Volume 95, Issue 2, 15 January 2004
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
95(2004); http://dx.doi.org/10.1063/1.1633645View Description Hide Description
Optical loss and polarizationcharacteristics of the photonic crystal stick waveguideresonator modes were investigated using both theory and experiment. A stick waveguideresonator with 12 missing air holes was found to have a very high mode originating from the lossless guided mode below the light line. Photoluminescencespectra show sharp resonance peaks at regular intervals in k space, satisfying the resonant condition. Linear polarizations parallel or perpendicular to the waveguide were observed, depending on the mode symmetry. This polarization selection is explained in terms of the far-field cancellation effect of the in-plane field components.
Polarized luminescence and absorption of highly oriented, fully conjugated, heterocyclic aromatic rigid-rod polymer poly-p-phenylenebenzobisoxazole95(2004); http://dx.doi.org/10.1063/1.1632021View Description Hide Description
Poly-p-phenylenebenzobisoxazole (PBO) is a fully conjugated, heterocyclic aromatic rigid-rod polymer having a collinear and coplanar backbone leading to excellent thermo-oxidative stabilities, mechanical tenacity, and optoelectronic properties. PBO is inherently a liquid-crystallinepolymer and can be obtained as uniaxially oriented fiber or film by extrusion of acidic solution. Schemes for making uniaxial freestanding films and monolayered luminescence devices for polarized optical absorption and emission were processed from a uniaxial PBO fiber. Wide-angle x-ray scattering revealed that the starting fiber and the resulting films were highly oriented. UV-Vis transmission spectra over 200 to 800 nm indicated that the PBO films also had polarized absorption with an attenuation coefficient ratio The photoluminescence(PL) of the PBO films was excited at 363 nm, showing an emission intensity ratio as high as 5. The anisotropic PBO film was sandwiched between an indium tin oxide substrate and an Al electrode for monolayer light-emitting diodes(LEDs), showing an electroluminescence(EL) intensity ratio together with a markedly decrease in threshold voltage. PL and EL results demonstrated that a highly polarized luminescence emission was achieved by using the uniaxially oriented PBO films. The polarization effects in absorption and luminescence were absent for isotropic PBO films or LEDs.
Enlargement of the nontransmission frequency range of multiple-channeled filters by the use of heterostructures95(2004); http://dx.doi.org/10.1063/1.1634367View Description Hide Description
Transmission characteristics are studied for hybrid structures combining defects and multiple heterostructures. It is shown that the nontransmission frequency range can be substantially enlarged and the phenomenon of multiple-channeled filtering can be realized by adjusting the number, position, and size of the defects. One, two, and three channeled filters are considered in the structures. Examples are studied theoretically by transfer matrix methods.