Self-pulsation dynamics in narrow stripe semiconductor lasers (original) (raw)

Self-pulsating semiconductor lasers: theory and experiment

IEEE Journal of Quantum Electronics, 1999

We report detailed measurements of the pump-current dependency of the self-pulsating frequency of semiconductor CD lasers. A distinct kink in this dependence is found and explained using rate-equation model. The kink denotes a transition between a region where the self-pulsations are weakly sustained relaxation oscillations and a region where Q-switching takes place.

Optical-feedback-sustained self-pulsations in semiconductor lasers

Physics and Simulation of Optoelectronic Devices VI, 1998

In this work we study the dynamics of a single-cavity semiconductor laser device, able to work in self-pulsating regime as a consequence of a nonlinearity distributed in the whole active region and driven by the electromagnetic-field intensity in the laser cavity. Numerical values of the nonlinearity degree necessary to establish the self-pulsating regime are given which can be used for a comparison with experimental measurements of semiconductor materials properties. The optical feedback influence on the self-pulsating device is also studied showing how pulsation characteristics are affected by the presence of a reflected signal and pointing out the feedback ability to cause their generation or quenching. The possibility of using current and optical feedback for the pulsation characteristics control and for the switch of the laser output is discussed.

Dynamics of coupled self-pulsating semiconductor lasers

We introduce and analyze a model for the dynamics of two coupled self-pulsating semiconductor lasers. We investigate the role of the complex coupling coefficient in the static and dynamic properties of the device. We find conditions for the emergence of coherent laser pulses, in which the two lasers display synchronous coherent self-pulsations (self-pulsating super modes). Nonlinear dynamics and two different routes to chaos are also individuated and discussed.

Intensity and polarization self-pulsations in vertical-cavity surface-emitting lasers

Optics Letters, 2002

We implement a dynamic model that describes the polarization behavior in vertical-cavity surface-emitting lasers that contain an absorbing region surrounding the active zone. We find four regions of qualitatively different behavior: stable linearly polarized operation, intensity pulsations of a linearly polarized component, pulsations of both total-intensity and polarization components, and polarization self-pulsation with constant total intensity. We characterize the four regions by computing the polarization-resolved optical and power spectra. The predicted behavior agrees with recent experimental results.

Short Pulse Generation from Semiconductor Lasers : Characterization, Modeling and Applications

This Thesis describes the research work that has been carried out on the generation of optical pulses, with duration of tens of picoseconds, from semiconductor lasers. The work is focused on 1550 nm Vertical Cavity Surface Emitting Lasers (VCSEL), which are promising optical transmitters due to their advantageous characteristics in the context of fiber optical communications with directly modulated sources. The high bandwidth expected for future optical networks requires the accurate knowledge of the transmitter electrical properties and of the laser generated optical pulses which carry the binary information. This Thesis describes the various achievements obtained in the characterization of these devices and the generated pulses, as well as their applications to an optical communication environment. VCSELs emitting at 1550 nm, based on quantum wells and tunnel junction, have been characterized by static and dynamic impedance measurements and modulation response up to 10 GHz. The electrical parasitics and the equivalent circuit of the device have been modeled, taking into account the effects of capture and escape of carriers in quantum wells, and the laser intrinsic parameters have been extracted from the measurements. The VCSELs have been used for pulse generation at different repetition rates using the gain switching technique and the duration, peak amplitude, jitter and spectral width of the pulses have been measured as a function of the gain switching conditions. The shortest duration achieved has been 55 ps. The effect of optical injection on the pulses generated by gain switched VCSELs has been investigated, obtaining a jitter reduction over a wide range of injection parameters. An Optical Code Division Multiple Access (OCDMA) encoder based on optical delay lines has been designed and implemented, using the optical pulses generated by the gain switched devices. Finally, a novel implementation of the Phase Reconstruction using Optical Ultrafast Differentiation (PROUD) technique has been proposed and demonstrated for optical pulse characterization in amplitude and phase. The optical differentiator required in the PROUD technique has been realized with a birefringent interferometer based on a polarization maintaining fiber and PROUD has been applied to the measurement of the instantaneous frequency of pulses generated from a gain switched semiconductor laser. The linewidth enhancement factor of the laser has been extracted from the time resolved chirp and intensity measurements. The accuracy of the proposed method has been validated by the comparison between the independently measured and recovered (from temporal amplitude and phase) pulse spectra.

Spatio-temporal dynamics of broad area semi-conductor lasers and its characterization

Chaos Solitons and …, 1999

We present experiments giving evidence for the onset of irregular spatio-temporal dynamics on picosecond timescales in broad area lasers and characterize the dynamical complexity. In particular, we present single shot streak camera measurements of the nearfield dynamics of a broad area laser with a 100 µm wide active area and successfully apply Karhunen-Loève Decomposition (KLD) directly to the experimental data. Only a limited number of KLD modes is necessary to recover all essential features of the dynamical behavior. This fact allows the estimation of the system's number of degrees of freedom.

Spatio-temporal dynamics in twin-stripe semiconductor lasers

Physica D: Nonlinear Phenomena, 1994

The twin-stripe semiconductor laser, a system of two evanescently coupled nonlinear oscillators, shows complex spatio-temporal behaviour. Its dynamics is studied theoretically by numerical integration of a model system of coupled partial differential equations. The overlap of the evanescent optical fields and the diffusion of charge carriers determine the amount of nonlinear transverse coupling between the laser stripes. The concept of cumulants of the bit-number of a dynamical system composed of two subsystems , and a characteristic spatio-temporal correlation function are introduced and applied to quantify the complexities in space and time as they are observed in the output signal of the twin-stripe laser. Depending on the distance between the adjacent oscillators, three dynamical regimes are identified: Sufficiently far apart, the two laser oscillators are uncoupled and the device shows a steady constant output signal. In the regime of medium coupling, randomly oscillating light pulses dominate the output signal. If both stripes are strongly coupled, both lasers oscillate with a (fixed) phase lag but chaotic intensities.

Spatio-temporal dynamics of semiconductor lasers: Theory, modelling and analysis

Progress in Quantum Electronics, 1996

The spatio-temporal dynamics of semiconductor lasers is studied theoretically on the basis of semiclassic laser theory. The carrier dynamics is described in a density-matrix approach and the coupled set of equations of motion for the active medium and the light field are derived. Several approximafions related to separations of length and time scales are discussed, resulting in a hierarchy of model equations leading from microscopic to macroscopic levels of description. By numerically solving space-dependent coupled partial differential equations for the (complex) optical fields, the interband polarization and the charge carrier distribution functions on the various levels of the hierarchy the formation and longitudinal propagation of unstable transverse optical filamentary structures is analyzed in a model configuration for typical doubleheterostructure multi-stripe and broad-area lasers. Spectral and spatial hole burning which is observed in the simulated carrier distributions reflects the interplay between stimulated emission and the relaxation dynamics of the carrier distributions as well as the polarization. Its details are strongly influenced by the momentum and density dependence of the microscopic relaxation rates. The transverse hole burning leads to complex spatio-temporal patterns in the macroscopic intensity picture. This complex spatio-temporal dynamic behavior in multi-stripe and broad-area lasers is analyzed by various theoretical tools which allows one to quantify the degree of complexity. CONTENTS * It should be mentioned that these assumptions break down if the the scattering probabilities are strongly peaked around a single final state as is the case in pure LO-phonon scattering or for carrier-carrier scattering at low densities, where most scattering processes are in the forward direction. (57,6s) In the present case of high densities with strong large-angle carrier-carrier scattering the assumptions are well satisfied. * Strictly speaking, p, is not exactly the linear part. Due do the band gap renormalization and the density dependent dephasing rate it includes already parts which are nonlinear in the field.

Improved Semiconductor-Laser Dynamics From Induced Population Pulsation

IEEE Journal of Quantum Electronics, 2006

This paper investigates theoretically the modification of dynamical properties in a semiconductor laser by a strong injected signal. It is found that enhanced relaxation oscillations are governed by the pulsations of the intracavity field and population at frequencies determined by the injected field and cavity resonances. Furthermore, the bandwidth enhancement is associated with the undamping of the injection-induced relaxation oscillation and strong population pulsation effects. There are two limitations to the modulation-bandwidth enhancement: Overdamping of relaxation oscillation and degradation of flat response at low frequencies. The injected-laser rate-equations used in the investigation reproduce the relevant aspects of modulation-bandwidth enhancement found in the experiment on injection-locked vertical-cavity surface-emitting lasers.