摘要:

Amorphous silicon–carbon based thin films deposited in a microwave plasma reactor using organosilane vapors from liquid sources show efficient photoluminescence (several %) when excited with ultraviolet (UV) light together with a low absorptivity (down to 1 cm−1at the long‐wavelength side) in the spectral range of the luminescence emission (400–550 nm). On the basis of these films we have prepared luminescent waveguiding layer structures which we propose for an application as a fast, sensitive, and selective UV detector integrated on silicon. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114649

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Normal spectral emissivity of liquid Si was determined by direct measurement of thermal radiations from a surface of the Si melt and a blackbody cavity. The spectral emissivity has little dependence on the wavelength. The emissivity is 0.27 for the wavelength from 500 to 800 nm and is about a half of that of solid silicon at the melting point. Temperature dependence of the emissivity is very small in the temperature range from the melting point to 1550 °C. Free‐electron model with a plasma frequency and relaxation time of the order of 1016Hz gives a good agreement with the experimental result. That indicates the dominant effect of the free electrons on the optical properties of the liquid Si. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114650

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Cyanobiphenyl liquid crystals absorb strongly in the ultraviolet. These absorption bands are highly dichroic. The dichroic ratio changes as a function of order parameter and orientation of the liquid crystals. Plots of the dichroic ratio as a function of film thickness demonstrate that the polymer alignment layer not only imposes an orientation on the liquid crystal director but also lowers the order parameter of the liquid crystal near the polymer surface. A sharp decrease in dichroic ratio occurs at film thicknesses near 35 nm, suggesting a phase transition which may be caused by the appearance of a biaxial phase or smectic layering at the air interface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114651

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Stretched‐pulse additive pulse mode‐locked fiber lasers use fibers with opposite signs of group velocity dispersion to introduce large changes of pulse width per pass and avoid excessive nonlinearity. We have investigated these intracavity pulse dynamics. Optimal points for output coupling and for the placement of the artificial absorber element in the cavity are determined for a fiber ring laser. The dispersion balance is important for the generation of clean sub‐100 fs pulses, but the net cavity length is found to be relatively uncritical. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114652

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report a simple interferometric method for simultaneous,insitumeasurement of both the thickness and the depth resolved optical losses of thin transparent films. The experimental arrangement is simple requiring only a laser and a detector regardless of the substrate. The originality of our method is based on the evaluation of the optical losses from the envelopes of the laser signal, while the thickness is measured conventionally by counting the number of signal periods. The technique has been tested while growing ZnO films in a planar rf magnetron sputtering system. Using the above method, the evolution of optical losses is easily observed during deposition, leading to the possibility of a real time control of the film quality. Both theoretical calculations and experimental results are presented in this letter. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114653

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A specific angular distribution of x rays from111In embedded in a thin‐film waveguide (Au film/Langmuir–Blodgett film/Au substrate) is observed by a non‐energy‐dispersive two‐dimensional detector (imaging plate). The angular distribution for the thickness of the upper Au layer of 90 A˚ can be explained by normal calculation of the optical electromagnetic wave solution of Maxwell’s equations for each interface and reciprocity. However, the angular pattern in the upper 400 A˚ Au thickness layer cannot be accounted for by the normal approach without considering the intensity of the x‐ray sheet beam emerging from the end of the multilayer. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114654

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We introduce and analyze a new type of high‐Qmicrocavity consisting of a channel waveguide and a one‐dimensional photonic crystal. A band gap for the guided modes is opened and a sharp resonant state is created by adding a single defect in the periodic system. An analysis of the eigenstates shows that strong field confinement of the defect state can be achieved with a modal volume less than half of a cubic half‐wavelength. We also present a feasibility study for the fabrication of suspended structures with micron‐sized features using semiconductor materials. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114655

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Second harmonic generation (SHG) in waveguides which are multimode at the second harmonic exhibit an intensity dependence in both the phase‐match wavelength and relative conversion efficiency of the different SHG modes because they are coupled to the same fundamental. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114656

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

PassiveQswitching of a flashlamp‐pumped alexandrite laser with a Cr4+:Y2SiO5(Cr4+:YSO) solid‐state saturable absorber has been demonstrated at room temperature. An output of a singleQ‐switched laser pulse of 20 mJ in energy and 70 ns in duration was obtained. The output wavelength of theQ‐switched laser pulse and the free‐running laser was 753 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114657

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a model to evaluate the vertical spectrum distribution of a laser beam in a grating pair stretcher or compressor at off‐horizontal plane incidence. The vertical spectrum displacement or vertical chirp in the output pulse has been calculated and shown quantitatively as functions of the off‐horizontal plane incident angle and the grating groove density. The resulting dispersion errors compared with that at horizontal incidence are also shown. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114658

出版商:AIP    

年代:1995

数据来源: AIP