Infrared Liquid Crystal Tunable Frequency Selective Surfaces

Abstract

In this paper, micron-scale metallodielectric and all-dielectric frequency selective surfaces (FSS) are synthesized with a liquid crystal (LC) superstrate to exhibit broadband tunable filter characteristics at mid-infrared (IR) wavelengths. The low loss and birefringence properties of LC span the visible to far-IR spectrum, providing potential for the development of a new class of infrared/optical switches. I. IntroductionThere is currently interest in developing tunable filters and switches for infrared (IR) and optical applications. Previous research has demonstrated the synthesis of frequency selective surfaces (FSS) for use as infrared (IR) band-reject and band-pass filters with applications in various IR signal-processing devices. Single-layer metallodielectric FSS have been synthesized and fabricated using fractal and genetic algorithm techniques to exhibit multiband filter responses in the far-IR [1,2]. Fabrication constraints were developed and incorporated within the genetic algorithm synthesis procedure to achieve designs that could be accurately fabricated [3]. For applications at optical wavelengths, the metallic losses start to affect the performance of metallodielectric FSS filters. Thus, for optical applications, all-dielectric frequency selective surfaces (DFSS) can be synthesized as planar, polarization insensitive filters [4]. The frequency responses of these metallodielectric and all-dielectric FSS can be altered by incorporating a tunable dielectric, such as liquid crystal (LC), into the FSS structure [5].

Electrically Tuned Microwave Devices Using Liquid Crystal Technology

“…In other reported examples, perpendicular and parallel alignment of nematic liquid crystal cells have been demonstrated for developing metamaterial structures with index of refraction tunable from negative, through zero, to positive values [58][59][60]. Although some of the reported FSSs and metamaterial structures operate at higher frequencies (e.g., terahertz), the development of new liquid crystal mixtures suggests future potential applications at microwave and millimeter-wave frequencies.…”

Characteristic Mode Design of Dual‐Band Reconfigurable Frequency Selective Surface

“…It is observed that the works in Refs. [8] and [11] have a wider operating bandwidth, but the complex technical requirements lead to a lower insertion loss (IL). Compared with the PIN diode-based RFSS in Refs.…”

“…To address these problems, the concept of reconfigurable frequency selective surface (RFSS) has been developed to enable frequency modulation or function switching. Several RFSS designs based on liquid crystals have been proposed in the literature [8,9] , with a dielectric constant that varies with bias voltage. However, the tuning ranges of liquid crystal-based RFSS are comparatively limited.…”

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

“…This shows that all-dielectric FSS have advantage over conventional metallic FSS under high power. Bossard 23 24 25 26 27 28 et al . also did impressive work in designing all-dielectric FSS at infrared or terahertz frequency using liquid crystal and single inhomogeneous dielectric layer.…”

“…also did impressive work in designing all-dielectric FSS at infrared or terahertz frequency using liquid crystal and single inhomogeneous dielectric layer. With the development of all-dielectric FSSs, tunable FSS 26 27 28 29 30 31 were further proposed and realized. These tunable FSSs are mostly based on liquid crystals, and yet some of them still need metallic screens.…”