ABSTRACT
Gratings ........................................................................................... 150 7.3.2 LC Droplet-Like Morphologic HPDLC Reection Gratings ........................................................................................... 152 7.3.3 Polymer Shrinkage ........................................................................ 155 7.3.4 Polymer Scaffolding Morphologic HPDLC Transmission
Gratings ........................................................................................... 156 7.3.5 Sliced Polymer Morphologic Transmission HPDLC Gratings ........................................................................................... 160 7.3.6 Degree of Phase Separation .......................................................... 162
7.4 HPDLC Applications for Organic Lasers ............................................... 162 7.4.1 Lasers ............................................................................................... 163 7.4.2 HPDLCs for External Feedback Elements .................................. 163 7.4.3 HPDLCs for DFB Laser Cavities .................................................. 163 7.4.4 2D HPDLCs for DFB Lasers.......................................................... 166 7.4.5 HPDLCs as External Feedbacks ................................................... 167 7.4.6 HPDLCs for Multiwavelength DFB Lasers ................................ 168 7.4.7 Electrically Tunable HPDLC Lasers ............................................ 169
7.5 Conclusions ................................................................................................. 173 References ............................................................................................................. 174
Polymers and liquid crystals (LCs) are intensively used for various optical devices. They are convenient to process and easy to integrate with other optical components [1-7]. LCs have liquid-like uidity and crystal-like molecular order in which the optical and electrical properties along the direction parallel and perpendicular to the LC molecule are anisotropic. This unique property makes LC devices easily respond to external elds such as electric eld, temperature, mechanical force, and magnetic or optical eld [8-18]. The combination between LCs and functional polymers can bring more opportunities for novel practical applications [19-22]. The LC and polymer systems or composites are mainly divided into two classes: polymer-dispersed liquid crystals (PDLCs) [23,24] and polymer-stabilized liquid crystals (PSLCs) [25-28]. In PDLCs, the LC exists in the polymer matrix in the form of microsized droplet. The concentration of LC is from 20 to 80 wt %. In PSLCs, the LC forms a continuous medium, while the polymer is in the form of a ber-like or sponge-like structure. The concentration of LC is usually less than 10 wt %.
