Biphotonically and electrically controllable lasing emissionin a laser-dye-doped holographic polymer-dispersed liquid crystal grating with an azo-dye dopant

• Main Authors: HUAI-PEI TONG, 童槐培
• Other Authors: Chia-Rong Lee
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/42213252631325210661

碩士 === 國立成功大學 === 光電科學與工程研究所 === 97 === This study demonstrates the electric and biphotonic controllability of the lasing emission based on the holographic dye-doped polymer-dispersed liquid crystal (H-DDPDLC) films. Experimental results show that the lasing emission decreases with increasing either the amplitude of the applied voltage or the intensity of the incident cw green beam. This is attributable to two factors. One is the decrease of the absorption of the laser dyes and thus the intensity of the emitted fluorescence. Another is the decay of the difference between the refractive indices in liquid crystal-rich and polymer-rich regions and thus the coupling coefficient of the fluorescence. The two factors cause the decay of the lasing emission. The difference operated in the two ways is that the applied field will align LC to be normal to the substrates of the cell and the illumination of the incident cw green beam will transform azo-dyes to bended cis-isomers to disturb the LC into isotropic phase. Furthermore, if the intensity of a strong red beam irradiated on the green-beam-illuminated cell gradually increases, the cis-dyes will cis–trans back isomerized to trans-state such that the isotropic LC can gradually return back the nematic phase and thus the lasing emission can gradually recovery.