Dual-polarized highly sensitive surface-plasmon-resonance-based chemical and biomolecular sensor
Mohammad Rakibul Islam, A. N. M. Iftekher, Kazi Rakibul Hasan, Md. Julkar Nayen, Saimon Bin Islam
Abstract
As the research work in surface plasmon resonance (SPR)-based photonic crystal fiber (PCF) is getting tighter, a perfectly circular-shaped PCF with elliptical air holes is proposed where the performance parameters are improved significantly. The performances among our designed elliptical, circular, and rectangular air holes are compared, and the best result is achieved with the elliptical air holes. The technique used for the investigation is the finite element method, and for the simulation of data COMSOL Multiphysics 5.3a software is used. The method covers a wider range of the optical spectrum from 0.59 to 1.05 µm. The highest confinement loss achieved through our design is 340 dB/cm. The wavelength sensitivity and amplitude sensitivity are 13,000 nm/RIU and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>1189.46</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">R</mml:mi> <mml:mi mathvariant="normal">I</mml:mi> <mml:mi mathvariant="normal">U</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , respectively. The sensor resolution is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>7.69</mml:mn> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> for our proposed design. The proposed sensor also achieved a maximum birefringence of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2.8</mml:mn> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , which is, to our knowledge, the highest birefringence reported so far for a PCF-SPR sensor. This enables the fiber to be operated in a dual-polarized mode. The RI for the analyte ranges from 1.33 to 1.40. Based on all the characteristics, the proposed PCF structure can be used effectively for chemical and biomolecular sensing.