摘要:

We report a high power mid-infrared interband cascade laser operating at temperatures up to 170 K. The threshold current densities of this laser are considerably lower than the previously reported values in cascade lasers. The structure was grown by molecular beam epitaxy on a GaSb substrate and comprises 23 periods of active regions separated by digitally graded multilayer injection regions. A peak optical output power of∼0.5 W/facetand a slope of 211 mW/A per facet, corresponding to a differential external quantum efficiency of 131&percent;, are observed at 80 K and at a wavelength of∼3.9 &mgr;m.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120076

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Metallic photonic band gap (MPBG) filter structures operating at far infrared wavelengths have been designed, fabricated, and characterized. The MPBGs are multilayer metallic meshes imbedded in a flexible polyimide dielectric. Depending on the periodic pattern of the metal grids, the filters have either simple high-pass or more complex transmission characteristics. The critical frequencies of the filters depend on the spatial periodicity of the metal grids and the interlayer separation. Optical transmission measurements on a high-pass structure show cutoff frequency of 3 THz and attenuation of more than 35 dB in the cutoff region, in good agreement with predicted results. Band-reject filters show similarly good attenuation and large fractional bandwidths. The filters maintain their optical characteristics after repeated bending, demonstrating mechanical robustness of the MPBG structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120077

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The performance of polymer light-emitting diodes (LEDs) having the configuration Al/MEH–PPV/ITO, whereMEH–PPV=poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene)has been improved by light iodine doping of the emissive MEH–PPV polymer layer whereby the turn-on voltage is reduced and the external quantum efficiency is increased by an order of magnitude. It differs from nondoped MEH–PPV LEDs in that light emission is observed in both forward and reverse bias modes. It is believed that the mobility of theI3−anions in the(MEH–PPV)x+y(I3)xy−species formed on doping the MEH–PPV compensate for injected charges at the electrodes, thus reducing the electron and hole injection barriers. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.120078

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Single mode channel waveguides were fabricated in soda lime glass by poling the samples at 280 °C with 2.5 kV bias voltage. The refractive index of the glass was reduced by 1.5&percent; due to the depletion of sodium ions, making possible the formation of waveguides in a depressed cladding configuration. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120079

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Rare-earth chelate-doped graded index (GI) polymer optical fibers (POF) are proposed and fabricated. The attenuation loss was measured to be 0.4 dB/m at 650 nm for a GI POF doped with 1 wt &percent; of europium (Eu) chelate. Lifetime shortening and spectral narrowing verified the occurrence of superfluorescence at 614 nm in the Eu chelate-doped GI POF pumped with xenon flashlamps. The demonstration of superfluorescence shows that rare-earth chelate-doped GI POFs are appealing as optical amplifiers and superfluorescent sources in a variety of communication and sensor applications. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120080

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The emission spectrum of a current injected InGaN/AlGaN surface emitting diode has been investigated. A clear redshift of the low energy edge with increasing injected current has been observed, and is attributed to the many body effects. The carrier density and band gap narrowing are obtained by fitting the line shape of the emission spectrum, using Landsberg model which includes many body effects. A redshift of around 92 meV of the low energy edge is obtained as injected current increases from 400 to 4000 mA. The band gap change can be described well in proportion to the 1/3 power of the carrier density, which is just suggested by the exchange energy of electron–electron, and hole–hole interactions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120081

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The phase shift between the pattern of light onto a photorefractive crystal and the resulting hologram at the very beginning of the recording process in two-wave mixing is analyzed and measured as a function of the applied electric field. These data allow one to compute the diffusion length of photoexcited charge carriers and to evaluate the actual electric field inside the crystal. A diffusion length of 0.14 &mgr;m is measured in a nominally undoped photorefractiveBi12TiO20crystal using a 532 nm wavelength laser illumination, in agreement with results obtained from other methods. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120116

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate high-power InAsSb/InPAsSb laser bars(&lgr;≈3.2 &mgr;m)consisting of three 100-&mgr;m-wide laser stripes of 700 &mgr;m cavity length, with peak output power up to 3 W at 90 K, and far-fields for the direction perpendicular to the junction as narrow as 12° full width half maximum. Spectra and far-field patterns of the laser bars are shown to have excellent characteristics for a wide range of operating conditions, suggesting the possibility of even higher light power emission with good beam quality. Joule heating is shown to be the major factor limiting higher power operation. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.120082

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present the results of pressure-dependent photoluminescence (PL) studies of single-crystalInxGa1−xN(0⩽x<0.15)films grown on top of thick GaN epitaxial layers by metalorganic chemical vapor deposition with sapphire as substrates. PL measurements were performed at 10 K as a function of applied hydrostatic pressure using the diamond-anvil-cell technique. The luminescence emissions from theInxGa1−xNepifilms were found to shift linearly toward higher energy with increasing pressure. By examining the pressure dependence of the PL spectra, the pressure coefficients for the emission structures associated with the direct band gap ofInxGa1−xNwere determined. The values of the pressure coefficients were found to be3.9×10−3 eV/kbarforIn0.08Ga0.92Nand3.5×10−3 eV/kbarforIn0.14Ga0.86N.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120083

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The modulation spectrum of semiconductor superlattices is shown to be a sensitive function of photon wavelength and local energy band-bending in the superlattice structure. The added dependence leads directly to the concept of a modulation spectroscopy surface for heterostructures as opposed to a simple plot in two dimensions of amplitude as a function of photon energy. The implications of these results for the use of modulation spectroscopy methods such as contactless photoreflectance spectroscopy, where the band bending cannot be controlled, are discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120084

出版商:AIP    

年代:1997

数据来源: AIP