Spontaneous Emission in 2D Arbitrary Inhomogeneous Environment Peng-Fei Qiao, Wei E. I. Sha, Yongpin P. Chen, Wallace C. H. Choy, and Weng Cho Chew * Department of Electrical and Electronic Engineering The University of Hong Kong Speaker: Y.P. Chen Sep 14, 2011

Motivation Control of spontaneously emitted light lies at the heart of quantum optics. It is essential for diverse applications ranging from lasers, light-emitting diodes (LED), solar cells, and quantum information. C Walther et al. Science 327, (2010) LED (photonic crystal cavity)Laser (metallic microcavity) M. Francardi et al. Appl. Phys. Lett. 93, (2008) Purcell factor

Classical View: Boltzmann statistics Photon intensity Spontaneous emission: an exited atom/molecule decay to the ground state and emits a photon History

Quantum Electrodynamics Theory Spontaneous emission rate by Fermi golden rule Mode expansion of dyadic green’s function Representation by Green’s tensor Local density of state (LDOS) Purcell factor The spontanoues emission of an atom can be a weak-coupling radiation process due to the vacuum fluctuations of electromagnetic field.

Numerical Solution of Green’s Function 2-D free-space case (FDFD method) TM wave TE wave convergence

Photonic Crystal A suitable modification of inhomogeneous environment is required so that the vacuum fluctuations controlling the SE can be manipulated. Photonic crystal (TM wave)Photonic crystal (TE wave) SE Depends on the dispersion relation of photonic crystal (bandgap & bandedge)

Plasmonic Nano-Cavity SE Depends on dispersion relation of SPP Plasmonic cavity

Photonic Yagi-Uda Nano-Antenna (Recent Work) Spontaneous emission can be redirected at any selected wavelength via tuning the compositions, sizes, and spatial locations of each element. selective wavelength

Conclusion The LDOS determining the radiation dynamics of emitting source and SE rate can be represented by the electric dyadic Green’s function. The numerical solution of the electric Green’s tensor has been obtained with the FDFD method by using proper approximations of the monopole and dipole sources. The SE rate and direction can be manipulated in photonic and plasmonic nanostructures via engineering their dispersion relations, which is of a great help to emerging optoelectronics. For more details, please see Pengfei Qiao, Wei E.I. Sha, Wallace C.H. Choy, and Weng Cho Chew, Phys. Rev. A 83, , (2011).

Acknowledgement Thanks for your attention!