摘要:

A nonlinear optical molecule, &bgr;,&bgr;-diacetyl-4-methoxylstyrene (DAMST), was synthesized and used as the electro-optic chromophore in a photorefractive polymeric composite. Its absorption peak lies at 320 nm and shows no absorption at wavelengths longer than 400 nm. In a 100 &mgr;m thickness film of DAMST:poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone with a weight ratio of 59:40:1, two-beam coupling gain was measured as high as 32 cm−1at a wavelength of 543 nm. A response time as short as 17 ms was estimated at an applied electric field of 84 V/&mgr;m with a writing beam intensity of 1 W/cm2. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122844

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Optical limiting effects in multiwalled carbon nanotubes have been observed in the visible and infrared spectral regions with nanosecond laser pulses. The multiwalled carbon nanotubes investigated include those suspended in distilled water and embedded in polymethyl methacrylate films. Among all the samples measured, the limiting performance of the carbon nanotube suspension is the best with the limiting threshold determined to be∼1,5, and13 J/cm2at 532, 700, and 1064 nm, respectively. The possible mechanism for the observed effects is discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122845

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The simultaneous application of low intensity optical and static electric fields to photoisomerizable electro-optic materials is shown to allow manipulation of the refractive index. A dc electric field was applied to the sample by means of a corona poling mechanism, which was illuminated within the absorption band using a low power laser. The application of the optical field caused a reduction in polar order in the material, with a corresponding change in the refractive index. The change of polar order was monitored by optical second harmonic generation. For typical experimental values, the variation in refractive index was calculated to be about 1&percent;, which is sufficient to change waveguiding conditions. Electroded samples also showed the effect. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.122846

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have experimentally observed room-temperature exciton resonances resulting from interband two-photon transitions between bound-to-continuum states. The excitons exhibit reduced binding energy and broadened resonances compared to that of excitons resulting from two-photon transitions between bound states. This trend is consistent with our theoretical prediction. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122847

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The electroluminescence (EL) of a dye nanocrystalline phase was revealed in single layer light-emitting diodes based on polymers doped with cyanine dye molecules. Observation of light emission in the visible range depended on the redox potentials of the dyes used. The 9,10-dithioanthracene-containing polyimides exhibiting efficient electron-hole transport appeared to be appropriate media for the generation of J-aggregate EL. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122848

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Single-sided alignment, in which only one of the two display substrates bears an alignment layer, stands to significantly simplify the manufacture and improve the yield and performance of active matrix displays. Using polybutylene terephthalate alignment layers, we show that single-sided alignment is feasible for electroclinic liquid crystals and can result in faster switching and larger tilt angle. Most importantly, single-sided alignment gave high contrast in excess of 170:1. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122849

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of hydrogenation on the room-temperature 1.54 &mgr;mEr3+photoluminescent properties of erbium-doped silicon-rich silicon oxide thin films is investigated. Two samples with 7 and 1 at. &percent; excess silicon and 0.4 at. &percent; erbium were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition ofSiH4andO2with cosputtering of erbium and subsequent rapid thermal anneal at900 °C.Hydrogenation by exposure to D plasma doubles the 1.54 &mgr;mEr3+luminescence intensity from the high excess silicon content sample but halves that from the low excess silicon content sample. The lifetimes and excitation power dependence ofEr+luminescence show that hydrogenation primarily affects the active erbium fraction, increasing it in case of the high excess silicon sample but decreasing it in case of the low excess silicon content sample. With proper treatments,Er3+luminescence lifetime of over 7 ms is obtained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122850

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Studies of dielectric spectroscopy, dc conductivity, and polarization switching allowed the observation of phase transition from the superionic to the insulating state in flux-grownKTiOPO4(KTP) crystals at low temperature where the high mobility of potassium ions is suppressed. A low temperature method of fabrication of engineered periodic domain structures in superionic KTP and isomorphic crystals is proposed. It enabled us to tailor homogeneous domain gratings with various periods in the range 4–39 &mgr;m for quasiphase-matched nonlinear optical converters in KTP plates over whole area of 30×30 mm2. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122851

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Quarter-wave reflectors consisting of sets of GaN andAl0.34Ga0.66Nlayers have been grown on sapphire substrates by atmospheric-pressure metal organic chemical vapor deposition. A periodic structure with flat interfaces was observed by high-resolution scanning electron microscopy. X-ray diffraction measurements were performed to characterize the structures, from which the Al contentxin theAlxGa1−xNlayers was determined to be 0.34. No cracks could be seen on the surface of the reflectors by optical microscopy. The measured peak reflectivity at 390 nm increases with the number of pairs and reaches as high as96±2&percent;in the 35-pair reflector. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122852

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A semiconductor laser whose cavities are “self-formed” due to strong optical scattering in highly disordered gain media is demonstrated. The lasers are made of zinc oxide polycrystalline films grown on amorphous fused silica substrates. Lasing occurs at an ultraviolet wavelength of ∼380 nm under optical pumping. Actual images of the microscopic laser cavities formed by multiple scattering have been captured. These results suggest the possibility of using disordered semiconductor microstructures as alternative sources of coherent light emission. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122853

出版商:AIP    

年代:1998

数据来源: AIP