Position sensitive, continuous wavelength tunable laser based on photopolymerizable cholesteric liquid crystals with an in-plane helix alignment

Position sensitive lasing with continuous wavelength tunability and emission in the cell-plane direction is demonstrated from a photopolymerized cholesteric liquid crystal film. The device has a gradually dilating helix lying in the cell-plane direction and is fabricated by applying a vertical electric field in a conventionally rubbed wedge cell while cooling the sample from the isotropic phase. Tuning range of similar to 100 nm is achieved by translating the device with respect to the pump beam. Photopolymerizable materials are especially useful in this configuration since a freestanding film, not requiring any external voltage to maintain the molecular ordering, can be prepared.