Current-modulated Vertical-cavity Surface-emitting Lasers Research Articles

Chaos and pulse packages in current-modulated VCSELs

We numerically study the dynamics of vertical cavity surface-emitting lasers (VCSELs) based on the current-dependent gain model subjected to current modulation. For a few hundred MHz frequency of injection current, the threshold current is reduced and polarization switching is accompanied by an anti-phase dynamics of polarization modes. Pulse packages are found and compared with those found in the literature. The behaviour of pulse packages is studied in terms of the modulation parameters. For a few GHz frequency of injection current, the dynamics of VCSELs presents chaotic behaviour.

Theoretical investigations on the polarization performances of current-modulated VCSELs subject to weak optical feedback

Based on the framework of the spin-flip model (SFM) for GHz level modulation frequency, the polarization performances of current-modulated vertical-cavity surface-emitting lasers (VCSELs) subject to weak optical feedback have been theoretically investigated. The results show that, for type 1 polarization switching (PS), the influences of optical feedback intensity and the current modulation amplitude on the high-frequency modulation response is not obvious. For low-frequency modulation, optical feedback will result in the output of a VCSEL having rich dynamics. A new style PS can be obtained under large-signal modulation through adjusting the modulation frequency. For type 2 PS the situation is more complex, and optical feedback increases the probability of polarization conversion and competition, while also affecting the PS point. The modulation amplitude also affects the output dynamics of the VCSEL.

Spectral signatures of the dynamics of current-modulated vertical-cavity surface-emitting lasers subject to optical feedback

The dynamics of current-modulated vertical-cavity surface-emitting lasers (VCSELs) with optical feedback has been studied experimentally. The nature of the dynamics is classified by measured power spectra. It is shown that when the depth of the current modulation is increased the VCSEL dynamics exhibits transitions from a regime governed by the optical feedback through a regime where both optical feedback and modulation contribute to a regime where the current modulation controls the dynamics. Such a transition through three regimes of dynamical behavior has also been identified, at different bias currents, when the modulation frequency is varied. A dynamical resonance having a complicated dependence on the external cavity length is also revealed. The measurements are in good qualitative agreement with theoretical predictions.

Nonlinear dynamics of current-modulated vertical-cavity surface-emitting lasers

A numerical analysis of the nonlinear dynamics of weakly index-guided vertical-cavity surface-emitting lasers (VCSELs) subject to high-frequency current modulation is performed. Chaotic behavior appears in the multi-mode regime due to transverse-mode competition. Chaotic operation is such that multi-stability of the chaos–chaos type is observed. Injection of appropriate optical pulses can switch between different chaotic solutions. The analysis of the nonlinear dynamics of high-frequency current-modulated single-mode VCSELs indicates that the chaotic behavior is not present for the considered range of current modulation amplitudes and frequencies. Only periodic behaviors are observed in such a way that multi-stability of different periodic solutions is also observed. Switching between different stable periodic solutions can be obtained by injecting external optical pulses. Finally, we show that spontaneous emission noise increases the number of available channels in chaotic optical communication systems in which frequency division multiplexing with multi-transverse-mode VCSELs is used.