A quantum dot strongly coupled to a photonic crystal resonator is used to investigate cavity quantum electro-
dynamics phenomena in solid state physics. Nonlinear optical phenomena such as photon blockade and photon
induced tunneling are observed in this system. The nonlinearity of this system is sensitive to intra-cavity photon
numbers close to unity, and it has been used to demonstrate conditional phase shifts of 28° at a single photon
level and a second order auto-correlation of g<sup>2</sup>(0) = 0.9 in the photon blockade regime.
The strong coupling regime between a single emitter and the mode of an optical resonator allows for nonlinear
optics phenomena at extremely low light intensities. Down to the single photon level, extreme nonlinearities can
be observed, where the presence of a single photon inside the resonator either blocks or enhances the probability
of subsequent photons entering the resonator. In this paper we experimentally show the existence of these
phenomena, named photon blockade and photon induced tunneling, in a solid state system composed of a
photonic crystal cavity with a strongly coupled quantum dot.
We coherently probe a quantum dot that is strongly coupled to a photonic crystal nano-cavity by scattering of a resonant laser beam.
The coupled system's response is highly nonlinear as the quantum dot saturates with nearly one photon per cavity lifetime. This system
enables large amplitude and phase shifts of a signal beam via a control beam, both at single photon levels. We demonstrate photon-photon
interactions with short pulses in a system that is promising for ultra-low power switches and two-qubit quantum gates.
We discuss recent our recent progress on functional photonic crystals devices and circuits for classical and quantum
information processing. For classical applications, we have demonstrated a room-temperature-operated, low
threshold, nanocavity laser with pulse width in the picosecond regime; and an all-optical switch controlled with
60 fJ pulses that shows switching time on the order of tens of picoseconds. For quantum information processing,
we discuss the promise of quantum networks on multifunctional photonic crystals chips. We also discuss a new
coherent probing technique of quantum dots coupled to photonic crystal nanocavities and demonstrate amplitude
and phase nonlinearities realized with control beams at the single photon level.
We have recently demonstrated an ultrafast photonic crystal laser and cavity coupled laser array with modulation
rates of 1THz at room temperature, a 20 GHz optical modulator with activation energies of 60 fJ and a quantum
dot photonic crystal laser with large signal modulation rates of 30GHz. These devices are enabled by the
enhanced light-matter interaction in photonic crystals, and serve as the building blocks of on-optical information
We have recently developed a technique for local, reversible tuning of individual quantum dots on a photonic
crystal chip by up to 1.8nm, which overcomes the problem of large quantum dot inhomogeneous broadening -
usually considered the main obstacle in employing such platform in practical quantum information processing
systems. We have then used this technique to tune single quantum dots into strong coupling with a photonic
crystal cavity, and observed strong coupling both in photoluminescence and in resonant light scattering from the
system, as needed for several proposals for scalable quantum information networks and quantum computation.
We have recently demonstrated a number of functional photonic crystals devices and circuits, including an ultrafast, roomtemperature,
low threshold, nanocavity laser with the direct modulation speed approaching 1THz, an all-optical switch
controlled with 60 fJ pulses and with the speed exceeding 20GHz, and a local, reversible tuning of individual quantum dots
on a photonic crystal chip by up to 1.8nm, which was then used to tune single quantum dots into strong coupling with a
photonic crystal cavity and to achieve a giant optical nonlinearity.
We demonstrate the coupling of PbS quantum dot emission to photonic crystal cavities at room temperature. The cavities are defined in 33% Al, AlGaAs membranes on top of oxidized AlAs. Quantum dots were dissolved in Poly-methyl-methacrylate (PMMA) and spun on top of the cavities. Quantum dot emission is shown to map out the structure resonances, and may prove to be viable sources for room temperature cavity coupled single photon generation for quantum information processing applications. These results also indicate that such commercially available quantum dots can be used for passive structure characterization. The deposition technique is versatile and allows layers with different dot densities and emission wavelengths to be re-deposited on the same chip.