摘要:

A method to control the coupling constant of a directional coupler switch made of electro‐optic polymer after completing the device fabrication is demonstrated. The method utilizes the selective postphotobleaching of the gap region to lower its effective refractive index while monitoring optical output power from each arm. The output power changes gradually and the crossover states are successively observed as the postphotobleaching proceeds. It is shown that the method can be utilized to tune the initial output to the crossover state to have a good switching extinction. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115218

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Tetragonal calcium manganese germanium garnet (Ca3Mn2Ge3O12) is determined to be optically negative. An analysis of the angular dependence of the transmission fora‐cut crystals reveals the presence of dichroism. Absorption is largest for extraordinarily polarized light. Both properties allow to determine and orient the crystallographic axes of Ca3Mn2Ge3O12samples. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115460

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Lasing has been observed in the blue (488 nm) and red (635 nm, 717 nm) bands in a new Nd3+:Pr3+co‐doped fluorozirconate (ZBLANP) glass fiber with 796 nm pump. An upconversion and resonant energy transfer mechanism is proposed to explain the visible transitions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115461

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The transverse spontaneous emission is used to characterize the gain suppression in semiconductor lasers during their operation for the first time. The carrier heating and the spectral‐hole‐burning are distinguished by using their different spectral behavior. The measurements show a very strong carrier heating in strained multi‐quantum‐well lasers which do not appear in bulk devices. Moreover, the total nonlinear gain coefficient is measured by using a modulation method; the results show a high value of &egr;=16.10−17cm3for the strained multi quantum‐well laser and an usual value of &egr;=2.10−17cm3for the bulk, consistent with the measurement of gain suppression spectrum. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115462

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An experimental investigation was made on the use of a PtSi Schottky barrier for blocking injected electron dark current in a back‐illuminated impurity‐band‐conduction (IBC) photodetector, a device used for detecting long‐wavelength infrared (LWIR) radiation. Measured results on the Schottky barrier height as well as current versus applied bias results are presented, and show that the desired blocking capability has been attained. At the low operating temperatures (∼10 K) of the IBC device, the injected dark current is below our measurement capability for applied biases of up to 10 V. Injected dark current in conventional devices occurs at biases of ∼1 V. The modified device configuration discussed here would enable one to store the mobile ionized donor charge for subsequent readout. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115463

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The vibrational properties of a finite one‐dimensional string‐mass chain are studied experimentally and theoretically. In the experiment both normal mode analysis and pulse analysis are used to obtain the eigenfrequencies of the string‐mass chain. The theoretical predictions are made based upon the numerical solution to the wave equation. The phononic band structure for a periodically massed string as well as Anderson localized gap modes for a disordered system are found. The theoretical and experimental results match satisfactorily well. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115464

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Spontaneous vitrification was observed in the Au–Ta system, although the atomic size difference between Au and Ta is very small. It was found that among the various compositions studied, vitrification was only achieved at a composition of around Au23Ta77. Comparative data were obtained by ion mixing of Au–Ta multilayered films to support the spontaneous vitrification results. The amorphization mechanism was discussed in terms of competition between the amorphous phase against the nucleation and growth of the existing equilibrium compound, which explained the favorable composition range as well as the thermal stability of the obtained amorphous alloy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115465

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have fabricated samples with C60implanted into porous silicon with the ionized cluster beam deposition approach for improving the light emission of C60. We have obtained intense and well‐resolved photoluminescence spectra under excitation of Ar+laser (514.5 nm) at room temperature. The depth analysis of secondary ion mass spectroscopy showed that C60had been incorporated into porous silicon. A large number of fine‐structure peaks in the photoluminescence spectrum indicated the strong coupling of vibrational progressions with electronic states of C60induced by the interaction between C60molecule and nanometer‐sized silicon particles. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115466

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon based structures were fabricated using scanning tunneling microscope on a Si(111) surface by the localized decomposition of gaseous silane at pressures of 10−5–10−6Torr. Continuous wires of width 5 nm could be produced while atomically resolved images of the nearby substrate were obtained. We argue that the fabrication process is effected by field‐assisted decomposition of silane on the tip surface, which subsequently migrates to the tunneling region at the tip apex where it field desorbs to the silicon surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115467

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have investigated the strain relaxation behavior ofbiaxialtensilestrainedGe1−xSixbuffer systems grown on Ge (001) by a high‐resolution x‐ray reciprocal space mapping technique. The molecular beam epitaxy grown structures contain a linearly graded buffer, followed by a uniform buffer and a modulation‐doped heterostructure with a high mobility two‐dimensional hole gas in a Ge channel. Our quantitative measurements of the in‐plane strain show that the lower part of the graded buffer is completely strain relaxed, while the top part of this region and the uniform alloy buffer are partly strain relaxed showing a linear increase of strain towards to surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115468

出版商:AIP    

年代:1995

数据来源: AIP