摘要:

In this article, we present a new numerical method for solving vectorial Maxwell equations which makes it possible to study the birefringence of any geometric pattern of isotropic optical fiber. The distinguishing feature of this method is its use of an iterative process to determine the modes of propagation. The major advantage is the ease of the procedure since the various mathematical steps required can be performed by commercially available software.

ISSN:0021-8979    

DOI:10.1063/1.353235

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The molecular flow, or effusion limit, of transport through a capillary is extended to include the regime where the effects of intermolecular scattering become important. This is accomplished through a generalization of the Clausing equation, which gives a fundamental kinetic theory description of molecular flow. The generalized integral equation obtained is solved numerically to obtain both throughput and angular distribution properties of the gas flow. The results show good agreement with experimental curves which clearly demonstrate the effects of intermolecular scattering.

ISSN:0021-8979    

DOI:10.1063/1.353236

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The general aberration theory for combined electromagnetic focusing‐deflection systems with curved axes will be applied to a scanning electron microscopic system and an electron lithographic system. All third order geometric and first order chromatic aberrations have been calculated along rectilinear/curvilinear axes. The important identities between some aberration coefficients will be verified numerically. The geometric and chromatic aberrations calculated along the matching curvilinear axis will be compared with those along the rectilinear axis. The computational trials may be of help for explaining the mechanism of moving/swinging objective lens and variable axis lens systems.

ISSN:0021-8979    

DOI:10.1063/1.353237

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Pulsed HF chemical lasers oscillating in the midinfrared region of the spectrum where water can strongly absorb are suitable for the organic tissue ablation. For such a medical application, a flexible energy delivery system using an optical fiber is indispensable. The fluoride glass optical fiber may be used for low‐loss optical energy delivery of the pulsed HF laser. Using an intracavity CO2absorption cell, we have optimized pulsed multiline HF chemical laser spectrum for low‐loss energy delivery through a fluoride glass optical fiber whose transmission loss is theoretically estimated to be minimum around 2.5 &mgr;m. The fractional output energy ofP1‐0(3) andP1‐0(4) lines, which are sitting in the lowest loss spectral region of the practical fluoride glass fiber, exceeded half the multiline output energy using a line selective intracavity CO2gas cell. TheP1‐0(4) line extracted from the resonator with a diffraction grating was successfully delivered through a 3‐m‐long commercial fluoride glass fiber (core/cladding diameter=450/500 &mgr;m). The delivered energy of 11.9 mJ was achieved with the corresponding energy fluence of 12 J/cm2and peak intensity of 22 MW/cm2at the exit core surface without optical damage.

ISSN:0021-8979    

DOI:10.1063/1.353238

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The propagation in sea water of an electromagnetic field in the form of a semi‐infinite wave train or a radar pulse generated by an electric dipole is investigated analytically for low frequencies. The frequency‐domain formula for the downward‐traveling field of a horizontal electric dipole excited by a sinusoidally modulated electric‐current pulse is Fourier transformed to obtain an explicit expression for the field at any distance in the time domain. Specific application is made to a wave packet of 25.5 cycles in a time duration of 1 s. The amplitude and phase velocity of the wave packet are determined together with the amplitudes of the initial and final transients. Graphs are displayed and discussed for a range of distances; these show that the amplitude of the wave packet decays more rapidly than the amplitudes of the transients. Possible application to remote sensing in the ocean is considered.  

ISSN:0021-8979    

DOI:10.1063/1.353216

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The organic crystal 4‐nitro‐4’‐methylbenzylidene aniline (NMBA) was identified as a promising nonlinear material by the powder technique. The material gave a second harmonic intensity 16 times that of urea. Large single crystals of dimensions 5×3×1 cm3were grown by the temperature lowering of a seeded supersaturated ethyl acetate solution. The principal dielectric axes were defined by orthoscopic examination. The dispersions of the refractive indices were determined to an accuracy of ±0.0015 using the minimum deviation technique and Maker fringe spacings. These dispersion curves were fitted to a Sellmeier equation which allowed the indices to be determined to ±0.0006. The nonlineardcoefficientsd11,d33,d31, andd13were evaluated at 1000, 1064, and 1300 nm using the Maker fringe technique. The coefficientd11was over 200 times larger than potassium dihydrogen phosphate (KDP)d36. In addition, the nondiagonal coefficientd31was similar to the phase‐matching coefficient in the organic material 3‐acetamido‐4‐dimethylamino‐nitrobenzene (DAN). Critically phase‐matched second harmonic signals were observed at all fundamental wavelengths. There was excellent agreement between the experimentally determined and theoretical phase‐matched incidence angles. Noncritical phase‐matched conditions have been calculated and are reported. Both angle and wavelength noncritical phase matching is possible with this crystal.

ISSN:0021-8979    

DOI:10.1063/1.353217

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A theoretical model is developed for chemical generators producing O2(1&Dgr;) at high pressure. Such generators are especially important for supersonic chemical oxygen‐iodine lasers. The model treats different types of generators, e.g., bubble‐column, film, aerosol, and jet generators. The main factor affecting the O2(1&Dgr;) yield under high pressure is liquid‐phase quenching enhanced by depletion of HO2−ions near the gas/liquid interface. Simple analytical expressions are derived for the O2(1&Dgr;) yield at the exit of the generator. Output characteristics of different specific generators are calculated and compared with available experimental results. O2(1&Dgr;) yield ≥0.5 can be achieved for oxygen pressure up to 50 Torr and flow rates of 3 mmol/cm2 s. For equal velocities of the gas and the liquid the maximum flux of the energy carried by O2(1&Dgr;) for jet or aerosol generators reaches 200 W/cm2. It can be increased by increasing the liquid velocity in the generator.

ISSN:0021-8979    

DOI:10.1063/1.353218

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Electron energy distribution functions in an asymmetric radio‐frequency (rf) discharge helium plasma were measured using an electrostatic energy analyzer looking opposite ways toward both the powered electrode and the bulk plasma. The grid and collector in the analyzer were connected to a series of parallel inductance‐capacitance (L‐C) filters to minimize rf interference. Electrons with high energies (15–30 eV) flowing from the electrode toward the bulk plasma were observed near the electrode. The energy is caused by the acceleration mechanism due to the rf sheath expansion, which should be the rf discharge sustaining mechanism. The electrons with high energies decreased in number with the distance from the electrode and became Maxwellian far from it. Electrons directed toward the electrode from the plasma were almost Maxwellian, and this situation was almost independent of the distance from the electrode.

ISSN:0021-8979    

DOI:10.1063/1.353193

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The electrostatic forces on an isolated particulate in a low‐pressure discharge are calculated assuming a screened Coulomb potential profile for the particle sheath. In the absence of particle sheath distortion due to a flowing plasma and assuming that there is no charge ‘‘bound’’ to the particle in the form of ions in trapped orbits, the monopolar and dipolar forces on the particle are essentially identical to the corresponding forces on a charged sphere in vacuum.

ISSN:0021-8979    

DOI:10.1063/1.353194

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Insitu, Fabry–Perot interferometry was used to study the translational dynamics of ions in a magnetically confined, radio‐frequency‐induction (RFI) plasma reactor. Radial ion motion was characterized through measurements of the Doppler profile of emission from Ar+ions. Radial ion energies depend on the operating power, pressure, and magnetic‐field configuration. In a magnetically confined RFI plasma at 1000 W, ion energies increase from 0.08 to approximately 0.25 eV as the operating pressure is lowered from 13 to 0.18 mTorr. Complementary Langmuir probe studies of the plasma potential as well as its variation across the radius of the reactor illustrate the influence of electric fields on the radial motion of ions in the RFI system. These measurements illustrate that radially directed ion motion in the RFI reactor is significantly less than that reported previously for a divergent‐field electron cyclotron resonance system.

ISSN:0021-8979    

DOI:10.1063/1.353195

出版商:AIP    

年代:1993

数据来源: AIP