摘要:

A complete structural phase diagram of annealed proton-exchanged X-cutLiTaO3is presented, to relate refractive index change to proton-induced lattice deformation. From this diagram, explanations for the previously observed phenomena of index increase upon annealing and index decrease with increasing proton concentration (above a certain value) are derived. We have analyzed the evolution of index profiles during postexchange annealing, describing how the presence of multiple phases within a waveguide can lead to large index variations and buried index profiles. Finally, we identify at least two high-concentration phases that exhibit large temporal instabilities. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122220

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Bilayer polymer light-emitting diodes with two blue light-emitting materials, poly(N-vinylcarbazole) (PVK) and poly(2-dodecyl-p-phenylene) (C12O-PPP), can emit blue or white light, depending on the solvent used in the fabrication of the second layer, C12O-PPP. If hexane (the nonsolvent for PVK) is used, the device emits blue light as a single layer device with C12O-PPP. However, if toluene (the cosolvent for the two polymers) is used, the device emits white light originating from an exciplex emission at the bilayer interface in addition to the exciton emission from C12O-PPP. At low temperatures, the intensity of the exciplex emission drops and that of the exciton emission becomes dominant. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121888

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An asymmetric “thick-lens” model for self-focusing in Kerr medium of finite thickness is presented by introducing a complex curvature radius of a Gaussian beam in nonlinear medium and a transfer matrix for the transition from linear to nonlinear medium. With this model the linearABCD-matrix formalism can be extended to nonlinear optical systems with a clear physical insight. The modulation of the cavity transverse mode of a resonator containing a Kerr medium is characterized by the asymmetry of the “thick lens.” The intracavity small-signal relative spot size variation outside as well as inside the Kerr medium can be calculated efficiently with the “thick-lens”-like matrix formalisms. Criteria for the design and optimization of a Kerr-lens mode-locked laser resonator with a hard or soft aperture are predicted. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121889

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A one-dimensional quasiperiodically domain-inverted optical superlattice has been designed and fabricated in a strontium barium niobate(Sr0.6Ba0.4Nb2O6)single-crystal plate. A third harmonic output generated through coupled second-order nonlinear parametric processes with a conversion efficiency of about 1.6&percent; was obtained when both the second harmonic and the third harmonic were simultaneously quasiphase matched in the crystal. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121890

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We model a three-color stacked organic light emitting device (SOLED) and determine the influence of microcavity effects on the color saturation of the layered, light emitting elements. Using the model, we design and demonstrate a SOLED with good color saturation and minimal viewing angle effects. The Commission Internationale de L’E´clairage chromaticity coordinates for the red, green, and blue subpixels of the SOLED are (0.68, 0.32), (0.32, 0.53), and (0.14, 0.19), respectively. The full color SOLED opens a path to full color, lightweight displays utilizing vertically stacked color elements to maximize the resolution and aperture ratio of the display. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121891

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Time-resolved photoluminescence (PL) spectra are reported for gas-suspended 1–10 nm diameterSiOxparticles formed by laser ablation of Si into 1–10 Torr He and Ar. Three spectral bands (1.8, 2.5 and 3.2 eV) similar to PL from oxidized porous silicon were measured, but with a pronounced vibronic structure. Particle size and composition were determined withZ-contrast transmission electron microscopy imaging and high resolution electron energy loss spectroscopy linescans of individual nanoparticles. Maximized violet (3.2 eV) PL from the gas-suspended nanoparticles was correlated with anex situSiO1.4overall particle stoichiometry. Cryogenically-collected gas-suspended nanoparticles produced web-like-aggregate films exhibiting very weak PL. Standard anneals restored strong PL bands without vibronic structure, but otherwise in agreement with the PL measured from the gas-suspended nanoparticles. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121892

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The optical vibrational modes of the ordered vacancy compoundsCuIn3Se5andCuGa3Se5have been obtained by Raman spectra at various temperatures. The totally symmetricA1mode appears around 155 and167 cm−1inCuIn3Se5andCuGa3Se5,respectively. All the lines observed, except theB1modes, present a reduction in their frequencies by about 10&percent; as compared to the corresponding values in theCuInSe2andCuGaSe2chalcopyrites. This is due to the presence in these compounds of an array of vacancies occupying particular sites in the cation sublattice. These tend to relax the stretching forces thus reducing the vibrational frequencies. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121893

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We compare the use of free-space electro-optic sampling (FSEOS) with photoconducting antennas to detect terahertz (THz) radiation in the range of 0.1–3 THz. For the same average THz power and low-frequency modulation, signal-to-noise ratio and sensitivity are better with antenna detection at frequencies smaller than 3 THz. When the modulation frequency is increased to more than 1 MHz in FSEOS, both detection schemes have comparable performance. Using a singular-electric-field THz emitter, we demonstrate the feasibility of a THz imaging system using real-time delay scanning in FSEOS and only 20 mW of laser power. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121894

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The applications of magnetic direct generation, a noncontact technique for generating acoustic waves, are limited by poor transduction efficiency. This letter describes an approach for substantially improving the transduction efficiency by application of a transduction format, enhanced direct magnetic generation, that utilizes continuous wave resonances and thin film generation. Glass plates coated with thin films of aluminium have been used as free-standing acoustic cavities to generate resonances with high transduction efficiencies andQfactors. These acoustic resonances have been excited without mechanical contact and their origin and characteristics are discussed with respect to resonances in 530 &mgr;m thick aluminized silica plates. The consequences of magnetic direct generation applied to thin metal films, as opposed to bulk metal, are also discussed, particularly with respect to high operating frequencies and acousticQfactors. It is possible that novel sensors and time standards may be constructed by exploiting this approach. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121895

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Three-dimensional bond-orientational order is studied using computer simulations with 4296 hard, monodisperse inelastic spheres flowing in a Couette geometry at a high shear rate. At an average volume fraction close to 0.6, a state with extended correlations in the orientations of particle clusters starts to develop for rough particles after sufficiently long run times. However, no clear evidence of crystallization is found in the system. Further tests of a sheared system comprised of smooth, inelastic spheres reveal crystallization consistent with the previous experimental observations. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121896

出版商:AIP    

年代:1998

数据来源: AIP