Single photon sources for integrated quantum photonics based on organic molecules

Efficient quantum light sources are basic ingredients for photonic quantum technologies. On the other hand, on-chip integration is necessary to envision a scalable platform for quantum information and communication. In the... [ view full abstract ]

Efficient quantum light sources are basic ingredients for photonic quantum technologies. On the other hand, on-chip integration is necessary to envision a scalable platform for quantum information and communication. In the first part of this contribution we demonstrate the potential of a novel hybrid technology which combines single organic molecules as quantum emitters and dielectric chips, consisting of ridge waveguides and grating far-field couplers [1] (panel A in figure). Dibenzoterrylene molecules (DBT) in anthracene crystals (Ac) are particularly suitable quantum systems for this task, due to outstanding photophysical properties [2,3] demonstrated both in bulk and in samples as thin as few tens of nanometers. Here the emitters are integrated by spin-coating onto the photonic chip. We demonstrate at room temperature the emission of single photons from DBT molecules into ridge waveguides with a branching ratio up to 40%, corresponding to an estimated on-guide brightness around 50MHz for CW pumping at saturation. These results are competitive with state-of-the-art single photon emission into propagating guided modes from solid state systems [4,5], while offering a novel platform with high versatility.

In order to surpass evanescent coupling and address the challenge of deterministic positioning, we have developed a single-photon source based on Ac nanocrystals [6] (average size of 200 nm) doped with DBT molecules (panel B). Nanocrystals (NC) are naturally prone to the integration in hybrid devices, including heterostructures and complex photonic devices, and can be useful for quantum technologies in general. In the second part of our contribution, we report on the unprecedented performances of single-photon emission from NCs in terms of spectral and intensity stability and emission purity, both at room and at cryogenic temperature. Moreover, when cooled down to 3 K, the 00-zero phonon line shows linewidth values (50 MHz) close to the lifetime-limit [7]. We will also report on our preliminary results related to the integration of the NCs in hybrid photonic devices.

[1] P. Lombardi et al., ACS Photonics 5.1 (2018)    [2] C. Toninelli et al., Opt. Express 18 (2010)

[3] J. B. Trebbia et al., Opt. Express 17 (2009)      [4] R. S. Daveau et al., Optica 4.2 (2017)

[5] M. Davanco et al., Nat. Comm. 8.1 (2017)       [6] P. Kang et al., Materials Research Bulletin 39 (2004)

[7] S. Pazzagli et al., ACS Nano 12(5) (2018)