Vertical-cavity surface-emitting laser emitting circularly polarized light

We demonstrate both theoretically and experimentally that a vertical-cavity surface-emitting laser with an overlay of cholesteric liquid crystal (CLC-VCSEL) becomes a coupled system with different spectral, threshold and polarization characteristics from those of the stand-alone VCSEL. Due to the existence of a band gap for circularly polarized light in the liquid crystal, the output light becomes almost circularly polarized with the opposite handedness of the CLC. We also show that it is even possible to replace the VCSEL top distributed Bragg reflector by a CLC overlay. (letter)