摘要:

Third‐order harmonic generation has been measured on highly oriented polydiacetylene (PDA) films prepared by the vacuum deposition method. Experimental values of the third‐order electric susceptibility &khgr;(3)measured for pumping laser polarized parallel to the polymer chain show a sharp three‐photon resonance to the1Buexciton in PDA. Potential usefulness of these highly oriented PDA evaporated films in nonlinear optical applications is suggested.

ISSN:0003-6951    

DOI:10.1063/1.101104

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Optical bistability with 10 mW input power is reported in a thermally stable, nonlinear AlGaAs e´talon. A 3‐&mgr;m‐thick silver layer, which serves both as high‐reflecting mirror and heat sink, makes it possible to operate the device at arbitrary duty cycles and pulse lengths up to 0.5 s, without any regenerative pulsations, at room temperature. The device operation depends on the plasma‐induced electronic nonlinearity, and switching times are typically 10 ns. Device performance is compared with results from a numerical model which takes diffraction, diffusion, and heat conduction into account.

ISSN:0003-6951    

DOI:10.1063/1.101105

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Ion bombardment at grazing angles of incidence is used to smoothen the boundaries within multilayer x‐ray mirrors. Increases in the reflectivity by a factor of 2 for soft x rays have been obtained for RhRu‐C mirrors with periods of 60 A˚.

ISSN:0003-6951    

DOI:10.1063/1.101106

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report a new technique for producing focused beams of neutrals, ions, and clusters using two‐stage laser ablation. We have produced a collimated beam and beams which were focused in one and two dimensions. The on‐axis density is 5×1015atoms/cm3for a barium beam focused in two dimensions over a distance of 10.7 cm. For a collimated beam the density is 1015atoms/cm3at the same distance.

ISSN:0003-6951    

DOI:10.1063/1.101107

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

cw output power levels of 76 and 55 W have been obtained from 1 cm monolithic AlGaAs laser diode arrays with an aperture width of 3 and 2 mm at a heatsink temperature of 0 and 23 °C, respectively. One of the diodes has been operated for over 5000 h at varying power levels between 5 and 10 W and at varying temperatures between 20 and 40 °C and operated successfully for over 3000 h at power levels over 7 W.

ISSN:0003-6951    

DOI:10.1063/1.101366

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Laser operation has been obtained at 551 and 671 nm by pumping 5% Er:YLiF4at 791 nm. Time dependence studies of the emission show that the excitation process has a component related to cooperative energy transfer, and a component related to stepwise multiple photon absorption. Self‐Q‐switched operation at 551 nm is seen to impart a time dependence to an otherwise cw output at 671 nm.

ISSN:0003-6951    

DOI:10.1063/1.101108

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have demonstrated that intense pulsed electron beams can be created by multiplication of lower current electron streams impinging on a high electron yield target. A 17 A electron beam of 1 &mgr;s pulse width was generated from a 2.5 A beam bombarding an activated Ag‐Mg target 2.5 cm in diameter.

ISSN:0003-6951    

DOI:10.1063/1.101109

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Very low resistance nonalloyed ohmic contacts of Pt/Ti to 1.5×1019cm−3Zn‐doped In0.53Ga0.47As have been formed by rapid thermal processing. These contacts were ohmic as deposited with a specific contact resistance value of 3.0×10−4&OHgr; cm2. Cross‐sectional transmission electron microscopy showed a very limited interfacial reacted layer (20 nm thick) between the Ti and the InGaAs as a result of heating at 450 °C for 30 s. The interfacial layer contained mostly InAs and a small portion of other five binary phases. Heating at 500 °C or higher temperatures resulted in an extensive interaction and degradation of the contact. The contact formed at 450 °C, 30 s exhibited tensile stress of 5.6×109dyne cm−2at the Ti/Pt bilayer, but the metal adhesion remained strong. Rapid thermal processing at 450 °C for 30 s decreased the specific contact resistance to a minimum with an extremely low value of 3.4×10−8&OHgr; cm2(0.08 &OHgr; mm), which is very close to the theoretical prediction.

ISSN:0003-6951    

DOI:10.1063/1.101110

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

High‐purity ultrafine AlN powder was synthesized by rf plasma through direct nitridation of Al. The specific surface area was about 30 m2/g under typical experimental conditions. Ultrafine AlN powder showed excellent sinterability, compared with conventional AlN powders, whose particle sizes were more than 0.5 &mgr;m. The thermal conductivity for the sintered body reached 220 W/m K when sintered at 1900 °C, and 110 W/m K when sintered at 1400 °C, by using YF3as a sintering aid.

ISSN:0003-6951    

DOI:10.1063/1.101111

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

InGaP crystals grown on (110) GaAs substrates by chemical vapor deposition have been structurally investigated by transmission electron microscopy. No superstructure spots are present in electron diffraction patterns from (110) plan view and (11¯0) and (001) cross sections. However, composition‐modulated structures with strong amplitude are found not only in the ⟨001⟩ but in the ⟨11¯0⟩ directions. They are found to be stable in the form of columnar domains during crystal growth. These results strongly suggest that atomic ordering and spinodal decomposition of the crystal are competing on the growth surface via surface diffusion of deposited atoms.

ISSN:0003-6951    

DOI:10.1063/1.101112

出版商:AIP    

年代:1989

数据来源: AIP