Polarization control and sensing with two-dimensional coupled photonic crystal microcavity arrays

We have experimentally studied polarization properties of the two-dimensional coupled photonic crystal microcavity arrays, and observed a strong polarization dependence of the transmission and reflection of light from the structures - the effects that can be employed in building miniaturized polarizing optical components. Moreover, by combining these properties with a strong sensitivity of the coupled bands on the surrounding refractive index, we have demonstrated a detection of small refractive index changes in the environment, which is useful for construction of bio-chemical sensors.Comment: 8 pages text and 4 figures on 4 pages. Submitted for publication on 07/14/0

Les pel·lícules del mes de juny

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Tunable photonic Bloch oscillations in electrically modulated photonic crystals

We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump AC or DC electric field, terahertz PBOs can appear and cover a terahertz band in electromagnetic spectrum

Experimental evidence of guided resonances in photonic crystals with aperiodically-ordered supercells

We report on the first experimental evidence of guided resonances (GRs) in photonic crystal slabs based on aperiodically-ordered supercells. Using the Ammann-Beenker (quasiperiodic, 8-fold symmetric) tiling geometry, we present our study on the fabrication, experimental characterization, and full-wave numerical simulation of two representative structures (with different filling parameters) operating at near-infrared wavelengths (1300-1600 nm). Our results show a fairly good agreement between measurements and numerical predictions, and pave the way for the development of new strategies (based, e.g., on the lattice symmetry breaking) for GR engineering.Comment: 10 pages, 5 figures (minor revisions

Optical structure and function of the white filamentary hair covering the edelweiss bracts

The optical properties of the inflorescence of the high-altitude ''Leontopodium nivale'' subsp. ''alpinum'' (edelweiss) is investigated, in relation with its submicrometer structure, as determined by scanning electron microscopy. The filaments forming the hair layer have been found to exhibit an internal structure which may be one of the few examples of a photonic structure found in a plant. Measurements of light transmission through a self-supported layer of hair pads taken from the bracts supports the idea that the wooly layer covering the plant absorbs near-ultraviolet radiation before it reaches the cellular tissue. Calculations based on a photonic-crystal model provides insight on the way radiation can be absorbed by the filamentary threads.Comment: 9 pages, 13 figures. Published pape