摘要:

A novel AlGaAs/AlAs–TiO2/SiO2hybrid distributed Bragg reflector is implemented in a planar vertical cavity (top)‐surface emitting laser (VCSEL) to control emission (near 850 nm) to a single TEM00‐like mode. This structure exhibits ≳30 dB side‐mode suppression ratio and constant divergence (or modal profile) throughout its operating range (i.e., the detrimental effects of thermal lensing inherent in implanted VCSELs are eliminated); moreover, a record low threshold voltage &bartil;1.6 V, (0.16 V above photon energy) is obtained, without sacrificing the producibility of the standard all‐epitaxial structure. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113842

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Raman spectroscopy is used to characterize the microscopic bond structure of Si1−x−yGexCyalloys epitaxially grown on Si substrates by C implantation into Si1−xGexepilayers and subsequent annealing. The Ge and C concentrations in these alloys can be chosen so that its average lattice constant equals the lattice constant of Si. Our Raman results suggest that in these strain‐compensated alloys the Si–Si bonds are not identical to those in bulk Si but experience a considerable local deformation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113843

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High‐power diode laser arrays emitting at 690 nm have been developed for solid‐state laser pumping. The laser diode bars (fill factor ≊0.7) have been fabricated from single quantum well AlGaInP‐based heterostructures. Using silicon microchannel heatsinks, a record high 360 W/cm2per emitting aperture is achieved under continuous wave operation.

ISSN:0003-6951    

DOI:10.1063/1.113844

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report observation of holographic surface relief gratings with relatively large amplitude on a second order nonlinear optical polymeric material. Surface relief gratings on these polymer films were created upon exposure to polarized Ar+laser beams at 488 nm without any subsequent processing steps. The surface structure of the relief gratings was investigated by atomic force microscopy. The depth of the surface relief in a typical case was 120 nm which is approximately 20% of the original film thickness. The diffraction efficiency of gold‐coated gratings was investigated as a function of wavelength and capability of recording orthogonal gratings on the same film was demonstrated. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113845

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Glass waveguiding films were prepared from titania and modified silica using the sol‐gel method and doped by the laser dye rhodamine B. The guided and amplified fluorescence (pumped by a double frequency Nd‐YAG laser) was coupled out either by static grating written on the film or by a prism. The gain of the emitted superradiance was determined from the amplified spontaneous emission intensity dependence on the pumped strip length. A maximum net gain of 54 dB/cm was measured. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113846

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The low‐temperature photoresponse properties for a PbZrxTi1−xO3/YBa2Cu3O7−xthin‐film heterostructure capacitor are reported. The fast optical readout effect measured for the device while the YBCO bottom electrode was superconducting indicates a fall time dependent on YBCO state. A simple equivalent circuit model confirmed that the temperature dependence of the YBCO electrode resistance is responsible for the variation of the fall time of the optical readout signal. Such heterostructures can be used to fabricate high power, radiation‐hard optical sensors which cover the whole visible range. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113847

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report polarized optical transmission and reflection measurements which are used to determine the orientation of polymer chains in spin‐cast thin films of soluble, electroluminescent polymers. We find that the polymer chains lie primarily in the plane of the film. This result has three important implications for polymer light emitting diodes: the electroluminescence is preferentially emitted propagating perpendicular to the polymer film; the relevant dielectric and electrical transport properties are those perpendicular to the polymer chains; and large area, uniform devices can be produced by spin casting. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113848

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An adjustable threshold color detector (ATCD) is demonstrated, based on a hydrogenated amorphous silicon (a‐Si:H) and silicon–carbide (a‐SiC:H)p+‐i‐n+‐i‐n+‐i‐p+multilayer. The ATCD is able to discriminate between blue (&lgr;=450 nm), green (550 nm), and red (≳650 nm) illumination by varying the externally applied voltage within a few volts. The operation of the detector can be explained regarding the ATCD as three independent devices connected in series: ap+‐i‐n+, an+‐i‐n+, and an+‐i‐p+. The novel feature is then+‐i‐n+cell. It acts as a short circuit under strong illumination, whereas in dark it is equivalent to two low quality back‐to‐back diodes which introduce a shift in the threshold in the photocurrent detection. Thanks to the large number of physical parameters such as layer thickness and band gap the ATCD appears extremely versatile. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113849

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A model for optical breakdown is presented, that takes the effects of avalanche ionization, electron–ion recombination, and electron diffusion into account. By assuming a rectangular temporal shape of the laser pulse, an analytical solution of the threshold parameters can be given. Especially, a square root dependence of the energy density on the pulse duration is found for pulse duration values between roughly 4 ps and 8 &mgr;s. The theory explains the results of several previous experiments investigating threshold parameters for a variety of target materials. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113850

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We show by a simple model that, in semiconductor amplifiers, the functional dependence of the four‐wave mixing signal on the output power of pump and probe depends on the underlying optical nonlinearity. The observation, at different pump‐probe detunings, of a different dependence of the conjugate power on pump and probe output permits the identification of the dominant optical nonlinearity at a given detuning. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113851

出版商:AIP    

年代:1995

数据来源: AIP