Incoherent Optical Feedback Research Articles

Dynamic regimes of time—delay signature of a semiconductor laser subjected to incoherent optical feedback

The effect of incoherent optical feedback to a semiconductor diode laser is numerically investigated using Lang-Kobayashi rate equations. The model constitutes for diode laser systems in which the feedback loop length is longer than the coherence length of the laser. The time delay signature (TDS) of the external cavity is found to exhibit dynamical regimes corresponding to the incoherent feedback. The occurrence of time delay signature and its characteristics such as temporal spread exhibit a definite relation to the regimes of incoherent optical feedback. Lasing efficiency, threshold current and turn-on-delay characteristics also exhibit concurring regimentation of incoherent optical feedback to a semiconductor diode laser.

Effect of phase conjugate coupled on routes to chaos in incoherent optical feedback semiconductor quantum dot laser

Effect of phase conjugate coupled on routes to chaos in incoherent optical feedback semiconductor quantum dot laser

Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback**Project supported by the National Natural Science Foundation of China (Grant Nos. 61178011, 11204248, 61475127, and 61275116), the Natural Science Foundation of Chongqing City, China (Grant Nos. 2012jjB40011 and 2012jjA40012), and the Open Fund of the State Key Lab of Millimeter Waves of China (Grant No.

Based on a semiconductor laser (SL) with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs (MFCs) is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing (or repetition frequency) of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented.

Local Dynamics of a Laser with Rapidly Oscillating Parameters

The dynamics of class B lasers with the incoherent optical feedback formed by quickly vibrating external mirrors is viewed. The problem of the stability of equilibrium in a model system with rapidly oscillating coefficients is studied. The averaged system with the distributed delay is received. It is determined that in the presence of fast delay oscillation the limit of instability of a balance state moves towards significantly greater values of the feedback coefficient. The dependence of the shift with increasing the amplitude modulation has a band structure, so the rapid oscillations of delay can stabilize or destabilize the equilibrium. Normal forms which show changes of the sign of Lyapunov quantityalong border are constructed. They describe characteristics of periodic and quasiperiodic modes close to the balance state.

Theoretical analysis of semiconductor ring lasers with short and long time-delayed optoelectronic and incoherent feedback

We report results on the asymptotic, bifurcation and numerical analysis of semiconductor ring lasers with negative optoelectronic feedback or incoherent optical feedback. We find that the dynamical behavior of both systems can be adequately described by two differential equations and one map with time delay on time-scales longer than the relaxation oscillations. On these timescales, the dynamics for both types of feedback is identical. We study the stationary solutions of this model and are able to obtain the analytical expressions of all local bifurcations. As we vary the feedback strength for small delay times comparable to the period of relaxation oscillations, the devices under consideration in the paper display both continuous wave operation and a period-doubling route to chaos. The intensities of two counter propagating modes of both systems exhibit in-phase chaotic behavior similar to single mode semiconductor lasers. However, for long delay times, the counter propagating modes show anti-phase chaotic oscillations. This anti-phase chaotic regime does not involve carrier dynamics and is a result of the bistable character of the semiconductor ring laser.

Dynamics of a Single-Mode Semiconductor Laser with Incoherent Optical Feedback

A new model of an injection semiconductor laser with optical feedback, which generalizes the Lang–Kobayashi equations to the case of incoherent feedback, is proposed. Within the framework of this model, the above-mentioned equations are supplemented by the stochastic variable, which simulates the random phase difference between the field inside the resonator and the field returning to the laser after travelling over the feedback loop. It is shown that transition from coherent to incoherent feedback in the case of weak feedback results in the replacement of dynamic chaos by almost stationary lasing with a slightly noisy intensity. However, a much stronger incoherent feedback can lead to chaotic oscillations. The proposed model has both noise and deterministic solutions, which indicates the impossibility to develop a purely dynamical model of a semiconductor laser with incoherent optical feedback.

Low-power optical bistability and hysteresis in the laser system with absorbing nanosuspension.

We demonstrate an optical bistability in a laser system with incoherent optical feedback and a nanosuspension as a nonlinear element. The optical transfer function is shown to exhibit a hysteresis loop for the light power in the range of a few milliwatts. It has been found that the optical bistability relies on the incoherent optical feedback and thermal defocusing nonlinear optical response of the nanosuspension.

Theory of Elimination of Emitted Optical Pulse/s Remotely

In this paper, the authors present a new theory that can be applied to remotely eliminate emitted optical pulse/s. The elimination of the optical pulses can be performed by increasing the threshold carrier density of the laser source during the time period of the injected pulse by exposing the laser diode to an incoherent external optical feedback (EOF) pulse at a specified value of external reflectivity. Consequently, the stimulated emission will not occur and approximately zero photon density will be achieved during the pulse width of the EOF signal. The proposed technique can be utilized to develop a new type of all-optical external encoder. In addition, it can be used to remotely control the laser source and, in turn, the whole optical communication system.

Theory of digital modulation of semiconductor laser diode remotely

The authors present a new theory that can be applied to modulate the semiconductor laser diode (LD) remotely. The proposed scheme utilizes the effect of incoherent external optical feedback (EOF) on the LD output optical signal. In particular, owing to the high increase in threshold carrier density, the LD will be impelled to turn off when the value of external reflectivity is equal to the laser back reflectivity. Thus, by exposing the LD, which is injected with a dc-current higher than threshold, to incoherent EOF digital signal (which conveys the transmitted information), the output optical signal of LD can be modulated accordingly.

Elimination of low-frequency fluctuations of backscattered Rayleigh radiation from optical fiber with chaotic lasers

We have experimentally demonstrated suppression of low-frequency fluctuations of backscattered Rayleigh radiation from optical fiber with chaotic single-longitudinal mode DFB and multi-longitudinal mode FP lasers subjected by incoherent optical feedback. Significant decreasing of Rayleigh power variations up to 15–20 dB for 10–1000 Hz frequency interval was recorded for both chaotic lasers. It was shown that chaotic DFB laser also efficiently suppresses stimulated Brillouin scattering in the test fiber.

Experimental characterization of DFB and FP chaotic lasers with strong incoherent optical feedback

We have experimentally investigated chaotic power oscillations in single-longitudinal mode DFB and multi-longitudinal mode FP lasers as a function of incoherent optical feedback strengths of up to 42%. We have demonstrated the existence of chaos in the output oscillations of both laser types using classical experimental tools such as RF spectrum, standard deviation, and maximum Lyapunov exponent, which all increase with increasing of feedback strength for both in single-longitudinal mode DFB lasers and multi-longitudinal mode FP lasers. It is also shown that power switching among longitudinal modes of multimode FP semiconductor laser is a considerable portion of the chaotic power oscillations for both strong and weak incoherent optical feedback.

Bidirectional chaos communication based on semiconductor laser with incoherent optical feedback

In this paper, a bidirectional chaos communication system based on semiconductor lasers with incoherent optical feedback is presented, and the synchronization characteristics and the communication performances of such a system are numerically investigated. The results show that when the parameters of the two lasers are matched, the good-quality chaos synchronization with zero lag time and simultaneously bidirectional message transmission can be realized and when the parameters of the two lasers are mismateched, the synchronization quality and communication performance are affected to a certain extent, but this system possesses good robustness against mismatched parameters and can still realize bidirectional chaos communication within a certain mismatched parameter range.

Frequency locking in a semiconductor laser with double incoherent optical feedback

Frequency locking (FL) in a semiconductor laser with double incoherent optical feedback is experimentally studied, and the characteristics of the locking states are analyzed through comparing the RF spectrum of double incoherent optical feedback and single incoherent optical feedback. Moreover, by varying the external loops length ratio, different orders of frequency locking states are observed. The influence of feedback strength and cavity length on locking performance is preliminarily investigated and the optimized FL state is obtained. This experimental investigation may offer a method to obtain frequency spacing tunable discrete broad-band signals.

On control of chaos and synchronization in the vibronic laser

It is shown theoretically that the method of time delayed incoherent optical feedback ensures control of chaotic dynamics in the vibronic alexandrite laser. The numerical solutions of the laser equations including the optical delayed feedback term are presented and the conditions for stabilization of the laser output are discussed. The possibility of synchronization of two chaotic vibronic lasers is reported when one of them is driven by the output of the other, thus giving the basis for secure communication.

Experimental investigations on the external cavity time signature in chaotic output of an incoherent optical feedback external cavity semiconductor laser

Chaotic dynamics of a semiconductor laser subject to incoherent optical feedback (IOF) are experimentally investigated, and the external cavity time are retrieved and measured from intensity time series of the laser output by using self-correlation function and the mutual information. Through moderating feedback strength and injection current of the laser, the external cavity time signature of the laser chaotic output is effectively attenuated, and then the security of such chaos encryption system can be assured to a certain degree.

Modeling multi-longitudinal-mode semiconductor lasers with incoherent feedback

We study numerically the dynamics of a multi-longitudinal-mode semiconductor laser subject to incoherent optical feedback. The feedback scheme is such that the polarization state of the feedback light is rotated 90\ifmmode^\circ\else\textdegree\fi{}, so that the natural laser mode, TE, is coupled unidirectionally into the orthogonal, unsupported mode, TM. We use traveling-wave equations for the slowly varying complex amplitudes of the two counterpropagating optical fields circulating in the Fabry P\'erot cavity, both with TE polarization, coupled to an equation for the carrier population. The carrier equation contains a time-delayed term that takes into account the effect of the incoherent feedback. The model considers a parabolic frequency-dependent gain and does not assume a priori a fixed number of active longitudinal modes. We find that moderate feedback levels reduce the total power and increase the number of oscillating longitudinal modes. Larger feedback levels lead to instabilities at both the external cavity frequency ${f}_{\mathit{ext}}$ and the relaxation oscillation frequency ${f}_{\mathit{ro}}$. These findings are in good qualitative agreement with experimental observations by Houlihan et al. [Opt. Commun. 199, 175 (2001)]. For even stronger feedback there is square-wave periodic modulation of the total power, with a repetition period close to twice the delay time. In this regime, which consists of a sequence of turn-on and turn-off events driven by the incoherent feedback, the longitudinal modes show in-phase behavior at a frequency close to ${f}_{\mathit{ro}}$ accompanied by a slower out-of-phase drift, which is related to variations of the maximum and minimum values of the oscillation amplitude of the modal intensities.

Simulation of chaotic synchronization communication system based on incoherent optical feedback and injection

In this paper, we numerically study chaotic synchronization communication system based on incoherent optical feedback and incoherent optical injection. The characteristics of the system, such as synchronization time, synchronization error, chaos shift keying encoding/decoding and modulation rate are analyzed. The results of simulation show that the system has good synchronization quality and good abilities of robust secure. The synchronization time is 1ns and the chaos shift keying encoding can reach a high rate of 1 Gbit/s. The system has a good ability of robust secure. It proves the feasibility of the optical secure communication.

Fast self-pulsing through nonlinear incoherent feedback

We consider a double-pass ring cavity with nonlinear incoherent optical feedback and analyze its response when it is driven by a continuous laser beam. This particular cavity is equivalent, in the temporal domain, to a simple spatial-pattern-generating system made from a Kerr slice and a feedback mirror. After formulating the evolution equations, we investigate the behavior of small-amplitude solutions and obtain an expression for the round-trip gains. We then explore the important effect of dispersion in the nonlinear medium. Finally, we show that stable modes are possible by solving numerically the full nonlinear equations.

Two-field description of chaos synchronization in diode lasers with incoherent optical feedback and injection

Synchronized chaotic dynamics are investigated theoretically and experimentally in a system of unidirectionally-coupled semiconductor lasers subject to delayed, polarization-rotated optical feedback and injection. Experimental data in the time and frequency domains demonstrate chaos synchronization with a lag between transmitter and receiver equal to the injection time, also known as driving synchronization. The natural polarization mode of the transmitter is shown to synchronize most efficiently to the orthogonal state of the receiver which is being injected. A full two-polarization model is used for both lasers, and is in good agreement with polarization-resolved experimental measurements.

Dynamic regimes in semiconductor lasers subject to incoherent optical feedback

The dynamics of a semiconductor laser subject to polarization-rotated (incoherent) optical feedback in the long cavity limit has been numerically and experimentally investigated. The results show that the induced dynamics can be grouped into four regimes (stable, chaotic, pulsed, and two state) and that the transverse-magnetic mode of the laser never lases in the ring cavity configuration studied. In addition, unlike the earlier short-cavity work, the boundaries between the regimes in the long-cavity case were found to be independent of the external-cavity delay time.