VCSELs with Integrated Surface Gratings for Polarization Dynamics Above 65 GHz

VCSELs are the industry-preferred transmitters for short-haul optical data transmission due to their low threshold currents and near-Gaussian beam profiles. In this short distance communication regime, information is usually coded in the light intensity via modulation of the pumping current. State-of-the-art intensity-modulated VCSELs reach modulation bandwidths up to around 35 GHz [1] with intensity relaxation oscillations being identified as capping mechanism preventing higher speeds. To circumvent this problem, encoding the information in the polarization state of the emitted light has been proposed by injecting spin-polarized carriers into the VCSEL [2]. Since the spin-photon interaction can be faster than the carrier-photon interaction, this type of pumping has resulted in demonstrated polarization dynamics over 200 GHz, typically observed as polarization oscillations in the circular polarization degree [2]. This frequency, associated to the resonance of the spin-photon interaction, was found to be proportional to the spectral separation of the lasing and non-lasing mode $\Delta f$ .