摘要:

Laterally gain-coupled distributed feedback GaInAsP/InP lasers were fabricated by focused ion-beam implantation and rapid thermal annealing of ridge waveguide structures. An absorption grating, which interacts with the evanescent light field, is formed by a periodic reduction of the band-gap absorption in the passive sections along the ridge. Room-temperature single-mode emission was observed at 1.5 &mgr;m with a 30 dB side-mode suppression ratio. Simultaneously, the increase of the band gap in the implanted section results in improved carrier confinement, which reduces the leakage current and improves the laser performance in comparison to unimplanted ridge waveguide lasers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122564

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Laser-diode heterostructures of InGaAlN containing a third-order diffraction grating for distributed optical feedback have been examined with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The grating was defined holographically and etched by chemically assisted ion-beam etching into the upper GaN confinement layer of the laser structure. After the etch step, it was overgrown with anAl0.08Ga0.92Nupper cladding layer. Threading dislocations were present that initiated at the sapphire substrate, but no new dislocations were observed at thegrating/Al0.08Ga0.92Ninterface. A comparison of TEM and SEM micrographs reveals that there is a compositional gradient in the AlGaN upper cladding layer; however, calculations show that it did not reduce the optical coupling coefficient of the grating. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122565

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The optical absorption properties were investigated for mesoporous silica loaded with different amounts (up to 5&percent; in weight) of silver (Ag) nanoparticles (less than 4 nm in diameter) into its pores. In contrast to the previously reported glasses containing Ag particles, in this Ag particle-loaded silica no apparent surface plasmon resonance peak of Ag particle, other than an absorption edge, was observed. This composite exhibits the optical features of a semiconductor with direct band gap. The absorption edge shifts in the range from about 200 to about 700 nm with an increasing Ag loading amount up to 5&percent; in weight, and hence, is controllable. Adsorption of oxygen in air on the surface of Ag particles within the pores, and scattering inside the porous structure were used to explain these results. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122566

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present a modal analysis of guiding structures patterned in a two-dimensional metallic photonic crystal. Measurements are carried out on a T-stub structure with various dimensions in the 22–40 GHz frequency band. The pronounced resonances extracted from measured transmissivity spectra are interpreted in terms of multimode propagation phenomena in the T-stub region. Experimental data are assessed by the solution of a suitable form of the 2D Helmholtz equation established for metallic propagation media. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122567

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Pulse compression is experimentally demonstrated by using a coupled-waveguide structure consisting of an InGaAsP/InP semiconductor as a highly dispersive element. In this structure, waveguide dispersion associated with supermodes is significantly enhanced. The maximum temporal compression factor was 4.3 (compression from 2.2 to 0.514 ps). This result indicates that the coupled-waveguide structure has the potential for use in a simple, compact, transmissive, and sign-free dispersion compensator. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122568

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Conditions for the optimization of short pulse amplification and gating times in vertical cavity laser amplifiers are elucidated using femtosecond photoexcitation. The experimental results pertaining to the temporal response are analyzed by a theoretical model taking into account the carrier heating and the Fabry–Perot nature of the cavity. A 20 dB amplification gain is obtained in a vertical cavity structure at 1.53 &mgr;m with a capacity to function at a rate >25 Gb/s. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122569

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Efficient organic electroluminescent (EL) devices were fabricated by using a highly fluorescent aluminum complex, tris(4-methyl-8-quinolinolato)aluminum(III)(Almq3),as an emitter layer. In addition to using this complex, a multilayer device structure, consisting of a hole-injecting layer, a hole transport layer, a dye-dopedAlmq3emitting layer, and an electron transport layer, was employed in order to reduce the driving voltage as well as to maximize carrier recombination efficiency. From this device, a maximum luminance of over140 000 cd/m2and an external quantum efficiency of 7.1&percent; was observed, which is the highest efficiency ever reported for organic EL devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122570

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A tapping-mode tuning fork force-sensing method for near-field scanning optical microscope is reported. Use of the tapping-mode tuning fork with mechanically asymmetric excitation generates better stability and sensitivity than in the shear force mode. Comparison of force curves for the two methods demonstrate that the tapping-mode tuning fork method provides a simpler and more sensitive method for near-field measurements. The method is demonstrated by imaging a sample consisting of 500 nm standard polystyrene spheres on silica in both air and water. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122558

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Cu-doped ZnS nanocrystals were prepared in an inverse microemulsion at room temperature as well as under a hydrothermal condition. X-ray diffraction analysis showed that the diameter of the Cu-doped ZnS nanocrystals particles was about 9 nm. These particles showed a strong photoluminescence intensity and a broad emission band from 490 to 530 nm. The half-width of emission was about 60 nm. Cu-doped ZnS nanocrystals/polymethylmethacrylate composite as a light-emitting layer was used to fabricate a single layer structure electroluminescent device which had low turn on voltage (less than 5 V). The green light of electroluminescence was observed at room temperature. The electroluminescence and photoluminescence spectra were nearly identical at room temperature. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122571

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A plasma diagnostic technique for measuring the electron density, electron temperature, and ion current near a surface in radio frequency (rf) discharges is proposed. The sensor uses a small wire probe to determine the plasma potential and a small metal electrode to measure the current and voltage profiles. The values of current, sheath voltage, and time derivative of sheath voltage at three distinct points during the rf cycle are used in conjunction with an analytical sheath model to determine the plasma parameters. The technique is demonstrated by implementing the diagnostic in a computer model of an inductively coupled plasma reactor which has an rf biased substrate. Although any three disjoint sets of measurements can ideally be used, a sensitivity analysis is used to show that certain sets may be more suitable in experimental systems where noise is present. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122572

出版商:AIP    

年代:1998

数据来源: AIP