Engineering metal oxide nanostructures for the fiber optic sensor platform

Poole, Zsolt L.; Ohodnicki, Paul R.; Chen, Rongzhang; Lin, Yuankun; Chen, Kevin P.

doi:10.1364/oe.22.002665

Cited by 37 publications

(25 citation statements)

References 45 publications

(62 reference statements)

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“…52,53 The Pd/TEOS film was modeled as a Maxwell-Garnett effective medium layer using tabulated values of the optical constant of bulk Pd metal. [55][56][57] The pronounced peak in the imaginary part of the refractive index for Au/TEOS and the corresponding broadband increase with decreasing wavelengths for Pd/TEOS give rise to the LSPR absorption peak and broadband absorption, respectively, monitored during the sensor tests described in detail below. For the Pd/TEOS film, the volume fraction of Pd particles was an additional adjustable parameters included.…”

Section: Resultsmentioning

confidence: 99%

Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

Wang

Ohodnicki

et al. 2015

Nanoscale

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Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.

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Section: Resultsmentioning

confidence: 99%

Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

Wang

Ohodnicki

et al. 2015

Nanoscale

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“…1(c). The effective medium theory has been prevalently adopted to assess the property of such a nanostructured structure, where the corresponding effective index n ceff is determined by the Maxwell-Garnett equation, which is given by [26][27][28][29]. Here, V H is the volume fraction of the high-index material within the cavity and n ceff is presumed to be tuned from n L to n H , according to V H .…”

Section: Proposed Uniformly Thick Tri-color Filtersmentioning

confidence: 99%

“…Such a cavity might behave as a quasihomogeneous medium, whose effective index is customized depending on the fill factor of the grating structure. Different types of structures have therefore been reported for implementing antireflection layers, guided-wave mode convertors, achromatic phase retarders, optical biosensors enabling an enlarged sensing region, and color filters [22][23][24][25][26][27][28][29][30]. To obtain RGB tricolor filters, the nanostructured cavity should have a broad range of effective index, which hinges on the chosen highand low-index materials in conjunction with the volume fraction of the high-index material.…”

Section: Introductionmentioning

confidence: 99%

Uniformly thick tri-color filters capitalizing on an etalon with a nanostructured cavity

et al. 2015

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Highly efficient tri-color filters having uniform thickness are proposed based on an etalon tapping into a nanostructured cavity, where a hexagonal lattice of nanopillars (NPs) with a high refractive index is embedded in a base material with a low index. The nanostructured cavity is presumed to behave as a homogeneous medium, which provides a wide range for the effective refractive index in accordance with both the volume fraction of the NPs and the index contrast between the NPs and the base. Hence, for the etalon-based filters, the resonance wavelength can be efficiently tuned by simply altering the effective index rather than the thickness of the cavity, so as to span the entire visible regime including red, green, and blue (RGB) colors. In particular, a hexagonal lattice of NPs was introduced to extend the available range of effective index due to its highly flexible volume fraction. The NP-base index contrast has been pertinently maximized to achieve effective indices leading to RGB colors, to the extent that the nanostructured cavity can be safely modeled as a homogeneous medium. The proposed RGB color filters were finally designed to have an identical thickness of 240 nm by setting the diameters of the NPs at 95, 70, and 40 nm, to achieve a periodicity of 100 nm, considering that TiO2 and Al2O3 can be practically selected as the material candidate for the NPs and the base, respectively. A high transmittance of ∼78% and a suitable 1 dB bandwidth of ∼51 nm were obtained for the tri-color filters, which were further confirmed to exhibit polarization-independent transfer characteristics.

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“…Different functional materials have been used to integrate with the fiber optics platform to enhance the sensitivities toward gas molecules as gas–matter–light interaction is much stronger than that of light gas 2a,6. Typical materials include polymers,1a,7 metal oxides coated with metallic catalysts,1b,8 and more recently 2D materials (e.g., graphene, graphene oxide,2d,10 and transition metal dichalcogenide materials) …”

Section: Introductionmentioning

confidence: 99%

2D Plasmonic Tungsten Oxide Enabled Ultrasensitive Fiber Optics Gas Sensor

Yao

Ren

et al. 2019

Advanced Optical Materials

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Functional materials coated on optical fibers have demonstrated great potential for optical gas sensing applications. However, their sensitivity is typically limited to the sub‐parts per million (sub‐ppm) range. Here, for the first time a 2D near‐infrared plasmonic tungsten oxide (WOx) enabled ultrasensitive fiber optics gas sensor on a side‐polished D‐shape single mode optical fiber is presented. The plasmon resonance wavelength range of 2D WOx is matched with a conventional telecommunications wavelength of 1550 nm for driving the optical fiber, therefore inducing a strong light–matter interaction. Upon the surface adsorption of gas molecules, free electrons in the 2D WOx body are redistributed changing the plasmon resonance properties and hence the transmission through the optical fiber. The sensor is selectively responsive to NO2 at concentrations down to 44 parts per billion (ppb) with a limit of detection of 8 ppb at a relatively low elevated temperature. Such an excellent sensing performance is significantly improved over the previously reported fiber optics NO2 sensors, which suggests the integration of 2D plasmonic degenerated semiconductors as a viable approach to develop high‐performance fiber optics gas sensors.

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Engineering metal oxide nanostructures for the fiber optic sensor platform

Cited by 37 publications

References 45 publications

Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures

Uniformly thick tri-color filters capitalizing on an etalon with a nanostructured cavity

2D Plasmonic Tungsten Oxide Enabled Ultrasensitive Fiber Optics Gas Sensor

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