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Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 16: POSTER: Computational Physics, Complex Systems

CPP 16.35: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Optical microresonators formed by cholesteric liquid crystals — •Jürgen Schmidtke1, Werner Stille1, and Heino Finkelmann21Physikalisches Inst., Albert-Ludwig-Universität, Freiburg — 2Inst. für Makromolekulare Chemie, Albert-Ludwig-Universität, Freiburg

Due to the periodic helical order of the mesogens, cholesteric liquid crystals (CLCs) act as polarization-sensitive, one dimensional photonic crystals. Indeed, modified fluorescence as well as photonic band edge lasing of dye doped CLCs has been repeatedly demonstrated.

In an analytical treatment[1], we discuss different ways to realize cholesteric optical microresonators by introducing artficial defects in the helical molecular order. A conventional defect can be realized, if one interrupts the cholesteric helix by an optically isotropic defect layer: the defect layer acts as the resonator cavity, which is sandwiched between dielectric mirrors formed by the cholesteric medium. A unique photonic defect can be realized in a CLC by an abrupt phase jump in the cholesteric helix (‘twist defect’[2]). A combination of defect layer and twist defect allows for an independent tuning of resonance frequency and resonator quality. We discuss the optics of these defects and the drastic effect of a finite sample thickness on the polarization properties of the resonant modes, and compare our findings with experimental results on the twist defect mode laser emission[3] of a polymeric CLC film.

[1] J. Schmidtke and W. Stille, Eur. Phys. J. E (in press)

[2] V. I. Kopp and A. Z. Genack, PRL 89, 083902 (2002)

[3] J. Schmidtke, W. Stille, and H. Finkelmann, PRL 90, 083902 (2003)

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