摘要:

We have studied the electrical properties of dislocations, stacking faults, and precipitates produced during 1200 °C aging of crucible‐grown silicon. The defects were examined by SEM in the charge collection mode, at temperatures from 77 to 300 °K. Undecorated Frank extrinsic stacking faults exhibit defect energy levels in the upper half of the gap (∼Ec−0.1 eV). The partial dislocations bounding these faults possess energy levels lower thanEc−0.3 eV. Finally, precipitates are observed to act as microplasma sites at low (T<300 °K) temperatures.

ISSN:0003-6951    

DOI:10.1063/1.89355

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The reflection and bulk‐wave loss characteristics of a SAW reflector grating comprised of shallow grooves are treated using the coupled‐mode approach well known in the area of optical gratings. This approach offers the following distinct advantages over the previously reported equivalent network approach: (i) it derives the grating characteristics directly in terms of the material constants of the substrate; (ii) it provides quantitative information on the power loss resulting from bulk‐wave radiation; and (iii) it can accommodate changes in groove profile or height among the individual grating elements, making this approach amenable for use in the design of tapered arrays. Computed reflection and bulk‐wave loss characteristics of a grating comprised of a varying number of identical trapezoidal grooves are presented.

ISSN:0003-6951    

DOI:10.1063/1.89356

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The behavior of a Gaussian laser beam propagating in a long absorptive plasma column is studied theoretically. The plasma is represented by a complex refractive index which varies quadratically with transverse position. With an absorption loss which is minimum at the axis, the width of the Gaussian beam will converge at large propagational distance to a constant which depends on the plasma characteristics alone. It is found that stable propagation of a Gaussian beam is obtained without requiring that the transverse variation of the real part of the refractive index be favorable to beam trapping.

ISSN:0003-6951    

DOI:10.1063/1.89357

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

This paper reports on the method of fabrication and first experiments of chirped (variable period) gratings in a dielectric waveguide. Such gratings, which are proposed as a new optical building block, are used in this work as focusing output couplers.

ISSN:0003-6951    

DOI:10.1063/1.89358

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

In graded‐index and step‐index fibers, splicing loss was measured under the condition that all the guided modes are equally excited by light‐emitting diodes. Measurements were made both for short and long fibers. For a short fiber, the graded‐index fiber has a larger splicing tolerance to misalignment than the step‐index fiber; while for a long fiber the former was somewhat more sensitive than the latter. This difference can be interpreted as showing that leaky modes, excited by transverse displacement in graded‐index fibers, affect transmission loss.

ISSN:0003-6951    

DOI:10.1063/1.89359

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Resonance ionization spectroscopy, a photoionization method in which all of a given quantum selected species are converted to ion pairs, has been used to develop a detector for a single atom. We have demonstrated the detection of one atom by using a pulsed dye laser to photoionize Cs to saturation and a proportional counter for the detection of single electrons. Some current applications, e.g., the slow transport and chemical reactions of atoms, are briefly discussed. Future applications may include the detection of rare events such as quarks, solar neutrinos, and superheavy elements.

ISSN:0003-6951    

DOI:10.1063/1.89360

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

The efficiency increase of photochemical reactions by a chirping laser is discussed. The optimal detuning rate is calculated for constant intensity pulses and for pulses with linear rise. Calculating a particular example for BCl3, it is shown that photochemical efficiency can be increased by an order of magnitude.

ISSN:0003-6951    

DOI:10.1063/1.89361

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Initial observations have been made of laser action in ArCl excimers pumped by a high‐voltage fast‐rise‐time Blumlein discharge circuit. The new laser emits at 175.0 nm and operates at atmospheric pressure. The gas from which the molecules are formed consists of 1% Cl2, 15% Ar, and 84% He. A gain coefficient of 0.012 cm−1has been determined for ArCl.

ISSN:0003-6951    

DOI:10.1063/1.89362

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

A technique for accurately measuringinsituthe size distribution of liquid aerosols is described. The method is based on the measurement of signal modulation when fluorescent particles cross the probe volume of a real fringe laser velocimeter. This provides an exact measurement of droplet diameter free from the errors associated with a similar scattered light technique.

ISSN:0003-6951    

DOI:10.1063/1.89347

出版商:AIP    

年代:1977

数据来源: AIP

摘要:

Studies of high optical power density propagation in Ti‐diffused LiTaO3waveguides are described. Optical damage at room temperature involving ’’blow‐out’’ of the central output spot into themline and clean‐up phenomena have been observed. Studies at elevated temperature (≈150 °C) indicate that self‐annealing of the damage allows these structures to sustain optical power densities up to 11 kW/cm2at 5145 A˚ without damage and power saturation. Use of high‐purity LiTaO3is required if room‐temperature operation at these high optical power densities is to be achieved.

ISSN:0003-6951    

DOI:10.1063/1.89348

出版商:AIP    

年代:1977

数据来源: AIP