Origins of Kerr phase and orientational phase in polymer-dispersed liquid crystals

Polymer-dispersed liquid crystals (PDLCs) modulate the amplitude and optical phase of light. The optical phase modulation of PDLC can be dissected into two parts: Kerr phase and orientational phase according to the electro-optical (EO) response. We investigated the origins of the Kerr and orientational phases in PDLCs and their connection with the two-step EO response. The Kerr phase is attributed to LC orientation in the center of LC droplets. The orientational phase results from orientation of LC molecules near LC-polymer interfaces. Both phases can be adjusted by varying the droplet size. The two-step EO response in small droplets (<333 nm) is related to the Kerr and orientational phases, and possibly to rotation of point defects. A modified PDLC model considering the Kerr and orientational phases is proposed. Our findings suggest the possibility of versatile photonic devices using pure optical phase modulation.