volume | PIER Journals

Abstract

A dual-core photonic crystal fiber surface plasmon resonance biosensor employing a hybrid Au-TiO₂ coating is presented for biosensing. The study is formulated as an extension of our earlier Au-only dual-core PCF-SPR design, with the main modification being the introduction of an ultra-thin TiO₂ dielectric overlayer to improve modal coupling and sensing performance. The numerical analysis tracks the resonance behavior for analyte refractive indices from 1.28 to 1.44 and shows a clear redshift of the resonance wavelength as the analyte index increases. The resonance wavelength moves from 400 nm to 650 nm, corresponding to an overall wavelength shift of 250 nm across the investigated range. The confinement-loss spectra also show stronger coupling at higher refractive indices, with the largest loss peaks observed near the upper end of the sensing range. In addition, the amplitude sensitivity reaches a maximum absolute value of about 842 RIU^-1, confirming a strong intensity response around resonance. Compared with the previous Au-only configuration, the hybrid structure provides a measurable improvement in amplitude response and extends the usable lower-end refractive-index range. These results indicate that the proposed hybrid-coated dual-core PCF structure is a promising platform for high-contrast refractive-index detection.

1. Naife, R. and A. Abbas, "Induced mode coupling in dual-core photonic crystal for high sensitivity via laser gold film coating," ARPN Journal of Engineering and Applied Sciences, Vol. 20, No. 23, 2045-2053, 2025. Google Scholar

2. Paul, Alok Kumar, Ajay Krishno Sarkar, Md. Hafizul Islam, and Monir Morshed, "Dual core photonic crystal fiber based surface plasmon resonance biosensor," Optik, Vol. 170, 400-408, 2018.
doi:10.1016/j.ijleo.2018.05.131 Google Scholar

3. Wu, Tiesheng, Yu Shao, Ying Wang, Shaoqing Cao, W. Cao, Fengchan Zhang, C. Liao, Jun He, Yijian Huang, M. Hou, and Yiping Wang, "Surface plasmon resonance biosensor based on gold-coated side-polished hexagonal structure photonic crystal fiber," Optics Express, Vol. 25, No. 17, 20313-20322, 2017.
doi:10.1364/oe.25.020313 Google Scholar

4. Candiani, A., S. Giannetti, A. Bertucci, R. Mwad Naife, H. Al-Janabi, M. Konstantaki, A. Cucinotta, S. Pissadakis, R. Corradini, and S. Selleri, "PNA-modified photonic crystal fibers for DNA detection," The European Conference on Lasers and Electro-Optics, Munich, Germany, May 2013.

5. Morshed, Monir, Md. Imran Hassan, Tusher Kanti Roy, Muhammad Shahin Uddin, and S. M. Abdur Razzak, "Microstructure core photonic crystal fiber for gas sensing applications," Applied Optics, Vol. 54, No. 29, 8637-8643, 2015.
doi:10.1364/ao.54.008637 Google Scholar

6. Knight, Jonathan C., "Photonic crystal fibres," Nature, Vol. 424, No. 6950, 847-851, 2003.
doi:10.1038/nature01940 Google Scholar

7. Russell, Philip S. J., "Photonic-crystal fibers," Journal of Lightwave Technology, Vol. 24, No. 12, 4729-4749, 2006.
doi:10.1109/JLT.2006.885258 Google Scholar

8. Sharma, Anuj K., Rajan Jha, and B. D. Gupta, "Fiber-optic sensors based on surface plasmon resonance: A comprehensive review," IEEE Sensors Journal, Vol. 7, No. 8, 1118-1129, 2007.
doi:10.1109/jsen.2007.897946 Google Scholar

9. Hassani, Alireza and Maksim Skorobogatiy, "Design criteria for microstructured-optical-fiber-based surface-plasmon-resonance sensors," Journal of the Optical Society of America B, Vol. 24, No. 6, 1423-1429, 2007.
doi:10.1364/josab.24.001423 Google Scholar

10. Dash, Jitendra Narayan and Rajan Jha, "SPR biosensor based on polymer PCF coated with conducting metal oxide," IEEE Photonics Technology Letters, Vol. 26, No. 6, 595-598, 2014.
doi:10.1109/LPT.2014.2301153 Google Scholar

11. Al Mahfuz, Mohammad, Md. Aslam Mollah, Moriom Rojy Momota, Alok Kumar Paul, Al Masud, Sanjida Akter, and Md. Rabiul Hasan, "Highly sensitive photonic crystal fiber plasmonic biosensor: Design and analysis," Optical Materials, Vol. 90, 315-321, 2019.
doi:10.1016/j.optmat.2019.02.012 Google Scholar

12. Ehyaee, Arefe, Masoud Mohammadi, Mahmood Seifouri, and Saeed Olyaee, "Design and numerical investigation of a dual-core photonic crystal fiber refractive index sensor for cancer cells detection," The European Physical Journal Plus, Vol. 138, No. 2, 129, 2023.
doi:10.1140/epjp/s13360-023-03749-0 Google Scholar

13. Johnson, P. B. and R. W. Christy, "Optical constants of the noble metals," Physical Review B, Vol. 6, No. 12, 4370, 1972.
doi:10.1103/physrevb.6.4370 Google Scholar

14. Lu, Ying, Cong-Jing Hao, Bao-Qun Wu, Mayilamu Musideke, Liang-Cheng Duan, Wu-Qi Wen, and Jian-Quan Yao, "Surface plasmon resonance sensor based on polymer photonic crystal fibers with metal nanolayers," Sensors, Vol. 13, No. 1, 956-965, 2013.
doi:10.3390/s130100956 Google Scholar

15. Ramola, Ayushman, Amit Kumar Shakya, Vinay Kumar, and Arik Bergman, "Recent advances in photonic crystal fiber-based SPR biosensors: Design strategies, plasmonic materials, and applications," Micromachines, Vol. 16, No. 7, 747, 2025.
doi:10.3390/mi16070747 Google Scholar

16. Lv, Jingwei, Jianxin Wang, Lin Yang, Wei Liu, Haihao Fu, Paul K. Chu, and Chao Liu, "Recent advances of optical fiber biosensors based on surface plasmon resonance: Sensing principles, structures, and prospects," Sensors & Diagnostics, Vol. 3, No. 9, 1369-1391, 2024.
doi:10.1039/d4sd00045e Google Scholar

17. Kaziz, Sameh, Fraj Echouchene, and Mohamed Hichem Gazzah, "Optimizing PCF-SPR sensor design through Taguchi approach, machine learning, and genetic algorithms," Scientific Reports, Vol. 14, No. 1, 7837, 2024.
doi:10.1038/s41598-024-55817-9 Google Scholar

18. Yang, Youpeng, Yafei Qin, Xinyu Lu, and Yu Zeng, "High-sensitivity three-core photonic crystal fiber sensor based on surface plasmon resonance with gold film coatings," Japanese Journal of Applied Physics, Vol. 60, No. 12, 122002, 2021.
doi:10.35848/1347-4065/ac2e68 Google Scholar

19. Bosch, María Espinosa, Antonio Jesús Ruiz Sánchez, Fuensanta Sánchez Rojas, and Catalina Bosch Ojeda, "Recent development in optical fiber biosensors," Sensors, Vol. 7, No. 6, 797-859, 2007.
doi:10.3390/s7060797 Google Scholar

20. Saitoh, K. and M. Koshiba, "Numerical modeling of photonic crystal fibers," Journal of Lightwave Technology, Vol. 23, No. 11, 3580-3590, 2005.
doi:10.1109/jlt.2005.855855 Google Scholar

21. Cubillas, Ana M., Sarah Unterkofler, Tijmen G. Euser, Bastian J. M. Etzold, Anita C. Jones, Peter J. Sadler, Peter Wasserscheid, and Philip St. J. Russell, "Photonic crystal fibres for chemical sensing and photochemistry," Chemical Society Reviews, Vol. 42, No. 22, 8629-8648, 2013.
doi:10.1039/c3cs60128e Google Scholar

22. Ramani, Umang, Hemant Kumar, Bipin K. Singh, and Praveen C. Pandey, "Design of surface plasmon resonance based both side polished photonic crystal fiber for highly efficient refractive index sensor," Optik, Vol. 248, 168062, 2021.
doi:10.1016/j.ijleo.2021.168062 Google Scholar

23. Ying, Yu, Tong Shang, Zhijun Gao, and Guangyuan Si, "Refractive index sensing characteristics of PCF-SPR based on dual-plasmon materials," Journal of Optics, Vol. 26, No. 12, 125101, 2024.
doi:10.1088/2040-8986/ad8456 Google Scholar

24. Rifat, A. A., Ghafour Amouzad Mahdiraji, Y. M. Sua, Y. G. Shee, Rajib Ahmed, Desmond M. Chow, and F. R. Mahamd Adikan, "Surface plasmon resonance photonic crystal fiber biosensor: A practical sensing approach," IEEE Photonics Technology Letters, Vol. 27, No. 15, 1628-1631, 2015.
doi:10.1109/lpt.2015.2432812 Google Scholar

25. Hasan, Md. Shahedul, Md. Anas Ebna Kalam, and Mohammad Faisal, "PCF based four-channel SPR biosensor with wide sensing range," IEEE Transactions on Nanobioscience, Vol. 23, No. 2, 233-241, 2024.
doi:10.1109/tnb.2023.3311611 Google Scholar

26. Sardar, Md. Ranju and Mohammad Faisal, "Numerical analysis of highly sensitive twin-core, gold-coated, D-shaped photonic crystal fiber based on surface plasmon resonance sensor," Sensors, Vol. 23, No. 11, 5029, 2023.
doi:10.3390/s23115029 Google Scholar

27. Emon, Wahiduzzaman, Avik Chaki, Tanu Prava Mondal, M. Faysal Nayan, and Russel Reza Mahmud, "Photonic crystal fiber-based SPR biosensor coated with Ag-TiO2 and Au-TiO2 for the detection of skin cancer: A comparison," Optical and Quantum Electronics, Vol. 56, No. 8, 1322, 2024.
doi:10.1007/s11082-024-07250-5 Google Scholar

28. Ding, Xin, Qiao Lin, Mengjie Wang, Shen Liu, Weiguan Zhang, Nan Chen, and Yiping Wang, "Design and simulation of high-performance D-type dual-mode PCF-SPR refractive index sensor coated with Au-TiO2 layer," Sensors, Vol. 24, No. 18, 6118, 2024.
doi:10.3390/s24186118 Google Scholar

29. Jain, Satyendra, Kuldeep Choudhary, and Santosh Kumar, "Photonic crystal fiber-based SPR sensor for broad range of refractive index sensing applications," Optical Fiber Technology, Vol. 73, 103030, 2022.
doi:10.1016/j.yofte.2022.103030 Google Scholar

30. Homola, Jiří, "Surface plasmon resonance sensors for detection of chemical and biological species," Chemical Reviews, Vol. 108, No. 2, 462-493, 2008.
doi:10.1021/cr068107d Google Scholar

31. DeVore, J. R., "Refractive indices of rutile and sphalerite," Journal of the Optical Society of America, Vol. 41, No. 6, 416-419, 1951.
doi:10.1364/josa.41.000416 Google Scholar

Dr. Riyadh Mwad Naife