On-Demand Polarization Controllable Liquid Crystal Laser

A polarization controllable band-edge liquid crystal (LC) laser configuration is presented that provides on-demand control of the polarization state of the laser using a four electrode in-plane configuration to drive a nematic LC layer. By controlling the orientation of the electric field, and thus the orientation of the optic axis of the nematic LC, as well as the retardance, any laser polarization state (e.g., circular, elliptical) can, in principle, be created that is aligned along any desired direction in a plane perpendicular to the propagation direction. After calibrating the tuneable nematic device with a He-Ne laser that has a well-defined polarization state, control of the LC laser polarization is then demonstrated, where it is shown that different polarization states and orientations thereof can be obtained by changing the relative combination and amplitudes of the voltages applied to each of the four electrodes. It is found, however, that achieving a pure linear polarization state is challenging, which may indicate that the polarization from the LC laser is not a well-defined circularly polarized state. These thin-film LC lasers with full polarization control are potentially important for a variety of different applications ranging from the biomedical to the display industries.