Position sensitive, continuous wavelength tunable laser based on photopolymerizable cholesteric liquid crystals with an in-plane helix alignment Applied Physics Letters 94, 093306 (2009);

A highly efficient photonic band edge dye-doped cholesteric liquid crystal (CLC) laser is demonstrated. By sandwiching an active CLC cell within a resonator consisting of two passive CLC reflectors, the lasing efficiency is dramatically enhanced. Theoretical analysis using the improved 4x4 transfer matrix and scattering matrix shows that the band edge laser mode can be supported by the external CLC resonator and its optimal output can be achieved by a relatively thin active CLC layer and thin passive CLC reflectors. Theoretical analysis agrees well with the experimental results.

We demonstrate a direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal (CLC) in a homogeneous cell coated with a metallic mirror on the inner side of a glass substrate. Due to coherent superposition of two orthogonal polarization states, the output laser light becomes linearly polarized and its output energy is greatly enhanced. Moreover, the linear polarization direction angle is proportional to the product of the CLC effective birefringence and cell gap. Hence direction tunable laser devices can be demonstrated by controlling the cell gap and the operating temperature.

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