Dynamics of long-wavelength VCSELs subject to dual-beam optical injection

We have studied experimentally and theoretically the nonlinear dynamics of a 1550 nm single transverse mode VCSEL subject to two-frequency orthogonal optical injection. In this type of injection both injected fields have a linear polarization that is orthogonal to that of the free-running VCSEL. We have found different behaviors that include irregular and periodic dynamics in the orthogonal polarization, periodic dynamics in both linear polarizations and a situation in which both linearly polarized modes lock to the most intense injection when its wavelength is close to the free-running laser wavelength. In this study we also analyze the generated high-frequency microwave signal found when the VCSEL is emitting only in the orthogonal polarization. The relative strength of peaks in the optical spectra at the frequencies of both master lasers depends on the behaviour of the VCSEL under single optical injection by the most intense master laser. The peak in the optical spectrum that appears at the frequency of the most intense master laser is larger than the peak that appears at the frequency of the other master laser, providing that there is stable locking when only light from the most intense laser is injected. In this case a significant emission of the VCSEL at the frequency of the most intense master laser is observed. On the contrary, if there is not stable locking when only light from the most intense laser is injected, the magnitude of both peaks becomes similar and a significant emission of the VCSEL at the frequency of the weakest master laser is observed. Good agreement is found between our experimental and theoretical results.