摘要:

An optical sensing scheme for measuring the mode phase shifts and mode amplitude modulation in a multimode fiber is proposed. The scheme uses a double phase conjugator based on photorefractive fiberlike Bi12TiO20(BTO) crystal that allows to detect high speed changes of environmental conditions with adaptation for slow variations. An acoustic sensor based on the proposed scheme is used to demonstrate the scheme’s feasibility. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115139

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A structure for an electro‐optically controlled liquid crystal diffraction grating is proposed, which can dramatically simplify the fabrication process of liquid crystal optical gratings. The structure consists of two alternating stripes. Each stripe is a hybrid liquid crystal cell with adjacent stripes oriented perpendicularly. This kind of electro‐optically controlled diffraction grating in principle gives 100% diffraction efficiency and no polarization direction dependence. The detailed fabrication process is presented. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115140

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A CdHgTe resonant cavity light emitting diode is proposed as a new infrared emitter. The device consists of a bottom Bragg reflector of 86% reflectivity, a half‐wavelength cavity,ndoped at the beginning (1018cm−3) andpdoped at the end (1018cm−3), containing an active layer at the antinode position, and a top gold mirror of 95% reflectivity which also serves as an Ohmic contact. The emission spectrum shows a narrow peak of 8 meV full width at half‐maximum (FWHM) at 300 K, which is much less than the inhomogeneous linewidth of CdHgTe quantum wells (QWs). This electroluminescent peak matches very well the cavity resonance wavelength and FWHM, as given by transmission measurements of the unbiased cavity. The directivity is also improved by the cavity effect. Thus, we have demonstrated that even a relatively lowQmicrocavity can greatly enhance the characteristics of an infrared emitter in the 2–5 &mgr;m range. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115141

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Data are presented characterizing the spontaneous coupling to both planar and index‐confined quasimodes of Fabry–Pe´rot microcavities. Index confinement is achieved using selective conversion of AlAs–AlxOythrough ‘‘wet’’ oxidation to fabricate lateral cavity sizes as small as 2 &mgr;m diam. Spectral tuning and angular radiation patterns show the increased spontaneous coupling that results from three‐dimensional confinement. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115142

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An aluminum‐coated tapered fiber probe, as used in near‐field scanning optical microscopy (NSOM), is heated by the light coupled into it. This can destroy the probe or may modify the sample, which can be problematic or used as a tool. To study these thermal effects, we couple modulated visible light of various power through probes. Simultaneously coupled infrared light senses the thermal effects. We report their magnitude, their spatial and temporal scales, and real‐time probe damage observations. A model describes the experimental data, the mechanisms for induced IR variation, and their relative importance. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115143

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A normal incident infrared detector has been fabricated using electron intersubband transition in a InGaAs/GaAs quantum well structure. With the light polarized in the plane of the layers (normal incident) a nominally forbidden absorption peak was observed. Such an absorption is most likely a result of spin‐flip intersubband transitions induced by the spin‐orbit coupling. In addition, for the light polarized in the plane of incidence, the usual intersubband absorption due to envelope function transition is observed. The responsivity of 0.2 A/W was obtained for the normal incident infrared on the detector. This work demonstrates the fabrication of high sensitivity quantum well infrared detectors operating in the normal incident mode without fabricating grating structures on the device for focal plane applications. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115144

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new strained InGaAs/InP/InAsP antisymmetric coupled‐quantum‐well (CQW) structure with significant enhancement of the blue and red Stark effects in the first heavy‐hole‐to‐electron excitonic transition is proposed in this letter. The calculated amount of blueshift is about 48 meV as the applied electric field varied from 0 to 90 kV/cm and the red Stark shift of about 56 meV can be achieved with an applied electric field in the 0 to −90 kV/cm range. The results of the strong Stark effect in the antisymmetric CQW structure may have potential applications in sophisticated new electronic devices, such as optical switching devices and tunable lasers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114309

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This study characterizes ion behavior of cathodic arc plasmas which have been used for the TiN coating. The ion currents are measured using a plane probe. The probe plane is vertical and parallel to the arc axis. Spectral intensities of Ti+and Ti++ions are also measured as a function of pressure (0.01–30 Pa). As a result of these measurements, it was found that at pressures below 0.1 Pa, the predominant ions in the plasma are Ti++which have a tendency to be directional or to have a beam component, whereas at pressures above 0.1 Pa, mainly Ti+ions of random motion are present. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114310

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

To investigate whether field evaporation of gold atoms is responsible for dot formation in an atomic force microscope (AFM) gold‐coated tip/vacuum/SiO2film/p‐type Si substrate configuration, we have performed elemental analysis of the dots and measured the dependence of the threshold voltage on SiO2thickness with both polarities for the dot formation. The experiments demonstrate that it is feasible to form gold dots on SiO2films 17–107 A˚ thick by adjusting the pulsed voltages applied to the gold‐coated AFM tip. Energy dispersive x‐ray spectroscopy (EDX) shows that the dots include gold. The threshold voltages increase almost linearly with the SiO2thickness. Furthermore, the voltage with negative polarity is lower than that with positive polarity. These results provide evidence that the dot formation on the SiO2film using AFM occurs by field evaporation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114311

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

By high‐frequency sputtering techniques we prepared high‐quality platinum/alumina artificial multilayers (Pt/Al2O3) with interface roughnesses below 0.2 nm and x‐ray reflectivities close to 100% at the first satellite reflection using a wavelength of 0.1542 nm. The multilayer structure remains stable up to at least 700 °C without loss in reflectivity. Further annealing causes a structural phase transition with the formation of a coherent superlattice structure, which is finally destroyed at 1000 °C. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114312

出版商:AIP    

年代:1995

数据来源: AIP