Solid State Cavity Quantum Optics

Fig. 1: Schematic of a photonic crystal membrane with L3 defect cavity and quantum dot.

Optics in nanoscience is often called nanophotonics - a field of research with the primary goal of understanding the interaction of electromagnetic radiation (photons) with subwavelength sized materials. Thus, to control and manipulate these light-matter couplings by tailoring the physical, chemical and quantum properties of the system is crucial. In this research project, we focus on the implementation of quantum dots as light emitters inside 2D photonic crystal membrane cavities, and investigate the effects of the altered local photonic density of states on the spontaneous emission properties of the quantum dots.

One of the future dreams of such nanophotonics research is that, by combining nano-electronic and nano-photonic structures, a new field of integrated photonics or quantum photonics will be opened up where light is used to represent, switch and distribute information and even to realise a photonic transistors that allow optical switching and logic operations to be performed using single photons. These dreams for the field of photonics are far behind electronics in terms of maturity. There are no large RAM-type photonic memories, photonic circuits are physically larger than their electronic integrated circuit counterparts and their functionality is rather limited even today. However, few or none of these issues are fundamentally impossible to overcome and the field is rapidly developing with the discovery and utilization of novel phenomena and the development of a wider range of potential applications that operate using the principles of quantum mechanics.

News

We experimentally investigate the nonresonant feeding of photons into the optical mode of a two-dimensional photonic crystal nanocavity by quantum dot multiexciton transitions. Power-dependent photoluminescence measurements reveal a superlinear power dependence of the mode emission, indicating that the emission stems from multiexcitons. By monitoring the temporal evolution of the photoluminescence spectrum, we observe a clear anticorrelation of the mode and single exciton emission; the mode emission quenches as the population in the system reduces toward the single exciton level while the intensity of the mode emission tracks the multiexciton transitions.

We present an experimental and theoretical study of a system consisting of two spatially separated self-assembled InGaAs quantum dots strongly coupled to a single optical nanocavity mode. We tune them into mutual resonance with each other and a photonic crystal nanocavity mode as a bias voltage is varied. Photoluminescence measurements show a characteristic triple peak during the double anticrossing, which is a clear signature of a coherently coupled system of three quantum states. We fit the entire set of emission spectra of the coupled system to theory and are able to investigate the coupling between the two quantum dots via the cavity mode, and the coupling between the two quantum dots when they are detuned from the cavity mode. We suggest that the resulting quantum V-system may be advantageous since dephasing due to incoherent losses from the cavity mode can be avoided.

Collaborations

• Ulrich Hohenester, Karl-Franzens-Universität Graz, Austria
• Atac Imamoglu, ETH Zurich, Switzerland
• Hideo Kosaka, Research Institute of Electrical Communication, Tohuku University, Sendai, Japan
• Peter Lodahl, DTU Fotonik, Technical University of Denmark
• JoséMaria Villa-Boas, Universidade Federal de Uberlandia

Funding

We gratefully acknowledge funding from:

• the German Science Foundation via SFB631 - Project B3
• Nanosystems Initiative Munich (NIM)
• the European Union, Framework 7 viaSOLID