Agarose-Gel Based Guided-Mode Resonance Humidity Sensor

Lee, K.J.; Wawro, Debra; Priambodo, Purnomo Sidi; Magnusson, Robert

doi:10.1109/jsen.2006.890129

Cited by 37 publications

(21 citation statements)

References 23 publications

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“…The coatings usually swell physically and experience a refractive index change in response to changes in relative humidity (RH). For example, Barian et al [18] demonstrated a tapered fiber coated with Agarose gel for humidity sensing based on the refractive index change of Agarose, which is linear over a wide range of RH values [19].…”

Section: Introductionmentioning

confidence: 99%

Agarose coated spherical micro resonator for humidity measurements

Mallik¹,

Liu²,

Kavungal³

et al. 2016

Opt. Express

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Abstract:A new type of fiber optic relative humidity (RH) sensor based on an agarose coated silica microsphere resonator is proposed and experimentally demonstrated. Whispering gallery modes (WGMs) in the micro resonator are excited by evanescent coupling using a tapered fiber with ~3.3 µm waist diameter. A change in the relative humidity of the surrounding the resonator air induces changes in the refractive index (RI) and thickness of the Agarose coating layer. These changes in turn lead to a spectral shift of the WGM resonances, which can be related to the RH value after a suitable calibration. Studies of the repeatability, long-term stability, measurement accuracy and temperature dependence of the proposed sensor are carried out. The RH sensitivity of the proposed sensor depends on the concentration of the agarose gel which determines the initial thickness of the deposited coating layer. Studies of the micro-resonators with coating layers fabricated from gels with three different Agarose concentrations of 0.5%, 1.125% and 2.25 wt./vol.% showed that an increase in the initial thickness of the coating material results in an increase in sensitivity but also leads to a decrease of quality factor (Q) of the micro resonator. The highest sensitivity achieved in our experiments was 518 pm/%RH in the RH range from 30% to 70%. The proposed sensor offers the advantages of a very compact form factor, low hysteresis, good repeatability, and low cross sensitivity to temperature.

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Section: Introductionmentioning

confidence: 99%

Agarose coated spherical micro resonator for humidity measurements

Mallik¹,

Liu²,

Kavungal³

et al. 2016

Opt. Express

View full text Add to dashboard Cite

show abstract

“…In addition to providing means for novel optical elements, such as wavelength selective mirrors, polarizers [1], waveplates [2], tunable filters [3][4][5][6][7] and ultrabroadband mirrors [8], such resonant gratings have increasingly found their way into a myriad of different sensing applications, such as chemical and environmental sensing [9,10], label-free biosensing [11][12][13], cancer screening [14,15], photonic crystal enhanced microscopy [16] and three dimensional imaging [17]. These resonant gratings, referred to here as photonic crystal slabs (PCS) [18], but also known as guided mode resonance filters or reflectors [1,19] and photonic crystal resonant reflectors [20] in the literature, are essentially slab waveguides in which the high refractive index waveguide core is in some way periodically modulated, such as by refractive index or thickness, and surrounded by cladding media of lower refractive indices [1,18].…”

Section: Introductionmentioning

confidence: 99%

All-polymer photonic crystal slab sensor

Hermannsson¹,

Sørensen²,

Vannahme³

et al. 2015

Opt. Express

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Abstract:An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10 −6 RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO 2 -based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications.

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“…As shown in Fig 4(a), an increase of humidity inside the chamber gives rise to the adsorption of more water vapors on the surface of the microsphere. As a result, the air inside the micro pores of the coating layer is replaced by water molecules due to the hygroscopic nature of the material and capillary forces, which in turn gives rise to an increase in the effective refractive index of the Agarose coating layer [16].…”

Section: Experimental Investigation and Discussionmentioning

confidence: 99%

Compact relative humidity sensor based on an Agarose hydrogel coated silica microsphere resonator

Mallik¹,

Liu²,

Kavungal³

et al. 2017

SPIE Proceedings

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Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) Compact humidity sensor based on a multi-layer ABSTRACTIn this paper we report on a novel approach to implementing a compact humidity sensor that utilizes whispering gallery mode (WGM) phenomena in a silica microsphere coated with Agarose hydrogel. The spectral positions of the WGM resonances for such a sensor depend strongly on the refractive index and thickness of the coating. The WGM's spectral shift occurs due to adsorption/desorption of the water vapor in response to changes in ambient humidity and also due to the corresponding changes of the coating thickness. We experimentally investigated the WGMs spectral shift for a 100 µm diameter silica microsphere coated with Agarose hydrogel over a wide range of relative humidity (RH) values from 30%RH to 70%RH at a constant temperature. Six dip coating cycles of 2.25% wt. /vol. Agarose hydrogel were carried out in sequence with a characterization of the sensor performed for each coating thickness. A resonance shift of 16 nm is achieved in our experiment for the six-layer Agarose hydrogel coating sensor.

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Agarose-Gel Based Guided-Mode Resonance Humidity Sensor

Cited by 37 publications

References 23 publications

Agarose coated spherical micro resonator for humidity measurements

Agarose coated spherical micro resonator for humidity measurements

All-polymer photonic crystal slab sensor

Compact relative humidity sensor based on an Agarose hydrogel coated silica microsphere resonator

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