Photonic band-structure effects in the reflectivity of periodically patterned waveguides

We report sharp resonant features in the reflectivity spectra of semiconductor waveguides patterned with periodic lattices of deep holes. The resonances arise from coupling of incident light to the photonic bands of the lattice. By varying the reflection geometry, large parts of the photonic band structure are determined. A scattering matrix treatment is used to obtain theoretical spectra which agree well with experiment. The waveguide is shown to have an important influence on the band structure, including marked polarization mixing and significant energy up-shifts

Optical Properties of Layered Superconductors near the Josephson Plasma Resonance

We study the optical properties of crystals with spatial dispersion and show that the usual Fresnel approach becomes invalid near frequencies where the group velocity of the wave packets inside the crystal vanishes. Near these special frequencies the reflectivity depends on the atomic structure of the crystal provided that disorder and dissipation are very low. This is demonstrated explicitly by a detailed study of layered superconductors with identical or two different alternating junctions in the frequency range near the Josephson plasma resonance. Accounting for both inductive and charge coupling of the intrinsic junctions, we show that multiple modes are excited inside the crystal by the incident light, determine their relative amplitude by the microscopic calculation of the additional boundary conditions and finally obtain the reflectivity. Spatial dispersion also provides a novel method to stop light pulses, which has possible applications for quantum information processing and the artificial creation of event horizons in a solid.Comment: 25 pages, 20 figures, submitted to Phys. Rev.

Photoluminescence observation of quantum confined stark effect caused by band bending near the surface of etched structures with GaAs/AlGaAs wells

The interaction of electronic and excitonic states confined in quantum wells (QW) with nearby sulphur-passivated surface was studied by photoluminescence (PL). The redshift (up to 12 meV for 50A QW) and quenching (down to 10-4 ) of QW PL line were observed with approaching of the surface closely to QW by wet etching. The predominant role of quantum-confined Stark effect (QCSE) caused by the near-surface band bending was revealed by the following observations: (1) long-range surface influence (>300A), (2) increasing of the redshift for the thicker QW's, (3) the redshift dependence on the excitation level. On the basis of QCSE theory all the parameters of depleted layer on excitation level are determined. The revealed model can be used for the explanation of the optical properties of etched nanostructures

Exciton polaritons in single and coupled microcavities

Recent work on strong coupling exciton–polariton phenomena in single and coupled microcavities is presented. We describe experiments for single cavities where the strong coupling nature of the excitations manifests itself. It is also shown that coupled cavities enable optically induced coupling between macroscopically separated exciton states to be achieved, and polaritons with strongly anisotropic properties to be realised. Results for both inorganic and organic microcavities are presented

Polariton-polariton Interactions and Stimulated Emission in Semiconductor Microcavities

Recent work on polariton-polariton scattering in semiconductor microcavities under continuous wave excitation conditions is reviewed. For weak non-resonant laser excitation, a marked bottleneck in the polariton distribution is observed, but which is suppressed by polariton-polariton scattering as the laser intensity is increased. However, the high excitation conditions necessary to observe stimulated emission lead to loss of strong coupling and conventional lasing in the weak coupling regime, By contrast for resonant excitation, polaritons are created directly in the polariton trap formed by the microcavity dispersion curve. Stimulated scattering of the bosonic quasi-particles occurs to the emitting state at the centre of the Brillouin zone, and to a companion state at high wavevector. The stimulation phenomena lead to condensation of the bosonic quasi-particles to two specific regions of k-space, and to the formation of a new state with macroscopic coherence. The prospects to achieve a polariton laser under conditions of non-resonant excitation are discussed