摘要:

This paper describes the first observation of the generation of surface waves in a broad frequency band (0.2<f<1.0 GHz) by conversion from bulk acoustic waves. The latter are obtained by acoustoelectric amplification from thermal background in GaAs samples at 300 K. The surface waves are generated in the form of narrow propagating domains. Both group and phase velocity measurements, carried out on the principal crystallographic surfaces, served to identify the surface waves.

ISSN:0003-6951    

DOI:10.1063/1.89429

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Chiral nematogens of natural pitchp0and layer thicknessdwere investigated over the regimed<p0<4din cells with &pgr;/2 twist imposed by wall orientation. The decay times in this regime were smaller than forp0⩾4d.

ISSN:0003-6951    

DOI:10.1063/1.89430

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Substitutional solid solutions of Ag in Cu have been formed by ion implanting Ag at concentrations up to 16 at.%. The physical states of the implanted alloys were deduced by ion channeling and transmission electron microscopy and their stability was examined by annealing to 400 °C. The implantation results are compared with those obtained previously by conventional rapid quenching techniques.

ISSN:0003-6951    

DOI:10.1063/1.89431

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The origin of the dislocation climb which takes place in the presence of electron‐hole recombination in laser structuresis discussed. TEM studies on lasers which have been degraded by either forward bias or by optical pumping show that the climb dipoles are extrinsic in both cases. In addition, completely isolated interstitial loops can form which also have the characteristic climb appearance of the larger dipoles. Existing theories for the origin of the interstitials required to account for the observed climb are considered in detail, and it is concluded that the climb structures can best be explained by the emission of both gallium and arsenic vacancies from the dislocation as a consequence of nonradiative processes occurring at the dislocation core.

ISSN:0003-6951    

DOI:10.1063/1.89432

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

An ultrafast ultrasonic tomograph has been developed in our laboratory for direct observation of the living tissues inside the human body. Acousto‐optic interaction is the basic principle of our system. The information carried by the acoustic wave is impressed on a light beam diffracted during the acousto‐optic interaction and an optical system is used for displaying a real image of an isonified object. A first and simple realization has been used to check the principle of operation. Directions for future improvements are iscussed.

ISSN:0003-6951    

DOI:10.1063/1.89436

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

A SAW filter is described which uses multistrip couplers with diferent periodicities in two adjacent tracks in order to transfer a surface wave from one track to the other over a restricted frequency band, i.e., to filter the signal. The principal advantage is good filtering with low insertion loss. Over 30‐dB out‐of‐band rejection with 3‐dB loss in the fanned multistrip coupler at a frequency of 216 MHz is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.89437

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Light guides fabricated by Ti diffusion intoy‐cut LiNbO3are attractive because of the possibility of using the larest electro‐optic coefficient (r33). However, the accompanying Li2O out‐diffusion gives rise to unwanted guided modes which are a problem in electro‐optic modulators. To overcome this problem it is necessary to reintroduce Li back into the crystal by some means. Here we report on a simplebut effective process (using Li2O) to suppress Li2O out‐diffusion and realize single‐mode Ti‐diffused LiNbO3light guides in ay‐cut orientation. A natural extension of the above process to Ti‐diffused LiTaO3light‐guiding structure should be possible.

ISSN:0003-6951    

DOI:10.1063/1.89438

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Optical transmission and reflection data are reported for Cd2SnO4films coated onto transparent substrates or silicon. It is shown that these coatings are candidates for transparent heat reflectors and selective absorber components in solar heat collectors.

ISSN:0003-6951    

DOI:10.1063/1.89439

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The bistable mechanical motion of a corona‐charged polypropylene film in the electric field developed between two electrodes is used in the construction of a new transmission light gate. The minimum switching voltage and time are, respectively, 500 V and 50 ms, in accordance with the proposed motion model. Optical and electrical characteristics of an electret display device using a 5×3 array of light gates are presented.

ISSN:0003-6951    

DOI:10.1063/1.89412

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Pulses of submillimeter radiation (&lgr;∼400 &mgr;m) with a peak power of approximately 1 MW have been generated by illuminating an intense relativistic electron beam with a counterstreaming microwave pump wave (&lgr;∼2 cm). This observation of powerful submillimeter radiation is consistent with a model of stimulated scattering which includes a resonance between the pump wave frequency and the electron cyclotron frequency as well as the occurrence of electrostatic oscillations at the beam plasma frequency.

ISSN:0003-6951    

DOI:10.1063/1.89413

出版商:AIP    

年代:1977

数据来源: AIP