摘要:

It has long been recognized thatWO3can be colored through electro-, photo-, and thermo-chromism processes. We report here thatWO3turned to a deep blue color upon just one pulse irradiation of the XeCl excimer laser (&lgr;=308 nm, pulse duration=36 ns, output energy=100 mJ/pulse). Scanning electron microscopy (SEM) images showed that a melted layer was formed on the surface of the sample. The color change was demonstrated by UV-visible diffuse reflectance. X-ray photoelectron spectroscopy (XPS) showed the partial reduction ofWO3and the appearance of conduction band electrons. Calorimetry measurement results indicated that reoxidation happened at 400–440 °C in air. From these experimental results combining with the calculation, it was concluded that the laser-induced coloration is different from ordinary photochromism induced by UV light, and may be attributed to thermochromism. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120064

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optically pumped stimulated emission and lasing in thin films of an absorbing host 8-hydroxyquinolinato aluminum(Alq) doped with small amounts of the laser dye DCM II is observed. Forster transfer of the excitation from the Alq molecules to the DCM II molecules results in a high absorption coefficient at pump wavelength (337 nm) as well as low absorption loss at the emission wavelengths (610–650 nm). ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120065

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present the results on aging mechanisms acting in high-power laser diode arrays (LDAs) employing Fourier-transform (FT) spectroscopy. The FT spectrometer was used as an excitation source for performing photocurrent (PC) measurements in two sets of aged LDA samples. The PC spectra reveal both the evolution of a defect band located in the optically active layer as well as modifications of the interband part of the spectrum upon aging. Such changes represent sensitive quantitative measures of the aging status and provide insight into the microscopic changes of the device structure upon aging. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120066

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The drift of the direct current (dc) quadrature bias voltage was monitored in electro-optic polymer Mach–Zehnder modulators for over 600 h. Traceable bias voltage was observed in polyurethane-Disperse Red 19 modulators. Electric field relaxation analysis showed that steady state dc and alternating current (ac) field distributions on polymer layers depended on the dielectric properties of the materials. The long-term bias stability of our modulators was originated from the low conductivity of the electro-optic polymer guiding layer. A concept of material electrical compatibility is introduced as a materials selection guideline for the fabrication of polymer modulators with the minimum bias drift. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120067

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A reflective liquid crystal diffraction grating is proposed which makes use of the maximum available surface area. The structure consists of alternating stripes, each a twisted-nematic domain with surface orientation perpendicular to that of its neighbors. All domains have the same twist sense. This device yields, in principle, 100&percent; diffraction efficiency independent of incident polarization. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120068

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The coupled wave theory is applied to calculate the diffraction efficiency of zone plates used in high orders of diffraction. In contradiction to the existing understanding about 30&percent;–50&percent; of the incident intensity can be diffracted by a single high order if the line-to-space ratio of the zone structures is in the range of 0.1–0.5 and the aspect ratios are larger than 30:1. Highly efficient diffractive transmission x-ray optics with high numerical apertures and resolving power can be developed without manufacturing extremely small zones which are necessary for zone plates used in the first order. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120069

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel waveguide structure for AlGaInP visible separate confinement heterostructure quantum well laser with inserting low-refractive-index AlAs layers is theoretically investigated using the transfer matrix method. By using this structure, we can significantly improve the transverse beam divergence and reduce the threshold current. Otherwise, the inserting AlAs can also be used as a wet etching automatic stopped layer. Because the thermal resistance of AlAs is smaller than that of AlGaInP, the thermal characteristics of this novel structure are also better than the conventional AlGaInP visible lasers. With the inserting AlAs layers, the transverse beam divergence and the threshold current density can be reduced from38°to8.84°and 787 to 666.8 A/cm2, respectively. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120063

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the photorefractive properties of a lowTgcomposite consisting of functionalized polysiloxane doped with a chalcone derivative. The high transparency of this doping molecule enabled the observation of high net gain at 514 nm. Orientational and Pockels contributions to the total refractive index variations were measured by frequency-dependent ellipsometry experiments. Finally, the field dependence of the gain coefficient is described using Kukhtarev’s model for the space charge field with an effective trap density as a single fitting parameter. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120040

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The process of vacuum gap formation in a microsecond plasma opening switch has been studied using a He–Ne laser interferometer. Time and spatially resolved density measurements are performed in the plasma opening switch, showing a density decrease during switch opening in almost the whole interelectrode gap. Despite fine triggering accuracy and generally good shot-to-shot reproducibility of voltage and current waveforms, measurements made with the same laser beam location indicated remarkable shot-to-shot variation. The unstable formation of the vacuum gap in the microsecond plasma opening switch may be a major limiting factor for efficient switch operation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120041

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on energy resolved field emission measurements of 0.3&mgr;mthick nitrogen containing diamondlike carbon (DLC). The film used in this study was deposited by filtered arc deposition onto a highlyp-doped Si(100) wafer. The film showed homogeneous field emission over the entire wafer area with an onset field for 1 nA emission current of 20–25 V/&mgr;m. The energy resolved field emission measurements were carried out with an applied electric field of 20–22V/&mgr;m. The field emitted electrons originate from the Fermi energy, indicating that no field penetration occurs. The energy distribution has a FWHM of 0.63 eV at an applied field of 21V/&mgr;m. The spectra could be deconvoluted using standard tunneling theory. The results of the deconvolution indicate an electric field strength of 6500V/&mgr;m at the emission site. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120042

出版商:AIP    

年代:1997

数据来源: AIP