Optical-induced Freedericksz transition of nematic liquid crystal doped with porphyrin (ZnTPP)

In this Letter, we studied the optical-induced Freedericksz transition of 5CB doped with 1% volume fraction of bio-molecule, porphyrinozinc(II) (ZnTPP). Excited by Ti:sappire laser with the 82 MHz repetition rate and 100 fs pulse duration, the optical Freedericksz threshold of a 23.6 μm-thickness planar alignment sample occurred at an intensity level of 0.35 mW/mm2 in contrast to the normally observed 83 mW/mm2 value for pure 5CB.