摘要:

A monitor for Al vapor density based on atomic absorption (AA) using a frequency‐doubled external‐cavity‐diode‐laser source at 394 nm has been demonstrated in both evaporation and sputtering processes. Closed loop operation was achieved for electron‐beam evaporated aluminum in a vacuum chamber using the AA signal for feedback. A series of runs in a dc sputtering chamber at the deposition rate of 900 A˚/min illustrates the system reproducibility and the possibility of controlling the sputtering process and measuring the spatial distribution of the sputtered atoms with the AA monitor. Coherent light in the blue‐UV region (380–430 nm) using quasi‐phase‐matched lithium niobate waveguides was demonstrated with efficiencies of 25–150%/W, a range of wavelengths that covers many technologically important elements in physical vapor deposition processes. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116785

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have deposited a silicon oxide (SiOx) film with a high optical transmittance in the DUV region by a focused ion beam induced deposition technique using a gallium ion beam and a mixture of oxygen and TMCTS(1,3,5,7‐tetramethylcyclotetrasiloxane) as a source gas. The optical transmittance of a 0.3 &mgr;m thick film is higher than 90% at the wavelength of 250 nm. The transmittance of the deposited SiOxfilm depends on both the source gas and ion beam irradiation conditions. A scaling to explain the transmittance along with the ion beam conditions is proposed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116724

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Photoquenching of DX‐like defects in heavily doped AlSb:Se is used to write persistent volume absorption holograms. Read‐out diffraction efficiencies of ∼0.5% were observed in samples 280 &mgr;m thick. The optical gratings are metastable, and semipermanent at liquid nitrogen temperatures, and are reversibly erased by heating the crystal above 140 K. The activation energy of regeneration of the stable DX state is obtained by measuring the decay times of the diffracted signal for temperatures between 100 and 116 K. We obtain a regeneration energy of 180 meV. Larger regeneration energies are important for eventual application of this material class to holographic optical memories. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116725

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Continuous wave (cw) operating temperature of 223 K was achieved with molecular beam epitaxy grown separate confinement buried heterostructure (SCBH) PbTe diode lasers with PbEuSeTe electrical and optical confinement layers. This is the highest cw operating temperature reported for midinfrared diode lasers. The active region of the SCBH diode lasers varies laterally to form a crescent‐shaped waveguide with a maximum thickness of 0.15 &mgr;m and a lateral width of 2 &mgr;m. Exceptionally low threshold currents of 102 mA at 200 K, 166 mA at 210 K, and 249 mA at 215 K were measured. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116726

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We show that silicon‐on‐insulator substrates, combined with a low index waveguide, can yield intrinsically wavelength‐selective devices for multiwavelength applications. We demonstrate a simple wavelength‐selective photodetector that resembles an asymmetric directional coupler with a polymer waveguide coupled to a silicon waveguide. Only certain wavelengths are phase‐matched between the two guides and transfer from the polymer to the silicon. Operating the device at the band edge of silicon, the coupled radiation is absorbed and generates photocurrent. The 400 &mgr;m long detector exhibits a linewidth of a few nm, limited by the uniformity of the silicon‐on‐insulator material. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116727

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Potassium lithium tantalate niobate, K3Li2(TaxNb1−x)5O15, or KLTN single crystals were grown by spontaneous crystallization method, and it has been demonstrated that the KLTN crystal has high potential as a nonlinear crystal for blue second‐harmonic‐generation (SHG) applications. Ta substitution for Nb site in K3Li2Nb5O15crystal improves the transparency in the blue light region and decolorizes the material. Compared with K3Li2Nb5O15, the K3Li2Ta5O15crystal exhibits a 60 nm blueshift of the absorption edge from 376 to 316 nm, and decreases its absorption coefficient from 2.3 to 0.3 cm−1at 400 nm. The phase‐matched frequency doubling of the Ti:sapphire infrared laser for blue SHG at room temperature has been demonstrated with the KLTN bulk crystal. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116728

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have fabricated a two‐dimensional photonic band structure based on macroporous silicon with a gap common to both polarizations and centered at 5 &mgr;m. A triangular lattice of circular air rods with a lattice constant of 2.3 &mgr;m was etched 75 &mgr;m deep in ann‐type silicon substrate by electrochemical pore formation in hydrofluoric acid. The porous layer was then micromechanically structured in such a way that 200 &mgr;m thick free‐standing bars of porous material were left over on the silicon substrate. These bars were then used for measuring the transmission of the photonic lattice. The results showed an excellent agreement with the theoretically calculated structure. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116729

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Raman scattering was used to characterize BaTiO3/YBa2Cu3O7−xthin film bilayer structure grown by pulsed laser ablation (PLA). The Raman spectra were compared with the x‐ray diffraction (XRD) spectra. The Raman peaks due to the tetragonal phase of BaTiO3(BTO) and to the 123 phase YBa2Cu3O7−x(YBCO) were observed at room temperature. XRD results showed that the BaTiO3thin film has highlyc‐axis oriented tetragonal phase and is fully epitaxial. However, some impurity phases were observed from the Raman spectrum of the BaTiO3thin film. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116730

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose a dielectric‐based, multistaged, laser‐driven electron linear accelerator structure operating in a vacuum that is capable of accelerating electrons to 1 TeV in 1 km. Our study shows that a GeV/m gradient is achievable using two 100 fs focused crossed‐laser beams, repeated every 300 &mgr;m, operated at a peak power of 0.2 GW and an energy density of less than 2 J/cm2on the accelerator structure. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116731

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Almost perfectly oriented heteroepitaxial diamond film was deposited on the (100)Si substrate by the carburization, bias‐enhanced nucleation, and growth process in a dense plasma using a bell‐jar‐type microwave‐plasma chemical vapor deposition (CVD) system with an ASTeX 1.5 kW magnetron plasma source. This dense plasma was a prerequisite for the perfect orientation and was not obtained simply by increasing microwave power, but was obtained by introducing a graphite block between the substrate and the substrate holder. The plasma was concentrated over the substrate especially at the four corners with a thickness of several millimeters. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116732

出版商:AIP    

年代:1996

数据来源: AIP