Optically induced birefringence in dye-doped blue phase liquid crystals

ABSTRACT

This paper investigates the photoinduced change of refractive index in dye (methyl red, MR)-doped blue phase (DDBP) cells by illumination of a pump beam. Through excitation of light irradiation with proper photon energy, MR can transform from trans-state to cis-state and successively diffuse and anisotropically adsorb on the inner glass substrate of the DDBP cell along the direction perpendicular to the polarisation of the pump beam. The adsorbed MR molecules can effectively rotate the orientation of the liquid crystal (LC) molecules and thereby modulate the effective refractive index of the DDBP cell. The SEM images of the adsorbed regions of the illuminated DDBP samples were also taken for discussing the relation between the pump intensity and the photoinduced birefringence.

Graphical Abstract

KEYWORDS:

• Adsorption
• blue phase
• azo-dye
• photoalignment

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research is financially supported by Clinical Research grants from Kaohsiung Armed Forces General Hospital, Taiwan [No. 106-16] and the Ministry of Science and Technology of Taiwan (Contract number: MOST 103-2112-M-006-012-MY3).