摘要:

The high‐speed coating of optical fibers must consider the possibility of a very hot fiber contacting coating material. In this case, the quality of coating may deteriorate if the fiber temperature is above a certain point. Hence, gas‐assisted cooling of fiber was investigated and its effectiveness compared with the self‐cooling case. A cylindrical air blower of 2.5 cm diameter and 20 cm length with a slit (0.2 cm×20 cm) along its axis was employed to cool the fiber entering the coating cup. Measured fiber cooling rates are compared to calculated ones and are in good agreement. It is shown that this technique can result in a twofold increase in coating speed without deteriorating the coating material.

ISSN:0021-8979    

DOI:10.1063/1.325788

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Details of an investigation of a new type of electro‐optic multimode waveguide modulator or switch are reported. The device makes use of the concept of imaging in a multimode waveguide. Simultaneous switching of a few low‐order modes is obtained electro‐optically by nonuniform modulation of the refractive‐index profile of the active waveguide section. Small fabrication tolerances can be compensated for by electrical means and the device can be realized in various sizes and configurations for easy and efficient coupling to lasers, fibers, and other components. Modulation, switching, and power division have been demonstrated in waveguide devices of various widths and lengths fabricated on Ti‐diffused LiNbO3. Coupling losses as low as 0.5 dB have been observed and extinction ratios of 13–20 dB with 20–80 V drive have been obtained.

ISSN:0021-8979    

DOI:10.1063/1.325789

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The operation of a new type CO chemical laser has been demonstrated in which a chain reaction is initiated by ac discharge through O2discharge tubes and the laser cavity. The chain reaction with CS/O2as the fuel/oxidizer,and O and S atoms as the chain carriers, is thought to be the basis of the operation. Gain and power measurements have been made and small‐signal gains of 1.1%/cm for bothP8(18) andP6(17) have been observed 7.5 mm downstream from the CS2transverse injectors. Laser oscillation has been observed directly below the CS2transverse injectors.

ISSN:0021-8979    

DOI:10.1063/1.325790

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

It was shown that an electric discharge plasma in air (240 A) highly attenuated a high‐power CO2laser beam. Maximum attenuation of 98% was obtained on the axis of the discharge column at 150 nsec after the start of the discharge.

ISSN:0021-8979    

DOI:10.1063/1.325791

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A pulsed four‐level solid‐state laser (Nd3+ : yttrium‐aluminum‐garnet) was developed to determine concentration profiles of the fission product cesium in multilayered spherical coated‐particle fuel. In addition, the system can be used for the simulation of cracked coatings by radial borings. The laser system with a Fabry‐Perot‐type resonator fulfills the requirements of small pulse width, absence of higher modes, and consistency of pulse energy. Control and timing is maintained with a ’’Qswitch’’ and a ’’Brewster polarisator’’. Single‐bore holes are ? 10 &mgr;m in diameter, and hole depths range up to 200 &mgr;m. The evaporated radioactive material is sampled with an efficiency ≳ 95% on a glass plate which is used for &ggr; and &bgr; counting. The formation of ’’deep’’ holes is theoretically explained by a self‐channeling mechanism and briefly discussed. Techniques used for radial‐distribution measurements for the fission product137Cs in different irradiated coated particles are presented. Radially bored particles simulating cracked coatings are heat treated and fractional releases are measured.

ISSN:0021-8979    

DOI:10.1063/1.325799

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The dependence of relaxation oscillation on carrier diffusion length in AlGaAs lasers is analyzed using multimode rate equations containing carrier diffusion and spontaneous emission terms. A parameter representing coupling between carrier and light field distribution is introduced. The carrier diffusion shortens the delay time, the relaxation oscillation period, and the decay time constant and also makes spectral narrowing faster. The damping factor is enlarged and relaxation oscillation is suppressed as the carrier diffusion length becomes large. The diffusion length, normalized by stripe widthLD/W, is estimated to be about 0.6 by comparing the numerical results with the experimental tendency of transient response. Furthermore, relaxation oscillation is suppressed as the oscillation beam spot size becomes smaller.

ISSN:0021-8979    

DOI:10.1063/1.325800

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Optical mode measurements have been used to determine the anisotropic diffusion coefficient and surface index changes for planar Ti : LiNbO3waveguides at 0.633 &mgr;m. Measured values for the diffusion coefficient at 1000 °C areDy=9.4×10−13andDz=1.4×10−12cm2/sec. The ratio of the extraordinary to the ordinary surface index change (&Dgr;ne/&Dgr;n0) was found to vary between 1.3 and 1.8, depending on diffusion temperature and Ti film thickness. Ti and Li concentration profiles were measured by secondary‐ion mass spectrometry. Additional high concentration peaks, 0.2–0.3 &mgr;m wide for both ions, were found superimposed on otherwise well‐behaved diffusion profiles. This observation is interpreted to result from a tendency towards Li‐Ti‐O compound (Li2TiO3or Li2Ti3O7) formation at the diffusion temperature in a dilute mixture with LiNbO3. Such compound formation has the effect of impeding the Ti diffusion into the LiNbO3substrate. Electron microprobe measurements were used to measure lateral diffusion from channel waveguides. Under nominally identical conditions, lateral diffusion coefficients varying by as much as a factor of 3 have been observed. The minimum lateral diffusion coefficients observed at 1000 °C wereDy=9.7×10−13andDz=1.4×10−12cm2/sec.

ISSN:0021-8979    

DOI:10.1063/1.325801

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We present results of intensity and line broadening investigations of spontaneous emission from atoms excited in a copper hollow‐cathode discharge. These measurements indicate a group of electrons exists in the discharge with a density of ≲1014e−/cm3and an effective electron temperature of 0.1 to 0.2 eV. The temperatures of atomic species present in the He‐Cu discharge have been measured. Finally, the Lorentz width of spontaneous emission from Cu II laser transitions is observed to be a large fraction of the Doppler width and is consistent with the observed homogeneouslike operation of the copper ion laser.

ISSN:0021-8979    

DOI:10.1063/1.325750

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The break‐up of stretching jets created by shaped explosive charges is treated from a dynamic and kinematic viewpoint. By examining the kinetic energy available in an idealized jet as it stretches and breaks and by including some material parameters typical of copper, the maximum permissible length of jet particles after break‐up is calculated. By assuming that relief waves propagate from break points in the jet while the process of break‐up continues in unrelieved parts of the jet, a distribution of number with respect to length is calculated for the jet particles resulting from break‐up, so as to yield a most probable length and a maximum length. The results of two different assumptions for the speed of the relief waves are compared with experimental data for a copper‐lined shaped charge.

ISSN:0021-8979    

DOI:10.1063/1.325751

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A novel form of surface electrical breakdown is described in which the breakdown field strength can be as low as 200 V/cm at atmospheric pressure. The surface discharge is a high‐pressure arc supplied with current through a resistive surface layer. Using a theoretically derived expression for the volt‐ampere characteristic of the arc, lower and upper bounds for the breakdown field can be calculated. The measured value lies between these bounds.

ISSN:0021-8979    

DOI:10.1063/1.325752

出版商:AIP    

年代:1979

数据来源: AIP