The birefringence and extinction coefficient of positive and negative liquid crystals in the terahertz range

ABSTRACT

Birefringence and extinction coefficients of positive nematic liquid crystal (NLC) MLC-2142 and negative NLC BHR28000-400 are measured by terahertz time-domain spectroscopy system (THz-TDS). Frequency ranging from 0.1 to 0.6 THz, the birefringence of positive NLC MLC-2142 increases with the increase of frequency, and keeps larger than 0.23, which exhibits application potential in tunable broadband LC THz device where a large birefringence is required. In contrast, the birefringence of BHR28000-400 decreases with the increased frequency, which shows a completely different optical property from the positive NLC. The extinction coefficient of the above two kinds of liquid crystals are also investigated.

Graphical Abstract

KEYWORDS:

• Positive liquid crystals
• negative liquid crystals
• birefringence
• THz

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [Project No. 61405088]; Basic Research of Shenzhen Science and Technology Innovation Council [Project No. JCYJ20150601155130435]; Returned Overseas Research Project Start-up Grant of Ministry of Education; Peacock Talent Programs Research Start-up Grant of Shenzhen Science and Technology Innovation Council.