摘要:

Interference patterns are written by two intersecting pulsed laser beams in thin films composed of Cu quantum dots in SiO glass. The rapid local optical heating of the metal clusters forming the quantum dots in the glass film results in the writing of patterns in the thin film. The high cluster temperatures attained drive the selective growth of the larger quantum dots and also result in a stress induced peeling of the film from the substrate. Estimates of the kinetics of the selective quantum dot growth agrees well with experimental observations. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117285

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Insulating host materials doped with trivalent cerium show quantum efficiencies of the Ce3+emission ranging from zero to unity. Comparing optical and photoelectrical properties of a very efficient scintillator material (Lu2(SiO4)O:Ce) to those of cerium doped oxides with quenched emission, the radical differences for these materials are demonstrated to originate from the location of the cerium energy levels with respect to the host conduction band. Photoionization and subsequent nonradiative relaxation processes responsible for the luminescence quenching are discussed in a donor–acceptor model for the impurity ion and a rule for luminescence efficiency is derived, applicable to a variety of phosphor and scintillator materials. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117286

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In order to estimate and compare the would‐be performances of both hexagonal and cubic GaN quantum‐well lasers, the optical gains of strained‐layer hexagonal and cubic GaN quantum wells are studied theoretically taking into account non‐Markovian relaxation. The 6×6 multiband effective‐mass Hamiltonians are used to calculate the band structures of both hexagonal—and cubic—quantum wells. As a numerical example, the optical gains of strained cubic and hexagonal quantum wells with various well widths are calculated. It is expected that the optical gains of the cubic‐phase quantum well are larger in magnitudes than those of the hexagonal GaN quantum well over the wide range of carrier densities due to the heavier effective mass of the HH1 band of the latter at the zone center. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117287

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose here a method for probe characterization based on lithography on a photosensitive polymer without film development. We record in near field conditions the light emitted by different kinds of probes in order to distinguishinsituthe near field contribution from the far field contribution of the tip. This information, which cannot be deduced from far field diffraction, allows an estimation of the field confinement and of the expected resolution of the microscope. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117288

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We developed an organic light emitting diode (LED) that emits orange light at the forward bias (ITO anode and Al cathode) and green light at the reverse bias (ITO cathode and Al anode). The organic LED has a triple layer structure where an emission layer with different doped guest dye on each side is interposed between two hole transport layers. Its brightness, maximum 20 cd/m2was not strong because electrons are blocked by the hole transport layer near the cathode. However, the EL efficiency (lm/W) for the reverse bias was 13 times higher than that for the forward bias. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117289

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose and demonstrate a novel nonoptical technique for regulation of tip–sample distance in a scanning near‐field optical microscope (SNOM). The fiber tip for the SNOM is attached to one prong of a quartz tuning fork. The fork is dithered with a gated sinusoidal signal. The vibration of the freely oscillating fiber tip, which manifests as the induced piezoelectric voltage on the fork electrodes, is monitored during the half‐period of the gated sinusoid for which the fork is not driven. The time‐multiplexing scheme, thus, allows the tuning fork to serve as a dither and a sensor with highQfactor, simultaneously. The gating technique could also potentially allow the SNOM to be used for the investigation of surface relaxation dynamics with high spatial resolution and submillisecond time resolution. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117290

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present the results of optical studies of InxGa1−xN alloys (0<x<0.2) grown by metalorganic chemical vapor deposition on top of thick GaN epitaxial layers with sapphire as substrates. Photoluminescence (PL) and photoreflectance measurements were performed at various temperatures to determine the band gap and its variation as a function of temperature for samples with different indium concentrations. Carrier recombination dynamics in the alloy samples were studied using time‐resolved luminescence spectroscopy. While the measured decay time for the alloy near‐band‐edge PL emissions was observed to be generally around a few hundred picoseconds at 10 K, it was found that the decay time decreased rapidly as the sample temperatures increased. This indicates a strong influence of temperature on the processes of trapping and recombination of excited carriers at impurities and defects in the InGaN alloys. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117291

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Surface relief diffraction gratings inscribed on azobenzene‐containing polymers are designed to act as light couplers into slab waveguides. The gratings are inscribed both directly in poly{4‐[2‐(methacryloyloxy)ethyl]azobenzene} (pMEA) waveguide material, and in an azopolymer cladding layer applied to polyimide, silicon nitride, and silicon oxynitride films. Input and output coupling of both 633 and 830 nm light is observed in the waveguides. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117292

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Second‐harmonic generation of surface‐emitted blue light has been achieved in (In,Ga)As/GaAs quantum well edge‐emitting lasers. The blue light is generated by the nonlinear interaction of the internal fundamental fields of a continuously pumped laser. These lasers exhibit room temperature threshold current densities as low as 200 A/cm2and produce about 2.6 nW of blue light for 9.8 mW of fundamental power. The peak emission of the blue light is at 487 nm and the spectral spread is about 1.7 nm. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117293

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A surface micromachined suspended interferometer and an atomic force microscope (AFM) are incorporated into a novel optical reading technique. The AFM tip mechanically deflects the suspended membrane as it scans past a data bit on the membrane surface. The data are read by monitoring the changing interference pattern generated in the optical aperture of the interferometer. When operated in parallel, there exists the potential for high speed, high density data reading. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117294

出版商:AIP    

年代:1996

数据来源: AIP