Influence of humidity on refractive index of polymers for optical waveguide and its temperature dependence

Watanabe, Toshio; Ooba, Naoki; Hida, Y.; Hikita, Makoto

doi:10.1063/1.120574

Cited by 79 publications

(78 citation statements)

References 16 publications

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“…The wavelength change in POFBG sensors varies linearly with humidity, if η and β are constant; however both η and β can be temperature or humidity dependent [6,7]. It should be pointed out that not every polymer shows this water affinity: Bragg gratings made in TOPAS polymer are insensitive to humidity [8] and are therefore suitable in applications where cross sensitivity to humidity needs to be avoided.…”

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confidence: 99%

“…It was estimated in [7] that the RI of d-PMMA increases as humidity increases at a rate of 1.13 × 10 −5 %RH −1 at 25°C . This RI humidity dependence decreases as temperature increases.…”

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confidence: 99%

“…(3). The maximum water absorption can vary for different PMMA fibers from 1.6% to 2.0% of total PMMA weight [6,7,10]. The volume change of PMMA caused by humidity can be estimated by using Eqs.…”

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Humidity responsivity of poly(methyl methacrylate)-based optical fiber Bragg grating sensors

2014

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The humidity response of poly(methyl methacrylate) (PMMA)-based optical fiber Bragg gratings (POFBGs) has been studied. The characteristic wavelength of the grating is modulated by water absorption-induced swelling and refractive index change in the fiber. This work indicates that anisotropic expansion may exist in PMMA optical fiber, reducing the humidity responsivity of the grating and introducing uncertainty in the responsivity from fiber to fiber. By pre-straining a grating, one can get rid of this uncertainty and simultaneously improve the POFBG response time. and affinity for water that leads to a swelling of the fiber and an increase of RI. The former feature offers a wellconditioned performance for overcoming the cross sensitivity issues existing in silica fiber [1], while the latter feature leads to an increase with humidity of the Bragg wavelength of a Bragg grating written in the fiber [2]. This is a potentially very useful property that has possible applications in the chemical processing, agricultural, food storage, paper manufacturing, semiconductor, and pharmaceutical industries, where humidity is monitored and controlled to ensure product quality. This property has also been exploited for the detection of saline concentration [3] and water in fuel [4]. There have been many reports on the use of PMMAbased fiber gratings for humidity sensing. However, the reported humidity responsivities show considerable variation (see, e.g., [1,2,5]). This variation has not been satisfactorily explained and causes great uncertainty concerning the POFBG's performance and applicability.The Bragg wavelength of a fiber grating depends on the effective core RI and the grating pitch, both of which depend on the temperature and the water content in the case of a PMMA-based POFBG. For constant temperature, the Bragg wavelength change of a POFBG against humidity can be expressed aswhere λ B is the initial Bragg wavelength, η is the normalized RI change with humidity %RH −1 , and β the swelling coefficient related to humidity induced volumetric change %RH −1 . The wavelength change in POFBG sensors varies linearly with humidity, if η and β are constant; however both η and β can be temperature or humidity dependent [6,7]. It should be pointed out that not every polymer shows this water affinity: Bragg gratings made in TOPAS polymer are insensitive to humidity [8] and are therefore suitable in applications where cross sensitivity to humidity needs to be avoided. Bragg gratings can be written into pure PMMA optical fibers by using UV illumination to induce polymerization of unreacted monomers that contribute to an increase in RI. Better performance has been achieved using dopedcore PMMA-based optical fibers [9]. Since additional dopants or copolymers are required to control the core index of step index fibers, the performance of PMMAbased fiber gratings may vary with the type of fiber used. The detailed composition of dopant and copolymer used in a specific PMMA-based optical fiber is often not known and neither are their dep...

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Humidity responsivity of poly(methyl methacrylate)-based optical fiber Bragg grating sensors

2014

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“…It is well known that PMMA suffers considerable water absorption, leading to swelling ͑volume change͒ of the polymer 29,30 and to changes in other properties such as refractive index, Young's modulus, and glass transition temperature. [31][32][33] In the data presented here we use the vacuum conductivity.…”

Section: Resultsmentioning

confidence: 99%

Gold-implanted shallow conducting layers in polymethylmethacrylate

Teixeira

Salvadori

Cattani

et al. 2009

Journal of Applied Physics

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Characterization of bias stress induced electrical instability in liquid-crystalline semiconducting polymer thin-film transistors J. Appl. Phys. 110, 084511 (2011) Influence of crystallization-induced amorphous phase confinement on -and -relaxation molecular mobility in parylene F J. Appl. Phys. 110, 063703 (2011) Variability of physical characteristics of electro-sprayed poly(3-hexylthiophene) thin films J. Appl. Phys. 110, 054515 (2011) Metallic-like conduction in Co-phthalocyanine/Fe-phthalocyanine composite films grown on sapphire substrates Appl. Phys. Lett. 99, 112102 (2011) Theoretical study of substitution effects on molecular reorganization energy in organic semiconductors J. Chem. Phys. 135, 104703 (2011) Additional information on J. Appl. Phys. PMMA ͑polymethylmethacrylate͒ was ion implanted with gold at very low energy and over a range of different doses using a filtered cathodic arc metal plasma system. A nanometer scale conducting layer was formed, fully buried below the polymer surface at low implantation dose, and evolving to include a gold surface layer as the dose was increased. Depth profiles of the implanted material were calculated using the Dynamic TRIM computer simulation program. The electrical conductivity of the gold-implanted PMMA was measured in situ as a function of dose. Samples formed at a number of different doses were subsequently characterized by Rutherford backscattering spectrometry, and test patterns were formed on the polymer by electron beam lithography. Lithographic patterns were imaged by atomic force microscopy and demonstrated that the contrast properties of the lithography were well maintained in the surface-modified PMMA.

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“…On the other hand, however, if the chain conformations of the polymers are random with no preferred orientation, i.e., , the birefringence will be zero because the molecular anisotropic ratio of will be cancelled out in macroscopic scale, resulting in . Recently, the factors influencing birefringence have been widely investigated, such as the spin-coating condition [27], substrate material [27], thermal treatment condition [27], [28], film thickness [27], [29], [31], humidity condition [29], [30], [32], and solvent system [31]. Most of the previously mentioned factors are related to molecular orientations in bulk materials.…”

Section: A Refractive Index and Birefringencementioning

confidence: 99%

Structure-property relationship of fluorinated co-poly(arylene ether sulfide)s and co-poly(arylene ether sulfone)s for low-loss and low-birefringence waveguide devices

Kang

Kim

Lee

et al. 2005

J. Lightwave Technol.

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Influence of humidity on refractive index of polymers for optical waveguide and its temperature dependence

Cited by 79 publications

References 16 publications

Humidity responsivity of poly(methyl methacrylate)-based optical fiber Bragg grating sensors

Humidity responsivity of poly(methyl methacrylate)-based optical fiber Bragg grating sensors

Gold-implanted shallow conducting layers in polymethylmethacrylate

Structure-property relationship of fluorinated co-poly(arylene ether sulfide)s and co-poly(arylene ether sulfone)s for low-loss and low-birefringence waveguide devices

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