摘要:

A cylindrical acoustic lens, inserted into the sound cell of a Bragg‐diffraction imaging system, can substantially improve the resolution. In the conventional system, the resolution for an object which spatially modulates the isonifying beam in a direction parallel to the propagation of the laser light is determined by the numerical aperture of the wedge‐forming optical lens. However, with the cylindrical acoustic lens in the system, the above resolution is instead determined by the numerical aperture of this acoustic lens. The use of this lens also eliminates the need for several optical components in the system and provides directly for an image with a correct aspect ratio.

ISSN:0003-6951    

DOI:10.1063/1.88639

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The LPE growth of Ga1−xAlxAs on the mesa‐etched and air‐exposed surfaces of Ga1−yAlyAs is described. The LPE is shown to begin and proceed at the intersection of the vertical plane (mesa‐etched side) and the horizontal plane (surface of the epitaxial layer). The melt‐back process has also been observed to proceed fast at an intersection such as this. The LPE technique combined with the mesa etching is shown to be effective in obtaining the growth on the top surface of Ga1−yAlyAs provided the aluminum fractionyis relatively small (y≲0.2). This process should prove useful in the fabrication of DFB lasers, as well as optical components such as GaAlAs waveguides and couplers.

ISSN:0003-6951    

DOI:10.1063/1.88640

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Using optical diffraction, we have measured the phase velocities of various ultrasonic modes in water films of different thicknesses sandwiched between two glass plates. The results agree well with theory.

ISSN:0003-6951    

DOI:10.1063/1.88641

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Microwave emissions are observed with a long time duration after a beam turn‐off from a magnetized plasma that is heated by a high‐intensity short‐pulsewidth relativistic electron beam (500 keV, 2 kA, 3 ns). The emission has a frequency spectrum which has peaks near cyclotron harmonics (f=nfce,n=2, 3,...). These microwave emissions can be attributed to electrostatic waves excited by hot electrons which are created in the beam‐plasma interaction.

ISSN:0003-6951    

DOI:10.1063/1.88642

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Recent improvements in diagnostic and computation techniques have made it possible to conduct sensitive experiments on plasma heating and thermal conductivity. The adequacy of classical absorption theory for low‐temperature (T<20 eV) subcritical density experiments is examined.

ISSN:0003-6951    

DOI:10.1063/1.88643

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Multiple‐energy Be+ion implantation has been used to create uniform‐carrier‐concentrationp‐type layers (≳1.5 &mgr;m thick) in GaAs. The implanted samples were annealed at 900 °C using pyrolytic Si3N4as an encapsulant. High activation of the implanted Be was observed. On samples with implanted hole concentrations of 2×1018/cm3, the measured carrier concentration as a function of depth is in good agreement with that expected from LSS range theory. For higher doses, diffusion of the implanted Be was observed.p+n−n+junctions formed by implantation into undoped epitaxial material have low leakage currents and sharp breakdowns at average electric fields in then−region of 1.5×105V/cm.

ISSN:0003-6951    

DOI:10.1063/1.88644

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Room‐temperature cw operation has been achieved for stripe‐geometry double‐heterostructure Ga0.12In0.88As0.23P0.77/InP diode lasers emitting at 1.1 &mgr;m. The heterostructures were grown by liquid‐phase epitaxy on melt‐grown InP substrates, and stripes were defined by using proton bombardment to produce high‐resistance current‐confining regions.

ISSN:0003-6951    

DOI:10.1063/1.88645

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Stimulated emission (4.2 °K) on the NXband recombination transition (formerly identified as NN‐pair band) in N‐implanted GaAs1−xPx(x≈0.37) is reported. The N is implanted (300 °K) at 200 keV to a peak concentrationnN∼5×1018cm−3(depth 3600 A˚), and to remove damage the crystal is later annealed at 950 °C for 0.5 h. The laser operation observed is the first involving an implanted isoelectronic trap, and occurs on the NXband at higher alloy composition than for any previous case.

ISSN:0003-6951    

DOI:10.1063/1.88646

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Saturation of the junction voltage has been observed to occur at the onset of lasing in cw stripe‐geometry (AlGa)As double‐heterostructure junction lasers. Simultaneous measurements of the nonlasing but amplified spontaneous emission confirm that saturation of the optical gain and spontaneous emission accompany the voltage saturation as expected. With well‐behaved lasers the observed saturation is maintained over currents to at least 50% above threshold. In other devices, a loss of saturation is commonly observed to occur simultaneously with a nonlinearity in the current dependence of the lasing emission.

ISSN:0003-6951    

DOI:10.1063/1.88625

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A three‐port multimode electro‐optic switch has been fabricated in a thinc‐cut plate of LiNbO3using opposed stripe‐and‐plane electrodes to create field‐induced channel waveguides. Fringing electric fields provided multimode optical coupling between channels. Using butt coupling to connect the device into a multimode fiber link, voltage‐controlled switching of laser and white‐light radiation have been demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.88626

出版商:AIP    

年代:1976

数据来源: AIP