Numerical study of optical feedback coherence in semiconductor laser dynamics.

All-optical schemes for controlling complex delay-induced and spatio-temporal dynamics in multi-stripe and broad-area semiconductor lasers are presented. The underlying control-principle is based on continuous delayed optical feedback. Its influence on the general spatiotemporal dynamics of semiconductor lasers is discussed. The delayed feedback control principle allows successful control of delay-induced chaotic behavior as well as the dynamic optical filamentation in broad-area and multi-stripe lasers. The suppression of spatiotemporal instabilities in semiconductor laser arrays is achieved by selectively stabilizing relevant transverse optical modes. The relevant values of delay-times and delay-phase are obtained from a nonlinear eigenmode analysis based on a complex extension of the Karhunen-Loeve decomposition. Thereby a destructive interference condition in the higher-order transverse modes conveying the instabilities is achieved. The stabilization technique is demonstrated on multi-stripe laser arrays. In high-power broad-area lasers the spatiotemporal filamentation processes occur on both macroscopic and microscopic scales. Numerical simulations on the basis of Maxwell-Bloch equations for spatially extended semiconductor lasers reveal the internal spatial and temporal scales on which control consequently has to occur. It is demonstrated that the combined filamentation and propagation effects may be controlled by suitable spatially structured delayed optical feedback allowing, in particular, the control of coherent regimes in originally temporally and spatially chaotic states.

The low-frequency fluctuations and high-dimensional chaos with 12.2 correlation dimensions were generated experimentally by a semiconductor laser with optical feedback. Extensive experimental and numerical studies were performed to reveal the evolution process from low-frequency fluctuations to chaos. Our results showed that there exists a obvious critical point for the semiconductor laser's bias current. When the bias current Ib is set below 1.03Ith, the peak-to-peak value of the low-frequency fluctuations increases at first and then decreases with the feedback strength decreasing, while its average period keeps decreasing. In this process, the output of the semiconductor laser never goes chaos. However, when the bias current Ib is set beyond 1.03Ith, chaos appears and is persistent in this range. Moreover, the peak-to-peak value of the low-frequency fluctuations increases continuouslly and its duration decreases with the decrease of the feedback strength. Three stages experienced in the process leading from stable emission and low-frequency fluctuation to chaos are established. Numerical simulations are well consistent with the experimental results.

With a proper perturbation, even a single-mode semiconductor laser can exhibit highly complex dynamical characteristics ranging from stable, narrow-linewidth oscillation to broadband chaos. In recent years, three approaches to invoke complex nonlinear dynamical states in a single-mode semiconductor laser have been thoroughly studied: optical injection, optical feedback, and optoelectronic feedback. In each case, the nonlinear dynamics of the semiconductor laser depends on five intrinsic laser parameters and three operational parameters. The dynamical state of a given laser can be precisely controlled by properly adjusting the three operational parameters. This ability to control the dynamical behavior of a laser, combined with the understanding of its characteristics, opens up the opportunity for a wide range of novel applications. This paper illustrates the utilization of the rich nonlinear dynamics of single-mode semiconductor lasers by focusing on the period-one oscillation for its applications in tunable photonic microwave generation, AM-to-FM conversion, and dual-frequency precision Doppler lidar.

We demonstrate scaling in amplitude and time of the dynamics of quantum well and quantum dot semiconductor lasers subject to optical feedback from long delays, providing insights into the underlying physics of both devices.

We experimentally investigate the complex dynamics of a multi-mode quantum-dot semiconductor laser with time-delayed optical feedback. We examine a two-dimensional bifurcation diagram of the quantum-dot laser as a comprehensive dynamical map by changing the injection current and feedback strength. We found that the bifurcation diagram contains two different parameter regions of low-frequency fluctuations. The power-dropout dynamics of the low-frequency fluctuations are observed in the sub-GHz region, which is considerably faster than the conventional low-frequency fluctuations in the MHz region. Comparing the dynamics of quantum-dot laser with those of single- and multi-mode quantum-well semiconductor lasers reveals that the fast low-frequency fluctuation dynamics are unique characteristics of quantum-dot lasers with time-delayed optical feedback.

The transient dynamics of a single-mode semiconductor laser subjected to both weak optical feedback and light injection is studied. Even at detuning values for which injection locking is not effective, turn-on jitter and frequency jitter can still be strongly reduced by adjusting either the length of the external cavity or the detuning.

We present a comprehensive study of the emission dynamics of semiconductor lasers induced by delayed optical feedback from a short external cavity. Our analysis includes experiments, numerical modeling, and bifurcation analysis by means of computing unstable manifolds. This provides a unique overview and a detailed insight into the dynamics of this technologically important system and into the mechanisms leading to delayed feedback instabilities. By varying the external cavity phase, we find a cyclic scenario leading from stable intensity emission via periodic behavior to regular and irregular pulse packages, and finally back to stable emission. We reveal the underlying interplay of localized dynamics and global bifurcations.

The present study includes a synchronization study on the modelling of rate equations and a study of the dynamics of a quantum dot semiconductor laser (QDSL). The dynamics of a quantum dot semiconductor laser depend on several factors including the delay time, as studied in this research via visual feedback, and by relying on practical results. A systematic study of communications for two quantum dots, the transmitter and receiver, and the possibility of synchronization between them, and a study of the relationship between the photon density, time, and the probability of filling the charge carriers over time. For different delay times ( 249 260 0.1)   to step and the pump current ratios , ( 1.5 ) T R th J J  and line width enhancement factor ( , ( 3.5) T R  are proven.

In this paper, we investigate the possibility of using optical injection to efficiently suppress the time-delay (TD) signatures of chaotic signals in a large experimentally accessible parameter range of semiconductor ring lasers (SRLs). We also study how this optical injection can improve the signal bandwidths. The injection signal is obtained from a master SRL with either optical self- or cross-feedback. For optical self-feedback configurations, it is found that the suppression of TD signatures is similar to what has been found in injected Fabry–Perot semiconductor lasers, i.e., narrow range of parameters with respect to the detuning and injection strengths. For cross-feedback configurations, however, the TD signatures can be suppressed in a wide range of parameters; meanwhile, the bandwidths are significantly improved for the same range of parameters. This is particularly useful for the security in chaos-based communications and also for generating random bits with improved properties.

The finite intraband relaxation time in semiconductor lasers leads to gain saturation at high laser powers. The nonperturbative solution of the single-mode density-matrix equations shows that both the optical gain and the refractive index become intensity dependent as a result of intraband relaxation dynamics. Gain and index nonlinearities are included in the rate equations, and how the modulation response and noise characteristics of semiconductor lasers are affected by such nonlinearities is studied. The intensity dependence of the frequency and the damping rate of relaxation oscillations leads to a fundamental limit imposed on the small-signal modulation bandwidth; the analysis provides an expression for the ultimate modulation bandwidth in terms of the material parameters. >

While solitary single-mode semiconductor lasers normally emit continuous-wave radiation, their rich nonlinear dynamics, such as periodic oscillations and chaos, can be excited through various perturbation schemes. These highly complex dynamical behaviors can be well controlled by properly adjusting the experimentally accessible parameters of perturbations. The ability to control the dynamical behavior of semiconductor lasers, together with the profound dynamical characteristics, not only provides valuable opportunities for the study of nonlinear laser dynamics but also opens up great possibilities for a wide range of novel applications.

Semiconductor laser with external optical feedback exhibits different dynamics, e.g., period-one (P1) oscillation, quasiperiodic oscillation and chaos, which has been used in different applications. Nanoscale sensing is of great importance in high-precision manufacture and control industry, like semiconductor integrated circuit and MEMS industry. In this work, we propose a two-dimensional nanoscale position sensing method using microwave photonic (MWP) signal induced by P1 dynamics of a semiconductor laser with two external optical feedbacks. Starting from the Lang Kobayashi equations, simulations were conducted, which show that the frequency of MWP signal induced by P1 dynamics has a unique mapping relationship with the external target position within the nanoscale range. Then, theoretical derivation was made to verify this relationship, based on which, a method for two-dimensional nanoscale position sensing was proposed. Lastly, experiments were performed to verify the related results, providing a potential useful two-dimensional nanoscale position sensing method.

An in-depth theoretical as well as experimental analysis of the nonlinear dynamics in semiconductor lasers with active optical feedback is presented. Use of a monolithically integrated multisection device of submillimeter total length provides access to the short-cavity regime. By introducing an amplifier section as a special feature, phase and strength of the feedback can be separately tuned. In this way, the number of modes involved in the laser action can be adjusted. We predict and observe specific dynamical scenarios. Bifurcations mediate various transitions in the device output, from single-mode steadystate to self-pulsation and between different kinds of self-pulsations, reaching eventually chaotic behavior in the multimode limit.

A full-time-domain approach to spatio-temporal dynamics of semiconductor lasers. I. Theoretical formulation

The nonlinear dynamics of semiconductor lasers have been thoroughly studied in recent years. These complex dynamical characteristics, which range from narrow-linewidth oscillation to broadband chaos, open up the opportunity for many novel applications, such as chaotic communications, chaotic lidar, chaotic radar, photonic microwave generation, dual-frequency precision radar/lidar, all-optical AM-to-FM conversion, and single-sideband radio-over-fiber transmission. The utilization of the rich nonlinear dynamics of single-mode semiconductor lasers for these interesting applications is discussed in this paper.