Quantum light-matter interactions form the basis of many quantum technologies and much fundamental research. Organic molecules are an impressive platform for the generation of quantum light, both as single photon emitters and as collective systems. In this work, I investigate quantum light-matter interactions with molecules of dibenzoterrylene in crystals of anthracene. I outline methods to grow dibenzoterrylene-doped anthracene crystals, and I characterize the optical properties of cryogenically cooled molecules. I prepare collective systems composed of pairs of molecules interacting through their free-space electromagnetic fields. I demonstrate a method to tune interacting molecules into resonance to form superradiant and subradiant collective states. Finally, I present a platform for solid-state cavity QED based on molecules of dibenzoterrylene coupled to a nanophotonic cavity. This demonstration establishes a route toward scalable deterministic photon generation with molecules. I also tune pairs of cavity-coupled molecules into resonance to form distributed collective states, opening the door to cavity-mediated many-body interactions.
Quantum light-matter interactions form the basis of many quantum technologies and much fundamental research. Organic molecules are an impressive platform for the generation of quantum light, both as single photon emitters and as collective systems. In this work, I investigate quantum light-matter interactions with molecules of dibenzoterrylene in crystals of anthracene. I outline methods to grow dibenzoterrylene-doped anthracene crystals, and I characterize the optical properties of cryogenically cooled molecules. I prepare collective systems composed of pairs of molecules interacting through their free-space electromagnetic fields. I demonstrate a method to tune interacting molecules into resonance to form superradiant and subradiant collective states. Finally, I present a platform for solid-state cavity QED based on molecules of dibenzoterrylene coupled to a nanophotonic cavity. This demonstration establishes a route toward scalable deterministic photon generation with molecules. I also tune pairs of cavity-coupled molecules into resonance to form distributed collective states, opening the door to cavity-mediated many-body interactions.
Single organic molecules hold great promise for generating, manipulating, and storing single photons. Such processes form the basis for new quantum-enhanced technologies such as sensing, communications, and computation. In this talk I will focus on a particularly promising molecule – dibenzoterrylene (DBT). When DBT is introduced into a solid crystal of anthracene it is photostable and emits light between 780 and 795 nm. When cooled to cryogenic temperature, DBT is isolated from phonon-induced dephasing meaning that the photons have a lifetime-limited. I will present recent results in growing DBT-doped anthracene crystals, introducing these to nanophotonic interfaces for enhancing the collection of photons, tuning the DBT emission wavelength to coincide with rubidium atomic absorption, and finally pump-probe spectroscopy experiments to find long-lived triplet states in DBT which will be useful for building a single-molecule quantum memory.
Placing single emitters inside optical cavities provides a way of drastically modifying their interaction with the electric field. Such systems can be used to test our fundamental understanding of quantum electrodynamics and to develop devices that exploit this new found knowledge. This thesis describes work towards coupling single dye molecules to optical fibre microcavities at cryogenic temperatures. I present the design of an oven growth chamber and develop a method to grow cosublimated crystals of anthracene doped with dibenzoterrylene. I then describe the characterisation of these samples using a confocal microscope setup both at ambient and cryogenic temperatures. The samples grown show bright, stable, single emitters in a defined orientation in the anthracene crystals. By varying the growth parameters of the homebuilt crystal growing chamber, we can control the density of dibenzoterrylene molecules and grow at an optimum density to use these crystals in conjunction with optical fibre microcavities. I show how optical fibre microcavities have been developed that can be cooled to the liquid helium temperatures required to take advantage of the lifetime-limited emission from single dibenzoterrylene molecules, that only occurs below 4K. I also present cavity quantum electrodynamic simulations of the cavities, showing what we expect to see when we take reflection spectra of single molecules coupled to these cavities. In addition, I describe the optical setup that has been developed to take these measurements. I conclude with proposed improvements to the cavity setup that will enable these reflection spectra to be more easily taken. This will allow these molecule-cavity systems to be used as infrared single photon sources for quantum optics experiments.
We present a hybrid solid-state cavity quantum electrodynamics (QED) platform that integrates a high density of coherent organic molecules with high-quality-factor nanophotonics. Thin anthracene crystals doped with dibenzoterrylene (DBT) are mechanically transferred onto prefabricated silicon nitride photonic crystal cavities, preserving both the cavity quality and molecular coherence. This approach decouples emitter synthesis from nanofabrication, providing a pathway for integrating other types of emitters. The high density of molecular emitters results in up to ten molecules being coupled to a single cavity. By tuning pairs of molecules into resonance within a single cavity mode, we observe cavity-mediated interactions in both dispersive and dissipative regimes. These results establish an accessible route to deterministic on-chip single- and multiphoton sources.
The on-chip integration of quantum light sources and nonlinear elements constitutes a major step toward scalable photon-based quantum information processing and communication. In this work we demonstrate the potential of a hybrid technology that combines organic-molecule-based quantum emitters and dielectric chips consisting of ridge waveguides and grating far-field couplers. In particular, dibenzoterrylene molecules in thin anthracene crystals are used as single-photon sources, exhibiting long-term photostability, easy fabrication methods, almost unitary quantum yield, and lifetime-limited emission at cryogenic temperatures. We couple such single emitters to silicon nitride ridge waveguides, showing a coupling efficiency of up to 42 ± 2% over both propagation directions. Our results open a novel path toward a fully integrated and scalable photon-processing platform.
Engineering the photonic environment using lattices of coupled resonators, which we refer to as lattice quantum electrodynamics (QED), provides a route to control both the spontaneous emission of individual quantum emitters and the photon-mediated interactions between them. Here we introduce an optical lattice QED platform based on individual dibenzoterrylene (DBT) molecules embedded in anthracene crystals and coupled to lattices of open optical microcavities. This hybrid architecture benefits from narrow-linewidth molecular emitters, site-resolved optical access, engineered coupled-resonator bands, and compatibility with established molecular frequency-tuning techniques. As a proof-of-principle demonstration, we observe emitter-photon bound states formed when the optical transition of a single molecule is tuned to the band gap of a Su-Schrieffer-Heeger (SSH) cavity lattice. These in-gap states display directional localization and photon emission on a single sublattice, inherited from the vacancy-induced topological edge modes of the underlying SSH lattice. Our results establish open-cavity lattices coupled to DBT molecules as a versatile architecture for engineering many-emitter quantum optical systems with controllable photon-mediated interactions.
Efficient quantum light sources and non-linear optical elements at the few photon level are the basic ingredients for most applications in nano and quantum technologies. On the other hand, a scalable platform for quantum ICT typically requires reliable light matter interfaces and on-chip integration. In this work we demonstrate the potential of a novel hybrid technology which combines single organic molecules as quantum emitters and dielectric chips [1]. Dibenzoterrylene molecules in anthracene crystals (DBT:Ac) are particularly suitable quantum systems for this task, since they exhibit long-term photostability in thin samples [2], easy fabrication methods and life-time limited emission at cryogenic temperatures [3]. We demonstrate at room temperature the emission of single photons from DBT molecules into ridge waveguides with a branching ratio up to 40%. The overall single-photon source efficiency, including emission into the guided mode, propagation losses, and emission into a quasi-gaussian mode in free space, is estimated around 16%. These results are competitive with state-of-the-art single photon emission into propagating guided modes from solid state systems [4], while offering a novel platform with unprecedented versatility. References [1] P. Lombardi et al., Arxiv: 1701.00459v1 (2017). [2] C. Toninelli et al., Opt. Express 18, 6577 (2010). [3] A. A. L. Nicolet et al., ChemPhysChem 8, 1929 (2007). [4] I. Zadeh et al., Nano Lett. 16, 2289 (2016); R. S. Daveau et al., Arxiv: 1610.08670v1 (2016). [5] J. Hwang et. al., New J. Phys. 13, 085009 (2011); H.-W. Lee et al., Phys. Rev. A 63, 012305 (2000).