Experimental Measurement of Temperature-Dependent Thermo-optical Parameters of Different Types of Olive Oil Using Terahe
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Experimental Measurement of Temperature-Dependent Thermo-optical Parameters of Different Types of Olive Oil Using Terahertz Time-Domain Spectroscopy Muhammad Mumtaz1,2 · M. Ahsan Mahmood1,2 · Arslan Shahzad1 · Sabih D Khan1 · M. Aslam Zia1 · Mushtaq Ahmed1 · Izhar Ahmad1 Received: 23 July 2019 / Accepted: 1 June 2020 / © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Terahertz time-domain spectroscopy has been used for the characterization of different types of olive oil, such as extra virgin, pure, extra light, and pomace olive oils. Temperature-dependent refractive indices and absorption coefficients have been measured in 0.2–1.6 THz spectral-frequency range. Temperature-dependent Sellmeier coefficients and thermo-optic coefficients of these oil samples have also been derived from the measured data. These results will benefit different oil-based optical devices requiring accurate knowledge of their refractive indices in THz range. Keywords Olive oil · Sellmeier coefficient · Refractive index · Terahertz time-domain spectroscopy · Absorption coefficient
1 Introduction Terahertz (THz) radiations are widely used in spectroscopy, imaging & sensing [1, 2], material characterization [3–7], industry [8], and defense applications [9]. For practical realization of such applications, the functional devices such as switches, filters, modulators, and polarizers are of vital importance. Different materials such as semiconductors [10, 11], polymers [12], and liquid crystals (LC) [13–15] have been tested for such applications, whose working principle is based on the modulation of refractive index. The liquid crystals in nematic phase with higher birefringence are actively being used for such applications in THz as well as in other spectral Izhar Ahmad
[email protected] 1
National Institute of Lasers & Optronics College (NILOP-C), Islamabad, Pakistan
2
Pakistan Institute of Engineering & Applied Sciences, Islamabad, Pakistan
International Journal of Infrared and Millimeter Waves
regimes [13–16]. Magnetically controlled birefringence of liquid crystals (E7, 5CB) has been employed to demonstrate the THz switches, band-pass filters and phase shifters [13–15]. Tsong-Ru Tsa et al. have demonstrated THz phase shifter with variation of electric field in the range of 0 to 600 V/cm on 5CB LC [17]. Modulation of refractive index of liquid crystal with temperature has also been employed for such devices [16]. However, for practical applications of such devices, cost is also a factor. There is an increasing demand for the replacement of these expansive elements with the effective and cheaper equivalents. Major constituents of olive oil, such as phospholipids, cholesterol, glycolipids, and fatty acids, behave as a lyotropic liquid crystal in nematic phase [18] and exhibit considerably high birefringence with potential applications as photonic liquid crystals for the optical communication [18], electro-optic (EO) devices and broad band waveguides [19, 20]. The modulation of refractive index of olive
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