Nonlinear Optical Effects in Liquid Crystals.
Abstract
D.C.-field induced optical second-harmonic generation in nematic and cholesteric liquid crystals is investigated. In addition, flexo-electric induces second-harmonic generation in nematic MBBA is studied. The experiments involve the detection of optical radiation at second-harmonic frequency when aligned thin film liquid crystals samples are irradiated with laser beam at the fundamental frequency. The laser used in a Q-switched Nd-YAG laser. Sample alignment is achieved either with rubbing technique or by coating glass spacers with 100 A thick of Si2. Experiments on nematic liquid crystals show that the temperature dependence of nematic order parameters can be obtained from the measurement of d.c.-induced second-harmonic generation. It is also demonstrated that flexoelectric effect can give rise to second-harmonic generation in nematic liquid crystal and the birefringence of nematic crystal can be used to achieve phase-matching. In the cholesteric liquid crystal, it is demonstrated that the lattice momentum associated with the one dimensional periodicity of cholesteric structure can be used to achieve phase-matching. Comparison of the measured temperature dependence of nematic order parameters with the predictions of the existing statistical theories of nematic ordering indicates that these theories are not quantitatively reliable. The phase-matchability of liquid crystals shows that these media may be useful as practical optical harmonic generators. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 10, 1980
- Accession Number
- ADA095368
Entities
People
- George K. Wong
Organizations
- Northwestern University