Hybrid VCSEL - liquid crystal systems

We study theoretically and experimentally spectral and polarization characteristics of hybrid systems of VCSELs integrated within liquid crystal (LC) cells. Three cases are considered: Nematic or cholesteric LC on top of VCSEL, coupled-cavity system with the second cavity next to the VCSEL's one filled in with nematic LC and a system with a nematic LC inside the VCSEL cavity. For the case of nematic liquid crystal - VCSEL coupled cavity system we demonstrate selection between two orthogonal directions of linear polarization of the fundamental mode by changing the LC length or by electro-optical tuning of the LC director. For the case of cholesteric liquid crystal-VCSEL system we demonstrate lasing on circularly polarized (CP) modes due to the LC band gap for CP light. The transition from nematic to isotropic phase of the LC when increasing temperature leads to a drastic change of the polarization of the generated light from left-handed circular to linear polarization. Finally, we investigate the possibility of efficient wavelength tuning by utilizing electrooptical effect in nematic LC layer integrated next to the active region in a VCSEL cavity.