摘要:

The published literature contains little information on the acoustic properties of thin dielectric films produced by sputter deposition. The longitudinal velocity and impedance of a sputter‐deposited glass film, one‐quarter wavelength thick, has been measured in the vicinity of 400 MHz. Such a layer produces a near‐optimum acoustic power transfer between sapphire and water. Curve fitting the predicted return loss against frequency to the experimental impedance transformer response provides a convenient method for the determination of the layer’s acoustic properties.

ISSN:0003-6951    

DOI:10.1063/1.89063

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A prototype of a system with periodically time‐varying dissipation is analyzed. It is found that parametric excitation can occur even if the average dissipation is positive, although it is necessary that the dissipation be negative (amplification) over part of the cycle. The pump amplitude threshold and unstable phase angle are found for the unstable region near &ohgr;1=2&ohgr;0. It is also shown that a periodic instability cannot be dynamically stabilized by periodically varying the dissipation.

ISSN:0003-6951    

DOI:10.1063/1.89064

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The dynamic response of a planar target irradiated by a tightly pinched intense relativistic electron beam is found to be very sensitive to in‐depth heating by the beam due to x‐ray deposition and to diode voltage fluctuations. We find that voltage fluctuations are primarily responsible for the observed wave structure preceding the large‐amplitude shock wave while x‐ray deposition affects the response to a lesser extent. The implications of these results for electron‐beam fusion target and accelerator designs are noted.

ISSN:0003-6951    

DOI:10.1063/1.89065

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Velocity interferometry and double‐pulse holography have been used to study material ejected from surfaces which are impulsively loaded with plane shock waves. Experiments performed on aluminum shocked to 25 GPa (250 kbar) provide the average mass and velocity distribution as well as the spatial distribution of material ejected from the surface. A total mass of about 3 &mgr;g/cm2was ejected when the shock arrived at the surface in the present experiments, and a substantial part of this material resulted from jetting at small pits on the surface.

ISSN:0003-6951    

DOI:10.1063/1.89066

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We report room‐temperature operation of a buried heterostructure distributed feedback diode laser. The device operates in a single TE polarized longitudinal mode over a temperature range from 232 to 324 K and exhibits a temperature sensitivity of 0.72 A˚/K. In comparison, the variation for a similar Fabry‐Perot diode is 3.4 A˚/K.

ISSN:0003-6951    

DOI:10.1063/1.89067

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A new optical waveguide of a single‐crystal Sr2Nb2O7film grown onto ab‐plate Sr2Ta2O7substrate by rf sputtering is reported. Waveguide propagation loss was 7.6 dB/cm for the TE0mode at 6328 A˚. An increased oxygen concentration in the sputtering gas is effective in lowering the optical waveguide propagation loss.

ISSN:0003-6951    

DOI:10.1063/1.89068

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Room‐temperature cw operation of a miniaturized LNP laser pumped with a 0.87‐&mgr;m semiconductor laser is reported. This device has a low threshold, 140 &mgr;W, for an Ar ion laser pump, which corresponds to 83 &mgr;W at 0.87 &mgr;m, and shows nearly single longitudinal mode operation, even at 10 times above threshold. By using a 0.80‐&mgr;m 25‐mW semiconductor laser pump and by an optimized output coupling design, 3.8‐mW output and 15% optical conversion efficiency are expected.

ISSN:0003-6951    

DOI:10.1063/1.89069

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We report modulation of light in planar optical waveguides of polydimethylsiloxane (PDMS) elastomers by a reversible electromechanical deformation of the thin film in the beam path. Modulation frequencies up to 140 kHz have been demonstrated in Dow Corning DC410 PDMS.

ISSN:0003-6951    

DOI:10.1063/1.89070

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A cw Rhodamine 6G dye laser with a thin optically contacted saturable absorber cell has been mode locked over an operating frequency range of 598–615 nm to produce pulses with durations as short as 0.3 ps. The pulses, with sech2intensity profiles, are practically bandwidth limited.

ISSN:0003-6951    

DOI:10.1063/1.89052

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The imaging characteristic of a curved (curvature &rgr;) light‐focusing plastic rod (LFR), with a constant quadratic gradient of refractive index and radiusrpis examined. It was found that curving a LFR produces limitation in the image field, and that the extent of the limiation is inversely proportional toarp&rgr; according to a relation derived theoretically. In the case of a partially curved LFR, the image location was found to shift periodically with increase in the curved portion.

ISSN:0003-6951    

DOI:10.1063/1.89053

出版商:AIP    

年代:1976

数据来源: AIP