摘要:

We report high‐brightness blue and green light‐emitting diodes (LEDs) based on II–VI heterostructures grown by molecular beam epitaxy on ZnSe substrates. The devices consist of a 2–3 &mgr;m thick layer ofn‐type ZnSe:Cl, a ∼0.1 &mgr;m thick active region of Zn0.9Cd0.1Se (blue) or ZnTe0.1Se0.9(green), and a 1.0 &mgr;m thickp‐type ZnSe:N layer. The blue LEDs produce 327 &mgr;W (10 mA, 3.2 V), with the light output sharply peaked at 489 nm, and exhibit an external quantum efficiency of 1.3%. The green LEDs produce 1.3 mW (10 mA, 3.2 V) peaked at 512 nm, corresponding to an external quantum efficiency of 5.3%. In terms of photometric units, the luminous performance (luminous efficiency) of the devices is 1.6 lm/W (blue) and 17 lm/W (green), respectively, when operated at 10 mA. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113534

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Effective band gaps of type‐II superlattices (SLs) can cover a wide infrared wavelength range, even beyond the narrowest band gap of any natural antimonide semiconductor alloys. This letter reports the first InAs/InAsxSb1−xtype‐II SL lasers with cw, optically pumped operation up to 95 K. The stimulated emission results from spatially indirect transitions of relatively extended electron states in the InAs/InAsxSb1−xSL conduction band to the hole states that are localized in the InAsxSb1−xlayers. The lasing wavelength is around 3.3–3.4 &mgr;m. Equivalent threshold current densities are estimated to be 3.3 and 56 A/cm2at sample temperatures of 5 and 95 K, respectively. The characteristic temperature (T0) is approximately 32 K. These results demonstrate that the InAs/InAsxSb1−xtype‐II SL clad by AlAs0.16Sb0.84ordered‐alloy layers is a promising material system for midwave infrared semiconductor lasers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113535

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the scalability of generating terahertz radiation by optical rectification with the electro‐optic materials LiNbO3, LiTaO3, and dimethyl amino 4‐N‐methylstilbazolium tosylate (DAST). A Ti:sapphire laser system, producing 215 fs, 20 mJ pulses at 810 nm, was used for the experiment. Using LiNbO3and LiTaO3, the peak of the generated terahertz electric field was found to scale linearly with increasing optical fluence for fluences up to 60 mJ/cm2, while with DAST the peak field scaled sublinearly in this fluence range. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113536

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A systematic method to enhance the efficiency of energy transfer in a Smith–Purcell free‐electron laser composed of a metallic grating and a relativistic electron beam is proposed. To maintain the synchronism between an electron beam and a slow electromagnetic wave propagated along a metallic grating, either one of the three grating parameters is adiabatically changed in the direction of wave propagation in accordance with the decrease in the drift velocity of the electron beam. The numerical simulation, which takes into account the reflection or scattering due to discontinuities in the grating parameters, demonstrates sufficient efficiency enhancement in energy transfer. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113537

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An AlxGa1−xAsp‐njunction light emitting diode, with athinIn2O3current spreading layer, on the top side, and anindirectband‐gapAlAs‐Al0.6Ga0.4As distributed Bragg reflector, on the bottom side, has been fabricated and characterized under continuous‐wave, room‐temperature operation. These relatively simple modifications yield a 15‐fold increase in electrical‐to‐optical power conversion efficiency at &lgr;∼675 nm, and a significant reduction in active region heating—in comparison with standard devices prepared and tested as controls. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113538

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We propose a design for a TE–TM polarization splitter based on the addition of antiresonant reflecting layers to the two adjacent channel walls of a standard directional coupler. The geometry of the proposed splitter is relatively easy to fabricate and should allow for an almost total separation between the TE and TM modes of a guided light wave. The analysis of the guided modes of the splitter serves to illustrate the efficiency of the ‘‘resonance method’’ for determining the modes of an arbitrary structure. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113539

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have observed the second harmonic radiation (124 nm) of a subpicosecond KrF laser using an ultrashort scale length plasma produced by the same laser. It is demonstrated that an ultrashort scale plasma with a steep density gradient acts as a reflective nonlinear medium. A model predicts that the second harmonic conversion efficiency of 10−4would be obtainable at 124 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113540

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The surface of an azoaromatic polymer film is optically altered to produce local highly efficient diffraction gratings. The gratings obtained are stable but can be erased by heating the polymer above its glass transition temperature and no permanent damage of the film is observed. Multiple gratings can be simultaneously written and gratings can be overwritten. Atomic force microscopy was used to investigate the gratings produced on the surfaces. Possible mechanisms responsible for the surface alteration are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113541

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the temperature dependence of optical second harmonic generation from a thin indium tin oxide (ITO)‐coated glass substrate (commonly used as a transparent electrode), from a polymer layer on ITO, and from an antimony tin oxide (ATO) coating. We have found that when thin isotropic polymer films are deposited on the ITO‐coated surface, the resulting second harmonic intensity is larger than the second harmonic intensity from ITO or polymer separately. We discuss how the ITO interface may act to induce polar order in the polymer and consider how interfacial second harmonic sources contribute to electric‐field‐induced second harmonic studies of dye‐doped polymers in which ITO is used as a transparent electrode. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113542

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Soda lime glass was implanted sequentially with Ti+and N+to doses ranging from 2 to 30×1016cm−2in order to study the resulting optical properties. Analysis of the implant distributions was made by using Rutherford backscattering and x‐ray photoelectron spectroscopy and revealed profiles which closely followed each other as designed by the selection of implant energies. Analysis of optical properties showed that the highest dose resulted in an increase in the fraction of infrared reflected by more than a factor of 4 versus 1.7 for the visible regime. The percentage of the total solar radiation rejected exceeded 60% at the highest dose, indicating that the buried layer is highly effective in reducing solar load. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113543

出版商:AIP    

年代:1995

数据来源: AIP