摘要:

The effects of energy transfer between electrons and holes on the small-signal modulation response of semiconductor lasers are theoretically investigated. We calculate the electron energy relaxation time due to electron–hole scattering from the first principle. We show that its value is comparable to the electron energy relaxation time due to the electron–LO phonon scattering with the effect of nonequilibrium LO phonons. In such a case, the nonlinear gain coefficient due to carrier heating defined in the small-signal modulation response of semiconductor lasers is no longer a simple sum of the term due to electron heating and that due to hole heating. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119388

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An approach is proposed to realize the integration of a 4>1 passive coupler with butt-jointed buried ridge structure distributive Bragg reflector lasers and transparent buried waveguides for Bragg section. The butt coupling facilitates an independent optimization of gain and Bragg sections and the proposed additional processing step, namely, localized hydrogenation of coupler regions, permits reducing dramatically the losses due to free holes in thep+-InP cladding layer. With a coupling efficiency of ∼90&percent; and losses as low as ∼0.4 dB/mm, the integrated emitter with uncoated facets yielded output powers up to 0.4 mW for each wavelength at 100 mA. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119387

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report Cs halide-modified Ga–La sulfide glasses, a new class of chalcohalide glasses with improved fiber-drawing and optical properties suitable forPr3+-doped fiber amplifiers at 1.3 &mgr;m. Cs halide-modified Ga–La sulfide glasses retain the essential characteristics of low phonon-energy and good rare-earth solubility of pure Ga–La sulfide glasses. However, they transmit further into the UV/visible region of the spectrum, and can meet the need of high thermal stability for fiber fabrication. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119389

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We propose and demonstrate a novel method to enhance the near-field optical intensity on the apertured probe with its foot removed asymmetrically by using a focused ion beam. The spatial distribution of the near-field optical intensity on the asymmetric probe was observed by scanning another sharpened symmetric probe over the aperture. The observed spatial distribution profile was in good agreement with a numerical result corresponding to theHE11mode. Furthermore, compared with the symmetric apertured probe, a 10 times enhancement of the near-field optical intensity on the asymmetric apertured probe was observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119390

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Cathodoluminescent phosphors excited at low voltages and high current densities often exhibit brightness saturation due to ground state depletion. A two-level model can be used to show that the luminance and saturation behavior of low voltage phosphors can be greatly improved by choosing phosphors with an activator decay time that is considerably less than the excitation dwell time. This is of considerable importance for field emission displays, where saturation due to ground state depletion has been found to be a factor limiting the achievement of the necessary luminance. Thus, fast activators may overcome ground state depletion and can lead to brighter displays. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119391

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electron injection process, which limits the electroluminescent performance of organic devices, has been enhanced tremendously by inserting a layer of LiF with appropriate thickness between the cathode and a quinacridone doped organic layer. Devices with an Al/LiF cathode demonstrated a luminance in excess of20 000 cd/m2and an external quantum efficiency of 3&percent;, which is comparable to devices with a Mg/LiF cathode. These devices show maximum luminance of45 000 cd/m2prior to failure in continuous bias operation. For the same LiF thickness, the operating voltage for devices with Al/LiF was lower than the corresponding operating voltage for devices with Mg/LiF or Mg alone. Tunneling theory is used to explain this enhancement. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119392

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show that the autocorrelation function of mode-locked laser pulses can be measured by interfering a pulse with its time-delayed replica in a conventional photoconductor to generate a pulsating grating that can be represented as a superposition of moving gratings. The resonance current peak resulting from matching the carrier drift velocity to the velocity of one of the grating components is proportional to the autocorrelation function. Unlike conventional autocorrelators, the proposed method uses no nonlinear effects and thus can be utilized for measuring weak pulses. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119393

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The nondestructive measurement of the internal roughness of Ohmic contacts on GaAs and InP using near-infrared interferometry through the rear of the wafer is investigated. The main difficulties were found to be associated with the thick high refractive index viewing window leading to conflicting requirements in the position of the interface along the optical axis for forming the image and the fringes. Two solutions are proposed: the first using a low numerical aperture objective, and the second using a rear surface reflecting GaAs reference mirror, giving an axial resolution of approximately 8 nm. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119394

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The acoustic radiation force on micrometer-sized polystyrene spheres was measured through observation of the sphere movement in a 500 kHz ultrasonic standing wave. The known spatial distribution of the force allowed verification of the correlation between the sphere velocity and the force. It was found that the linear dependency of the force on the cube of the sphere radius, as predicted by Yosioka, began to fail when the sphere radius was below 5 &mgr;m. This can be accounted for by the presence of a shell layer surrounding the sphere, which increased the effective radius of the sphere. This may point to applications of the acoustic radiation force in the handling of moicrospheres smaller than hitherto thought possible. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119395

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A model, based on ion transport along the plasma in vacuum arcs, is proposed to explain the evolution of charge states. Physical arguments implementing such a model are given, and the charge state fluxes are evaluated. The systematic trends of the particle current fractions are seen to be alike for the theoretical and experimental values, and good quantitative agreement is found for electron temperatures, higher than the generally accepted values. Comments regarding the future work and the effect of a magnetic field are stated. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120021

出版商:AIP    

年代:1997

数据来源: AIP