摘要:

An efficient phenomenological model describing the temperature dependence of the output power of multiquantum well (MQW) lasers is presented. The model can predict all the general features of the experimental results. The effect of series resistance, thermal resistance, cavity length, leakage current, and facet reflectivity on the maximum achievable power are analyzed in a systematic manner. The calculated maximum operating temperature(Tm),defined as the heat sink temperature at which the saturated output power vanishes due to heating, is in reasonable agreement with reported experimental results. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120201

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated the characteristics of green–blue II–VI semiconductor diode lasers at room temperature in high magnetic fields. Small spectral shifts, less than 2 meV during the sweep of a field up to 29 T, were measured in ZnCdSe/ZnSSe single quantum well index guided diode devices. This behavior is in contrast with expectations for a noninteracting electron-hole gas in a quantum well system at comparable pair densities(∼1012 cm−2),implying that the optical gain spectrum shifts diamagnetically. The measured diamagnetic shifts are in close agreement with the low injection electroluminescence and absorption spectra at then=1heavy-hole excitonic transition of the ZnCdSe QW. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120202

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An organic electroluminescent device consisting of ITO/aromatic amine/tris(8–quinolinolato)aluminum(Alq3)/Pd was fabricated. The light emission was found to occur when hydrogen gas was present in the ambience and ceased when hydrogen was removed from the Pd electrode. The light emission induced by hydrogen gas was attributed to the work function lowering of the Pd electrode at the Pd–Alq3interface by adsorption of hydrogen. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120203

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A multimode time domain model is used to study the large signal dynamics of complex distributed feedback lasers with nonuniform grating pitch and coupling coefficient. Lasers with longitudinal variation of their grating pitch &Lgr; (corrugation-pitch-modulated lasers) can exhibit poor steady-state side mode suppression ratios. Numerical simulations show that an adequate profile of the coupling coefficient &kgr; (stronger coupling at the center of the cavity) can help to achieve improved steady-state single mode operation with respect to conventional Bragg-detuned cavities (uniform coupling coefficient). However, it is found that in such lasers(z-dependent &kgr;), side modes are liable to be excited during the turn-on transient interval. A careful study of the turn-on transient is needed to determine the maximum (keeping dynamic single mode regime) bias current. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120204

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An alternative method for producing efficient white light-emitting polymer diodes based on a blend of two polymers is reported. The white light emission is composed of a broad blue emission of laddertype (polyparaphenylene)(m-LPPP) and a red-orange emission of a new polymer, poly(perylene-co-diethynylbenzene) (PPDB). The red-orange electroluminescence emission is promoted by an excitation energy and charge transfer fromm-LPPP to the PPDB. A concentration of 0.05&percent; PPDB in the polymer blend is required in order to obtain white light emission. By inserting an insulating material in the blend, so that a maximum external quantum efficiency of 1.2&percent; is obtained. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120205

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate that fiber-optic probes with an intermediate section followed by a rapidly tapering tip lead to transmission efficiency enhancement of better than four orders-of-magnitude at 60 nm tip diameter and more than five orders-of-magnitude at smaller than 40 nm tip diameter over typical taffy-pulled fiber probes. Our highest resolution probes have a tip diameter of 30 nm with a transmission efficiency of 0.02&percent;, and as an example we image tobacco mosaic virus with a resolution better than 35 nm. The probes are made in a two-step process involving pulling and then etching that permits both high efficiency and control of the mechanical resonance properties. The efficiency is enhanced by reducing the distance that the electromagnetic mode travels in the cut-off mode of the fiber probe. The higher resolution is achieved because sharper tips can be made through the etching process. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120206

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The transmission of light waves through a perturbed photonic crystal has been investigated. The perturbed photonic crystal was constructed by randomly repeated stacking of a number of identical unit cells. Although most of the light waves are localized by the randomness, there still exist light waves with special wavelengths which are in extended states. This produces a high-quality resonant tunneling with a very narrow transmission coefficient peak. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120207

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Design, growth, and operation of an unipolar light emitting diode based on the material system GaAs/AlGaAs is reported. We present mid-infrared transmission, photocurrent, and electroluminescence measurements on a quantum cascade structure with intersubband transition energies greater than the optical phonon energy. Electroluminescence powers up to a few nanowatts at 6.9&mgr;m have been measured. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119329

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A passive integrated optical waveguide refractometer based on bendloss changes in a spiral-shaped channel waveguide is proposed and fabricated inSi3N4/SiO2technology. The experimentally determined performance and the theoretical predictions, based on a simple model for so-called “whispering gallery modes,” agree very well. The minimum detectable refractive index change was measured to be&Dgr;n=1.3×10−5.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120208

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An array of microdisks with a diameter of about 9 &mgr;m and spacing of 50 &mgr;m has been fabricated by dry etching from a 50 Å/50 ÅGaN/AlxGa1-xN (x∼0.07)multiple quantum well (MQW) structure grown by reactive molecular beam epitaxy. Optical properties of these microdisks have been studied by picosecond time-resolved photoluminescence (PL) spectroscopy. Photoluminescence emission spectra and decay dynamics were measured at various temperatures and pump intensities. With respect to the original MQWs, we observe strong enhancement of the transition intensity and lifetime for both the intrinsic and barrier transitions. The intrinsic transition is excitonic at low temperatures and exhibits an approximate tenfold increase in both lifetime and PL intensity upon formation of the microdisks. This implies a significant enhancement of quantum efficiency in microdisks and a bright future for III-nitride microcavity lasers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120209

出版商:AIP    

年代:1997

数据来源: AIP