Time-delay Suppression Research Articles

Quantum dot laser dynamics and external filtered modes under the influence of double-filtered optical feedback

We study the dynamics and solution structure of a semiconductor quantum dot (QD) laser system that gets delayed FOF from two filter loops: the double-filtered optical feedback (DFOF) laser. Two filters are utilized in optical communication applications to regulate and stabilize the laser output, which served as the inspiration for this study. The entire mathematical model of the DFOF laser consists of delay differential equations for the inversion of the QD laser with the two filters. We focus on continuous-wave DFOF QD laser systems because reliable laser source operation is essential for optical communication applications. These basic responses are called external filtered modes (EFMs), and they significantly affect the stability and structure of the EFMs as well as the laser’s performance in comparison to the single FOF QD laser. The parameter C eff is a measure of the interference between the two filter fields, and it is identified as a key to the EFM structure. To analyse how the structure and stability of the EFMs depend on all the filter and feedback loop parameters, we make extensive use of the EFM surface in the (Ω(ω s), C eff , Y s )-space of frequency s, filter phase difference C eff , and population inversion Y s of the QD laser. In general, the EFM surface is the natural object that should be taken into account to comprehend the dynamical characteristics of the DFOF laser. In general, our study involved searching for regions in the QD laser output with stable amplitude and frequency. The time delay suppression is dependent on the spectral width Λ of the filter and how far it is from the solitary laser frequency, according to numerical calculations. In addition to studying the dynamic behavior using a bifurcation diagram at the filter working areas, the results showed two stages of operation due to the occurrence of phase entanglement stochastic.

External Filtered Modes of a Quantum Dot Laser Under the Influence of Double-Filtered Optical Feedback

When semiconductor lasers SLs are exposed to filtered optical feedback (FOB), they behave in two different ways. Under weak or strong feedback, the first is a singularly stable longitudinal mode with a small linewidth. The second is the so-called coherence breakdown condition, which also includes low frequency fluctuations (LFF) and chaotic oscillations. The latter has received a lot of attention recently due to the possible uses of chaotic lasers in chaotic lidar, covert communications, and chaotic correlation time-domain optical reflectometers, while the former has received a lot of research in recent years. We investigate the behavior of a quantum dot (QD) semiconductor laser subject to FOF from two separate external cavities both, numerically and experimentally. Our findings show that the second FOF allows for rich adjustment of the laser frequency. Our analysis of double-filtered optical feedback (DFOF) lasers is on fundamental solutions, sometimes referred to as continuous waves (CW) or external filtering modes (EFM), which result in a QD laser output with constant amplitude and frequency. The time delay suppression is dependent on the spectral width of the filter and how far it is from the solitary laser frequency, according to numerical calculations.

Design of Multi-Scale Negative Group Delay Circuit for Sensors Signal Time-Delay Cancellation

This paper develops an innovative method of sensors’ time-delay suppression. The proposed delay cancellation technique is highlighted with a theoretical concept and time-domain experimental demonstrations by using the negative group delay (NGD) function. The analytical investigation is elaborated with an NGD topology constituted by a simple active $RC$ network. It is established theoretically that this active cell behaves like a low-pass NGD topology. The synthesis equations enabling to calculate the NGD cell parameters as a function of the desired NGD and gain are formulated. Frequency- and time-domain analyses showing the NGD function in multi-time scale are discussed. The NGD function verification is fulfilled with the design and fabrication of a proof-of-concept prototype. Nano-, micro-, and milli-second NGD effects are numerically and experimentally proved. As expected, time-domain experimental demonstrations showing arbitrary waveform signal in outstanding time-advance are realized. Moreover, the feasibility of the signal delay cancellation with 1- and 8-m length cables is experimented. The developed NGD time-delay cancellation demonstrations open the potential applications for the sensor performance improvement.

The Role of Master Laser with Feedback in Time-Delay Signature Suppression of Semiconductor Laser Subject to Chaotic Optical Injection

The important role of parameters in master laser with optical feedback for the elimination of time-delay (TD) signature in semiconductor laser subject to chaotic optical injection is investigated systemically. The experimental results show that TD signature suppressed chaotic signals can be credibly generated by increasing the feedback strength of the master laser, which is quite different from the trends observed in semiconductor laser (SL) with optical feedback. Systematically numerical analysis is also carried out as a validation, and it is shown that with low bias current and strong feedback strength, parameter regions contributing to successful TD suppression are much wider. Furthermore, it is shown that the influence of frequency detuning in TD concealment will change with the increase of feedback strength. All the numerical results are in perfect accordance with experimental observation.

Simultaneous Suppression of Time-Delay Signature in Intensity and Phase of Dual-Channel Chaos Communication

In this paper, we propose a novel dual-channel optical chaos system with a time-delay (TD) feature simultaneously suppressed in all observables, i.e., in both intensity and phase. A hybrid optical and electro-optic feedback for a single vertical-cavity surface-emitting laser (VCSEL) is verified to induce simultaneous TD suppression for the polarization-resolved components of the chaotic output. A comprehensive mathematical model is developed to incorporate the optical and electro-optic time delays into the rate equations of the VCSEL. The suppression of TD signature is then examined by means of autocorrelation function and delayed mutual information. The results show that the output chaotic signal has the TD feature well eliminated in both the intensity and phase over certain regions of parameter space identified using the peak signal to mean ratio technique. The independent evolution of the two orthogonal VCSEL modes renders the polarization-resolved output modes appropriate for the enhanced dual-channel chaos applications. To the best of our knowledge, this is the first time that a dual-channel chaos communication system is reported with simultaneous suppression of the TD feature in all the transmitted observables.