Browsing by Author "Zhang, XC"

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Electrically controlled room temperature terahertz phase shifter with liquid crystal
(2004-02-01)
Tsai, TR
;
Chen, CY
;
Pan, RP
;
Pan, CL
;
Zhang, XC
We present the use of electrically controlled bire-fringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves up to terahertz frequencies. This device. was operated at room temperature and a maximum phase shift of 4.07degrees was demonstrated at 1.07 THz when the interaction length was 38.6 mum. The driving voltage and corresponding field were 176.8 V (rms) and 589.3 V/cm, respectively.
Terahertz time-domain spectroscopy studies of the optical constants of the nematic liquid crystal 5CB
(2003-05-01)
Tsai, TR
;
Chen, CY
;
Pan, CL
;
Pan, RP
;
Zhang, XC
The optical constants of a nematic liquid crystal, 4'-n-pentyl-4-cyanobiphenyl (5CB), in the frequency range 0.3-1.4 THz were determined by terahertz (THz) time-domain spectroscopy. The real parts of the extraordinary refractive index n(e) and the ordinary refractive index n(o) of 5CB varied from 1.74 to 2.04 and from 1.59 to 1.83, respectively. Liquid-crystal 5CB exhibits a relatively small absorption loss in this frequency range. The birefringence of 5CB was found to be as large as 0.21. The experimental results indicate that liquid-crystal 5CB is potentially useful for device applications in the THz frequency range. (C) 2003 Optical Society of America.