Continuous-wave photoluminescence excitation spectra of multiple narrow-stepped quantum wells at room temperature have been measured for the first time. It has been observed that photoluminescence intensity increases ...
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Continuous-wave photoluminescence excitation spectra of multiple narrow-stepped quantum wells at room temperature have been measured for the first time. It has been observed that photoluminescence intensity increases stronger than proportionally to the square of the laser intensity. This phenomenon can be attributed to the radiative recombination between free carriers in parallel with the dominant nonradiative recombination on the saturable interface traps. Intensity-dependent trapping efficiency and ratio between electron and hole nonradiative decay times, and the ratio between trapping and nonradiative recombination rates have been derived from the experiment.
In this note we consider the input-output stability of feedback systems consisting of a continuous-time, linear, time-varying plant with a discrete-time, linear time-varying controller. These results generalize some o...
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In this note we consider the input-output stability of feedback systems consisting of a continuous-time, linear, time-varying plant with a discrete-time, linear time-varying controller. These results generalize some of the results of Chen and Francis where the plant is restricted to be time-invariant.
We demonstrate that the optimal phase-matching conditions for the high-order optical multiwave mixing and harmonic generation, which are given by the perturbation theory, remain valid in the strong-field limit under q...
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We demonstrate that the optimal phase-matching conditions for the high-order optical multiwave mixing and harmonic generation, which are given by the perturbation theory, remain valid in the strong-field limit under quite general assumptions about induced nonlinear polarization.
Two narrow linewidth Nd:YAG unidirectional non-planar ring oscillator lasers were electronically phase locked using photorefractive two-wave mixing in an iron-doped indium phosphide (InP:Fe) crystal as an optical phas...
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Two narrow linewidth Nd:YAG unidirectional non-planar ring oscillator lasers were electronically phase locked using photorefractive two-wave mixing in an iron-doped indium phosphide (InP:Fe) crystal as an optical phase detector. The phase lock loop phase error signal was derived from a low-amplitude sinusoidal phase modulation signal impressed on the strong local oscillator beam at a frequency large compared to the inverse of the photorefractive-grating formation time. A 60-mW pump laser was phase locked to a 10-nW signal laser beam with an rms phase error less than 0.1 rad. No spatial mode matching, phase conjugate mirror configuration or optical coupling between the two laser cavities were required.
We investigate certain statistical properties of the state vector in a stochastic multipoint boundary value system. We give necessary and sufficient conditions for the state vector to be stationary, and we prove that ...
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We investigate certain statistical properties of the state vector in a stochastic multipoint boundary value system. We give necessary and sufficient conditions for the state vector to be stationary, and we prove that the state vector is locally reciprocal.
A new upper bound to the probability of error in detecting one of M equally probable signals in additive white Gaussian noise is presented. This bound is easy to calculate, can be applied to any signal set. It is alwa...
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A new upper bound to the probability of error in detecting one of M equally probable signals in additive white Gaussian noise is presented. This bound is easy to calculate, can be applied to any signal set. It is always better than the union and minimum distance bounds. Examples demonstrate the use of the bound.< >
The extended-linearization methodology is applied to the nonlinear servomechanism problem for the case of time-varying exogenous signals. This yields a new approach to establishing exponential stability properties of ...
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The extended-linearization methodology is applied to the nonlinear servomechanism problem for the case of time-varying exogenous signals. This yields a new approach to establishing exponential stability properties of trajectories that evolve on a certain invariant manifold which we call the zero-error manifold. Advantages of the approach are that the underlying theory is relatively simple, and that a requirement of small derivatives for the exogenous signals is used rather than a requirement that the exogenous signals remain small. Thus, certain cases of unbounded exogenous signals can be treated. Also, a transmission zero condition for existence of the requisite zero-error manifold is given.
The two-photon absorption coefficient and the intensity-dependent refractive index associated with it are calculated for semiconductor quantum wells and quantum wires. It is shown analytically that in the limit of lar...
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The two-photon absorption coefficient and the intensity-dependent refractive index associated with it are calculated for semiconductor quantum wells and quantum wires. It is shown analytically that in the limit of large dimensions the nonlinear response of quantum-confined structures becomes isotropic and approaches the nonlinear response of the bulk semiconductor despite the different gauges used in the calculations. The theoretical results are compared with the experiment, and the practical implications are discussed.
The inversion problem for nonlinear systems is considered from both the internal viewpoint (state-equation representations) and the external viewpoint (Volterra-series representations). In order to circumvent difficul...
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The inversion problem for nonlinear systems is considered from both the internal viewpoint (state-equation representations) and the external viewpoint (Volterra-series representations). In order to circumvent difficulties in the known, exact inversion theory, a method for obtaining what will be called a partial inverse system is proposed. For a given nonlinear system, a cascade system, typically containing differentiators, is found such that the overall nonlinear system has a family of constant operating points with inputs and outputs identical. Furthermore, the linearization of the overall system about each of these constant operating points is the identity system.
Continuous-wave intensity-dependent photoluminescence spectra of multiple narrow asymmetric coupled quantum wells at room temperature have been measured. At low laser intensity, the total photoluminescence intensity i...
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Continuous-wave intensity-dependent photoluminescence spectra of multiple narrow asymmetric coupled quantum wells at room temperature have been measured. At low laser intensity, the total photoluminescence intensity is primarily proportional to the square of the laser intensity due to dominant nonradiative recombination of free carriers at nearly saturated interface traps. At high laser intensity, however, the total photoluminescence intensity approaches a level proportional to the laser intensity due to radiative recombination of free carriers. Based on this transition behavior, which has been observed for the first time to the best of our knowledge, and our simple theory, the transition intensity, the nonradiative decay time of the carriers, and the intensity-dependent carrier density and photoluminescence quantum efficiency have been determined.
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