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Liquid crystal lasers

  1. Oct 14, 2012 #1
    I'm writing an essay on liquid crystal lasers and have written the intro to my paper. Can I just double check with you all that I haven't written anything that's wrong? Thanks. Please let me know if I should also post the source I used. It's the first time I've posted something qualitative so not sure if I'm compiling with the rules here at physics forum.



    1 Introduction

    Liquid crystals (LCs) have important properties such as fluidity and positional order. The former property enables control of polarization of light passing through LCs by altering the optical birefringence using external electric fields. The latter, due to chirality, is responsible for LCs’ photonic qualities. A common type of photonic LCs used in lasers is cholesteric LCs (CLCs)[1]. CLCs display reflection in accordance to the Bragg effect, where the refractive index changes periodically. From the dispersion relation, it can be deduced that constructive interference occurs only when the wavelength is equal to chiral pitch. Also, the helical structure determines the reflection of either left or right-handed circular polarized light. Since CLCs are anisotropic, the rate R of photon emission is given by:

    R=M|E.μ|^2 (1)

    where M is the density of state for corresponding eigenstate E and μ is the dipole moment. To optimize lasing, it is ideal for R to be large. Therefore, R is maximized by CLCs’ anisotropic geometry, such that E is parallel to μ.
     
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