Tong Huai-Pei, Li Yu-Ren, Lin Jia-De, Lee Chia-Rong
Institute of Electro-Optical Science and Engineering and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan 701, Republic of China.
Opt Express. 2010 Feb 1;18(3):2613-20. doi: 10.1364/OE.18.002613.
This work demonstrates, for the first time, an all-optically controllable distributed feedback (DFB) laser based on a dye-doped holographic polymer-dispersed liquid crystal (DDHPDLC) grating with a photoisomerizable dye. Intensity of the lasing emission can be reduced and increased by raising the irradiation intensity of one CW circularly-polarized green beam and the irradiation time of one CW circularly-polarized red beam, respectively. The all-optical controllability of the lasing emission is owing to the green-beam-induced isothermal nematic-->isotropic and red-beam-induced isothermal isotropic-->nematic phase transitions of the LCs via trans-->cis and cis-->trans back isomerizations of the azo-dye, respectively, in the LC-droplet-rich regions of the grating. The former (latter) mechanism can reduce (increase) the index modulation and thereby the coupling strength in the DFB grating, resulting in the decay (rise) of the lasing emission. Thermal effect is excluded from possible mechanisms causing such an optical controllability of the lasing emission.
这项工作首次展示了一种基于掺杂染料的全息聚合物分散液晶（DDHPDLC）光栅和光致异构染料的全光可控分布反馈（DFB）激光器。通过分别提高一束连续波圆偏振绿光的辐照强度和一束连续波圆偏振红光的辐照时间，可以降低和增加激光发射的强度。激光发射的全光可控性归因于在光栅富含液晶微滴的区域中，通过偶氮染料的反式→顺式和顺式→反式反向异构化，绿光诱导的液晶等温向列相→各向同性相转变以及红光诱导的液晶等温各向同性相→向列相转变。前一种（后一种）机制可以降低（增加）折射率调制，从而降低（增加）DFB光栅中的耦合强度，导致激光发射衰减（增强）。热效应被排除在导致激光发射这种光可控性的可能机制之外。
