Tunable and high purity room-temperature single photon emission from atomic defects in hexagonal boron nitride (1611.03515v1)

Abstract: Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single-photon purity. We report high single photon count rates exceeding 10^7 counts/sec at saturation, which is the highest single photon detection rate for room-temperature single photon emitters, to our knowledge. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.

• The paper demonstrates strain engineering to tune hBN emitter wavelengths by 6 meV, achieving a more homogeneous spectral profile.
• The paper utilizes focused ion beam processing to boost photon purity, reaching emission rates up to 13.8×10^6 counts/s with a g^(2)(0) of 0.077.
• The paper confirms that hBN emitters maintain stability and optical properties when transferred across substrates, supporting scalable photonic integration.

Tunable High-Purity Room-Temperature Single-Photon Emission from hBN Defects

This paper investigates the properties of single-photon emitters (SPEs) in hexagonal boron nitride (hBN), focusing on emission tunability and photon purity. The authors explore strain control as a mechanism to achieve more homogeneous spectral distribution and reduce multi-photon emissions, properties that are critical for scalable photonic quantum technologies.

hBN is part of the van der Waals materials family, which are considered promising for developing solid-state quantum information processing devices. Such materials allow for novel electronic and optical functionalities due to their unique two-dimensional structure. The antisite crystallographic defect NV_BN in hBN confines electronic levels deeply within the band gap, leading to stable and robust SPEs. However, the emission spectrum of these emitters is historically broad, which complicates the creation of consistent single-photon sources necessary for quantum applications.

Key Findings

• Strain-Induced Spectral Tunability: The researchers demonstrated the capacity to adjust hBN emitters' emission wavelength by applying external strain, thus tuning the emission across a range of 6 meV. By exploiting the elastic properties of two-dimensional materials, strain engineering was employed to modify the electronic energy levels, demonstrating a tangible method for emission control.
• Photon Purity Enhancement: Through focused ion beam (FIB) processing, the authors achieved significant enhancements in the purity of single-photon emission. Photons were emitted at a rate of up to $13.8 \times 10^6$ counts/s with a high level of purity $g^{(2)}(0) = 0.077$, which is superior to other known solid-state emitters at room temperature. The reduction in background fluorescence was pivotal to this improvement.
• Emitter Stability and Transferability: The paper shows that these high-quality emitters retain their optical properties when transferred to different substrates, underscoring the practicality of integrating hBN-based emitters with existing photonic devices.

Experimental Approach

The paper utilized ion irradiation of hBN flakes and subsequent high-temperature annealing to reduce defects and contaminants that contribute to broad spectrum emissions. By transferring prepared hBN samples to a bendable polycarbonate substrate, the response of quantum emitters under controlled strain was examined. Photophysical properties were characterized using photoluminescence (PL) mapping and second-order correlation function measurements.

Implications and Future Directions

The findings pave the way for more efficient development of integrated photonic quantum information systems. The ability to tune emission wavelengths expands the possibilities for creating indistinguishable photons across multiple emitters, crucial for multiplexed quantum computing and secure communication networks.

Future developments could explore the integration of these emitters into photonic circuits and further refine the techniques for achieving more predictable and broader-spectrum tunability. The combination of strain engineering and advanced material processing techniques may lay the groundwork for scalable quantum photonic technologies leveraging the superior mechanical and optical properties of 2D materials like hBN.

While the present paper primarily focuses on hBN, the methodologies and insights could inspire research into other van der Waals materials, widening the scope for discovering novel quantum emitters and advancing quantum information science.