Low-frequency fluctuation in multimode semiconductor laser subject to optical feedback

Dynamics of a semiconductor laser subject to moderate optical feedback operating in the low-frequency fluctuation regime is numerically investigated.Multimode Lang-Kobayashi(LK)equations show that the low-frequency intensity dropout including the total intensity and sub-modes intensity is accompanied by sudden dropout simultaneously,which is in good agreement with experimental observation.The power fluctuation is quite annoying in practical applications,therefore it becomes important to study the mechanism of power fluctuation.It is also shown that many factors,such as spontaneous emission noise and feedback parameter,may influence power fluctuation larger than previously expected.     

Quantum dot semiconductor laser with optoelectronic feedback

The optoelectronic feedback (OEF) in quantum dot semiconductor lasers (QD SLs) is studied theoretically where a model includes wetting layer ground state and excited state for QDs are included separating electrons and holes in their dynamics. Both positive and negative OEF are studied. The time series of photon density, the phase portraits of carriers in the states are studied. The parameters affecting OEF are examined where an excitability is seen. The QD SL is found to be more sensitive to the changes in time delay compared with other SLs and a complicated routs are seen in the behavior of QD SL.     

Analysis of the fast recovery dynamics of a semiconductor laser with feedback in the low-frequency fluctuation regime

We experimentally investigate the temporal evolution of the power of an external cavity semiconductor laser in the low-frequency fluctuation regime with subnanosecond resolution. We show, for the first time to our knowledge, that generally the laser power drops to a value significantly different from the solitary laser power. We demonstrate the analogy between the recovery of the laser intensity and the turn-on transient of a semiconductor laser.     

Coherence and correlation in laser excitation of semiconductor quantum wells

Il Nuovo Cimento D - The concept of coherence due to optical excitation of an ensemble of two-level atoms is relatively simple and well established. For the laser-excited electron-hole pairs or...     

Quantum electrodynamics in a laser and the electron laser collisionQuantum electrodynamics in a laser and the electron laser collision

Quantum electrodynamics in a laser is formulated, in which the electron-laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron- laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of y-ray laser generation by use of this kind of collision is discussed.     

Model of lock-in in a ring laser and a semiconductor laser gyro

It is assumed that the process of lock-in in a ring laser has a finite transient time. This assumption serves as a basis for developing a semiconductor laser gyro. A semiconductor optical amplifier is applied as an amplifying medium, and a ring resonator represents a long optical fiber. The injection of an external single-frequency light into a ring resonator with subsequent circulation of counterpropagating waves is used. The light characteristics of the semiconductor laser gyro are discussed, and the rotation sensitivity of the gyro is demonstrated.     

Energy fluctuation and correlation in Tsallis statistics

We investigate the fluctuation of the energy in the framework of Tsallis statistics and find the correlation plays an important role in energy fluctuations. In Tsallis statistics, the correlation is induced by the nonextensivity of Tsallis entropy and exists between particles even if the particles are dynamically independent. By taking the generalized ideal gas as an example, we get that when the particle number N is large enough, the relative fluctuation of the energy is proportional to 1/N instead of in Boltzmann statistics. Thus, the relative energy fluctuation is much smaller in Tsallis statistics than that in Boltzmann statistics. Besides, we demonstrate that the introduction of correlation between particle energies leads to smaller energy fluctuations in Tsallis statistics.     

Quantum correlation between two qubits induced by a common heat bath

In terms of geometric discord, we study quantum correlations between two qubits interacting with a common heat bath. A necessary and sufficient condition for zero discord for arbitrary two-qubit density matrix is derived. With this condition, we show that a common heat bath can always induce two-qubit quantum correlations if both qubits are initially prepared in arbitrary superposition of “pointer basis”.     

Quantum conductance through a uniform scatterer in a narrow-wire semiconductor

The quantum conductance for electrons scattering from a uniform scatterer in a narrow-wire semiconductor is calculated. Instead of getting the conductance directly from the calculation of transmission coefficient, we calculate the reflection coefficient instead. The transmission coefficient is then calculated by using the conservation law, T=I−R. This alternative method can avoid the instability of the conductance obtained by including more evanescent modes for a finite-range scatterer in a narrow-wire semiconductor. This method is applied to a semi-infinite strip potential barrier and a rectangular potential barrier in a narrow wire. The quantum stepwise conductance is obtained in both cases. For a repulsive rectangular potential barrier, there are oscillations in each stepwise conductance. For an attractive rectangular potential barrier, there exist multiple quasi-bound states below the sub-band energies which can cause the drop of the quantum conductance. The effect of the continuum quasi-bound states diminishes as the energy of the incident electron increases, but the influence of the discrete quasi-bound states still persists.     

Closed-loop design of a semiconductor laser

We provide what we believe is the first closed-loop prediction of a semiconductor laser performance using fully microscopic many-body models for the spontaneous emission, gain, and carrier recombination losses due to Auger processes without having to resort to phenomenological adjustable fit parameters.     

Raman fiber laser pumped by a semiconductor disk laser and mode locked by a semiconductor saturable absorber mirror

A 1.6μm mode-locked Raman fiber laser pumped by a 1480nm semiconductor disk laser is demonstrated. Watt-level core pumping of the single-mode fiber Raman lasers with low-noise disk lasers together with semiconductor saturable absorber mirror mode locking represents a highly practical solution for short-pulse operation.     

Quantum fluctuations in atomistic semiconductor devices

Atomistic Green function simulations of model 25 nm×25 nm Si MOSFETs predict strong fluctuation effects derived from mode fluctuations in the quantum transport through the inhomogeneous 2DEG channel caused by the spatial distribution of non-self-averaged discrete dopants.     

Quantum optical effects in semiconductor microcavities

Investigations of quantum effects in semiconductor quantum-well microcavities interacting with laser light in the strong-coupling regime are presented. Modifications of quantum fluctuations of the outgoing light are expected due to the non-linearity originating from coherent exciton–exciton scattering. In the strong-coupling regime, this scattering translates into a four-wave mixing interaction between the mixed exciton–photon states, the polaritons. Squeezing and giant amplification of the polariton field and of the outgoing light field fluctuations are predicted. However, polariton–phonon scattering is shown to yield excess noise in the output field, which may destroy the non-classical effects. Experiments demonstrate evidence for giant amplification due to coherent four-wave mixing of polaritons. Noise reduction below the thermal noise level was also observed. To cite this article: E. Giacobino et al., C. R. Physique 3 (2002) 41–52     

Excitability in a semiconductor laser with saturable absorber

We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.     

Quantum processes in a two-mode laser field

The probabilities of the emission of a photon by an electron and e ⁺ e ^?-pair photoproduction in a field which is a superposition of two electromagnetic plane waves with different frequencies and propagating in the same direction are obtained. The case where the frequencies of the two modes are commensurate is studied in detail. This case is interesting primarily because of the existence of effects due to the interference of amplitudes, corresponding to a different number of photons absorbed from different modes but having the same total 4-momentum. It is shown that the optimal field for observing interference effects is a field such that the ratio of the mode frequencies is 3. The probabilities of radiation and pair-photoproduction processes in the field of a monochromatic plane wave and in a two-mode field, obtained by splitting the initial wave into two waves, are compared. It is shown that the total probability of the emission of a photon by an electron in a two-mode field is lower than and the probability of pair photoproduction is higher than the probabilities of the same processes in the initial wave. The increase in the pair-photoproduction probability is explained by the fact that additional channels for reactions which are forbidden in the initial monochromatic field open up in a two-mode field.     

Quantum polarization fluctuation of a multi-Gaussian Shell-model beam in a slant turbulent channel

The influence of atmospheric turbulence on the quantum polarization fluctuations of multi-Gaussian Schell-mode (MGSM) beams is studied in detail. An analytical formula for the quantum degree of polarization of a MGSM beam propagating in a slant turbulent channel is derived. Our results show that the degree of polarization of a MGSM beam is affected more by the atmospheric turbulence than that of a GSM beam. The numerical simulations also show that a MGSM beam with higher photon-number level, shorter wavelength, bigger transverse beam width is less affected by the turbulence.