摘要:

Improved polycrystalline ceramic laser rods, composed of cubic solid solutions of 89–96.5 mole% Y2O3, 10–2.5% ThO2, and 1% Nd2O3, were synthesized by a conventional sintering process. This material, called Nd‐doped Yttralox (NDY) ceramic, was produced with laser threshold energies lower than that of the best commercially available Nd:glass laser rod and with a lasing efficiency ∼94% that of laser glass at 40 J of input energy under pulsed mode conditions. In a similar operating mode a NDY rod, containing 5 mole% ThO2and having dimensions 7.6×0.46 cm, delivered 0.41 J of optical energy when using an input energy of 162 J, a pump pulse of 150 &mgr;sec, and output mirror reflectivity of 70%. The lasing efficiencies depended strongly on the method of powder preparation and processing, composition, and the cooling rate from the sintering temperature. The dependence of the fluorescent linewidth on the NDY composition provides a means of appreciably varying the material gain coefficient. Active attenuation coefficients for AR ‐ coated NDY laser rods were about 2% per cm as compared to 0.76% per cm for an OI ED‐2 laser glass rod measured in the same optical cavity. The absorption component of the optical attenuation was measured to be 0.38% per cm at &lgr; = 1.06 &mgr;, indicating that the scattering component is the major contribution to the attenuation coefficient. Considerable evidence is presented which shows that submicroscopic scattering centers exist in the solid ‐ solution matrix and are related to composition fluctuations arising from (i) chemical segregation in the starting powder which is not entirely eliminated during the high ‐ temperature sintering process and (ii) the formation of extended defects or ordered zones in the solid ‐ solution phase during specimen cooling from the sintering temperature.

ISSN:0021-8979    

DOI:10.1063/1.1663077

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The usefulness of the electro‐optically tuned wavelength‐modulated cw dye laser for derivative spectroscopy of solids is demonstrated. The derivative spectrum corresponding to the4I9/2→4G5/2+2G7/2transitions of the trivalent neodymium ion in crystalline YAG at room temperature was studied and new features were observed.

ISSN:0021-8979    

DOI:10.1063/1.1663078

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Carrier transport in SiO2has been studied by exciting hole‐electron pairs in an oxide film by a pulsed electron beam. The energy of the beam (4–8 kV) was chosen to minimize excitation in the Si substrate upon which the SiO2was grown. Measurements of oxide current vs applied voltage were made with beam intensity and energy as parameters for SiO2layers of three thicknesses. It is demonstrated that normalized current‐vs‐field curves are independent of beam intensity, beam energy, and film thickness over the range studied. These results indicate that the analysis used by various workers to determine the mobility‐lifetime (&mgr;&tgr;) product for SiO2is invalid. Observed dependences of current on applied field can best be explained by geminate and/or columnar recombination. The present findings indicate that both holes and electrons traverse most of the SiO2without appreciable permanent trapping. The amount of positive charge trapped at or near the SiO2&sngbnd;Si interface is a significant fraction of the ``collected'' charge, indicating that some of the holes that move to the interface do not penetrate it.

ISSN:0021-8979    

DOI:10.1063/1.1663079

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Ion‐implanted MOS transistors were fabricated and their electrical characteristics, such as threshold voltage, effective mobility, etc., were measured. In the11B+‐implantedp‐channel case, threshold voltageVTcan be shifted linearly with implant dose. These shifts &Dgr;VTwere entirely determined by the net dose entering silicon. On the other hand, in the11B+‐implantedn‐channel case, threshold voltage shift &Dgr;VTvaried sublinearly with dose and showed strong dose profile dependence. The profiles were varied with changing implantation energies and annealing times. These results can be interpreted in accordance with the rapid decrease of the maximum surface depletion layerXdmaxwith the implant dose increase. Numerical calculations of threshold voltage shifts accounting for nonuniformly implanted profiles were compared with observed results. Good agreement was obtained. Effective mobilities &mgr;effof11B+‐implantedp‐ andn‐channel MOS transistors also showed different dose dependences. In the low‐dose region, effective mobilities of11B+‐implantedp‐channel MOSFET remained almost unchanged, but those of then‐channel case decreased monotonically with dose increase. Qualitative arguments, taking into account surface scattering and impurity scattering effects, and rough calculations are presented.

ISSN:0021-8979    

DOI:10.1063/1.1663080

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

GaAs single heterojunction laser diodes were prepared by epitaxially growing all the layers of the structure. The doping in then‐type confining layer and thep‐type active layer were varied as was the thickness of the active layer. The effect of these device parameters on the temperature variation of the threshold current and efficiency was determined. A correlation was observed between an abrupt increase in the threshold current on one hand and the onset of optical pulse delay effects on the other hand. Coincident changes in the spectrum and far‐field pattern were also observed. A dielectric slab model is used to explain the experimental results. It is also postulated that there was a strong saturable absorption mechanism associated with then‐type region.

ISSN:0021-8979    

DOI:10.1063/1.1663081

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Amorphous germanium films were implanted to high boron levels, ∼1021/cm3peak concentrations. Before and after implantation the conductivity measurements fit the relation log&sgr;∼T−1/4and no evidence of intravalence absorption was observed indicating that the Fermi level was near the center of the band gap. Thermoelectric power measurements indicated that the samples were weaklyntype before implantation andptype after implantation. The position of the fundamental absorption edge shifted to lower energy upon implantation and to higher energies upon subsequent anneals. Implanted recrystallized films were stronglyptype, exhibited intravalence absorption, and had very low dc activation energies.

ISSN:0021-8979    

DOI:10.1063/1.1663082

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Two types of radiation emission have been detected during the on state of threshold switching events in noncrystalline chalcogenide thin films having a transparent SnO2(NESA) bottom electrode and a heat conducting top electrode. The common form of the radiation is an emission at about 1.2–1.4 &mgr;m which (i) is propagated through a wide solid angle, (ii) is relatively independent of time during the on‐state pulse (iii) has an integrated intensity which is approximately a linear function of on‐state power and a superlinear function of on‐state current, and (iv) requires a minimum on‐state current for initiation. The second type of emission is between 0.75 and 3 &mgr;m and is detected rather rarely. This latter emission has a characteristic intensity which is a steeply peaked function of on‐state time and appears to be possibly highly collimated. The peaked emission has been detected in pulsed modes using single set pulses and has also been detected continuously using low‐frequency repetitive threshold set pulses. Both radiation effects appear to be nonthermal in origin.

ISSN:0021-8979    

DOI:10.1063/1.1663083

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We report resonant multiphoton ionization in neon. The study of the interaction volume shows that the size of the focused region depends on the laser power, order of interaction, and energy of photon. Thus we have chosen a resonant approach. The results show a discrepancy of 6 cm−1between the experimental multiphoton resonance and the theoretically predicted one. We explain this discrepancy by the perturbative effect of the intense electromagnetic field of the laser on the resonant atomic level 11p[3/2]1,2of neon.

ISSN:0021-8979    

DOI:10.1063/1.1663084

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The modulus of the wave function of an electron bound to a N isoelectronic trap in GaAs1−xPx:N or In1−xGaxP:N is enhanced neark= O because of the presence of the &Ggr; conduction‐band minimum. The band structure enhancement (BSE) and its effect on the quasidirect behavior of indirect GaAs1−xPx:N and In1−xGaxP:N has been investigated as a function of crystal compositionx (x>xc). To evaluate the modulus of the wave function of the trapped electron, the Koster‐Slater one‐band one‐site model has been employed. The effect of BSE on no‐phonon recombination transitions involving the trapped electron is accentuated by orders of magnitude as the crystal composition is changed to bring the &Ggr; conduction‐band minimum,E&Ggr;, near the N‐trap level,EN. Absorption data taken onx= 1.0 andx= 0.53 GaAs1−xPx:N are consistent with the calculated increase in the probability density in the &Ggr; region asE&Ggr;decreases relative toEX. In order to assess the importance of the enhanced recombination probability on the performance of GaAs1−xPxLED's, the internal quantum efficiency has been calculated as a function of crystal composition. This calculation utilizes a model of the electron and hole recombination kinetics at isoelectronic impurities along with the standard band‐to‐band recombination kinetics. The calculated efficiency weighted by the photopic response of the eye agrees with LED brightness data and confirms that the optimum range of crystal compositions in which to fabricate GaAs1−xPx:N LED's is 0.6≤x≤0.8. This result is in good agreement with current GaAs1−xPx:N LED fabrication processes and the optimization procedure on Zn‐diffused planar devices that has arisen empirically. That is, brightness data on state‐of‐the‐art GaAs1−xPx:N and GaP:N Zn‐diffused LED's support the analytical results developed here. The implications of BSE for In1−xGaxP:N LED's are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1663085

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

AQ‐switched ruby laser was used to study the anti‐Stokes Raman radiation scattered at 180° in liquid carbon disulfide. Frequency‐doubled ruby light at 3473 Å was used to excite amplifier cells containing either rhodamine B or rhodamine 6G. Several orders of stimulated backscattered Raman anti‐Stokes radiation were observed. Some of the higher‐order lines were enhanced by a dye amplifier technique for ease of observation. The radiation was observed by means of a Czerny‐Turner spectrograph.

ISSN:0021-8979    

DOI:10.1063/1.1663086

出版商:AIP    

年代:1974

数据来源: AIP