摘要:

Frequency upconversion of cw infrared radiation at 1.06 &mgr;m into the visible inEr3+/Yb3+-codopedGa2S3:La2O3chalcogenide glass samples is presented. Intense green and red emission bands around 530, 555, and 670 nm, respectively, are observed in addition to near-infrared 830 and 925 nm less intense signals. Energy transfer processes and nonradiative phonon-assisted decays account for the population of the2H11/2,4S3/2,and4F9/2emitting levels. The dependence of the red emission with theYb3+concentration is also analyzed. The potential application of the Er/Yb-codopedGa2S3:La2O3glass for upconversion based optical devices is discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120884

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report electroluminescence degradation studies of tris (8-hydroxyquinoline) aluminum(Alq3)organic light-emitting devices (OLEDs) under ambient conditions.Alq3films and organic bilayer anode/naphthyl-substituted benzidine derivative/Alq3/cathode devices are studied via electroluminescence, photoluminescence, polarization microscopy and atomic force microscopy, and via microscopic infrared spectroscopy. Results reveal that humidity induces the formation of crystallineAlq3structures in originally amorphous films. The same phenomenon is found to occur in OLEDs and causes cathode delamination at theAlq3/cathode interface that results in the formation of black (nonemissive) spots in the devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120867

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on ultrafast excitonic nonlinearities in ion-implanted InGaAs/InAlAs multiple quantum wells. We find that irradiation with energeticO+andNi+ions can reduce the carrier lifetime from 1.6 ns down to 1.7 ps without significantly altering the excitonic absorption properties, making efficient fast saturable absorbers in the 1.3–1.5 &mgr;m wavelength range. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120885

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The temperature dependence of optical poling of a side-chain azobenzene–polyimide film with high glass transition temperature was experimentally investigated. With the increase of the sample temperature the light-induced second-harmonic generation increased first, and then decreased as the temperature was near its glass transition temperature. The light-induced second-order nonlinear optical coefficientd33for the optimum temperature was determined to be 6.9 pm/V, which was about 2.7 times that obtained at room temperature. Compared with optical poling at room temperature, this thermal-assisted optical poling not only enhancedd33of the polyimide film, but also improved the polar order stability of molecules. Optical storage based on optical poling was also demonstrated experimentally. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120886

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An optically addressed spatial light modulator with electrolyte bisphtalocyanine of lutetium incorporated in the alignment layer is shown to be capable of memorizing a grey scale image. The relationship between the memorized grey scale and the illumination is shown. The temperature, the concentration ofLu(Pc)2and the spontaneous polarization of liquid crystals are found to have the effect on the memorization rate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120887

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A theory for using near-field optical microscopy to probe quantum nanostructures is presented. Optical transition rates are determined for dots excited by the near field of a tip. Local-field corrections are neglected. Results for different tip/dot configurations and sizes show that near-field excitation can enhance light-hole transitions, excite selection-rule breaking transitions with rates comparable to allowed transitions, and map electron–hole pair wave functions. Conversely, dot response can be used to characterize tip near fields.

ISSN:0003-6951    

DOI:10.1063/1.120868

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method is proposed for the accurate measurement of phase shift in electron holography. The method is based on the use of moire´ fringes resulting from the subtraction of a null electron hologram by a real object hologram recorded under slightly different experimental conditions. This method does not require any optical or digital reconstruction of the electron hologram, and is shown to be highly sensitive to the phase shift of the electron wave passing through an object. Using experimental results obtained from a single particle of silicon, we demonstrate that the sensitivity of this method to phase shift may easily be amplified by more than 11 times compared with the conventional method using an ordinary electron hologram. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120888

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The acoustic signature provided by laser-generated ultrasound in polymer matrix composites is difficult to interpret on account of the dispersive nature of these materials. In order to simulate such wave forms, a double numerical inverse transform is used to calculate the surface displacement generated by a line impact. This calculation method is preferred due to the frequency dependence connected with the viscoelastic rheology. The focusing effects that anisotropy gives rise to are represented. In addition, the spreading of the signals issued from absorption is correlated with the anisotropic changes of the slowness versus frequency. The predicted displacements are in good agreement with the result of experiments performed with a composite plate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120889

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Measurements are reported on an inductively coupled large-area(71×61 cm2)plasma source driven by a 13.56 MHz traveling wave. Launching a traveling wave eliminates standing wave effects to obtain a uniformly excited processing plasma. The driving coil consists of a series connection of eight parallel rods, embedded in the plasma inside thin quartz tubes for efficient power delivery. The network required to launch a traveling wave through the driving coil is described. Our measurements confirm that a radio frequency traveling wave is launched and that a high-density plasma is produced. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120890

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The early stages of the growth of plasma-deposited hydrogenated amorphous carbon films onc-Si have been studied byin situinfrared ellipsometry. Different types of polymeric films have been obtained under soft plasma conditions. From the evolution of optical properties, a uniform growth is observed for films having the highestsp2carbon atom content. In contrast, when the film bulk is a highly saturated polymer, where carbon configurations are mostlysp3,an interlayer of about 20 Å is evidenced, correlated with the formation ofsp2CHnbonds. Moreover, infrared data tend to prove that this interlayer formation is incompatible with the presence of SiC at the interface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120891

出版商:AIP    

年代:1998

数据来源: AIP