Limits...
Tunable terahertz fishnet metamaterials based on thin nematic liquid crystal layers for fast switching.

Zografopoulos DC, Beccherelli R - Sci Rep (2015)

Bottom Line: A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values.Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components.Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications.

View Article: PubMed Central - PubMed

Affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM), Roma 00133, Italy.

ABSTRACT
The electrically tunable properties of liquid-crystal fishnet metamaterials are theoretically investigated in the terahertz spectrum. A nematic liquid crystal layer is introduced between two fishnet metallic structures, forming a voltage-controlled metamaterial cavity. Tuning of the nematic molecular orientation is shown to shift the magnetic resonance frequency of the metamaterial and its overall electromagnetic response. A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values. Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components. Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications.

No MeSH data available.


Effective metamaterial index calculated at the (a) high and (b) low resonant frequencies of the fishnet metamaterials for various geometrical parameters and for both limiting cases of the LC alignment (legend as in Fig. 5).The shaded areas indicate the available tunability range offered by the selected nematic material.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4536660&req=5

f6: Effective metamaterial index calculated at the (a) high and (b) low resonant frequencies of the fishnet metamaterials for various geometrical parameters and for both limiting cases of the LC alignment (legend as in Fig. 5).The shaded areas indicate the available tunability range offered by the selected nematic material.

Mentions: The main observations concluded for this specific design (W = 110 μm and w = 40 μm) are also valid when the MM structural parameters are varied. The resonant frequencies as a function of W and w for the investigated LC-THz-MM are shown in Fig. 5, for both limiting cases of the LC alignment. The shaded areas indicate the tunability range achievable by switching between the two LC states, showing that tuning ranges higher than 200 GHz are possible for the selected nematic material. The corresponding variations of the effective MM index are shown in Fig. 6, calculated at the two resonant frequencies fH and fL, which correspond to the rest and fully switched cases, respectively. The MM index at fL is slightly positive when the MM is off-resonance and obtains a large negative value on-resonance, revealing the possibility for continuous tuning from positive to zero and finally negative values. The corresponding behaviour at fH is more complex, since the exact value of w determines the position of fco and therefore the sign of the MM index.


Tunable terahertz fishnet metamaterials based on thin nematic liquid crystal layers for fast switching.

Zografopoulos DC, Beccherelli R - Sci Rep (2015)

Effective metamaterial index calculated at the (a) high and (b) low resonant frequencies of the fishnet metamaterials for various geometrical parameters and for both limiting cases of the LC alignment (legend as in Fig. 5).The shaded areas indicate the available tunability range offered by the selected nematic material.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4536660&req=5

f6: Effective metamaterial index calculated at the (a) high and (b) low resonant frequencies of the fishnet metamaterials for various geometrical parameters and for both limiting cases of the LC alignment (legend as in Fig. 5).The shaded areas indicate the available tunability range offered by the selected nematic material.
Mentions: The main observations concluded for this specific design (W = 110 μm and w = 40 μm) are also valid when the MM structural parameters are varied. The resonant frequencies as a function of W and w for the investigated LC-THz-MM are shown in Fig. 5, for both limiting cases of the LC alignment. The shaded areas indicate the tunability range achievable by switching between the two LC states, showing that tuning ranges higher than 200 GHz are possible for the selected nematic material. The corresponding variations of the effective MM index are shown in Fig. 6, calculated at the two resonant frequencies fH and fL, which correspond to the rest and fully switched cases, respectively. The MM index at fL is slightly positive when the MM is off-resonance and obtains a large negative value on-resonance, revealing the possibility for continuous tuning from positive to zero and finally negative values. The corresponding behaviour at fH is more complex, since the exact value of w determines the position of fco and therefore the sign of the MM index.

Bottom Line: A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values.Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components.Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications.

View Article: PubMed Central - PubMed

Affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM), Roma 00133, Italy.

ABSTRACT
The electrically tunable properties of liquid-crystal fishnet metamaterials are theoretically investigated in the terahertz spectrum. A nematic liquid crystal layer is introduced between two fishnet metallic structures, forming a voltage-controlled metamaterial cavity. Tuning of the nematic molecular orientation is shown to shift the magnetic resonance frequency of the metamaterial and its overall electromagnetic response. A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values. Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components. Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications.

No MeSH data available.