Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer
The refractive index is an important optical property of materials which can be used to understand the composition of materials. Therefore, refractive index sensing plays a vital role in biological diagnosis and therapy, material analysis, (bio)chemical sensing, and environmental monitoring. Convent...
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MDPI AG
2025-05-01
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| author | Yuru Li Hongming Fei Xin Liu Han Lin |
| author_facet | Yuru Li Hongming Fei Xin Liu Han Lin |
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| description | The refractive index is an important optical property of materials which can be used to understand the composition of materials. Therefore, refractive index sensing plays a vital role in biological diagnosis and therapy, material analysis, (bio)chemical sensing, and environmental monitoring. Conventional optical refractive index sensors based on optical fibers and ridge waveguides have relatively large sizes of a few millimeters, making them unsuitable for on-chip integration. Photonic crystals (PCs) have been used to significantly improve the compactness of refractive index sensors for on-chip integration. However, PC structures suffer from defect-introduced strong scattering, resulting in low transmittance, particularly at sharp bends. Valley photonic crystals (VPCs) can realize defect-immune unidirectional transmission of topological edge states, effectively reducing the scattering loss and increasing the transmittance. However, optical refractive index sensors based on VPC structures have not been demonstrated. This paper proposes a refractive index sensor based on a VPC Mach–Zehnder interferometer (MZI) structure with a high forward transmittance of 0.91 and a sensitivity of 1534%/RIU at the sensing wavelength of <i>λ</i> = 1533.97 nm within the index range from 1.0 to 2.0, which is higher than most demonstrated optical refractive index sensors in the field. The sensor has an ultracompact footprint of 9.26 μm × 7.99 μm. The design can be fabricated by complementary metal–oxide semiconductor (CMOS) fabrication technologies. Therefore, it will find broad applications in biology, material science, and medical science. |
| format | Article |
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| institution | OA Journals |
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| language | English |
| publishDate | 2025-05-01 |
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| spelling | doaj-art-640ecfcf35314b3fb8ede8ee3b3bf9492025-08-20T02:23:05ZengMDPI AGSensors1424-82202025-05-012511328910.3390/s25113289Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder InterferometerYuru Li0Hongming Fei1Xin Liu2Han Lin3College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, ChinaCollege of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, ChinaCollege of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, ChinaCentre for Atomaterials and Nanomanufacturing, School of Science, RMIT University, Melbourne, VIC 3000, AustraliaThe refractive index is an important optical property of materials which can be used to understand the composition of materials. Therefore, refractive index sensing plays a vital role in biological diagnosis and therapy, material analysis, (bio)chemical sensing, and environmental monitoring. Conventional optical refractive index sensors based on optical fibers and ridge waveguides have relatively large sizes of a few millimeters, making them unsuitable for on-chip integration. Photonic crystals (PCs) have been used to significantly improve the compactness of refractive index sensors for on-chip integration. However, PC structures suffer from defect-introduced strong scattering, resulting in low transmittance, particularly at sharp bends. Valley photonic crystals (VPCs) can realize defect-immune unidirectional transmission of topological edge states, effectively reducing the scattering loss and increasing the transmittance. However, optical refractive index sensors based on VPC structures have not been demonstrated. This paper proposes a refractive index sensor based on a VPC Mach–Zehnder interferometer (MZI) structure with a high forward transmittance of 0.91 and a sensitivity of 1534%/RIU at the sensing wavelength of <i>λ</i> = 1533.97 nm within the index range from 1.0 to 2.0, which is higher than most demonstrated optical refractive index sensors in the field. The sensor has an ultracompact footprint of 9.26 μm × 7.99 μm. The design can be fabricated by complementary metal–oxide semiconductor (CMOS) fabrication technologies. Therefore, it will find broad applications in biology, material science, and medical science.https://www.mdpi.com/1424-8220/25/11/3289refractive index sensortopological photonic crystalvalley photonic crystalMach–Zehnder interferometersensitivity |
| spellingShingle | Yuru Li Hongming Fei Xin Liu Han Lin Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer Sensors refractive index sensor topological photonic crystal valley photonic crystal Mach–Zehnder interferometer sensitivity |
| title | Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer |
| title_full | Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer |
| title_fullStr | Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer |
| title_full_unstemmed | Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer |
| title_short | Design of Refractive Index Sensors Based on Valley Photonic Crystal Mach–Zehnder Interferometer |
| title_sort | design of refractive index sensors based on valley photonic crystal mach zehnder interferometer |
| topic | refractive index sensor topological photonic crystal valley photonic crystal Mach–Zehnder interferometer sensitivity |
| url | https://www.mdpi.com/1424-8220/25/11/3289 |
| work_keys_str_mv | AT yuruli designofrefractiveindexsensorsbasedonvalleyphotoniccrystalmachzehnderinterferometer AT hongmingfei designofrefractiveindexsensorsbasedonvalleyphotoniccrystalmachzehnderinterferometer AT xinliu designofrefractiveindexsensorsbasedonvalleyphotoniccrystalmachzehnderinterferometer AT hanlin designofrefractiveindexsensorsbasedonvalleyphotoniccrystalmachzehnderinterferometer |