Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer
We present an experimental study of a sensitivity-enhanced surface plasmon resonance (SPR) sensor utilizing a cladding etched multimode polymer optical fiber (POF) coated with a layer of gold followed by an indium tin oxide (ITO) layer. Our findings indicate that POF SPR sensors with an ITO overlaye...
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MDPI AG
2025-03-01
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| author | Getinet Woyessa Ole Bang |
| author_facet | Getinet Woyessa Ole Bang |
| author_sort | Getinet Woyessa |
| collection | DOAJ |
| description | We present an experimental study of a sensitivity-enhanced surface plasmon resonance (SPR) sensor utilizing a cladding etched multimode polymer optical fiber (POF) coated with a layer of gold followed by an indium tin oxide (ITO) layer. Our findings indicate that POF SPR sensors with an ITO overlayer exhibit higher sensitivity compared to those coated solely with gold. Additionally, increasing the thickness of the ITO layer increases the sensitivity of the sensor at the expense of a broader SPR spectrum. We determined that the optimal ITO thickness for maximizing sensitivity is 25 nm. The sensor coated with 40 nm gold and 25 nm ITO demonstrated a refractive index sensitivity of 2258 nm per refractive index unit (nm/RIU) with a figure of merit and resolution of 10.13 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi mathvariant="normal">R</mi><mi mathvariant="normal">I</mi><mi mathvariant="normal">U</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2.74</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo> </mo><mi mathvariant="normal">R</mi><mi mathvariant="normal">I</mi><mi mathvariant="normal">U</mi></mrow></semantics></math></inline-formula>, respectively, within the range of 1.33 to 1.37 RIU. Notably, this sensitivity is 70% greater than that of a POF SPR sensor coated only with 40 nm gold. Long-term stability tests conducted in a hydrated environment confirmed that the ITO layer remains unaffected over time and that the maximum SPR wavelength drift was only 1.2 nm. The standard deviation of the three-round measurements also revealed that the sensor has good repeatability. We believe that this sensor offers a simple structure and a relatively easy fabrication process, eliminating the need for side polishing while providing a large interaction area, making it a promising candidate for high-sensitivity biosensing applications. |
| format | Article |
| id | doaj-art-e30951d18ef64165b18939f6fbcf15a1 |
| institution | Kabale University |
| issn | 1424-8220 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | MDPI AG |
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| series | Sensors |
| spelling | doaj-art-e30951d18ef64165b18939f6fbcf15a12025-08-20T03:43:40ZengMDPI AGSensors1424-82202025-03-01256186310.3390/s25061863Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO OverlayerGetinet Woyessa0Ole Bang1DTU Electro, Department of Electrical and Photonics Engineering, Technical University of Denmark (DTU), DK-2800 Kongens Lyngby, DenmarkDTU Electro, Department of Electrical and Photonics Engineering, Technical University of Denmark (DTU), DK-2800 Kongens Lyngby, DenmarkWe present an experimental study of a sensitivity-enhanced surface plasmon resonance (SPR) sensor utilizing a cladding etched multimode polymer optical fiber (POF) coated with a layer of gold followed by an indium tin oxide (ITO) layer. Our findings indicate that POF SPR sensors with an ITO overlayer exhibit higher sensitivity compared to those coated solely with gold. Additionally, increasing the thickness of the ITO layer increases the sensitivity of the sensor at the expense of a broader SPR spectrum. We determined that the optimal ITO thickness for maximizing sensitivity is 25 nm. The sensor coated with 40 nm gold and 25 nm ITO demonstrated a refractive index sensitivity of 2258 nm per refractive index unit (nm/RIU) with a figure of merit and resolution of 10.13 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi mathvariant="normal">R</mi><mi mathvariant="normal">I</mi><mi mathvariant="normal">U</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2.74</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo> </mo><mi mathvariant="normal">R</mi><mi mathvariant="normal">I</mi><mi mathvariant="normal">U</mi></mrow></semantics></math></inline-formula>, respectively, within the range of 1.33 to 1.37 RIU. Notably, this sensitivity is 70% greater than that of a POF SPR sensor coated only with 40 nm gold. Long-term stability tests conducted in a hydrated environment confirmed that the ITO layer remains unaffected over time and that the maximum SPR wavelength drift was only 1.2 nm. The standard deviation of the three-round measurements also revealed that the sensor has good repeatability. We believe that this sensor offers a simple structure and a relatively easy fabrication process, eliminating the need for side polishing while providing a large interaction area, making it a promising candidate for high-sensitivity biosensing applications.https://www.mdpi.com/1424-8220/25/6/1863surface plasma resonancepolymer optical fibergoldindium tin oxiderefractive index sensorbiosensor |
| spellingShingle | Getinet Woyessa Ole Bang Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer Sensors surface plasma resonance polymer optical fiber gold indium tin oxide refractive index sensor biosensor |
| title | Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer |
| title_full | Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer |
| title_fullStr | Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer |
| title_full_unstemmed | Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer |
| title_short | Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer |
| title_sort | sensitivity enhancement of polymer optical fiber surface plasmon resonance sensor utilizing ito overlayer |
| topic | surface plasma resonance polymer optical fiber gold indium tin oxide refractive index sensor biosensor |
| url | https://www.mdpi.com/1424-8220/25/6/1863 |
| work_keys_str_mv | AT getinetwoyessa sensitivityenhancementofpolymeropticalfibersurfaceplasmonresonancesensorutilizingitooverlayer AT olebang sensitivityenhancementofpolymeropticalfibersurfaceplasmonresonancesensorutilizingitooverlayer |