Characterization of the Dynamics of Optically-Injected Nanostructure Lasers

The direct-modulation of semiconductor lasers is the simplest and most compact approach to pass data onto an optical fiber; however, their intrinsic limitations under direct-modulation such as wavelength chirp and inherent relaxation oscillation frequency constraints impede their high-speed and long-distance capabilities. The injection-locking of semiconductor lasers improves the injected laser\u27s operational characteristics under direct-modulation, attracting a large degree of interest over the past decade. These improvements include increasing the modulation bandwidth through the enhancement of the resonance frequency, suppressing nonlinear distortion, and reducing relative intensity noise, mode-hopping, and chirp. The nonlinear dynamics associated with optically-injected semiconductor lasers has also attracted great interest due to potential applications including: all-optical amplitude-modulation to frequency-modulation conversion, chaotic-communication, and photonic microwave generation. In this dissertation, the optical-injection of quantum-dash and quantum-dot Fabry-Perot semiconductor lasers is investigated in the context of modeling the impact of their characteristically large nonlinear gain component. The impact of the large degree of gain compression on the differential and nonlinear carrier relaxation rates observed in nanostructure lasers under large operational photon densities is also investigated under strong optical-injection conditions. A novel small-signal microwave modulation response function is derived and shown to improve upon current models at modeling the microwave modulation response under optical-injection. The nonlinear dynamics observed under weak injection strengths are theoretically analyzed using a novel dimensionless rate equation model where including the impact of the nonlinear carrier relaxation rate is shown to improve the agreement with experimentally collected data. The novel tools derived to analyze the operation of the optically-injected system encompass the physical nature of the injected laser in a more complete manner than previously derived approaches. Theoretical predictions derived here show that large nonlinear carrier relaxation rates, along with suitably small linewidth enhancement parameter values of nanostructure lasers suppress the instability of the optically-injected system. The quantum-dash laser\u27s potential for implementation as a tunable photonic oscillator for use in radio-over-fiber applications or directly-modulated slave laser in a coherent optical communication system is described, along with the quantum-dot laser\u27s highly stable operation under optical-injection

Measuring the universal synchronization properties of coupled oscillators across the Hopf instability

When a driven oscillator loses phase-locking to a master oscillator via a Hopf bifurcation, it enters a bounded-phase regime in which its average frequency is still equal to the master frequency, but its phase displays temporal oscillations. Here we characterize these two synchronization regimes in a laser experiment, by measuring the spectrum of the phase fluctuations across the bifurcation. We find experimentally, and confirm numerically, that the low frequency phase noise of the driven oscillator is strongly suppressed in both regimes in the same way. Thus the long-term phase stability of the master oscillator is transferred to the driven one, even in the absence of phase-locking. The numerical study of a generic, minimal model suggests that such behavior is universal for any periodically driven oscillator near a Hopf bifurcation point.Comment: 5 pages, 5 figure

Numerical study of ultrashort-optical-feedback-enhanced photonic microwave generation using optically injected semiconductor lasers at period-one nonlinear dynamics

This study numerically investigates the enhancement of photonic microwave generation using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics through ultrashort optical feedback. For the purpose of practical applications where system miniaturization is generally preferred, a feedback delay time that is one to two orders of magnitude shorter than the relaxation resonance period of a typical laser is emphasized. Various dynamical states that are more complicated than the P1 dynamics can be excited under a number of ultrashort optical feedback conditions. Within the range of the P1 dynamics, on one hand, the frequency of the P1 microwave oscillation can be greatly enhanced by up to more than three folds. Generally speaking, the microwave frequency enhances with the optical feedback power and phase, while it varies saw-wise with the optical feedback delay time. On the other hand, the purity of the P1 microwave oscillation can be highly improved by up to more than three orders of magnitude. In general, the microwave purity improves with the optical feedback power and delay time, while it only varies within an order of magnitude with the optical feedback phase. These results suggest that the ultrashort optical feedback provides the optically injected laser system with an extra degree of freedom to manipulate/improve the characteristics of the P1 microwave oscillation without changing the optical injection condition

Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Semiconductor laser dynamics induced by optical feedback for photonic microwave sensing

As one of the most widely used light sources today, semiconductor lasers (SLs) are an important part of many optical systems, especially for sensing, communications, metrology, and storage applications. SLs have the advantages of small size, easy integration, and miniaturization. The massification of electronic devices has furthered this agenda, allowing the creation of portable systems capable of supporting optical sensing systems. Essentially, SLs are inherently nonlinear devices, in nonlinear systems, the folding and stretching behaviors of variables result in di↵erent dynamical routes. It is worth noting that under the conditions of a stable operation, an SL biased by constant current usually emits laser light with a constant intensity. However, with the introduction of external optical feedback (OF), the laser light can become unstable. SL will undergo from steady state, switching status, to period-one (P1) oscillation by crossing Hopf-bifurcation. In the P1 state, the system produces a modulation of the laser optical output power for the generation of microwave photonics (MWP) signals. In this thesis, we operate SL with OF scheme in P1 dynamics, and found that the proposed system has the great capability to achieve both displacement and absolute distance sensing applications with high resolution and wide measurement range, by using time-frequency information, relaxation oscillation information, and nonlinear dynamic characteristics carried in that SLs emit signals. The contributions of each chapter in this thesis are described in the following: In Chapter 3, we propose an SL with OF set at the P1 dynamics to generate the MWP signal for displacement sensing. Di↵erent from the traditional MWP generation method, the designed laser nonlinear dynamics are used by slightly perturbing the SL source with the help of external feedback light to make the system work in the P1 dynamic state, thereby generating regular microwave oscillation. By using the fourth-order Runge-Kutta method to numerically solve the famous Lang-Kobayashi differential equation, the boundary of di↵erent laser dynamic states is delimited, so that the system can generate stable and sustainable MWP signals in P1 dynamics. A set of parameter selection rules for designing an SL based MWP displacement sensing system is obtained. In addition, a measurement algorithm for recovering the displacement from an MWP sensing signal is developed. By making full use of the sensing information carried in both amplitude and frequency of the MWP signal, displacement sensing with high resolution and high sensitivity can be achieved. Both simulations and experiments are conducted to verify the proposed method and show it is capable of realizing high measurement sensitivity, and high resolution for displacement sensing. In Chapter 4, utilizing the rich nonlinear dynamics of an SL with OF, under the proper controllable system parameters, the system enters the P1 dynamics through Hopf-bifurcation. In the P1 state, the detailed relationship between the relaxation oscillation frequency of MWP signals and external cavity length is studied through solving the Lang-Kobayashi delayed di↵erential equations. The displacement measurement formula is thus obtained. In addition, the relevant signal processing algorithm is developed by considering mode-hopping, frequency-hopping, and sawtooth-like phenomena that occurred in the relaxation oscillation. The displacement measurement can be enhanced in a wider sensing range by fully using the relaxation oscillation frequency relationship. Verification results in simulation and experiment show that the proposed MWP displacement sensing system based on SL with OF contributes to designing a prototype of a compact displacement sensor with wide measurement range and high resolution. In Chapter 5, OF induced switching status between two nonlinear dynamic states (stable and P1 states) is observed in the SL with OF system. Without the need for any electronic or optical modulation devices, the laser intensity can be modulated in a square wave form due to the switching via utilizing the inherent SL dynamics near Hopf-bifurcation boundary. The periodicity in the switching enables us to develop a new approach for long-distance sensing compared to other SL with OF based absolute distance measurement systems and lift the relevant restrictions that existed in the systems. Moreover, the impact of system controllable parameters on the duty cycle of the square wave signals generated was investigated as well, aiming to maintain the proposed system robustly operating at the switching status

Fundamentals and applications of spatial dissipative solitons in photonic devices : [Chapter 6]

We review the properties of optical spatial dissipative solitons (SDS). These are stable, self‐localized optical excitations sitting on a uniform, or quasi‐uniform, background in a dissipative environment like a nonlinear optical cavity. Indeed, in optics they are often termed “cavity solitons.” We discuss their dynamics and interactions in both ideal and imperfect systems, making comparison with experiments. SDS in lasers offer important advantages for applications. We review candidate schemes and the tremendous recent progress in semiconductor‐based cavity soliton lasers. We examine SDS in periodic structures, and we show how SDS can be quantitatively related to the locking of fronts. We conclude with an assessment of potential applications of SDS in photonics, arguing that best use of their particular features is made by exploiting their mobility, for example in all‐optical delay lines

Recent advances in solid-state organic lasers

Organic solid-state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid-state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light emitting diodes. Organic lasers are broadly tunable coherent sources are potentially compact, convenient and manufactured at low-costs. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive feature of dyes and semiconductors. We also outline the laser architectures used in state-of-the-art organic lasers and the performances of these devices with regard to output power, lifetime, and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, or towards integrated low-cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics

Wave-mixing analysis for THz-signals generation in dc-biased semiconductor optical devices at room temperature

Wave-mixing at 370-GHz in a SOA and FP semiconductor laser is investigated by using a FROG-system. A comparison of the optical time-fluctuations measured at their output stresses the importance of a resonant cavity in THz-signals generation from semiconductor optical devices