22 research outputs found
Symmetry characterization of eigenstates in opal-based photonic crystals
The complete symmetry characterization of eigenstates in bare opal systems is
obtained by means of group theory. This symmetry assignment has allowed us to
identify several bands that cannot couple with an incident external plane wave.
Our prediction is supported by layer-KKR calculations, which are also
performed: the coupling coefficients between bulk modes and externally excited
field tend to zero when symmetry properties mismatch.Comment: 7 pages, 5 figures, submitted to Physical Review
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Linear and nonlinear wave propagation in negative refraction metamaterials
We discuss linear and nonlinear optical wave propagation in a left-handed medium (LHM) or medium of negative refraction (NRM). We use the approach of characterizing the medium response totally by a generalized electric polarization (with a dielectric permittivity {tilde {var_epsilon}}(w, {rvec k})) that can be decomposed into a curl and a non-curl part. The description has a one-to-one correspondence with the usual approach characterizing the LHM response with a dielectric permittivity {var_epsilon}<0 and a magnetic permeability {mu}<0. The latter approach is less physically transparent in the optical frequency region because the usual definition of magnetization loses its physical meaning. Linear wave propagation in LHM or NRM is characterized by negative refraction and negative group velocity that could be clearly manifested by ultra-short pulse propagation in such a medium. Nonlinear optical effects in LHM can be predicted from the same calculations adopted for ordinary media using our general approach
Photo-patterning of highly efficient state-of-the-art phosphorescent OLEDs using orthogonal hydrofluoroethers
Photolithography offers a scalable solution for large area pixel patterning of organic light-emitting diode (OLED) displays. It has been limited due to the incompatibility of traditional processing steps with the majority of organic materials. In this work, photolithographic structuring of state-of-the-art phosphorescent red p-i-n OLEDs is demonstrated using fluorinated polymers in combination with hydrofluoroether solvents. This is the first report on photolithographically patterned OLEDs with state-of-the-art efficiency and good long-term stability
Orthogonal processing: A new strategy for organic electronics
The concept of chemical orthogonality has long been practiced in the field of inorganic semiconductorfabrication, where it is necessary to deposit and remove a layer of photoresist without damaging theunderlying layers. However, these processes involving light sensitive polymers often damage organicmaterials, preventing the use of photolithography to pattern organic electronic devices. In this articlewe show that new photoresist materials that are orthogonal to organics allow the fabrication ofcomplex devices, such as hybrid organic/inorganic circuitry and full-colour organic displays. Theexamples demonstrate that properly designed photoresists enable the fabrication of organic electronicdevices using existing infrastructure. © The Royal Society of Chemistry 2011