Tunable metamaterial
Liquid crystal tuning for metamaterials
Liquid crystal tuning for metamaterials
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### Liquid crystal metamaterial tunable in the near\-infrared

Tuning in the near infrared range is accomplished by adjusting the [permittivity](/wiki/Permittivity "Permittivity") of an attached [nematic liquid crystal](/wiki/Nematic_phase "Nematic phase"). The liquid crystal material appears to be used as both a [substrate](/wiki/Substrate_%28materials_science%29 "Substrate (materials science)") and a jacket for a [negative index metamaterial](/wiki/Negative_index_metamaterial "Negative index metamaterial"). The metamaterial can be tuned from [negative index](/wiki/Refractive_index "Refractive index") values, to zero index, to positive index values. In addition, negative index values can be increased or decreased by this method.

### Tunability of wire\-grid metamaterial immersed into nematic liquid crystal

Sub\-wavelength metal arrays, essentially another form of metamaterial, usually operate in the microwave and optical frequencies. A liquid crystal is both transparent and anisotropic at those frequencies. In addition, a liquid crystal has the inherent properties to be both intrinsically tunable and provide tuning for the metal arrays. This method of tuning a type of metamaterial can be readily used as electrodes for applying switching voltages.

### Tuning NIMs with liquid crystals

Areas of active research in optical materials are metamaterials that are capable of negative values for index of refraction (NIMs), and metamaterials that are capable of zero index of refraction (ZIMs). Complicated steps required to fabricate these nano\-scale metamaterials have led to the desire for fabricated, tunable structures capable of the prescribed spectral ranges or resonances.

The most commonly applied scheme to achieve these effects is *electro\-optical tuning*. Here the change in refractive index is proportional to either the applied electric field, or is proportional to the [square modulus](/wiki/Square_modulus "Square modulus") of the electric field. These are the [Pockels effect](/wiki/Pockels_effect "Pockels effect") and [Kerr effect](/wiki/Kerr_effect "Kerr effect"), respectively. However, to achieve these effects electrodes must be built\-in during the fabrication process. This introduces problematic complexity into material formation techniques. Another alternative is to employ a nonlinear optical material as one of the constituents of this system, and depend on the optical field intensity to modify the refractive index, or magnetic parameters.

### Liquid crystal tuning of silicon\-on\-ring\-resonators

Ring resonators are optical devices designed to show resonance for specific wavelengths. In silicon\-on\-insulator layered structures, they can be very small, exhibit a high [Q factor](/wiki/Q_factor "Q factor") and have low losses that make them efficient wavelength\-filters. The goal is to achieve a tunable refractive index over a larger bandwidth.


Can negative index metamaterials have effects on physical properties beyond refractive index?