摘要:

Pronounced differences of behavior are seen in the electroabsorptive properties of semiconductor microcrystallites in glass, depending on their size. A rapid transition from confined ‘‘quantum‐dot’’ properties to well‐developed ‘‘bulk‐crystal’’ behavior is observed.

ISSN:0003-6951    

DOI:10.1063/1.105195

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Highly nondegenerate four‐wave mixing (NDFWM) in the pump‐probe detuning region of more than 1 THz has been observed in an InGaAsP multiple quantum well laser for the first time. Each of the probe and signal frequencies is closed to cavity resonance modes for the pump laser and those outputs are enhanced. The highly NDFWM process is based on a mechanism whose response time is less than 0.2 ps.

ISSN:0003-6951    

DOI:10.1063/1.105196

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the successful operation of a highly efficient visible and near‐infrared optical parametric oscillator (OPO) that uses &bgr;‐BaB2O4as the nonlinear medium and is pumped at 354.7 nm. An energy conversion efficiency of 41% corresponding to a quantum conversion efficiency as high as 57% has been achieved in a 10‐mm‐long crystal. Pump depletion is estimated to be 70% or so. This OPO can generate an average output power to 507 mW at 490 nm and can be continuously tuned from 415 to 2411 nm. The reverse frequency conversion process has also been observed in the OPO. The reason for its high efficiency is discussed.

ISSN:0003-6951    

DOI:10.1063/1.105197

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have found that the use of a saturable dye cell, placed at the center of a Fabry–Perot cavity, produced more stable mode‐locked pulses without satellite pulses than a contacted dye cell configuration in active‐passive mode locking of a pulsed Nd:YAG laser. The mode‐locked pulse width was measured to be 23 ps and the energy stability of its frequency‐doubled output was within ±3%. The displacement of the dye cell position from the exact center of the cavity was found not to be critical.

ISSN:0003-6951    

DOI:10.1063/1.105198

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

It has been demonstrated that the H−output current from a small multicusp source can be substantially enhanced if the hydrogen plasma is seeded with barium. Operating with a barium washer insert at the extraction aperture, it is found that the extractable H−current is increased by a factor of 3 if the insert bias potential is optimized. By use of a mixture of xenon and hydrogen gas, it is further demonstrated that the positive hydrogen ions are responsible for the observed H−enhancement.

ISSN:0003-6951    

DOI:10.1063/1.105199

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Stoichiometric films of bismuth titanate, Bi4Ti3O12, have been grown for the first time by the technique of pulsed excimer laser deposition. Ferroelectric films were obtained at temperatures as low as 500 °C on Si(100), MgO(110), and Pt‐coated Si(100) substrates. Hysteresis measurements using a Pt‐coated Si sample yielded a saturation polarization value of about 28 &mgr;C/cm2, consistent with a randomly oriented titanate film structure. A preliminary metal‐insulator‐semiconductor sandwich structure of the form Bi4Ti3O12‐CaF2(100 A˚)‐Si was grown and used to examine polarization induced memory switching effects.

ISSN:0003-6951    

DOI:10.1063/1.105200

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The antiferromagnetic arrangement of the magnetic moments of Fe layers in sputtered Fe/Cr multilayered structures is directly demonstrated from polarized neutron reflectometry studies. Such an antiferromagnetic interlayer exchange coupling is also consistent with magnetization studies on a series of [Fe/Cr]Nstructures. A remanent magnetization is observed for structures containing an odd number of bilayers but no remanent moment is found for an even number of bilayers. By examining the dependence of saturation field on the number of bilayers it is shown that the antiferromagnetic coupling strength is independent of the number of bilayers and is the same for superlattice and sandwich structures.

ISSN:0003-6951    

DOI:10.1063/1.105201

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Cavity‐enhanced detection is used to monitor minute vapor plumes produced by focusing a pulsed laser beam onto a surface placed inside a resonant optical cavity. The photovaporization signals from a variety of different materials are examined, with emphasis being placed on their amplitude and temporal structure.

ISSN:0003-6951    

DOI:10.1063/1.105246

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Experimental verification along with detailed simulation of up‐hill dopant diffusion in the vicinity of a damage layer consisting of dislocation loops is presented. The effect of dopant up‐hill diffusion, predicted on the basis of the so‐called dopant–point defect pair diffusion model, is explained by the additional dopant current driven by the gradient of point defect concentration. The gradient of point defects (self‐interstitials, in the present case) is caused by the strong absorption of self‐interstitials by dislocation loops in the damage layer. The present simulation of phosphorus diffusion in preamorphized silicon crystal shows that the pertinent phosphorus profiles, displaying the up‐hill diffusion, allow reliable extraction of parameters governing the coupled phosphorus and self‐interstitial diffusion dynamics. Three different derivations of the pair diffusion model are investigated. It is shown that the pair diffusion model is consistent with a derivation of transport equations from the master equation assuming that the elementary jump frequency &Ggr;0is enhanced locally by the presence of self‐interstitials according to &Ggr;0(CI/C*I). It is also shown that the same assumption made on the level of the final diffusion equation leads to incomplete formulation of the relevant dynamics.

ISSN:0003-6951    

DOI:10.1063/1.105202

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We present a systematic study of the ballistic electron contribution to the current‐voltage (I‐V) characteristics of vertically integrated resonant tunneling diodes (RTDs) separated by doped spacer layers (Wsp). A magnetic field (B) transverse to the tunneling direction was used to tune the electron’s longitudinal energy. The results confirm the isolated circuit element picture of theWsp=1000 A˚ sample and the strongly coupled description of the 0 A˚ sample. This work shows that even for some nominally isolated RTDs (in this work forWsp= 400 and 500 A˚), theI‐Vcharacteristics can undergo strikingB‐induced changes. This effect is due to resonant charge buildup in the well of the collector RTD from the relatively weak ballistic component of the current traversing the doped spacer region. A simple model that includes a calculation of the conduction‐band profile and quantum well energy levels under bias gives good agreement with the data.

ISSN:0003-6951    

DOI:10.1063/1.105203

出版商:AIP    

年代:1991

数据来源: AIP