摘要:

Spatially dependent small signal gain measurements in a continuous wave rf excited Ar–He–Xe (59.5/40/0.5) gas discharge are presented. Maximum values for the small signal gain of the 2.03 and 2.65 &mgr;m xenon transitions of about 22&percent; and 37&percent;/cm, respectively, were obtained at a total pressure of 120 mbar, an input power per unit electrode area of 20 W/cm2and at a rf driving frequency of 115 MHz. With a spatial resolution better than 0.5 mm, a strongly inhomogeneous gain distribution in the transverse direction was measured. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118779

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the observation of an enhanced temperature sensitivity for transient repoling near to the domain freezing temperature in ferroelectric strontium barium niobate. This work has important consequences for the use of optical fields to control domain patterns in such materials. We model the repoling characteristics of the material using a Vogel–Fulcher type response and present results showing the degree of repoling as a function of field and temperature, for short duration repoling times. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118780

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate polymer light-emitting electrochemical cells (LECs) made of a blend ofp-andn-type luminescent conjugated polymers. These two polymers, poly[9-(3,6,9-trioxadecyl)- carbazole-3,6-diyl] (TOD–PC, ap-type polymer) and poly[2,3-di(p-tolyl)–quinoxaline-5,8-diyl] (DT–PQX, an-type polymer), are blue and blue–green emission polymers, respectively, both with high photoluminescent quantum efficiency. However, the photoluminescence of the polymer blend is completely quenched, due to the charge transfer between the two polymers. A new and faint orange–yellow photoluminescence emission, which has photonic energy consistent with the energy difference of the &pgr; band of TOD–PC and the &pgr;*and of DT–PQX, has been observed. LECs fabricated from this polymer blend show strong current injection and bright electroluminescence at this new emission color, which is believed to be due to the interpolymer radiative recombination of the electrons from then-type polymer and holes from thep-type polymer. Such an independentpdoping of TOD–PC andndoping of DT–PQX in the blend and interpolymer radiative recombination provide an interesting way of generating new emission colors in the LEC system. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.118781

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thermal stability of the electroluminescent (EL) devices using various hole-transporting materials based on triphenylamine, and a typical emitting material, tris(8-quinolinolato) aluminum has been systematically studied. The thermal stability of the EL devices is clearly seen to depend on the glass transition temperature(Tg)of the hole-transporting material. The highest thermal stability up to 155 °C is obtained in the device using the pentamer of triphenylamine. It has been found that the linear linkage of triphenylamine is useful to attain highTgrather than the branch linkage. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118782

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The reflectivity of a 9 nm AlAs layer embedded in a GaAs matrix was measured using a near-field scanning optical microscope. Results for freshly cleaved surfaced are understood considering the electrostatic nature of the electric field in the near field of a subwavelength aperture. The optical contrast arises from the different index of refraction of AlAs and GaAs, with topography associated effects playing no role. While keeping the wavelength of the incident radiation and the aperture dimensions fixed,|E|was mapped on planes perpendicular to the tip axis, as a function of the height of the tip above the sample. The results were compared with a finite element calculation for the scattered light. In the analysis, we model the sample with a position dependent dielectric constant. Good agreement between the model and the experimental data was found. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118783

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electric field-induced luminescence quenching in thin films made from common organic electroluminescent material of aluminum (III) 8-hydroxyquinoline(Alq3)is reported. The dependence of luminescence quenching on excitation wavelength and electric field is attributed to field-assisted hopping separation of charge in localized excited states. The effect extrapolated to high electric fields can reduce the luminescence yield by as much as 60&percent; limiting electroluminescence quantum efficiency in high-field-driven light emitting diodes based on theAlq3emitter. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118784

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We investigate the influence of a finite absorber relaxation time on passively mode-locked semiconductor lasers. We find that the mode-locking mechanism of Haus is surprisingly susceptible to small perturbations and small changes in the parameters. Even when the absorber relaxation time is much larger than the pulse duration, it typically is still short enough to be a crucial part of the physics of mode-locking. Allowing for a finite absorber relaxation time, we find that stable operation of a mode-locked semiconductor is possible over a wide range of parameters. We argue that the pulse duration is inversely proportional to the square root of the pulse energy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118785

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Self-assembled chromophoric multilayers having large second-order optical nonlinearities can be combined with linear guiding materials such as polymethylmethacrylate to produce two-component frequency doubling waveguides. This approach introduces considerable flexibility in optimizing the trade-off between the overlap of waveguide mode profiles and linear absorption. Extremely low waveguide propagation losses can be achieved because electric field poling and the accompanying poling-induced optical scattering are obviated. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118786

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have developed a versatile, pulsed source of cold(&Dgr;E=0.018eV), low-energy positrons(E≈0–9 eV). Multiple pulses of105positrons, each 10&mgr;s in duration, are extracted from a thermalized, room temperature positron plasma stored in a Penning trap. The frequency, duration, and amplitude of the pulses can be varied over a wide range. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118787

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The presence of bumps on or near the wafer in plasma processing reactors can significantly affect plasma parameters. We have used a gridded energy analyzer to measure ion fluxes, energy distributions, and angular distributions near such bumps on a grounded electrode in an inductively coupled discharge in a Gaseous Electronics Conference Reference Cell. We find that the bumps affect the ion energy distributions only slightly, lower the ion fluxes by more than a factor of 2 and dramatically alter the ion angular distributions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118814

出版商:AIP    

年代:1997

数据来源: AIP