Extreme events in Q-switched lasers

F. M. DE AGUIAR; J. R. RIOS LEITE; C. METAYER; T. QUINIOU; A. SERRES; J. TREDICCE; M. AGÛERO; M. KOVALSKY; A. HNILO; C. BONAZZOLA; A. LACAPMESURE; N. MIRON GRANESE

Viña del Mar

Congreso; III Dynamics Days South America; 2014

Universidad de Chile, Facultad de Ciencias Físicas y Matemáticas, Departamento de Física (DFI)

Since optical rogue waves (RWs) were first reported by Solli et al. in 2007 [1], the study of extreme pulses in optical systems has been a very active research field [2]. In semiconductor lasers, ultrahigh intensity pulses occur when the laser is subjected to optical injection [3].RWs induced by the interplay of multistability and noise in a erbium-doped fiber laser (EDFL) have also been reported [4].Here we consider the nonlinear dynamics of a class-B laser with loss modulation [5], described by dS/dt = - S (1 + m cos( ω t) ? N) (1) dN/dt = - Γ (N -A + S N) (2)where the time is in units of the photon lifetime; S and N are the normalised photon intensity and population inversion, respectively; Γ is the ratio of the population inversion to the photon lifetimes, A is the pump current parameter; and m and ω are the amplitude and frequency of the modulation respectively.In Fig.1, we show a typical bifurcation diagram of the maxima of intensity, Smax, as a function of m. It is easy to observe that after reaching chaos, chaotic attractors expand abruptly in phase space. Furthermore, just before reaching a fully developed chaos, it is possible to observe the coexistence of a chaotic and periodic attractors at low m values. Fig. 2 displays a typical time trace of the normalised laser intensity I = S/ < S > for m values in the region of coexistence. Here, < S > is the average photon density in a long wave train. Notice that the trajectory in phase space spends most of time in a dense region of the strange attractor, only occasionally performing a long excursion, resulting in a high pulse, as shown in Fig.3. Then such high intensity pulses are extreme events in the chaotic behaviour giving a long tail in the probability distribution of the maxima of intensity.The theoretical results are compared to experimental data obtained from a solid state laser with electro-optically modulated losses. The comparison shows a good qualitative agreement between numerical and experimental results.