摘要:

We have studied the effect of pulsed laser ablation conditions on the deposition of biocompatible apatite coatings on Ti and Ti–6Al–4V alloy at room temperature. We have made detailed analyses of the spatial distribution of the macroparticles (MP) and of the Ca/P ratio in the coatings. We find that (i) two types of MP are observed, differing in size, shape, and stoichiometry, and (ii) the size distribution of the MP has a maximum depending on the laser fluence and gas pressure in the deposition chamber. Manipulation of the laser deposition conditions allows fine control over both morphology and stoichiometry of coatings. Experimental results are explained on the basis of a theoretical model which includes the analysis of cluster‐type ablation mechanisms due to the high pressures of gas evolved in thermal decomposition of the target material under laser irradiation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113992

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

TM‐dopedBaYYbF8films were epitaxially grown on both (100) and (111) GaAs substrates usingCaF2or LiF as intermediate layers. TheBaYYbF8phase was found to be a previously unreported cubic phase with a lattice constant of 0.5711 nm, which is different from a monoclinic phase reported for bulk crystals. The films produced UV and visible radiation with wavelengths at 360 nm (UV), 450–480 nm (blue), and 500–550 nm (green) when pumped by laser radiation at 647 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113993

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The high‐repetition switching capabilities of a recently developed symmetric Mach–Zehnder (SMZ) all‐optical switch are experimentally investigated. Using a series of four control pulses at intervals of 100 or 25 ps, nearly full switching is achieved at the corresponding intervals. The results experimentally show that the repetition rate, as well as the switching speed, of the SMZ all‐optical switch is not restricted by the slow relaxation of the utilized high‐efficiency band‐filling effect. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113994

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependence of the threshold in a vertical‐cavity surface‐emitting laser is investigated. Comparison of theory with experiment indicates that many‐body Coulomb interactions play an important role. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113995

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Efficient tunable ultraviolet generation by intracavity frequency doubling of a continuous wave Ti:sapphire laser was demonstrated. Maximum output is obtained of 460 mW at 398 nm corresponding to a total infrared‐to‐ultraviolet conversion efficiency over 70%. High conversion efficiency was resulted from a critically phase‐matched, temperature‐tuned lithium triborate crystal and a novel resonator design. The observed laser damage of the crystal coatings is also discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113996

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Mask molecular beam epitaxy has been used to monolithically integrate vertical‐cavity surface‐emitting lasers (VCSELs) emitting at two wavelengths. This technique allows successive selective and nonselective growth in a chamber by using a movable mask. Varying the cavity thickness at selected areas enables the growth of VCSELs spaced 500 &mgr;m apart and emitting at wavelengths 10 nm apart. Both lasers have threshold current densities of 1.3–1.4 kA/cm2, a range comparable to that of typical VCSELs grown by conventional molecular beam epitaxy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113997

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thin films of potassium titanyl phosphate (KTiOPO4) for photonic applications have been fabricated on fused quartz substrates by pulsed excimer laser ablation. The textured films were optically uniaxial with the symmetry axis oriented normal to the film surface. The principle component of the second order electric susceptibility was oriented parallel to this symmetry axis and was determined to be about 16 times the magnitude of quartz for the fundamental wavelength of 1.064 &mgr;m. This configuration, with the largest nonlinear optical response for polarizations perpendicular to the film surface, is desirable in TM guided wave applications. Planar optical waveguide measurements were performed and the linear waveguide loss was measured. The frequency dependence of &khgr;(2)(&ohgr;) was determined and found to be uniform for visible second harmonic wavelengths. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113998

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Theoretical estimates of the temperature distributions are obtained in structures where thin copper films mounted on special membrane wafer transmission electron microscopy (TEM) specimens are exposed to low energy (63–114 eV) ion bombardment in a magnetically enhanced (ME) plasma reactor. The substrate temperatures are experimentally measured as a function of rf power in the plasma reactor and of time. The temperature rise in the copper films is obtained based on a two‐dimensional heat transfer finite element analysis with input of a heat flux at the surface due to ion bombardment. The results indicate that copper heating due to ion bombardment is minimal because of rapid heat transfer through the underlying structure and the observed microstructural changes in copper films during plasma processing must be attributed to other causes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113999

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low energy electron‐enhanced etching of Si(100) has been achieved by placing the sample on the anode of a dc discharge in hydrogen/helium mixtures. Over a broad range of gas composition, gas pressure, and discharge current, nonpatterned samples gave etch yields of 0.01–0.02 atoms/electron, and average etch rates of 2000–3000 A˚/min. Postetch examination by atomic force microscopy revealed surface roughness of 2–3 nm. These results are related to incident flux of H atoms and electrons through a simple model of the anode sheath layer above the sample. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114000

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have used an atomic force microscope with a conducting tip to investigate the layering of hexadecane on graphite. Discrete jumps were observed in both the tip–sample conductance and separation as individual liquid layers are penetrated. These conductance measurements extend solvation studies to higher force scales than have been previously achieved, and can be used to determine when the tip makes contact with the substrate. The layering also enables the formation of stable tunneling junctions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114001

出版商:AIP    

年代:1995

数据来源: AIP