By Sylvia Schikora
The stabilization of volatile states hidden within the dynamics of a process, particularly the keep an eye on of chaos, acquired a lot recognition within the final years. during this paintings, a widely known regulate technique known as not on time suggestions keep an eye on is utilized for the 1st time solely within the all-optical area. A multisection semiconductor laser gets optical suggestions from an exterior Fabry-Perot interferometer. The keep an eye on sign is a phase-tunable superposition of the laser sign, and provokes the laser to function in an in a different way volatile periodic kingdom with a interval equivalent to the time hold up. The regulate is noninvasive, as the mirrored sign has a tendency to 0 whilst the objective country is reached.
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Additional resources for All-Optical Noninvasive Delayed Feedback Control of Semiconductor Lasers
Dotted lines: freerunning values. 5, τl ≈ τ. g. gray line in Fig. 6 (a) and (b)). The width of this precursor is proportional to the RO damping, and, thus, a measure for the stability of the cw state. The inﬂuence of FP feedback to such a regime is evaluated experimentally. The AFL is driven in cw operation close to a Hopf bifurcation. Here, a distinct precursor appears in powerspectrum (gray line in Fig. 6 (b)). 03. The laser emission is adjusted to resonance according to the description in the previous paragraph.
For τ ≈ T0 /2, the RO are stronger damped (Fig. 6 (b)), and the stability of the stationary state is improved. The contrary choice τ = T0 decreases the stability of the involved stationary state, and improves the regularity of the occurring RO (Fig. 6 (a)) [BJS04, FS07]. The latter aspect is referred to in literature as ‘coherence control’, and will be further considered in the following section. 2 Controlling the Coherence of Oscillations The last experiment touched a ﬁeld of control theory which has not been mentioned so far, and which is actually beyond the scope of this thesis: the control of 38 3 Stable States with Resonant Fabry-Perot Feedback coherence by DFC.
Then, IP is increased stepwise and the laser is driven through the Hopf bifurcation. Increasing IP also affects the emission wavelength, and this way deteriorates the resonant adjustment. Thus, each current shift affords a slight accommodation of the temperature in order to maintain resonance. The necessary overall temperature variation is far below 1 K. The essential characteristics of the Hopf bifurcation are not affected by the applied temperature corrections. The Hopf bifurcation is crossed along a line of constant wavelength in the current-temperature plane.