This book covers the most important results of studying liquid crystal microlasers for the last decade although the pioneering works on this type lasers have been made much earlier (for the history see Chapter 1). In fact, it is the first book on the subject. The main part of the book deals with low-threshold distributed feedback lasers on dye-doped cholesteric liquid crystals. These are helical materials that possess intrinsic periodicity and manifest optical properties of one-dimensional photonic crystals easily controllable by external factors such as temperature, mechanical stress, UV radiation, electric field, etc. The problems of tuning frequency, polarization and directionality of laser light and some technological aspects are discussed in Chapters 2, 4, 11 and 13. A review of pioneering works on lasing from dye-doped helical liquid crystal polymers is presented in Chapter 7. The laser effects in the cholesteric blue phase that is, in fact, the genuine three-dimensional photonic crystal, are described in Chapters 12 and 13. A special attention has been paid to investigations of the so-called defect modes (Chapters 2 and 4).
The break of ideal periodicity of the helix of a cholesteric liquid crystal creates extraordinary narrow transmission bands in the otherwise forbidden photonic stop-band. Within these spectral lines the lasing threshold is especially low. The problems of the laser threshold and other theoretical issues are discussed in Chapters 1, 6, 8 and 12 whereas Chapter 9 makes an accent on the enhancement of the output efficiency of cholesteric microlasers. Nematic liquid crystals are very sensitive to electric field but they are not periodic.
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