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Enhancing the laser power by stacking multiple dye-doped chiral polymer films.

We demonstrate a method for enhancing the laser efficiency by stacking multiple dye-doped chiral polymer films. No laser emission was observed from a single 8 mum film. By stacking two films together, the laser efficiency is dramatically enhanced. Further increasing the number of stacked films, the output laser power is further increased. It is also observed that the output laser power in the forward direction is almost the same as that in the backward for the two- and three-layered films. However, in the six-layered film the output laser power is much stronger in the backward direction than the forward one. This is due to the absorption of the laser dyes and the distributed feedback in the chiral polymer films.