摘要:

Dominant factors influencing domain broadening in periodically poled ferroelectric domain structures for quasi-phase-matched nonlinear optical converters are studied. It is shown that fabricated patterned switching electrode gives rise to a high tangential field causing polarization inversion behind an isolated layer of the patterned electrode. The domain broadening depends on basic electron parameters of a ferroelectric crystal such as surface electron concentration and electron mobility. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121969

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An adjustable broadening function instead of the conventional Lorentzian one is incorporated in the dielectric function model for hexagonal GaN. One-electron contributions atE1critical points and higher-state(m>1)exciton terms, which were incorrectly disregarded in the previous study, are taken into account. Model parameters were determined using the acceptance-probability-controlled simulated annealing. As a result, excellent agreement with experimental data for both real and imaginary parts in the range from 1.5 to 10 eV is obtained. Average discrepancy between experimental and calculated data for the real part of the index of refraction equals2.75×10−4,and for the imaginary part is1.66×10−3.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121970

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Light emission from ap-ndiode biased in controlled avalanche breakdown has been measured over the photon energy range 1.4–3.4 eV. Previously published models are compared with measured data to associate specific mechanisms with avalanche photon emission in silicon. A multimechanism model fitting the measured spectrum is presented. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121971

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated second-harmonic generation in short-period periodically-poled bulk and waveguide potassium titanyl phosphate crystals to generate blue light using subpicosecond laser pulses. For the bulk, the highest conversion efficiency is≈5.5&percent;,which is about two orders of magnitude larger than that achieved previously. For the waveguide, the highest conversion efficiency is≈32&percent;,which is about a factor of 4 higher than that obtained before. These measured values are in good agreement with our theoretical results. We have observed saturation of conversion efficiency, which sets a limit to the maximum efficiency that can be achieved. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121972

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We study electronic transitions between a subband and a lower subband doublet which is driven by a coherent microwave (MW) field in a semiconductor double well structure. Within a microscopic three-band model, we show that variation of the MW phase allows manipulation of the optical gain provided the probe pulse duration is shorter than the period of the MW-field-generated interband polarization in the doublet. Moreover, we find that optical gain without inversion can be achieved in spite of subpicosecond dissipative mechanisms provided by electron-phonon coupling and electron tunneling into and out of the double well. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121973

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The influence of the introduction of a dopant molecule, namely DCM, in a matrix of a naphthalimide derived polymer (PNI) is studied by means of UV-visible absorption spectroscopy, photoluminescence emission and excitation spectrometry, and 2D photoluminescence spectrometry. We demonstrate that, contrary to previous observations on similar systems, energy transfer occurs between PNI and DCM. Moreover, photoluminescent (PL) and electroluminescent (EL) emissions are assigned to arise from the same excited state. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122025

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present a scanning acoustic force microscope (SAFM) for the study of surface acoustic wave (SAW) phenomena on the submicron lateral scale. Until now, SAWs with in-plane oscillation components could only be studied effectively via nonvanishing out-of-plane oscillation contributions. By operating the microscope in lateral force mode, where both bending and torsion of the cantilever are detected, additional amplitude-dependent signals are found, which are due to the interaction with purely in-plane polarized surface oscillations. To demonstrate the capabilities of this type of SAFM, Love waves were studied on the surface of layers deposited on ST-cut quartz with SAW propagation perpendicular to the crystalX-axis. The phase velocity of the wave as well as the amplitude of a standing wave field was measured and compared to calculated values. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122026

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 &mgr;m, we were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure. High-pressure discharges in xenon were found to be strong sources of excimer radiation. Highest intensities at a wavelength of 172 nm were obtained at a pressure of 400 Torr. At this pressure, the vacuum ultraviolet (VUV) radiant power of a single discharge operating at a forward voltage of 220 V and currents exceeding 2 mA reaches values between 6&percent; and 9&percent; of the input electrical power. The possibility to form arrays of these discharges allows the generation of flat panel VUV lamps with radiant emittances exceeding 50 W/cm2. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122027

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Spatial profiles and buffer-gas pressure dependences of fullerenes contained in primary carbon soots are measured in order to investigate production ratios of higher fullerenes toC60in an arc-discharge fullerene generator. It is found thatC74is efficiently produced in the arc periphery-plasma region whileC60is mainly produced in the core-plasma region, being the most dominant higher fullerene under the condition of a higher helium-gas pressure(>100 Torr).©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122028

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Cr films sputtered onto {100} Si substrates at room temperature were found to be under residual tension, as revealed by wafer curvature measurements. A 150 nm thick Cr film was bombarded with 300 keV Ar ions after deposition. The intrinsic residual tensile stress increased slightly and then decreased with further increase in the ion dose. For ion doses>1×1015 ions/cm2,the stress in the film became compressive and increased with increasing dose. Transmission electron microscopy revealed that the grain boundaries in as-deposited Cr have columnar porosity. A Cr film, ion irradiated to a dose of5×1015 ions/cm2,showed no grain boundary porosity. The changes in the residual stress during ion irradiation are explained by considering Ar incorporation in the film and the manner in which irradiation may change the interatomic distances and forces. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122029

出版商:AIP    

年代:1998

数据来源: AIP