Spin-lasers with periodic gratings: toward ultrafast polarization modulation

The main goal of this study is to explore possibilities of using cavities with dielectric or semiconductor grating as a main building block of spin-injected vertical-cavity surface-emitting lasers (spin-VCSELs) for ultrafast data transfer up to hundreds of Gb/s. Spin-VCSELs allow direct control of emitted polarization by means of electron spin injection. Compared to intensity-modulated VCSELs, the information is encoded into polarization state of light. Shorter response time is offered as a result of introducing anisotropy, in this case via periodic grating, which couples circularly-polarized photons, emitted in spin-polarized quantum wells. Precise modeling of the lasing regime is essential and based upon theory developed in our previous work. Eigenmodes of cavity with periodic structures are extracted using effective medium theory implemented in the transfer matrix formalism. Mathematical tools allow us to calculate optimal parameters of birefringent grating and consequently to design the cavities with required functionality. Particular focus is put on calculation of photon lifetimes, generalized confinement factors and frequencies of eigenmodes, which are necessary for studying dynamical performance of grating-based spin-VCSELs. According to the numerical model, desired gratings and grating-based cavities can be fabricated using PVD deposition of dielectric material sophisticated by lithographic techniques along with sample etching.