Vertical-Cavity Surface-Emitting Laser With a Chiral Nematic Liquid Crystal Overlay

We demonstrate measurement results of the light emission of vertical-cavity surface-emitting lasers (VCSELs) with chiral liquid crystal (CLC) overlay (CLC-VCSEL). Two different CLC materials with different chiral-phase temperature range are presented and compared. The CLC layer acts as an external cavity for the VCSEL for one circular polarization state that results in complex polarization behavior inside the VCSEL cavity. We find that the emission of the device is purely circularly polarized with a degree of circular polarization higher than the degree of linear polarization of the stand-alone VCSEL. The threshold current of the CLC-VCSEL is decreased, and the emission wavelength of the CLC-VCSEL can be temperature tuned over a larger range compared with that of the stand-alone VCSEL. Numerical results reveal that the small reflection at the top CLC has a much larger influence on the laser dynamics than the stand-alone configuration.