摘要:

We have measured the birefringence enhancement due to lateral selective oxidation of AlAs in GaAs/AlAs optical waveguides. The birefringence was measured by imaging the surface-emitted second harmonic generated by the nonlinear interaction of counterpropagating TE and TM modes. In a waveguide containing a single AlAs layer the birefringence is enhanced from&Dgr;n=0.017(before oxidation) to&Dgr;n=0.038(after oxidation). In an oxidized multilayer GaAs/AlAs waveguide, a birefringence as high as&Dgr;n=0.22is measured. This birefringence is sufficient to phase-match the difference frequency generation of 3–5 &mgr;m infrared radiation from two near-infrared pumps. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119336

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple method using the singularities of an optical resonator to determine the thermal lens of end-pumped laser crystals is reported in this letter. At certain resonator parameters the transverse structures of the laser beam become a superposition of many transverse cavity modes of equal resonance frequencies. Because the resonator parameters depend on the thermally induced lens in the active medium, the strength of the lens can be determined by means of measuring the shift of the degeneration resonator length depending on the pumping power. The method is applied to an end-pumped Nd:YAG laser. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119337

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate preliminary results for an 8.5 &mgr;m laser emission from quantum cascade lasers grown in a single step by gas-source molecular beam epitaxy. 70 mW peak power per two facets is recorded for all devices tested at 79 K with 1 &mgr;s pulses at 200 Hz. For a 3 mm cavity length, lasing persists up to 270 K with aT0of 180 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119338

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Light emission from single-layered electroluminescent devices is described in which (Eu, Gd) coordination complexes,(Eu0.1Gd0.9)(TTA)3(TPPO)2,and electron transport material oxadiazole derivative, 2-(4-biphenyl)-5-(4-t-butylphenylyl)-1,3,4-oxadiazole, are dispersed in a hole-transporting host polymer poly(N-vinylcarbazole) film. The color of the emitted electroluminescence changes smoothly from green-white to red with temperature varying from 77 to 300 K. This phenomenon is discussed in terms of temperature dependent yields of phosphorescence from the triplet state of the Gd and Eu chelates and the intermolecular energy transfer from Gd-chelate to Eu-chelate cages. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119339

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Birefringence induced by the electro-optic effect is demonstrated in vertical-cavity surface-emitting lasers (VCSEL). This is done by comparing two types of optically pumped VCSELs: VCSELs with standard pin-doping and VCSELs with symmetrical pip-doping. The observed birefringence in these VCSELs differs by an order of magnitude, a difference that we ascribe to the presence and absence, respectively, of electro-optic birefringence. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119340

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Pressure-induced shift of fluorescence emission in garnets and other oxides is investigated for applications as optical pressure sensors. We report high pressure studies on the fluorescence emission from neodymium-doped yttrium aluminum perovskite(Nd3+:YAlO3)to 80 GPa at room temperature. Unusual nonlinear blueshift of wavelength with pressure was found for several fluores cence peaks in the wavelength region of 850–900 nm. These peaks are identified as the lines associated with transitionNd3+:4F3/2→4I9/2inYAlO3.The blueshift of these emissions is compared with the redshift of the same system in neodymium-doped yttrium aluminum garnet(Nd3+:Y3Al5O12).The shift with pressure is related to the change in the Stark level splitting with pressure. In view of the strong red emission from diamond anvils at ultrahigh pressures, this near infrared emission ofNd3+:YAlO3holds promise as an ultrahigh pressure sensor. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119341

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a two-dimensional model to simulate the enhanced harmonic emission from ionized argon clusters irradiated by an ultrashort(∼25 fs) laser pulse at moderate intensity(∼1014 W/cm2). The low-order harmonics (below the 15th) are enhanced by nearly two orders of magnitude relative to those of monomer argon. Furthermore, the harmonic plateau is extended to a higher frequency. The clustering environment is responsible for the enhancement of harmonic emission. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119342

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This letter describes a microscopic gain theory for an InGaN/AlGaN quantum well laser. The approach, which is based on the semiconductor Bloch equations, with carrier correlations treated at the level of quantum kinetic theory in the Markovian limit, gives a consistent treatment of plasma and excitonic effects, both of which are important under lasing conditions. Inhomogeneous broadening due to spatial variations in quantum well thickness or composition is taken into account by a statistical average of the homogeneously broadened spectra. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120155

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present an x-ray absorption spectroscopy study at the CuKedge on Cu-doped soda-lime and BK7 glass waveguides obtained by ion exchange under various preparation conditions. The total electron yield and x-ray fluorescence yield collection modes were used to evidence the chemical behavior of surfacial and deep Cu ions. In all the samples copper is found preferentially asCu+throughout the whole exchanged region. The first coordination shell is formed by two to three oxygen atoms at 1.86 Å, much shorter than the Na–O bond (2.3 Å) in soda-lime glasses. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120156

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A special case of the x-ray multiple diffraction phenomenon, the Bragg surface diffraction (BSD), has been investigated under lattice damage due to ion implantation in GaAs (001) samples. The BSD profile is very sensitive to the diffraction regime (dynamical or kinematical) and provides information regarding crystalline perfection and lattice strains in both directions—parallel and perpendicular—to the sample surface. Results from grazing-incidence x-ray diffraction and reciprocal space mapping are also reported. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120157

出版商:AIP    

年代:1997

数据来源: AIP