摘要:

The dispersion of the refractive indices for the epitaxialPb1−xLaxTiO3thin films withx=0.28 and 0.23 grown on the MgO (100) andAl2O3(0001) substrates, respectively, has been investigated. The refractive indices in the wavelength range of 435–1523 nm were measured by a prism coupling method. At a wavelength range of 632.8 nm, the refractive index of a PLT film grown with (100) orientation was determined to be 2.609. The transmission spectrum was used as an additional measurement for the dispersion of the refractive index and showed a good agreement with the prism coupling measurements. The dispersion of refractive index fits well to a single-term Sellmeier relation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118340

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A model is presented for optically controlling the gain of a semiconductor laser by introducing photons from a second coherent source into the side of the laser. We find that the threshold current of the laser increases in direct proportion to the overlap between the two modes and the photon density from the coherent source. An easy-to-use, closed-form expression relates the optical power emitted from the laser to the bias and threshold currents. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118342

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Efficient, high-power, Al-free active-region diode lasers emitting at &lgr;=0.83 &mgr;m have been grown by low-pressure metalorganic chemical vapor deposition. Threshold-current densities as low as 220 A/cm2,maximum continuous wave (cw) power of 4.6 W, and a maximum cw wallplug efficiency of 45&percent; are achieved from 1 mm long, uncoated devices withIn0.5(Ga0.5Al0.5)0.5Pcladding layers. Further improvement is obtained by replacing thep-In0.5(Ga0.5Al0.5)0.5Pcladding layer with thin (0.1 &mgr;m) electron-blocking layers ofAl0.85Ga0.15AsandIn0.5(Ga0.5Al0.5)0.5P,and ap-In0.5(Ga0.9Al0.1)0.5Pcladding layer. Such devices provide a record-highT0of 160 K and reach catastrophic optical mirror damage (COMD) at a record-high cw power of 4.7 W (both facets). The corresponding COMD power-density level (8.7 MW/cm2)is ∼2 times the COMD power-density level for uncoated, 0.81-&mgr;m-emitting AlGaAs-active devices. Therefore, 0.81-&mgr;m-emitting, Al-free active-region devices are expected to operate reliably at roughly twice the power of AlGaAs-active region devices. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118343

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A bilayer is used as an electrode for organic electroluminescent devices. The bilayer consists of an ultrathin LiF layer adjacent to an electron-transporting layer and an aluminum outerlayer. Devices with the bilayer electrode showed enhanced electron injection and high electroluminescence efficiency as compared with aMg0.9Ag0.1cathode. Similar effects were observed when replacing MgO for LiF. The improvements are attributed to band bending of the organic layer in contact with the dielectrics. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118344

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Second harmonic generation in gallium-lanthanum-sulphide (Ga:La:S) and germanium sulphide + Ga:La:S glasses is investigated. It is shown that microcrystals of Ga:La:S and &agr; phase of gallium-sulphide (&agr;-Ga2S3), whose presence in the glass matrix is revealed by energy dispersive spectroscopy and x-ray diffraction analysis, are responsible for the frequency doubling process. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118345

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Sharp room temperature exciton features and complete recovery of the excitonic absorption with 21 ps time constant are demonstrated in neutron irradiated (Ga,Al)As/GaAs multiple quantum wells. Carrier lifetime reduction is consistent with the EL2 midgap defect which is efficiently generated by fast neutrons. Influence of gamma rays accompanying neutron irradiation is discussed. Neutron irradiation provides a straightforward way to control carrier lifetime in semiconductor heterostructures with minor deterioration of their excitonic properties. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118346

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Previously it has been shown that resonant-cavity, separate absorption and multiplication (SAM) avalanche photodiodes (APDs) exhibit high peak external quantum efficiency (∼75&percent;), low dark current, low bias voltage(<15V), and low multiplication noise(0.2<k<0.3). We describe the frequency response of resonant-cavity AlGaAs/GaAs/InGaAs SAM APDs. A unity-gain bandwidth of 23 GHz and a high gain-bandwidth product of 130 GHz have been achieved. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118341

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

AmorphousKNbO3films are prepared by a low-cost sol–gel method. These films show a smooth surface morphology and have good waveguiding properties. Ferroelecticlike hysteresis loops are observed in these amorphousKNbO3films with a remanant polarization of about6&mgr;C/cm2.After corona poling, a stable effective second harmonic generation coefficient of 0.523 pm/V is achieved. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118347

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ultrasonic vibrations of a single-piezoelectric crystal ofLiNbO3and CdS can excite luminescence of gas near the crystal surface. Light excitation starts at ultrasonic intensity above a certain threshold. This threshold lies in the range 3–10W/cm2and corresponds to the unpinning of dislocations and beginning of their reversible motion in the piezoelectric crystal. The effects constitute a new class of acousto-optic and dislocation phenomena having the main feature of energy transformation from ultrasound in solid to luminescence of gas at normal atmospheric pressure. The unpinning of dislocations is shown to be critical for sonoluminescence excitation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119252

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dynamic model of multi-MA current commutation in a double wire arrayZ-pinch load is proposed and studied theoretically. Initially, the load is configured as nested concentric wire arrays, with the current driven through the outer array and imploding it. Once the outer array or the annular plasma shell formed from it approaches the inner array, the imploded plasma might penetrate through the gaps between the wires, but the azimuthal magnetic field is trapped due to both the high conductivity of the inner wires and the inductive coupling between the two parts of the array, causing a rapid switching of the total current to the inner part of the array. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118339

出版商:AIP    

年代:1997

数据来源: AIP