Mapping of external cavity modes for a laser diode subject to phase-conjugate feedback

Abstract

We numerically investigate the dynamics of a semiconductor laser subject to phase-conjugate optical feedback. We explore the effects of the laser model and feedback parameters for the generation of time-periodic oscillations of the output power at harmonics of the external cavity frequency, i.e., dynamical solutions that have been named external cavity modes. We point out that both the experimentally tunable and other parameters have an influence on the frequency of such dynamics. Since the delay has to exist, it is not the relevant parameter as we show that the feedback rate fixes the frequency of the periodic self-pulsations. The interaction length of the crystal and the ratio between carrier and photon lifetimes tend to filter out high frequencies as they increase. Finally, the linewidth enhancement factor unlocks high frequencies as it increases. We conclude by providing a situation which leads to periodic solutions with higher frequencies using a set of realistic values of parameters.

Optimized properties of chaos from a laser diode

“…This frequency equals 8.84 times the frequency of the external cavity (1.02 GHz), which is about the ninth harmonics of the frequency of the external cavity. This observation agrees with earlier theoretical predictions that tell us that the frequency of the ECMs is close but not always equal to the harmonics of the external cavity frequency, and even more, varies with the feedback strength [27,28].…”

“…However, if γ ≥ 0.06, an increase of the current strongly enhances the PE(τ ). The value of γ associated with the onset of ECMs decreases with the pump current [28]. Hence the drop of spectral flatness and PE(τ ) described in section III B will occur at a lower value of γ as the pump current decreases.…”

Wideband chaos from a laser diode with phase-conjugate feedback

“…κ is the dimensionless feedback strength, α is the linewidth enhancement factor and P is the pump above threshold. We choose α = 2, P = 0.6016, T = 1200 and τ r = 50 which are taken from our previous study of the same laser system [27].…”

Manipulating the chaos bandwidth of a semiconductor laser subjected to phase-conjugate feedback

“…18 We set the parameters as in table 1, chosen on the basis of a previous study of the position of the external cavity modes. 20 These values have been chosen to simulate a laser with relaxation oscillations of 3.6 GHz, a pumping current equal to 1.6016 times the threshold current, an external cavity single-trip length of 52.5 cm and a cubic phase-conjugate mirror with edges of 5 mm.…”