Self- and cross-correlation measurements in two-mode semiconductor ring lasers (original) (raw)
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Self–and Cross–Correlation Measurements in Two–Mode Semiconductor Ring Lasers
2004
In this work we present experimental results on the auto-correlation and cross-correlation properties of the two counterpropagating modes of a monolithic semiconductor ring laser. The ring laser can operate in a bidirectional regime where the two modes have equal power, and also in a unidirectional regime where one of the modes is almost suppressed. Auto-correlation measurements, that are carried out using an unbalanced Mach-Zehnder fiber interferometer, allows to determine the coherence length and linewidth of the ring laser. Cross-correlation measurements are carried out using a modifed interferometric setup , and they reveal that the two counterpropagating modes are phaselocked.
IEEE Journal of Selected Topics in Quantum Electronics, 2000
We perform an experimental investigation of the linear autocorrelation and cross correlation properties of the two counterpropagating modes of a monolithic semiconductor ring laser (SRL). The ring laser can operate in a bidirectional regime where the two modes are active at the same time and have equal power, and also in a unidirectional regime where one of the modes is suppressed. Autocorrelation measurements are carried out using an unbalanced optical fiber Mach-Zehnder interferometer that allows us to determine the linewidth of each mode of the ring laser. Cross correlation measurements are performed using a modifed optical fiber interferometric setup where the two counterpropagating modes are directly superposed on a photodetector. This measurement reveals that in the bidirectional regime the two modes are phase-locked and allows us to evaluate the degree of their correlation.
Spectral Investigation of the Operation of Multi-longitudinal Mode Semiconductor Ring Lasers
2007
We spectrally investigated the regimes of operation of multi-mode semiconductor ring lasers. We report here on an InAs/InGaAsP/InP quantum dot ring laser. The field emitted by both sides of the device is detected with either a power meter or a 6GHz resolution multi-wavelength meter. We present here the mode-resolved PI-curves for different values of the bias current, the dominant wavelength and the side-modesuppression ratio. Opposite to single mode devices, whose dynamics is determined by the coupling of two counter-rotating waves which compete for a common gain, we observed a nontrivial partitioning of power between the two directions and the different longitudinal modes.
Exploring Multistability in Semiconductor Ring Lasers: Theory and Experiment
Physical Review Letters, 2009
We report the first experimental observation of multi-stable states in a single-longitudinal mode semiconductor ring laser. We show how the operation of the device can be steered to either monostable, bistable or multi-stable dynamical regimes in a controlled way. We observe that the dynamical regimes are organized in well reproducible sequences that match the bifurcation diagrams of a two-dimensional model. By analyzing the phase space in this model, we predict how the stochastic transitions between multi-stable states take place and confirm it experimentally. PACS numbers: 42.65.Pc, 42.55.Px,42.60.Mi Multi-stability is a general feature of nonlinear systems which attracts attention in a broad set of subjects including hydrodynamics [1], plasma physics [2], biology [3], neural networks [4, 5], chemical reactions [6] and optical systems . The phase space of a multi-stable system is in general very intricate due to the strongly interwoven basins of attractions of the coexisting stable structures, and is often further complicated by the presence of structures such as chaotic saddles . For this reason, the dynamics of a multi-stable system is characterized by a larger complexity than their bistable counterpart, leading to phenomena such as attractor hopping or chaotic itineracy . While being of broad interdisciplinary interest, multi-stability is especially interesting in the case of semiconductor lasers, due to their large number of applications and their wealth of dynamical regimes (see and reference therein). However, the fast time scales involved, the presence of spontaneous emission of photons blurring off the structures, the difficulty to control the internal parameters, the inaccessibility of some dynamical variables, all make the experimental reconstruction of the phase space of semiconductor lasers an extremely challenging task. Therefore, despite the large number of theoretical work , the dynamical complexity of multi-stable semiconductor lasers remains experimentally unaddressed. In this contribution, we experimentally address the phase space of Semiconductor Ring Lasers (SRLs), which are a novel class of semiconductor lasers characterized by circular geometry . We have focused our investigation on SRLs for several reasons. From the theoretical point of view, many dynamical regimes including multi-stable ones have been predicted [18] but not observed yet. From the technological point of view, an understanding of the phase space of SRLs would be highly desirable to improve performances in applications such as all-optical memories and allow for a better control of the device . We start our investigation with a comprehensive model , which allows us to predict bifurcation sequences and FIG. 1. Experimental SRL set-up. Four waveguide contacts are depicted of which only the one denoted by Iw is biased.
Alternate oscillations in semiconductor ring lasers
Optics Letters, 2002
We report on fabrication and characterization of single-longitudinal-and transverse-mode semiconductor ring lasers. A bifurcation from bidirectional stable operation to a regime with alternate oscillations of the counterpropagating modes was observed experimentally and is theoretically explained through a two-mode model. Analytical expressions for the onset and the frequency of the oscillations are derived, and L I curves numerically evaluated. Good quantitative agreement between theory and measurements made over a large number of tested devices is obtained.
Experimental analysis of the optical spectra of directionally bistable semiconductor ring lasers
Semiconductor Lasers and Laser Dynamics III, 2008
The optical spectrum of monolithic Semiconductor Ring Lasers (SRLs) is measured simultaneously for both lasing directions with a grating-based OSA, in the regimes of bidirectional and unidirectional operation. In the unidirectional operation regime the SMSR is larger than 25 dB, and the directional extinction ratio (i.e., the ratio of the power emitted in the two opposite directions) is larger than 20 dB. The influence of the current injected in the active output waveguides that act as SOAs is outlined. In the unidirectional regime the linewidth of the SRL is measured by an heterodyne technique, revealing linewidth values around 2 MHz.
Semiconductor ring lasers coupled by a single waveguide
Applied Physics Letters, 2012
We experimentally and theoretically study the characteristics of semiconductor ring lasers bidirectionally coupled by a single bus waveguide. This configuration has, e.g., been suggested for use as an optical memory and as an optical neural network motif. The main results are that the coupling can destabilize the state in which both rings lase in the same direction, and it brings to life a state with equal powers at both outputs. These are both undesirable for optical memory operation. Although the coupling between the rings is bidirectional, the destabilization occurs due to behavior similar to an optically injected laser system. V C 2012 American Institute of Physics.
Experimental analysis of the optical spectra of directionally bistable semiconductor ring lasers
SPIE Proceedings, 2008
The optical spectrum of monolithic Semiconductor Ring Lasers (SRLs) is measured simultaneously for both lasing directions with a grating-based OSA, in the regimes of bidirectional and unidirectional operation. In the unidirectional operation regime the SMSR is larger than 25 dB, and the directional extinction ratio (i.e., the ratio of the power emitted in the two opposite directions) is larger than 20 dB. The influence of the current injected in the active output waveguides that act as SOAs is outlined. In the unidirectional regime the linewidth of the SRL is measured by an heterodyne technique, revealing linewidth values around 2 MHz.
Operating regimes of gaas-algaas semiconductor ring lasers: experiment and model
IEEE Journal of Quantum Electronics, 2003
Theory and experiments of single-mode ridge waveguide GaAs-AlGaAs semiconductor ring lasers are presented. The lasers are found to operate bidirectionally up to twice the threshold, where unidirectional operation starts. Bidirectional operation reveals that just above threshold, the lasers operate in a regime where the two counterpropagating modes are continuous wave. As the injected current is increased, a new regime appears where the intensities of the two counterpropagating modes undergo alternate sinusoidal oscillations with frequency in the tens of megahertz range. The regime with alternate oscillations was previously observed in ring lasers of the gas and dye type, and it is here reported and investigated in semiconductor ring lasers. A theoretical model based on a mean field approach for the two counterpropagating modes is proposed to study the semiconductor ring laser dynamics. Numerical results are in agreement with the regime sequence experimentally observed when the injected current is increased (i.e., bidirectional continuous-wave, bidirectional with alternate oscillations, unidirectional). The boundaries of the different regimes are studied as a function of the relevant parameters, which turn out to be the pump current and the conservative and dissipative scattering coefficients, responsible for an explicit linear coupling between the two counterpropagating field modes. By a fitting procedure, we obtain good numerical agreement between experiment and theory, and also an estimation for the otherwise unknown scattering parameters.
Dynamical behavior of semiconductor ring lasers
2011 Fifth Rio De La Plata Workshop on Laser Dynamics and Nonlinear Photonics, 2011
A basic rate equation model for the counter-propagating fields in semiconductor ring lasers, accounting for saturation and backscattering effects, consists of five real equations. By applying asymptotic techniques, we are able to reduce these original rate equations to two real ones. A bifurcation study of this reduced system is performed, which greatly enlarges our physical understanding of the dynamical behaviour of these ring lasers.