Improvement in rise time of liquid crystals with patterned benzocyclobutene as alignment layer for photonic applications

Liquid crystal (LC) response time plays a crucial role on the switching of the LC-based devices in photonic applications. It is significantly influenced by the surface structure of the substrate. Therefore, an alignment layer is typically deposited to give a preferred direction to the LC molecules in contact to the surface. In this paper, the rise time of LC on a patterned benzocyclobutene (BCB) was studied and compared with that on a conventional rubbed polyimide (PI) alignment layer. A faster rise time was achieved for the LC cell with patterned BCB alignment layer than that of PI alignment layer. The shortest rise time (tr) reached in our study is 0.06 ms for LC aligned on the patterned BCB layer and 0.18 ms for rubbed PI layer under a field strength of 3.3V/μm for a LC film thickness of 3μm. Therefore the patterned BCB as alignment layer is very potential in the LC based polymer waveguide devices. When the BCB can act both as waveguide materials and alignment materials, the technique also can reduce a fabrication step of LC based polymer waveguide devices. Thus the study can enhance the application of LC based optical waveguide devices for photonics technology.