron nitride are especially interesting, as they offer much desired characteristics such as narrow emission lines and photostability. Here, we study the dependence of the emission on the excitation wavelength. We find that, in order to achieve bright single photon emission with high quantum efficiency, the excitation wavelength has to be matched to the emitter. This is a strong indication that the emitters possess a complex level scheme and cannot be described by a simple two or three level system. Using this excitation dependence of the emission, we thus gain further insight to the internal level scheme and demonstrate how to distinguish different emitters both spatially as well as in terms of their photon correlations.