Integration of Single Photon Emitters in 2D Layered Materials with a Silicon Nitride Photonic Chip (1904.08841v1)

Abstract: Photonic integrated circuits (PICs) enable miniaturization of optical quantum circuits because several optic and electronic functionalities can be added on the same chip. Single photon emitters (SPEs) are central building blocks for such quantum circuits and several approaches have been developed to interface PICs with a host material containing SPEs. SPEs embedded in 2D transition metal dichalcogenides have unique properties that make them particularly appealing as PIC-integrated SPEs. They can be easily interfaced with PICs and stacked together to create complex heterostructures. Since the emitters are embedded in a monolayer there is no total internal reflection, enabling very high light extraction efficiencies without the need of any additional processing to allow efficient single photon transfer between the host and the underlying PIC. Arrays of 2D-based SPEs can moreover be fabricated deterministically through STEM patterning or strain engineering. Finally, 2D materials grown with high wafer-scale uniformity are becoming more readily available, such that they can be matched at the wafer level with underlying PICs. Here we report on the integration of a WSe$_{2}$ monolayer onto a Silicon Nitride (SiN) chip. We demonstrate the coupling of SPEs with the guided mode of a SiN waveguide and study how the on-chip single photon extraction can be maximized by interfacing the 2D-SPE with an integrated dielectric cavity. Our approach allows the use of optimized PIC platforms without the need for additional processing in the host material. In combination with improved wafer-scale CVD growth of 2D materials, this approach provides a promising route towards scalable quantum photonic chips.

Integration of Single Photon Emitters in 2D Layered Materials with a Silicon Nitride Photonic Chip

This paper explores the integration of single photon emitters (SPEs) embedded in two-dimensional transition metal dichalcogenides (TMDCs), specifically WSe$_{2}$, onto silicon nitride (SiN) photonic chips. The authors address the incorporation of SPEs into photonic integrated circuits (PICs), aiming to facilitate efficient single photon transfer and scalable quantum photonic chips.

Overview of Integration Techniques and Results

The integration process involves coupling SPEs to the guided modes of SiN waveguides. Through dry transfer techniques, a WSe$_{2}$ monolayer is successfully placed onto a SiN waveguide structure. This integration strategy emphasizes utilizing heterostructures built from 2D materials, thereby enhancing compatibility with existing PIC technology, while avoiding the necessity for fabricating complex photonic structures within the host material.

The efficacy of this approach is demonstrated through photoluminescence (PL) studies conducted on mechanically exfoliated WSe$_{2}$ flakes. The PL from the 2D-SPEs not only engages free-space radiation but notably couples into the waveguide mode, confirming the emitters' integration with the photonic chip. The coupling of these quantum emitters to the waveguide highlights the promise of utilizing TMDCs for efficient photon routing on PIC platforms.

The paper reports detailed spectral analyses of various spot emissions on the WSe$_{2}$ flake across different excitation scenarios. Narrow lines with linewidths between 2.5 and 4 meV are observed, and single photons are confirmed by second-order correlation measurements, indicating antibunching behavior and verifying the quantum nature of the emission. The waveguide-coupled saturation count rate peaks at approximately 100 kHz, constituting a significant advantage for PIC applications where scalability and integration simplicity are critical.

Implications and Future Work

The integration of 2D-based SPEs with SiN waveguides leverages the inherent properties of TMDCs such as high light extraction efficiency and ease of interfacing through Van der Waals epitaxy, suggesting a move towards simpler and more scalable quantum photonic technologies. Furthermore, since 2D materials demonstrate promising electrical tunability, the method could eventually support more dynamic photonic applications.

The theoretical exploration of cavity-emitter systems within the paper further addresses optimization strategies in single photon extraction efficiency ($\eta$) and indistinguishability ($V$). Detailed simulations point to particular conditions under which near-unity extraction efficiencies can be achieved and emphasize the role of cavity design in achieving both high-quality factor and low mode volume for practical quantum photonic applications. The analysis underscores the potential advancements in maximizing $\eta V$ through careful design considerations of the integrated systems, aiming for ideal photon sources in future photonic architectures.

Conclusion

This research underscores the viability of integrating TMDC-based single photon sources into established photonic platforms, fostering advancements in quantum technologies by advocating simpler fabrication techniques and enhancing the scalability of quantum photonic circuits. Potential improvements in system performance and emitter integration pave the way for substantial progress in quantum photonics, particularly as wafer-scale growth of 2D materials advances. The proposed approaches and theoretical insights serve as a foundation for further innovation in the development of efficient PIC-integrated quantum emitters.