Mid-infrared T-shaped photonic crystal waveguide for optical refractive index sensing

• Published in: Sensors and actuators. B, Chemical Vol. 245; pp. 765 - 773
• Main Authors: Turduev, Mirbek, Giden, Ibrahim H., Babayiğit, Ceren, Hayran, Zeki, Bor, Emre, Boztuğ, Çiçek, Kurt, Hamza, Staliunas, Kestutis
• Format: Journal Article Publication
• Language: English
• Published: Lausanne Elsevier B.V 01.06.2017; Elsevier Science Ltd
• Subjects: Bio-chemical sensing; Biosensors; Cristalls fotònics; Crystal lattices; Crystal structure; Crystals; Design parameters; Detection; Detectors òptics; Fotònica; Física; Infrared radiation; Label free optical sensors; Optical measuring instruments; Optical properties; Photonic crystals; Photonics; Refractive index based sensors; Refractivity; Sensitivity; Slotted waveguides; T shape; Àrees temàtiques de la UPC; Label free optical sensors; Bio-chemical sensing; Refractive index based sensors; Photonic crystals; Slotted waveguides
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2017.02.016

•The T-shaped slot concept is utilized for the first time in order to design an optical sensor.•The sensor has the highest sensitivity of 1040nm/RIU within the range of analytes refractive indices n=1.05–1.10.•The overall sensitivity corresponding to higher refractive indices n=1.10–1.30 takes the value around 500nm/RIU.•Realistic 3D PC slab sensor has an average sensitivity of 530nm/RIU in n=1.10–1.25 and an average sensitivity of 390nm/RIU in n=1.00–1.30.•The proposed optical sensor is compact and has simple, fast excitation and a label-free detection mechanism.•The designed T-shaped slot optical sensor can be important for rapid label-free diagnosis in biochemical sensing applications. In this paper, we propose and design a new type of an integrated optical sensor that performs sensing in a wide wavelength range corresponding to mid-infrared (mid-IR) spectrum. By engineering the structural parameters of square-lattice photonic crystal (PC) slab incorporated with a T-shaped air-slot, strong light confinement and interaction with the analytes are assured. Numerical analyses in the time and frequency domain are conducted to determine the structural parameters of the design. The direct interaction between the slot waveguide mode and the analyte infiltrated into the slot gives rise to highly sensitive refractive index sensors. The highest sensitivity of the proposed T-slotted PC sensor is 1040nm/RIU within the range of analytes’ refractive indices n=1.05–1.10, and the overall sensitivity corresponding to the higher refractive index range of n=1.10–1.30 is around 500nm/RIU. Moreover, for a realistic PC slab structure, we determined an average refractive index sensitivity of 530nm/RIU within the range of n=1.10–1.25 and an average sensitivity of 390nm/RIU within the range of n=1.00–1.30. Furthermore, we speculate on the possible approach for the fabrication and the optical characterization of the device. The assets of the device include being compact, having a feasible measurement and fabrication technique, and possessing label-free sensing characteristic. We expect that the presented work may lead to the further development of the mid-IR label-free biochemical sensor devices for detection of various materials and gases in the near future.