Slide 1

By : Majid Sodagar Supervisor : Dr. Sina Khorasani Faculty : Electrical Engineering Date : Nov. 2008 1 Slide 2 Literature Review Main Theme Exciton Transfer Matrix Method Matrix Diagonalization Photonic Crystal Cavity Finite Difference Time Domain Quality Factor Photon-Exciton Interaction Time Domain Evolution Energy Splitting Conclusion 2 Slide 3 Nature, Vol. 445, 2007 = 24.1GHz=100 eV = 8.5GHz=35 eV g = 76 eV Investigating the strong coupling regime using self assembled InAs QD 3 Switzerland, US Q = 13000 Slide 4 This shows the promising potential of photonic crystal waveguides for efficient single-photon sources. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. Phys. Rev. Lett. 101, 113903 (2008) 4 Germany SE DR Slide 5 J. Phys.: Condens. Matter 20, 454209 (2008) Discuss the recently discovered non-resonant coupling mechanism between quantum dot emission and cavity mode for large detuning. Spectral dotcavity detuning is discussed on the basis of shifting either the quantum dot emission via temperature tuning or the cavity mode emission via a thin film deposition technique. 5 Germany Slide 6 6 Nature photonics, VOL 2, (2008) Japan fully confined electrons and photons using a combination of three dimensional photonic crystal nanocavities and quantum dots. Important due to polarization issue. Applications : Triggered single-photon sources quantum logic gate for optical fibre-based quantum cryptography communication and quantum repeater systems Slide 7 D-Wave 16-bit Q-Computer CQED: All optical quantum information and computation Quantum cryptography Realization of quantum repeaters Single photon sources Qbit realization Strong coupling regime: Fabrication of high-efficiency microcavity LEDs Low-threshold vertical-cavity surface emitting lasers Microsphere lasers Entanglement Weak coupling regime: Modification of the emission diagram Enhancement or inhibition of the SE rate Funneling of SE photons into a single mode Control of the SE process on the single photon level 7 Slide 8 Disk-Like Quantum Dot Electron-Hole Pair (Exciton) Photonic Crystal Slab (PCS) Methods of Photon Confinement : In plane : Distributed Bragg Reflection Normal : Total Internal Reflection 8 Slide 9 R 0 =150nm Z 0 =4nm Ga 1-x Al x As GaAs Ga 1-x Al x As X=0.36 V ze = 300 meV V zh = 150 meV Strain for GaAs : xx = yy = -910 -4 zz = 8.310 -4 a v = -1.116 eV b = -2 eV Pikus-Bir Deformation Potentials Hydrostatic Strain Uniaxial Strain V 9 Slide 10 EgEg Electron Electron-Hole No Binding Energy Exciton Binding Energy E exciton Exciton types: Frenkel : Localized near single atom Smaller Bohr radius Strong coupling Wannier : Electron holes are far apart in CV and VB Larger Bohr radius Weak coupling 10 e e Slide 11 Envelope Part Bloch Part Wave Function Macroscopic Potential Contributing to Envelope Part Microscopic Potential Contributing to Bloch Part 11 Using real potential in Schrdinger equation makes it unwieldy. Slide 12 Electron wave function Influenced by only one band (CB) Simple Schrdinger equation S-Like orbital was taken as Bloch part Hole wave function Influenced by three bands (HH,LH,SO) using 66 Luttinger Hamiltonian Combination of P x, P y and P z including spin was taken as Bloch part In contrast to CB, there is a twofold degeneracy in VB besides the closeness of SO 12 Energy 0 Wave Vector Band structure for typical III-V and IV group semiconductor Slide 13 Disk like Quantum Dot Thickness 37 Frequency Density of States Rabi Oscillation can occur for 2C > c High quality factor Big coupling constant Lorentzian approximation for DOS Time |U(t)| 2 Full Photons Full Exciton Photon-Exciton Combination Slide 38 Uncoupled State For Two Eigen frequencies : Detuning Dressed States = 110 eV g = 159 GHz = 2~50 eV Strong Coupling Regime 38 Our system at resonance : g1=0, g2=50, g3=150 GRad Slide 39 39 Electronic and hole states were found Excitonic state were evaluated by diagonalization A relatively high quality factor PC cavity were designed and simulated. Coupling coefficient between cavity modes and excitonic states were derived This structure is capable of operating in strong coupling regime Investigating more complicated system such as bi-excitons and more photons Realizing the physical structures Applying the concept in engineering Slide 40 End. Thanks for your Patience 40