Polished photonic crystal fiber refractive index sensor based on surface plasmon resonance

Abstract

A polished photonic crystal fiber sensor based on surface plasmon resonance for refractive index (RI) detection is proposed and analyzed by finite element analysis. The design of polishing can greatly increase the birefringence of photonic crystal fiber and ensure a uniform coating film, thus improving sensor performance. The outer air of the structure is arranged in half of an octagonal shape, and the inner layer is arranged in a quadrilateral shape, which can effectively improve coupling strength in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>y</mml:mi> </mml:math> -polarization direction. The sensor works mainly in visible and infrared wavelengths with a detection range of 1.33 to 1.38. Through analysis of external RI changes, pore structure parameters, and silver mold thickness, the maximum sensitivity is 14800 nm/RIU, maximum amplitude sensitivity is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>766.7008</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> , resolution is up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>6.7568</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:mspace width="thickmathspace"/> <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:math> , and maximum figure of merit is 548.1481. The sensor is suitable for biomedicine, environmental monitoring, chemistry, and other fields.