Self-phase modulation in azo-dye-doped liquid crystal films

Andy Ying-Guey Fuh; Chia-Wei Chu; Hui-Chi Lin; Hung-Chang Jau; Ming-Shian Li

doi:10.1117/12.859242

17 August 2010 Self-phase modulation in azo-dye-doped liquid crystal films

Andy Ying-Guey Fuh, Chia-Wei Chu, Hui-Chi Lin, Hung-Chang Jau, Ming-Shian Li

Proceedings Volume 7775, Liquid Crystals XIV; 777505 (2010) https://doi.org/10.1117/12.859242
Event: SPIE Photonic Devices + Applications, 2010, San Diego, California, United States

Abstract

This work studies photo-induced reorientation in azo-dye-doped liquid crystal (ADDLC) films by observing the diffraction patterns produced by self-phase modulation (SPM). The experimental results show that not only the magnitude but also the sign of the refractive index change (Δn) of an ADDLC sample pumped by a green laser can be modulated by the beam intensity (IG). The reason is that different IG give rise to different trans/cis concentration ratios, and then induce different overall torques on LC molecules. The trans and cis isomers contribute negative and positive torques, respectively, that reorient LC molecules perpendicular and parallel to the polarization of the pump laser. The reorientation effect in the ADDLC sample illuminated by the biphotonic lasers (green and red lasers) is also investigated by observing the self-phase modulation diffraction pattern. The results indicate that red light can induce |Δn| to decrease and increase at low and high IG, respectively. Besides, the dye-induced torque can be changed from negative to positive by adding red light. This is due to the fact that cis isomers produce an extra positive torque to the LCs after absorbing red light.

Citation Download Citation

Andy Ying-Guey Fuh, Chia-Wei Chu, Hui-Chi Lin, Hung-Chang Jau, and Ming-Shian Li "Self-phase modulation in azo-dye-doped liquid crystal films", Proc. SPIE 7775, Liquid Crystals XIV, 777505 (17 August 2010); https://doi.org/10.1117/12.859242

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