Empirical Model of Optical Sensing via Spectral Shift of Circular Bragg Phenomenon

Mackay, Tom G.; Lakhtakia, Akhlesh

doi:10.1109/jphot.2010.2042589

Cited by 19 publications

(22 citation statements)

References 34 publications

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“…Comprising helical nanowires, CSTFs have been designed and verified to function as circular polarization filters [22] of the wideband [23,24], narrowband [25], and multiband [24] varieties. Spectral shifts of narrowband filters due to fluid infiltration have also been modeled [26] and demonstrated [27,28] for optical sensing. Very significantly, the planar interface of a CSTF and a metal has been theoretically shown [29,30] to support the propagation of multiple surface-plasmon-polariton (SPP) waves-all of the same frequency but different phase speed, attenuation rate, and field configuration-and preliminary experimental evidence [31] is promising.…”

Section: Introductionmentioning

confidence: 99%

“…The periodic nonhomogeneity of CSTFs engenders an especially interesting property not shared by homogeneous materials [39]: a CSTF can support more than one mode of SPP-wave propagation at its interface with a metal [29,30,31], thereby opening up the possibility of simultaneous detection of more than one type of analyte molecule. We note that CSTFs also offer an alternative sensing route, based on spectral shifts of the circular Bragg phenomenon brought about by the infiltrating fluid containing analytes [26], that could conceivably be harnessed in parallel with SPP-based detection to further extend the efficacy of the optical biosensing device.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Chiral Sculptured Thin Films as Platforms for Surface-Plasmonic-Polaritonic Optical Sensing

Mackay

Lakhtakia

2012

IEEE Sensors J.

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Biomimetic nanoengineered metamaterials called chiral sculptured thin films (CSTFs) are attractive platforms for optical sensing because their porosity, morphology and optical properties can be tailored to order. Furthermore, their ability to support more than one surface-plasmon-polariton (SPP) wave at a planar interface with a metal offers functionality beyond that associated with conventional SPP-based sensors. An empirical model was constructed to describe SPP-wave propagation guided by the planar interface of a CSTF -infiltrated with a fluid which supposedly contains analytes to be detected -and a metal. The inverse Bruggeman homogenization formalism was first used to determine the nanoscale model parameters of the CSTF. These parameters then served as inputs to the forward Bruggeman homogenization formalism to determine the reference relative permittivity dyadic of the infiltrated CSTF. By solving the coresponding boundary-value problem for a modified Kretschmann configuration, the characteristics of the multiple SPP modes at the planar interface were investigated as functions of the refractive index of the fluid infiltrating the CSTF and the rise angle of the CSTF. The SPP sensitivities thereby revealed bode well for the implementation of fluid-infiltrated CSTFs as SPP-based optical sensors.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling Chiral Sculptured Thin Films as Platforms for Surface-Plasmonic-Polaritonic Optical Sensing

Mackay

Lakhtakia

2012

IEEE Sensors J.

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“…The shift of the peak on infiltration of the chiral STF by an isotropic material can be predicted using a nanoscopic-to-continuum homogenization model 38 based on the Bruggeman formalism, 39 as has been shown for chiral STFs made by using a simpler process than the SBD process. 40 But chiral STFs made with the SBD process have not been characterized sufficiently well to use the same model. Nevertheless, qualitative predictions can be made.…”

Section: Resultsmentioning

confidence: 99%

On alignment of nematic liquid crystals infiltrating chiral sculptured thin films

et al. 2013

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A structurally right-handed chiral sculptured thin film (STF) with a central 90 degtwist defect was made by thermal evaporation of chalcogenide glass and the use of a serial bideposition process to exhibit a narrowband hole in the spectrum of the right-circularly polarized light reflected when right-circularly polarized light is normally incident on the chiral STF. In an attempt to build a tunable filter, the chiral STF was then infiltrated with a highly birefringent nematic liquid crystal (LC), which caused a linear reflectance peak to redshift by ∼350 nm. But the circular Bragg phenomenon exhibited by the uninfiltrated chiral STF was greatly diminished owing to the similarity in the constitutive properties of the LC and the chalcogenide glass. No temperature dependence of the shifted peak was observed, which provided clear evidence that the LC molecules are not ordered inside the chiral STF but are randomly aligned instead.

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“…But that tunability is not possible because of the random alignment of LC molecules inside the chiral STF. The shift of the peak on infiltration of the chiral STF by an isotropic material can be predicted using a nanoscopicto-continuum homogenization model [38] based on the Bruggeman formalism [39], as has been shown for chiral STFs made by using a simpler process than the SBD process [40]. But chiral STFs made with the SBD process have not been characterized sufficiently well to use the same model.…”

Section: Resultsmentioning

confidence: 99%

On alignment of nematic liquid crystals infiltrating chiral sculptured thin films

et al. 2012

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A structurally right-handed chiral sculptured thin film (STF) with a central 90º-twist defect was made by thermal evaporation of chalcogenide glass and the use of a serial bi-deposition process to exhibit a narrowband hole in the spectrum of the right-circularly polarized light reflected when right-circularly polarized light is normally incident on the chiral STF. The chiral STF was then infiltrated with a highly birefringent nematic liquid crystal (LC), which caused a linear reflectance peak to redshift by ~350 nm, but the circular Bragg phenomenon exhibited by the uninfiltrated chiral STF was greatly diminished owing to the similarity in the constitutive properties of the LC and the chalcogenide glass. No temperature dependence of the shifted peak was observed, which provided clear evidence that the LC molecules are not ordered inside the chiral STF but are randomly aligned instead.

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Empirical Model of Optical Sensing via Spectral Shift of Circular Bragg Phenomenon

Cited by 19 publications

References 34 publications

Modeling Chiral Sculptured Thin Films as Platforms for Surface-Plasmonic-Polaritonic Optical Sensing

Modeling Chiral Sculptured Thin Films as Platforms for Surface-Plasmonic-Polaritonic Optical Sensing

On alignment of nematic liquid crystals infiltrating chiral sculptured thin films

On alignment of nematic liquid crystals infiltrating chiral sculptured thin films

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