Liquid-Crystals for Tunable Photonic Crystals, Frequency Selective Surfaces and Negative Index Material Development

Abstract

In the second approach, we calculated a change in the position of minimum of the real part of the refractive index against frequency. For molecules orientation along z-direction, the n Re reaches minimum value at f zmin 5 85.2 GHz while for x direction at f xmin 5 83.7 GHz. The relative change in the resonance position is of about 1.8% (Fig. 7). This feature of the proposed cell can be used for building a tunable filter for applications in M band. CONCLUSIONWe proposed a novel design of the tunable metamaterial cell with TWs used as electrodes for IPS, which has negative real part of the refractive index in M band. Realistic geometric and material parameters were assumed, which makes fabrication of the proposed cell feasible with available technology. The tunability of the design was validated using numerical simulations. The relative change of real part of the refractive index reaches 59.5%. It makes it possible to use the proposed cell as a phase shifter operating in M band.ABSTRACT: A microstrip triangular-ring antenna structure designed using the log-periodic principle has been proposed. The antenna elements and the feeding networks have been designed and the antenna simulations are done using Ansoft HFSS software. Shorting posts have been used at the center of the edges of the ring to adjust the shift in the resonant frequency. The simulated and tested results show that the ring antenna with three posts resonated at the same frequency as the triangular patch giving an enhanced gain and a size reduction of 81%. A log periodic array of three triangular rings is also designed and analyzed which gives a good frequency independent behavior in the frequency range of 6.6-11.6 GHz. V C 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:41-46, 2014; View this article online at wileyonlinelibrary.com.

Experimental study of thermally controlled metamaterial containing a liquid crystal layer at microwave frequencies

“…Introducing them into the periodic structure * Corresponding author. Email: rkowerdziej@wat.edu.pl of a metamaterial allows its parameters to be tuned [2][3][4]. Tunability of the liquid crystalline layer in our study was achieved by applying a temperature field ( Figure 1).…”

Transient responses of liquid crystals for optical switching with microseconds: nanoseconds response speed

“…Due to their fluidity and large birefringence that extends from optical to very long wavelength regime, nematic liquid crystals (NLC) have become a favorite material for incorporation into various photonic structures including photonic crystal inverse opals 24 , frequency selective surfaces 25 , channel waveguide and micro-ring resonator 26,27 , nanostructured plasmonic and metamaterials [28][29][30][31][32][33][34][35] . By inclusion of dye or azo-molecular dopants, and a variety of plasmonic nmparticulates, enhanced nonlinear or electro-optics response as well as metamaterials with emergent properties have been obtained 6,32 .…”

MULTIPLE TIME SCALES OPTICAL NONLINEARITIES OF LIQUID CRYSTALS FOR OPTICAL-TERAHERTZ-MICROWAVE APPLICATIONS (Invited Review)

“…The requirement of strong boundary surface anchoring/alignment to fabricate NLC cells invariably creates an immobile layer, c.f. Figure 13(a) that tends to diminish the overall response of the NLC-infiltrated structures such as inverse opal photonic crystal or micro-ring resonator [7,11]. In complex non-planar structures with numerous tight corners and crevices such as fishnet or splitring metamaterials other sub-wavelength structures and resonators [12][13][14][15][16][17][18][19][20][21][22][23][24][25] non-uniform director axis alignment, c.f.…”

“…The fluid nature of NLC's and their compatibility with other widely used materials ranging from semiconductors to polymers and plasmonics (metals) enable easy integration of such 'crystal' into a large assortment of non-planar structures ranging from nm-sized photonics elements [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] such as inverse opal photonic crystals and plasmonic/metamaterial structures, c.f. Figures 2(c)-(d), to millimeter-or bulkier microwave devices for tunable -delay line, -phase shifter, -wavelength selector and beam steering devices [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], to name a few.…”