• NARINDER KUMAR

      Articles written in Pramana – Journal of Physics

    • Effective optical properties of the one-dimensional periodic structure of $\rm{TiO_{2}}$ and $\rm{SiO_{2}}$ layers with a defect layer of nanocomposite consisting of silver nanoparticle and E7 liquid crystal

      PAWAN SINGH KHEM B THAPA NARINDER KUMAR DEVENDRA SINGH DEVESH KUMAR

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      In this work, the dielectric property of a nanocomposite (NC) consisting of silver nanoparticle and E7 liquid crystal (LC) has been investigated theoretically at different temperatures. The study shows that the surface plasmon resonance (SPR) and filling fraction of the silver nanoparticle significantly change the dielectric property of the NC. To study the optical property of the defective periodic structure, the NC was considered as a defect layer in a semifinite one-dimensional periodic structure (1DPS) of $\rm{TiO_{2}}$ and $\rm{SiO_{2}}$ layers, i.e. $\rm{(TiO_{2}|SiO_{2})^{5}|NC|(TiO_{2}|SiO_{2})^{5}}$. The optical properties of the 1DPS with the NC as the defect layer have been studied by the simple transfer matrix method (TMM). Moreover, the transmission and absorption characteristics of the 1DPS in the presence of silver nanoparticle in the NC have been studied with different orientations of the LC molecule.

    • Even–odd effect of the homologous series of nCHBT liquid crystal molecules under the influence of an electric field: A theoretical approach

      NARINDER KUMAR SHIVANI CHAUDHARY PRANAV UPADHYAY A K DWIVEDI DEVESH KUMAR

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      In this work, we present the effect of electric field on 4-(trans-4$^\prime$-n-alkyl-cyclohexyl) isothiocyanatebenzene(nCHBT) liquid crystal (LC) molecules. Under the influence of an electric field, the birefringence exhibits the even–odd effect while order parameter, HOMO–LUMO gap, magic angle, isotropic polarisability, range of director angle and the refractive index do not exhibit any even–odd effect. The extension of the alkyl chain length of the nCHBT liquid crystal molecule exhibits the even–odd effect for the dipole moment and temperature from nematic to isotropic phase transition while the HOMO–LUMO gap remains constant. Still, order parameters, isotropic polarisability and refractive index have continuously increased. The odd carbon atom numbers present higher values than the even carbon atom numbers of the alkyl chain for the phase transition temperature. The nCHBTLC molecule expresses the order parameter, and birefringence is reciprocal to each other. For the whole series, there is an increase in order parameter, and a decrease in birefringence. The influence of the external electric field is analternative to the temperature for the optical parameter of nCHBT LC.

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