On-chip nonclassical light sources
Armand, Konstantinos, Tomas, Kai, Kevin
Quantum information processing and cavity QED with quantum dots in photonic crystal nanocavities
Armand, Konstantinos, Tomas, Kai, Kevin
Nanometallic cavities
Yousif, Kevin, Tom, Tomas
Silicon Carbide photonics
Tom, Kai, Marina
Electrically injected nanocavity lasers and modulators
Silicon Germanium photonics
Nonlinear optics in nanophotonic structures
Sonia, Marina, Linda
Nanophotonic devices for biomedical applications
Alex, Jan
Objective-First Design for Nanophotonics
Videos of our research

On-chip nonclassical light sources

Fig.1. Left: Ladder of dressed states in a strongly coupled quantum dot-cavity system. Right: The anharmonicity of this ladder can be employed to achieve photon blockade (input laser frequency tuned to first order dressed states - see blue arrow in the left figure), or photon induced tunneling (input laser frequency tuned to higher order dressed states - e.g., 2nd order dressed states, as shown by the red arrow in the left figure).

The goal of this project is to build nonclassical light sources on a chip by employing the photon blockade and photon-induced tunneling effects. This is implemented with photonic-crystal nanocavities containing embedded quantum dots (QDs) using the strong optical nonlinearities achievable in cavity quantum-electrodynamics (cQED) at the single-photon level. In particular, we are working toward the on-demand, deterministic generation of single photons and multi-photon states in a solid-state platform. In contrast to the single photon generation schemes based on atomic and molecular optics, one does not need complex setups for atom cooling and trapping, as everything is done in an integrated structure fabricated on a chip using processes compatible with semiconductor manufacturing.

In the most basic scheme (Fig. 1), the nonclassical light is generated by filtering a stream of photons coming from a classical coherent light source (producing photons with Poisson statistics) through a single photonic-crystal nano-cavity containing a single, strongly coupled QD. Due to the highly nonlinear character of the interaction between the input light and a strongly coupled cavity-QD system, the admission of a single photon into the cavity may enhance (photon-tunnelling) or diminish (photon-blockade) the probability for a second photon to enter the cavity [1]. This means that the output light can be engineered to have highly nonclassical photon statistics, such as a stream of single photon states. Furthermore, higher order photon states (consisting of, e.g., two or three photons), can be preferentially generated by tuning the frequency of the input light (Fig. 2) [2]. A source of such higher order photon states, also known as Fock states, can then be used for efficient generation of NOON-states. These large entangled photon states are particularly interesting for quantum metrology and high resolution quantum lithography and sensing.

Beyond studies based on a simple cavity containing a resonant QD, we explore cQED and non-classical light generation in more complex systems, such as bimodal nanocavities [3], photonic molecules [4], and cavities coupled to four-level emitters [5]. In addition, we have recently begun to optimize the frequency detuning between the QD and the cavity as a way of enhancing the nonclassical character of the transmitted light [6].

Fig. 2: Numerically calculated photon statistics at the output of the QD-cavity system driven by Gaussian pulses with duration τ ∼ 25 ps. The simulation parameters are g⁄2π = 40 GHz, κ⁄2π = 4 GHz, and Eo⁄2π = 9 GHz which correspond to the highest achievable coupling strength with this type of cavity and quantum dot and to the highest quality factor (Q ∼ 25,000) measured in our laboratory; γ⁄2π=1 GHz and pure QD dephasing γd is neglected. Upper: Probability of an n photon state, P(n), inside the QD-cavity system as a function of laser-cavity detuning Δ. Lower: The corresponding second- and third-order correlation functions (plotted in log scale). The magnified sections of the plots (both in linear scale) show the frequency range (marked by the vertical dashed lines) in which the two-photon state is dominant over the other states [P(2)>P(1)+P(3)], and g(2)(0)>1 while g(3)(0,0)<1.

Recent publications:

  1. Arka Majumdar, Michal Bajcsy, Jelena Vuckovic, Probing the ladder of dressed states and nonclassical light generation in quantum-dot-cavity QED, Physical Review A 85, 041801(R) (2012)
  2. Armand Rundquist, Michal Bajcsy, Arka Majumdar, Tomas Sarmiento, Kevin Fischer, Konstantinos G. Lagoudakis, Sonia Buckley, Alexander Y. Piggott, and Jelena Vuckovic, Nonclassical higher-order photon correlations with a quantum dot strongly coupled to a photonic-crystal nanocavity, Physical Review A 90, 023846 (2014)
  3. Arka Majumdar, Michal Bajcsy, Armand Rundquist, and Jelena Vuckovic, Loss-enabled sub-Poissonian light generation in a bimodal nanocavity, Physical Review Letters 108, 183601 (2012)
  4. Arka Majumdar, Armand Rundquist, Michal Bajcsy, and Jelena Vuckovic, Cavity quantum electrodynamics with a single quantum dot coupled to a photonic molecule, Physical Review 86, 045315 (2012)
  5. Michal Bajcsy, Arka Majumdar, Armand Rundquist and Jelena Vuckovic, Photon blockade with a four-level quantum emitter coupled to a photonic-crystal nanocavity, New Journal of Physics 15, 025014 (2013) 
  6. Kai Müller, Armand Rundquist, Kevin A. Fischer, Tomas Sarmiento, Konstantinos G. Lagoudakis, Yousif A. Kelaita, Carlos Sanchez Munoz, Elena del Valle, Fabrice P. Laussy, Jelena Vuckovic, On-chip generation of indistinguishable photons using cavity quantum-electrodynamics, arXiv:1408.5942 
last modified on Thursday December 12, 2013