88 research outputs found
Monte Carlo Simulation of Laser Diodes Sub-Poissonian Light Generation
When laser diodes are driven by high-impedance electrical sources the
variance of the number of photo-detection events counted over large time
durations is less than the average number of events (sub-Poissonian light). The
paper presents a Monte Carlo simulation that keeps track of each level
occupancy (0 or 1) in the conduction and valence bands, and of the number of
light quanta in the optical cavity. When there is good electron-lattice thermal
contact the electron and hole temperatures remain equal to that of the lattice.
In that case, elementary laser-diode noise theory results are accurately
reproduced by the simulation. But when the thermal contact is poor (or, almost
equivalently, at high power levels) new effects occur (spectral-hole burning,
temperature fluctuations, statistical fluctuations of the optical gain) that
are difficult to handle theoretically. Our numerical simulation shows that the
frequency domain over which the photo-current spectral density is below the
shot-noise level becomes narrower as the optical power increases.Comment: 22 pages, 3 figures, 1 table, submitted to Optical and Quantum
Electronic
Two-level laser light statistics
The statistics of the light emitted by two-level lasers is evaluated on the
basis of generalized rate equations. According to that approach, all
fluctuations are interpreted as being caused by the jumps that occur in active
and detecting atoms. The intra-cavity Fano factor and the photo-current
spectral density are obtained analytically for Poissonian and quiet pumps. The
algebra is simple and the formulas hold for small as well as large pumping
rates. Lasers exhibit excess noise at low pumping levels.Comment: 9 pages, 3 figures, in Optics Communication format (elsevier
Tunable plasma wave resonant detection of optical beating in high electron mobility transistor
We report on tunable terahertz resonant detection of two 1.55 µm
cw-lasers beating by plasma waves in AlGaAs/InGaAs/InP high-electron-mobility
transistor. We show that the fundamental plasma resonant frequency and its odd
harmonics can be tuned with the applied gate-voltage in the range 75-490 GHz.
The observed frequency dependence on gate-bias is found to be in good agreement
with the theoretical plasma waves dispersion law.Comment: Applied Physics Letters to be published (2006) -
Rate-equation approach to atomic-laser light statistics
We consider three- and four-level atomic lasers that are either incoherently
(unidirectionally) or coherently (bidirectionally) pumped, the single-mode
cavity being resonant with the laser transition. The intra-cavity Fano factor
and the photo-current spectral density are evaluated on the basis of rate
equations.
According to that approach, fluctuations are caused by jumps in active and
detecting atoms. The algebra is considerably simpler than the one required by
Quantum-Optics treatments.
Whenever a comparison can be made, the expressions obtained coincide. The
conditions under which the output light exhibits sub-Poissonian statistics are
considered in detail. Analytical results, based on linearization, are verified
by comparison with Monte Carlo simulations. An essentially exhaustive
investigation of sub-Poissonian light generation by three- and four-level atoms
lasers has been performed. Only special forms were reported earlier.Comment: 9 pages, 7 figures, RevTeX
Carnot cycle for an oscillator
Carnot established in 1824 that the efficiency of cyclic engines operating
between a hot bath at absolute temperature and a bath at a lower
temperature cannot exceed . We show that linear
oscillators alternately in contact with hot and cold baths obey this principle
in the quantum as well as in the classical regime. The expression of the work
performed is derived from a simple prescription. Reversible and non-reversible
cycles are illustrated. The paper begins with historical considerations and is
essentially self-contained.Comment: 19 pages, 3 figures, sumitted to European Journal of Physics Changed
content: Fluctuations are considere
Mode oscillation and harmonic distortions associated with sinusoidal modulation of semiconductor lasers
This paper investigates mode dynamics, operation characteristics and signal distortions associated with sinusoidal modulation of semiconductor lasers. The study is based on intensive integrations of the multimode rate equation model of semiconductor lasers over wide ranges of the modulation frequency and depth. The rate equations take into account both spectral symmetric and asymmetric suppressions of modal gain. The higher harmonic distortions as well as the half harmonic distortion associated with the period doubling effect are investigated. The study is applied to both cases of single-mode and multimode oscillations of the non-modulated laser. The obtained results showed that the modulated signal has six distinct waveforms depending on the modulation conditions; three types have continuous periodic waveforms and the others have periodic pulsing waveforms. The modulated laser is found to oscillate in a single mode under weak modulation where the modulated signal is continuous, whereas the pulsing signals are associated with multimode oscillation. The higher harmonic distortions of single-mode laser are lower than those of two-mode lasers, and become serious at modulation frequencies around the relaxation oscillation frequency. These distortions are highest when the laser output is pulsating and the pulses are superposed by relaxation oscillations. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012
Comparison of the bifurcation scenarios predicted by the single-mode and multimode semiconductor laser rate equations
We present a detailed comparison of the bifurcation scenarios predicted by single-mode and multimode semiconductor laser rate equation models under large amplitude injection current modulation. The influence of the gain model on the predicted dynamics is investigated. Calculations of the dependence of the time averaged longitudinal mode intensities on modulation frequency are compared with experiments performed on an AlxGa1-xAs Fabry-Pérot semiconductor laser.K. A. Corbett and M. W. Hamilto
Monte Carlo modeling of the dual-mode regime in quantum-well and quantum-dot semiconductor lasers
Monte Carlo markovian models of a dual-mode semiconductor laser with quantum well (QW) or quantum dot (QD) active regions are proposed. Accounting for carriers and photons as particles that may exchange energy in the course of time allows an ab initio description of laser dynamics such as the mode competition and intrinsic laser noise. We used these models to evaluate the stability of the dual-mode regime when laser characteristics are varied: mode gains and losses, non-radiative recombination rates, intraband relaxation time, capture time in QD, transfer of excitation between QD via the wetting layer... As a major result, a possible steady-state dual-mode regime is predicted for specially designed QD semiconductor lasers thereby acting as a CW microwave or terahertz-beating source whereas it does not occur for QW lasers
Globalization and the Inequality-Unemployment Tradeoff
Over the last 20 years, advanced economies have experienced an "unemployment versus inequality" tradeoff that is critically uneven across countries. To explain this, we propose an extended HOS model in which: the factors are skilled and unskilled labor; there is a continuum of goods; the world comprises two North countries (one egalitarian and one nonegalitarian) and the South; there is no factor price equalization; globalization consists in the South cornering a growing share of world production. In the North, globalization entails an inequality-unemployment tradeoff and the adjustment to globalization is more painful for the country that was initially inequality-oriented. Copyright � 2010 Blackwell Publishing Ltd.
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