Efficient Light Collection from Single-Photon Emitters in 2D Materials

Single-photon sources are crucial components for quantum networks and communications. Recently, single-photon sources in 2D materials have emerged as robust solid-state light emitters. For collecting and making use of single photons emitted from 2D materials, different strategies can be envisioned, whether the photons are needed on-chip or in free space.<br/>We present waveguide-coupled single-photon emitters in the layered semiconductor GaSe as promising on-chip sources [1]. GaSe crystals are placed on Si₃N₄ waveguides, resulting in a modified mode structure efficient for light coupling. Using optical excitation from within the waveguide, we find nonclassicality of the generated photons routed on a photonic chip. Thus, our work provides an easy-to-implement and robust platform for integrated photonic quantum technology.<br/>For far-field collection, we present polymer microlenses, which are 3D-printed directly on single-photon emitters in commercially available hBN nanocrystals. First, a regular array of hBN nanocrystals is created using capillary assembly [2]. Subsequently, we 3D-print elliptical polymer microlenses onto the nanocrystals. The light emission is efficiently collimated to angles below 5° [3]. The small angle of emission of the new single-photon source allows for using collection lenses with very low numerical apertures &gt; 0.06, including optical fibers.<br/>In summary, we have demonstrated two methods to efficiently harvest single photons from 2D materials, rendering these single-photon sources highly promising for quantum optics and photonic quantum technologies.<br/><br/>References<br/>[1] P. Tonndorf, et al., Nano Lett. 17, 5446 (2017)<br/>[2] J. Preuß et al., 2D Mat. 8, 035005 (2021)<br/>[3] J. Preuß et al., Nano Lett. 23, 407 (2023)