摘要:

A real‐time holographic technique is described for the detection of ultrasound pulses on unpolished surfaces of common engineering materials. Results obtained on a rough aluminum surface offer a detection resolution limit of 0.1 A˚.

ISSN:0003-6951    

DOI:10.1063/1.98609

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A gain‐guiding tapered stripe laser was fabricated using a Ga0.5In0.5P/(Al0.5Ga0.5)0.5In0.5P double heterostructure wafer grown by metalorganic chemical vapor deposition. The laser showed a continuous wave (cw) threshold current of 48 mA, a maximum temperature for cw operation of 81 °C, an aspect ratio of about 2, and an astigmatism near 25 &mgr;m. The emission wavelength was 684 nm. Thirty‐two devices have been operating without significant degradation for more than 2000 h at 50 °C with a constant output power of 3 mW.

ISSN:0003-6951    

DOI:10.1063/1.98610

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A novel small rotation or small birefringence measurement scheme based on the dynamics of the helicoidal eigenstates of a passive Fabry–Perot cavity with two quarter‐wave plates is described. When the system is inserted between two crossed polarizers, the sensitivity of the method is shown to be proportional to the square of the finesse of the cavity. For a finesse of 50, the observed noise floor corresponds to an estimation of the minimum detectable small rotation of 3×10−8rd. We discuss possible improvements and potential possibilities of the method.

ISSN:0003-6951    

DOI:10.1063/1.98611

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Optical amplification gain up to 17.7 dB has been realized in monolithically integrated distributed‐feedback lasers. Master laser lasing wavelength and slave laser amplified spontaneous emission wavelength must be tuned within 0.03 nm.

ISSN:0003-6951    

DOI:10.1063/1.98612

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The first continuous wave (cw) operation at room temperature of a GaAlAs short‐wavelength distributed feedback (DFB) laser is reported. The cw operation at a wavelength of 759 nm was realized by use of the buried twin‐ridge substrate (BTRS) structure which has an excellent current confinement efficiency in the active region. The hybrid liquid phase epitaxy and the metalorganic chemical vapor deposition growth technology were used for the fabrication of short‐wavelength GaAlAs DFB BTRS lasers.

ISSN:0003-6951    

DOI:10.1063/1.98560

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The first measurements of electroabsorption in AlGaAs/GaAs multiple quantum wells grown on transparent GaP substrates are reported. High quality quantum well materials with sharp, well defined excitonic resonances are grown by employing a GaAsP intermediate layer between the quantum wells and the substrate. Good surface morphology and abrupt interfaces have been achieved with etch pit densities of 4×105cm−2. A 7.5‐meV shift of the absorption edge to lower energies is observed for field strengths of 8×104V/cm. These structures are well suited for photonic switch array fabrication.

ISSN:0003-6951    

DOI:10.1063/1.98561

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report the measured dependence of the near‐infrared optical emission from sulfur‐related impurity centers in crystalline silicon on the sulfur concentration in the sample. The results suggest that each impurity complex contains only a single sulfur atom. Additional experiments support the possible presence of oxygen in the impurity center. We also report the observation of concentration quenching of the emission and the observation of absorption by the ground state of the impurity complex.

ISSN:0003-6951    

DOI:10.1063/1.98562

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Localized  epitaxial  Co5Ge7  and  CoGe2 have  been  grown  in  cobalt  thin  films  on (111)Ge  in  the solid phase epitaxy regime. The orientation relationships between epitaxial germanides and the substrates as well as the configuration of the interfacial dislocations were analyzed by transmission  electron  microscopy (TEM) in detail.  Surface morphology was examined by scanning  electron  microscopy.  The  results  obtained  from  Read  camera  glancing  angle  x‐ray diffraction and Rutherford backscattering channeling analysis were found to corroborate with those from TEM examinations.

ISSN:0003-6951    

DOI:10.1063/1.98563

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Thin, silicon‐rich tungsten silicide layers, deposited using the co‐sputtering technique and annealed within the temperature range 750–950 °C, were investigated using the acoustic material signature technique, transmission electron microscopy, and the Rutherford backscattering technique. The effective elastic constants were determined from the dispersion curves calculated using a Tiersten model [J. Appl. Phys.40, 2 (1969)] and fitted to the experimental dispersion data. It is shown that for the annealing temperatures used the elastic properties of thin silicide films are correlated with the annealing temperature‐dependent content of the excess silicon present within the grain boundaries.

ISSN:0003-6951    

DOI:10.1063/1.98564

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Controlled size clusters of Au with a diameter of 13 A˚, prepared using a multiple expansion cluster source, have been supported on highly oriented pyrolytic graphite and observed with a scanning tunneling microscope. A reliable constant‐current signature for a metallic cluster supported on a graphite substrate is identified. Images of the supported Au clusters are found to exhibit a narrow size distribution and a diameter which is in close agreement with the diameter predicted from conditions in the multiple expansion cluster source.

ISSN:0003-6951    

DOI:10.1063/1.98565

出版商:AIP    

年代:1987

数据来源: AIP