Exploring the potential of double perovskite oxide Ca₂TiFeO₆ coated D-shaped optical fiber SPR sensor: a theoretical analysis

Abstract Surface plasmon resonance (SPR)-based biosensor is a very sensitive analytical instrument that identifies chemical interactions by monitoring variations in the refractive index of a medium close to a plasmonic metal surface. It is extensively utilized in drug research, environmental monitoring, and medical diagnostics because of its advantages of real-time and label-free detection of biomolecules. By considering the importance of biosensors, this work explores the simulation of highly sensitive fiber-optic sensors coated with double perovskite oxide as a bio recognition layer over silver on the surface of a D-shaped optical fiber. The integration of double perovskite oxide materials, known for their exceptional optoelectronic properties, with the plasmonic silver layer significantly sharpened the SPR dip and enhanced sensitivity. Surface plasmon polaritons were created by stimulating evanescent waves on the fiber surface and free electrons on the metal surface. By analyzing the structural characteristics of the D-shaped fiber-optic, silver layer and considering the effect of the double perovskite oxide layer’s thickness, the optical fiber SPR sensor was optimized using the finite element method (FEM). In this work, the maximum sensitivity of sensors is recorded <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>6.9</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mtext>RI</mml:mtext> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>U</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mrow> <mml:mtext>1</mml:mtext> </mml:mrow> </mml:mrow> </mml:msup> </mml:mrow> </mml:mrow> </mml:math> when the external refractive index varied from 1.34 to 1.38 with a 30 nm thickness of silver, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>0.1</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> polishing depth of fiber’s cladding and a single layer of double perovskite oxide layer of 18 nm operating in the visible and near infrared regime. The findings indicate that optical fiber sensing applications could benefit greatly from the utilization of a double perovskite oxide layer.