摘要:

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) consisting of a film of aluminum tris-(8 hydroxyquinoline)(Alq3)grown on the surface of a film ofN′-diphenyl-N,N′-bis(3-methylphenyl)1-1′biphenyl-4-4′diamine.The resulting heterojunction OLED was found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown device has an external quantum efficiency of0.40±0.05&percent;and a turn-on voltage of approximately 6 V. The rapid throughput demonstrated with LP-OVPD has the potential to facilitate low cost mass production of conventional small molecule based OLEDs, and its use of low vacuum in a horizontal reactor lends itself to roll-to-roll deposition of organic films for many photonic device applications. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120281

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A mechanism for a large enhancement of nonlinear response due to microcavity effect is theoretically proposed for excitons coupled strongly with radiation field. For an appropriate choice of microcavity parameters, the energy of a coupled mode of cavity and exciton coincides with the transition energy between exciton and biexciton states. This scheme leads to a remarkable enhancement of a degenerate pump-probe signal due to the simultaneous enhancement of the internal field and nonlinear susceptibility. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120433

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the observation of two-mode intensity bistability in intracavity-coupled in-plane lasers and oxide-confined vertical-cavity surface emitting lasers (VCSELs) operating under room-temperature CW conditions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119430

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the long-term reliability measurement on uncoated Al-free InGaAsP/GaAs(&lgr;=808 nm)lasers at high-power and high-temperature operation. No degradation in laser performance has been observed for over 30 000 h of lifetime testing in any of randomly selected several 100-&mgr;m-wide uncoated lasers operated at 60 °C with 1 W continuous wave output power. This is the first and the most conclusive evidence ever reported that directly shows the high long-term reliability of uncoated Al-free lasers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119431

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Corrugated quantum well infrared photodetectors (C-QWIPs) utilize total internal reflection to couple normal incident light into the detectors. In this work, we performed a systematic study on C-QWIPs with cutoff wavelength&lgr;cranging from 5 to 17.3 &mgr;m and device areas ranging from50×50 &mgr;m2to500×500 &mgr;m2.We found that the coupling efficiency of the C-QWIPs is, indeed, independent of both the detection wavelength and the pixel size, as expected. Compared to devices with a standard 45° edge coupling, the C-QWIP increases the background photocurrent to a dark current ratio by a factor between 2.4 and 4.4, thereby increasing the background limited temperature by 3–5 K. At the same time, the detectivityD*is also increased by a factor around 2.4. For&lgr;c=9.4 &mgr;m,the peak detectivityDp*and the blackbody detectivityDbb*at 78 K are measured to be4.5×1010 cm Hz/Wand4.5×109 cmHz/W,respectively. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119432

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate quasiphase matched second harmonic generation by use of annealed proton-exchanged 87° Z-cut MgO 5 mol &percent; dopedLiNbO3(MgO:LN) waveguides supporting a TE-mode guided wave. Formation of a domain inversion was achieved by applying electric fields in 3° Y-cut and 87° Z-cut MgO:LN. In 3° Y-cut and 87° Z-cut MgO:LN substrates, a polarization axis inclines at an angle &thgr; equal to 3° to the surface. The domain inversion was formed in a direction parallel to the polarization axis like needles stuck into the substrate. The depth of the domain inversion was 2.5 &mgr;m with a period of 4.75 &mgr;m. The depth was about 2.5 times deeper than that in X- and Y-cut substrate at an angle &thgr; equal to 0°. By forming a waveguide on the domain-inverted substrate, a blue light of wavelength 475 nm, and a power of 37 mW has been obtained and a normalized second harmonic conversion efficiency was300&percent;/W cm2with interaction length of 10 mm, using a tunable external cavity laser diode as a fundamental wave source. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119433

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Photorefractive-induced damage effects at 488 nm wavelength inLiNbO3,LiTaO3,andBa1−xSrxTiyNb2−yO6(BSTN) optical waveguides are compared for the extraordinary mode of polarization. The damage effects are strongest inLiNbO3and weakest in BSTN. At an input power density of3000 W/cm2,the output power from passive channel waveguide inLiNbO3is more than 12 dB lower than in BSTN. Optically induced index changes measured using a Fabry–Perot interferometric method show a nonlinear behavior with increasing input intensity for all these materials. For incident power densities greater than200 W/cm2on the waveguides, the optically induced index-change damage increases at a rate of2.8×10−3 cm2/&mgr;WinLiNbO3,4.9×10−4 cm2/&mgr;WinLiTaO3,and3.1×10−4 cm2/&mgr;Win BSTN. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119434

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show how temporally and spatially resolved lasing spectra may be interpreted to obtain quantitative information on the lattice temperature and refractive index distribution in an optically pumped GaInAsSb/AlGaAsSb quantum well 1.8 &mgr;m midwave-infrared laser. We present this technique as a method for evaluating and comparing high power laser structures in terms of optical and thermal efficiency. We also suggest how this method might provide insight into the particulars of filamentation and heat transport in both electrically and optically pumped structures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120283

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An extremely low threshold for lasing from a specially formulated system involving self-assembled, aggregated molecules enables the system to function as a mirrorless laser. Superradiant energy states created in coherently coupled aggregated molecules emit photons that stimulate emission from other spatially distributed superradiant states. This study focuses on a cyanine dye (specifically,1,1′-3,3′-tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanineiodide) adsorbed onto silica colloid on which the dye aggregates, forming excitonic states involving coherent domains in which a finite number of molecules act cooperatively in the process of emitting photons. It is found that lasing from such a system is induced at a threshold of ca. 39 pJ/pulse, which corresponds to a factor of3×10+4times smaller than the lowest lasing threshold reported in the literature. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119435

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The initial stages of the reaction of Co withSi0.79Ge0.21(100)were studiedin situwith extended x-ray absorption fine structure spectroscopy and reflection high energy electron diffraction. The Si:Ge ratio in the first coordination shell of Co in sub-monolayer Co films was found to increase with film thickness and annealing temperature, indicating preferential formation of Co–Si bonds. The impact of the observed preference for Co–Si bonding on the morphology of epitaxialCoSi2/Si1−xGexheterostructures is discussed. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.119436

出版商:AIP    

年代:1997

数据来源: AIP