摘要:

A submicrometer photodiode probe with a sub‐50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al–Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114223

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Characteristics of a phase‐change optical disk using a (Ge–Sb–Te)‐(Cr–Te) recording film containing a high‐melting‐point component Cr–Te are studied. The high‐melting‐point component Cr–Te precipitates in the recording film, and prevents a material flow of the recording film during repeated rewrites in which the recording film is melted. There is no drawback such as noise increase by the addition of Cr–Te. Thus the phase‐change optical disk using this recording film shows very small distortion in the reproduced signal wave form even after 2×104rewrites of high‐density recording signals that are liable to cause the material flow by forming long and short recording marks on the disk. With a phase‐change optical disk, it is easy to overwrite (rewrite without prior erasure) information, which makes it highly suitable for digital recording of motion pictures and sound. They are expected to be used as rewritable compact disks, rewritable CD‐ROM disks, rewritable video disks, and small recording media for personal computers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113966

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Optimized double heterostructure (DH) vertical‐cavity top‐emitting lasers are grown by molecular beam epitaxy. Both the doping profile and the laser structure are optimized to achieve high performance. Continuous wave 2 mW output power at room temperature is obtained for nominal 10 &mgr;m diam DH vertical‐cavity top‐emitting injection lasers. A single fundamental longitudinal and transverse mode is maintained up to 1.7 mW. It lases in continuous waves at a temperature of 80 °C. A lasing power range of ∼0.8 mW is sustained within a 10% change in the output linearity, which is much larger than a value of less than 0.1 mW for quantum well lasers. This demonstrates that its output linearity is far more superior than the one of compared quantum well lasers, which is explained in detail. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113967

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Tunable blue and ultraviolet single mode laser light has been generated by frequency quadrupling the output of a semiconductor laser with two successive frequency doubling stages. The laser source is based on a commercial high power semiconductor laser near 972 nm which combines a low power single mode master oscillator with a high power amplifier. The doubling stages consist of nonlinear crystals which are placed inside compact optical buildup resonators. Up to 156 mW tunable blue radiation near 486 nm and 2.1 mW ultraviolet light near 243 nm have been produced. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113968

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This letter describes a confocal scanning beam macroscope/microscope that can image specimens up to 7 cm in diameter using both photoluminescence and reflected light. The macroscope generates digital images (512×512 pixels) with a maximum 5 &mgr;m lateral resolution and 200 &mgr;m axial resolution in under 5 s, and in combination with a conventional confocal scanning laser microscope can provide quality control at a macroscopic/microscopic level for porous silicon specimens, wafers, detectors, and similar devices. This combination of instruments can also be used as a method for evaluating preparation parameters involved in the manufacture of porous silicon. Various confocal and nonconfocal photoluminescence and reflected‐light images of porous silicon are shown using both a macroscope and a conventional confocal scanning laser microscope. A 3D profile of a porous silicon structure reconstructed from confocal slices is also shown. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113969

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present results of a theoretical investigation into a nonlinear thin‐film multilayer device that exhibits passive anisotropic optical transmission—the analogue of the electronic diode. This optical diode is a nonlinear, asymmetric, distributed Bragg reflector. Material parameters for a nonlinear polymer (polydiacetylene 9‐BCMU) and rutile are used in alternating layers to model a realistic device. The diode exhibits more than five times as much transmittance in one direction as in the opposite direction. It has a thickness of only 2 &mgr;m and is polarization insensitive. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113970

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We propose here a model of the scintillation from complex oxide single crystals doped with Ce3+ions to explain the correlation observed between scintillation light yield and intrinsic luminescence of the matrix. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113971

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

While the parallel‐plate capacitive model is often employed to describe the electrical behavior of a plasma sheath, the simple question of how far apart the two plates are for a given plasma cannot be easily answered yet because of the lack of a workable definition of the sheath edge. The sheath edge estimated with the Child–Langmuir equation may misplace as much as 40% of the total space charge outside the sheath. An alternative practical definition of the sheath edge is proposed that includes almost all space charge within the sheath. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113972

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report atomic resolution images of chemical vapor deposition grown epitaxial diamond (100) films obtained in ultrahigh vacuum (UHV) with a scanning tunneling microscope. A (2×1) dimer surface reconstruction and amorphous atomic regions are observed. The (2×1) unit cell is measured to be 0.51±0.01×0.25±0.01 nm2. The amorphous regions are identified as amorphous carbon. A radial structure 1.5 nm in diameter is observed on a plane at a 20° slope to the (2×1) surface. Tunneling current versus voltage spectra in UHV and Raman spectra are also obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113973

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Porous carbon–carbon preforms, 10.8 cm o.d.×4.4 cm i.d.×3.0 cm thick have been densified in a one‐cycle, 26 h process. The disks are heated by induction, creating an inside‐out thermal gradient, and are exposed to cyclopentane vapor in a water‐cooled vacuum chamber. Rough‐laminar carbon microstructure is obtained; a compressive strength of 268 MPa is measured at 1.79 g/ cm3density. The densification rate is monitored in real time. The precursor utilization efficiency is 20%–30%. Our patented process can be applied to other materials, has significant scale‐up potential and is economically competitive. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113974

出版商:AIP    

年代:1995

数据来源: AIP