摘要:

We present a list of more than 800 far‐infrared laser lines emitted by optically pumped molecular lasers whose frequencies have been measured. For each line, frequency, wavelength, wave number, lasing molecule, CO2pump line, and, if available, the assignment of the lasing transition, are given. The list is accompanied by a survey of the techniques of frequency measurement in the far infrared. Accuracies and limitations of the various techniques are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.337433

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Quenching of NF (a1&Dgr;) and NF (b1&Sgr;) was studied in a subscale upconversion gain medium that was based on energy transfer from NF (b1&Sgr;) to IF. Quenching of NF (b1&Sgr;) by IF was found to occur at gas‐kinetic rates that were large compared to the energy‐transfer rate, indicating low efficiency for the laser. Significant quenching of NF (a1&Dgr;) by IF was also found to occur at a slower rate than was evident for the NF (b1&Sgr;) state.

ISSN:0021-8979    

DOI:10.1063/1.337535

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A time‐resolved magnetic spectrograph was used to measure the energy spectrum of an intense (0.7 TW/cm2) proton beam. A thin gold foil placed at the focus of an ion‐diode Rutherford‐scattered protons by 90° into the spectrograph, reducing the beam intensity to a level suitable for magnetic analysis. The scattered protons were collimated and then deflected in a samarium‐cobalt permanent magnet. The deflected protons were recorded simultaneously on CR‐39 and eightp‐i‐ndiodes. A Monte Carlo computer code was used to calculate the sensitivity and resolution of the spectrograph. Data taken on the Proto I accelerator shows a 150–250‐keV‐wide proton‐energy spectrum at each instant in time.

ISSN:0021-8979    

DOI:10.1063/1.337536

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Three canonical equations governing the characteristics of the second‐order reflection grating for the transverse magnetic mode are derived. Based on the solution of the canonical equations, the input coupling efficiency for the Gaussian beam is deduced. The characteristics of the four different operating schemes of the reflection grating are compared with reference to such applications as the frequency selective filter, the output coupler, and the input coupler.

ISSN:0021-8979    

DOI:10.1063/1.337537

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A study of upconversion processes in Er3+ions in CaF2has led to an unambiguous demonstration of IR lasing produced by upconversion pumping alone. The study has shown: (1) strong upconversion lines originating from the4I11/2state; (2) the existence of both two‐photon and three‐photon upconversion processes; (3) an optimum concentration of 5–10 mol % for Er3+; and (4) upconversion efficiencies for the visible bands as high as 10% at 77 K and 1% at 300 K. Measurements of lasing between the4I11/2and4I13/2levels show that even though the lifetime of the upper (4I11/2) state is only half that of the lower state, self‐quenching does not occur. Upconversion is implicated for this transition both by the nonpersistence of a ‘‘red shift’’ during a lasing pulse, and by the opposite dependence on concentration of laser threshold energy and upconversion‐produced fluorescent intensity. A simple theoretical model shows that a 2.8‐&mgr;m laser operating between the4I11/2and4I13/2levels can be pumped solely by upconversion of ions in the excited4I13/2state produced by absorption of a 1.54‐&mgr;m pulse. In addition, (1) a minimum of 1.54‐&mgr;m pump energy is required; (2) lasing occurs with a delay inversely proportional to the pump energy; and (3) lasing can persist for as long as the lifetime of the lower (4I13/2) state. These predictions have been experimentally verified. The lasing experiments give a lower limit for the upconversion coefficient of &agr;=10−16cm3 s−1.

ISSN:0021-8979    

DOI:10.1063/1.337486

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The growth by molecular‐beam epitaxy of high‐quality Ga0.85In0.15As0.13Sb0.87active layers with Al0.4Ga0.6As0.035Sb0.965cladding layers on GaSb substrates by molecular‐beam epitaxy is reported. The lattice match of the active layer to the substrate is &Dgr;a/a∼4 ×10−3. Optically pumped laser oscillation was observed from 80 to 300 K withT0=55 K forT<225 K andT0=32 K for 225<T<300 K.

ISSN:0021-8979    

DOI:10.1063/1.337487

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Use is made of theT‐matrix method to examine the effect of surface profile modeling errors in studying the scalar scattering responses of impenetrable, periodic surfaces. It is shown that even small errors can alter the maximum surface slope significantly, thereby taxing the resources of numerical procedures and severely limiting their scopes of applicability. However, it is possible that the power diffraction coefficients are not very different when calculations are made with and without these errors. Possible implications for using such methods in order to understand the scattering behavior of fractal surfaces are discussed.

ISSN:0021-8979    

DOI:10.1063/1.337488

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Preionized plasma has been compared with vacuum and with neutral gas as a medium for the propagation of intense ion beams across magnetic fields. Two cusp‐injection ion ring experiments have been used to study the effectiveness of these three cusp‐fill media for space‐charge neutralization, as shown by the subsequent spreading of the injected rings. In the ion ring experiment a ≲100‐ns ion beam was injected into ∼20‐eV plasma fills of ≲1012/cm3, giving much better propagation than vacuum, but not as good as 100‐mTorr H2gas. In the long‐pulse ion ring experiment with ≳200‐ns beam rise time, plasma fill and vacuum gave similar propagation. The results suggest that for complete neutralization of space charge in ion beams propagating across magnetic fields, background media must be provided to meet certain minimum requirements of conductivity and collisionality which depend upon the beam current and rise time.

ISSN:0021-8979    

DOI:10.1063/1.337794

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Using a laser‐induced fluorescence (LIF) technique, SiF2and CF2radicals are detected during the downstream etching of silicon with a discharge of CF4gas. It is confirmed that SiF2radical is desorbed from the surface in the etching of silicon by fluorine atom. Addition of O2gas to the CF4discharge enhances the LIF intensity of SiF2radical and extinguishes that of CF2. Mechanism of the increase of etching rate of silicon by addition of O2is discussed on the basis of the results of LIF measurements. The etching rate of silicon is proportional to the LIF intensity of SiF2, when the microwave power of the discharge is changed. The relationship between the intensity of chemiluminescent continuum and the concentration of SiF2is revealed, which suggests that the chemiluminescence is attributed to the emission of SiF@B|3which is produced by the reaction between SiF2and fluorine atoms in the gas phase. There is no signal of SiF2during the etching of either SiO2or SiNx.

ISSN:0021-8979    

DOI:10.1063/1.337489

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new type of discharge realized in a diode consisting of a cathode and a special type of hollow anode is presented. The distinctive arrangement of dark and luminous regions between the cathode and anode with a characteristic hollow anode glow has been observed in the discharge. The optical spectrum strongly depends on the discharge current, and can be practically a spark or arc spectrum without any lines of anode or cathode material.

ISSN:0021-8979    

DOI:10.1063/1.337490

出版商:AIP    

年代:1986

数据来源: AIP