摘要:

The relationship between gas concentration and laser power output is examined for mixed noble gas ion lasers. Specifically, a parametric study was carried out on argon‐krypton lasers with cw three‐color power outputs of over 3 W, balanced to give white light as defined by CIE illuminant C. It is found that provided total gas density is maintained constant, argon and krypton gases may be mixed at will in ion laser discharges to obtain the required output balance, implying a mutual compatibility of discharge conditions for argon and krypton lasers. This compatibility is explained by showing that at the same gas densitites of argon or krypton, expected electron temperatures are approximately the same. Under these conditions, excitation rates of laser levels are proportional to the fractional gas concentrations.

ISSN:0021-8979    

DOI:10.1063/1.1662956

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Experimental results are presented and analyzed in order to demonstrate the importance of scattering by charge centers at or near the Si/SiO2interface in the determination of the transport properties of inversion layer carriers in MOS structures. The measured mobility behavior clearly shows the relative importance of the effects of charges as a function of temperature and applied bias. The observations are compared with the existing theory of Coulomb scattering, and an attempt is made to present a theory which more correctly predicts the experimentally determined behavior.

ISSN:0021-8979    

DOI:10.1063/1.1662957

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Experimental results are presented to support the contention that the light output of SiC electroluminescent diodes can be dominated by radiative tunneling over a wide temperature range. A spectral peak shift to higher photon energy with increasing junction voltage has been observed, as well as a temperature‐independent slope of the light intensity‐voltage curves. Both of these properties are characteristic of radiative tunneling. In addition, the value of the temperature‐independent slope agrees with that calculated from a simple tunneling model using data from capacitance measurements. An energy‐band scheme is proposed which leads to the tentative conclusion that the radiative recombination process is donor‐acceptor pair recombination of tunneling carriers in the depletion layer.

ISSN:0021-8979    

DOI:10.1063/1.1662958

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We study the stability conditions for resonant cavities with spherical mirrors made from graded‐index (GRIN) rods. The spherical mirror is made by putting a high‐reflective (HR) coating on one of the flat ends of a GRIN rod segment. It is shown that one or two GRIN mirrors can be used to make all the usual resonator configurations. In particular, two GRIN mirrors attached to a solid‐state dielectric laser rod can be substituted for curved mirrors ground on the rod ends; the ends need only be reasonably flat. We present the following experimental verification: (i) The cw operation of a resonant cavity consisting of a flat/flat Nd : YAG rod with a GRIN mirror attached to one end, and (ii) the construction and operation of anarrayof GRIN mirrors which defines several independent simultaneously oscillating resonators within a single flat/flat Nd : YAG rod. We suggest the possibility of building a compact array of many closely packed miniature resonators by cementing a large number of GRIN mirrors to the top of a 5‐mm‐thick Nd : YAG disk, the bottom of which is HR coated. The disk can be diode pumped through the circumference and/or the bottom.

ISSN:0021-8979    

DOI:10.1063/1.1662959

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Coupled‐mode theory is applied to distributed feedback lasers having step variations in the longitudinal distributions of both the gain and the coupling. Threshold solutions for the required laser gain and the longitudinal mode spectra are presented for the modified geometries. Numerical computations show that these modifications on the uniform structures considered heretofore allow for optimization of the laser characteristics such as lowering the threshold gains and providing controllable higher‐order‐mode rejection, as well as unidirectional operation.

ISSN:0021-8979    

DOI:10.1063/1.1662960

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The in‐line transmission of polycrystalline high‐density ceramics is discussed in terms of light scattering by pores. The Mie theory for light scattering is applied to calculate scattering coefficients using generalized parameters. Results are shown for scattering by spherical pores with uniform size and with a lognormal size distribution. Specific examples are given of the calculated transmission of alumina in the wavelength region 0.4–5 &mgr;m. Experimentally determined transmission curves of normally sintered and of hot‐pressed alumina are compared with calculated curves. The porosity, the position of the maximum, and the width of the lognormal distribution are treated as variables in the calculation. Good agreement with the experimental data is obtained.

ISSN:0021-8979    

DOI:10.1063/1.1662961

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Observations of high‐energy CO2laser pulse transmission through artificial fogs with water contents ranging from 1 to 20 g/m3are presented. The transmitted energy is found to be in fair agreement with theoretical predictions and fog was found to behave as a saturable absorber for intense CO2laser pulses.

ISSN:0021-8979    

DOI:10.1063/1.1662962

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new diagnostic technique can be used to measure simultaneously the excess free‐carrier lifetime &tgr; and the diffusion lengthLwith spatial resolution in semiconductor samples. The technique uses pulses of above‐band‐edge light to generate carriers near the sample surface. The carrier density evolution into the bulk is measured by means of the free‐carrier absorption of an ir laser beam. Computer fitting the time variation of the absorption at any beam position to the carrier transport equation yields &tgr; andL, enabling the diffusion coefficientD=L2/&tgr; to be evaluated. Using 104‐W/cm2injection light and a 3.39‐&mgr;m laser probe on a 1500‐&OHgr; cm silicon sample yielded bulk values in good agreement with calculated and independently measured values.

ISSN:0021-8979    

DOI:10.1063/1.1662963

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The photovoltaic and rectification properties of Al/Mg phthalocyanine/Ag sandwich cells are reported. At low voltages, the current in the forward direction varies exponentially with voltage. A charge density of[inverted lazy s]1018/cm3is estimated fromC‐Vmeasurements. The short‐circuit photocurrentJsc&agr;Fm(m [inverted lazy s]0.5), whereFis the incident light intensity. The open‐circuit photovoltageVoc&agr; logFas expected for a Schottky barrier orp‐njunction. TheJ‐Vcurve in the photovoltaic mode is characteristic of a cell with large series resistance. From the photovoltaic action spectra, the electron diffusion length is estimated to be[inverted lazy s]1.5×10−6 cm. The action spectrum is dependent on the direction of the incident radiation. A theory is presented which explains the results. The junction is attributed to a Schottky barrier ofVd∼ 0.6 eV and width ∼ 2.5 × 10−6cm estimated fromC‐Vmeasurement. The values determined from photovoltaic measurements are in agreement. The lifetime of electrons is estimated to be ∼ 10−9sec and the mobility ∼ 0.1 cm2/V sec. The quantum efficiency for carrier generation is ∼ 1.5 × 10−3. At 690 nm, with light incident on the Al side, the photovoltaic efficiency is about 0.01%, one of the highest ever reported for organic photovoltaic cells.

ISSN:0021-8979    

DOI:10.1063/1.1662965

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The spontaneous and coherent properties of a laser with strong TE polarization (Eparallel to the junction) are measured and discussed in terms of the nonlinear theory of injection lasers. The laser cavity is 330 × 100 × 0.25 &mgr;m with a symmetrical double heterojunction, sawed sides, and cleaved facets. Its dispersion is that of the normal modes of a rectangular box. The current dependence of spontaneous emission indicates a modest increase in population inversion across the lasing region, the maximum overdrive papameter reaching only 0.4. The power dependence of the overdrive parameter deduced from the spontaneous emission agrees well with that from the lateral profile of the external beam. Within a rather large uncertainty from several factors, the calculated value of 25% for the extra prorated loss of the TM modes compared to TE modes arising from facet reflection accounts quantitatively for the persistence of complete polarization to maximum safe output. The critical power associated with the optical nonlinearity is around 5 mW per cavity mode, in agreement with other reported values, and is shown to be independent of facet area as predicted.

ISSN:0021-8979    

DOI:10.1063/1.1662966

出版商:AIP    

年代:1974

数据来源: AIP