Effect Of Spontaneous Emission Noise Research Articles

Noise induced stabilization of chaotic free-running laser diode

In this paper, we investigate theoretically the stabilization of a free-running vertical-cavity surface-emitting laser exhibiting polarization chaos dynamics. We report the existence of a boundary isolating the chaotic attractor on one side and a steady-state on the other side and identify the unstable periodic orbit playing the role of separatrix. In addition, we highlight a small range of parameters where the chaotic attractor passes through this boundary, and therefore where chaos only appears as a transient behaviour. Then, including the effect of spontaneous emission noise in the laser, we demonstrate that, for realistic levels of noise, the system is systematically pushed over the separating solution. As a result, we show that the chaotic dynamics cannot be sustained unless the steady-state on the other side of the separatrix becomes unstable. Finally, we link the stability of this steady-state to a small value of the birefringence in the laser cavity and discuss the significance of this result on future experimental work.

Performance analysis of orthogonal optical chaotic division multiplexing utilizing semiconductor lasers

In this paper, we numerically investigate the performance of orthogonal optical chaotic division multiplexing (OOCDM) based on active–passive decomposition utilizing semiconductor lasers. To the best of our knowledge, it is the first time that two necessary conditions including chaotic synchronization condition and orthogonal condition of chaotic carriers are defined to quantify the performance of OOCDM. The chaotic characteristics of the output optical powers, including time traces, RF power spectra, and auto-correlation function, are numerically analyzed. The effects of spontaneous emission noise and the following internal and external parameter mismatch on the performance of OOCDM are analyzed in detail, which include gain saturation coefficient, photon lifetime, carrier decay rate, carrier number at transparency, differential gain, linewidth enhancement factor, and pumping current. The numerical results show that the proposed OOCDM system is robust towards spontaneous emission noise and parameter mismatch for certain relative mismatch ratios.

Effects of spontaneous emission noise in semiconductor lasers on chaotic optical communication systems

A chaotic optical communication system based on external optical feedback is constructed. By introducing the Langevin noise sources, the master-slave rate equations including spontaneous emission noise characteristics are deduced. Utilizing the obtained mathematical model, two kinds of possible chaos synchronization in the system, i.e. complete chaos synchronization and generalized mode-locking chaos synchronization, are studied. The effects of the spontaneous emission noises of the two lasers on the two types of synchronization as well as the chaotic outputs of the transmitter and receiver are discucsed. Finally, for a sequence of pseudorandom digital bits at 2.5Gb/s bit rate, the encoding/decoding process basing on chaotic masking method is presented, and the effects of noise on decoding performance are examined.

Effect of Spontaneous Emission Noise and Modulation on Semiconductor Lasers Near Threshold with Optical Feedback

The dynamical behavior of power dropouts in a semiconductor laser with optical feedback, pumped near threshold current, is strongly influenced by quantum noise. This is clearly demonstrated by experiments with modulations on the pumping current or the feedback strength. For the cases without modulation and with only current modulation, the dropouts occur randomly. However the feedback strength modulation locks the dropout events periodically. By numerically modeling these three cases using the Lang–Kobayashi equations with a stochastic term to take into account spontaneous emission noise, it is shown that the observed behavior of the dropouts can be readily reproduced for all three cases. Noise plays a signifcant role in explaining the observed dropout events. A simple explanation of the observed dropout phenomenon is presented, based on the adiabatic motion of the ellipse formed by the steady state solutions of the rate equations due to slow time modulations of the injection current or the feedback strength.

Modeling of mode control and noise in self-pulsating phaseCOMB lasers

Self-pulsations (SPs) in phase-controlled mode beating lasers (PhaseCOMB) are very attractive for all-optical clock recovery at ultra-high bit rates. In this paper, we apply the comprehensive simulation tool Longitudinal Dynamics in Semiconductor Lasers, developed by us, for studying the SP features of PhaseCOMB lasers, considering the effects of spontaneous emission noise, longitudinal spatial hole burning, and gain dispersion. In particular, the importance of mode control for adjusting the PhaseCOMB operating conditions is pointed out. The simulation results are confirmed by measurements on fabricated devices.

Chaotic synchronization and evolution of optical phase in a bidirectional solid-state ring laser.

We present results on experimental and theoretical studies of chaos in a solid-state ring laser with periodic pump modulation. We show that the synchronized chaos in the counter-propagating waves is observed for the values of pump modulation frequency fp satisfying the inequality f1 < fp < f2. The boundaries of this region, f1 and f2, depend on the pump-modulation depth. Inside the region of synchronized chaos we study not only dynamics of amplitudes of the counter-propagating waves but also the optical phases of them by mixing the fields of the counter-propagating waves and recording the intensity of the mixed signal. We demonstrate experimentally that in the regime of synchronized chaos the regular phase jumps appear during intervals between adjacent chaotic pulses. We improve the standard semi-classical model of a SSRL and consider an effect of spontaneous emission noise on the temporal evolution of intensities and phase dynamics in the regime of synchronized chaos. It is shown that at the parameters of the experimentally studied laser the noise strongly affects the temporal dependence of amplitudes of the counter-propagating waves.

Noise amplification in a stochastic Ikeda model

The effect of spontaneous emission noise on the light circulating in a ring cavity with a nonlinear absorbing medium is studied by means of a set of stochastic delay-differential equations based on the deterministic Ikeda model. Noise fluctuations are found to be amplified as the first bifurcation from the steady state of the system is approached.

Self-amplified transceivers for local-access star networks

We describe a cost-effective approach to fiber-amplified networks based on dual use of lasers and other components for both signal and pump functions. The concept is demonstrated in a broadband, passive star network suitable for local access applications, using bidirectional transmission on a single fiber. Sensitivity improvement of 8.2 dB is achieved in the downlinks operating at 1.55-μm wavelength, while uplinks at 1.48 μm provide both pump and data. A model for receiver sensitivity incorporating the effects of spontaneous emission noise is used to explain the effect of optical filtering and to assess the potential for further improvement.

Mode beating and spontaneous emission noise effects in a variable-waveguide model for the dynamics of gain-guided semiconductor laser arrays

The spatio-temporal dynamics of gain-guided semiconductor laser arrays are studied by means of a generalized variable-waveguide model deduced from the semiclassical Maxwell-Bloch equations including spontaneous emission noise. Lateral confinement of the optical field is provided by the permittivity distribution associated with the spatial distribution of carriers. The laser field is then described by a set of noise-driven rate equations for the complex amplitudes of the slowly varying modal functions coupled to the carrier distribution evolution, which is sensitive to mode beating effects. The model is applied to a four-stripe gain-guided array, where the influences of spontaneous emission noise and mode beating on the final state are discussed. We show that, in this model, mode beating plays a determinant role in the dynamic behavior of the system, while spontaneous emission noise does not affect this behavior except during transient evolution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Nonlinear Laser Noise and Coherence

The effect of spontaneous emission noise on the coherence properties of a laser operating above thresbold is considered on the basis of a noise-driven van der Pol oscillator model. The oscillator constants are derived from the theory of Lamb. The noise function is represented as a sequence of randomly phased, damped sine pulses with a Doppler spread of frequencies. The noise function is normalized on the basis of equilibrium considerations at positive temperatures. The nonlinear linewidth, intensity fluctuations, and intensity correlation function are derived.