Spin polarization modulation for high-speed vertical-cavity surface-emitting lasers

Abstract

The spin polarization modulation in birefringent vertical-cavity surface-emitting lasers (VCSELs) is investigated theoretically and experimentally for obtaining tailored polarization modulation characteristics suitable for high-speed data communications. A spin-flip rate equation analysis reveals that the spin polarization modulation response of VCSELs is flattened by shortening the electron spin relaxation time and its 3-dB bandwidth is broadened to a range determined by a frequency split between two orthogonal polarization modes. Optical modulations of spin polarized electrons in commercially-available InAlGaAs quantum well VCSELs demonstrate a wide 3-dB bandwidth of 23 GHz determined by the frequency split, which indicates that the spin relaxation time in the InAlGaAs quantum well VCSEL is around 20 ps at room temperature and suitable for use in high-speed data communications at a telecom wavelength of 1.55 μm.