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• A highly sensitive Quasi D-Shape Photonic Crystal Fiber Surface Plasmonic (QD-PCFSP) biosensor is offered and numerically analyzed. • Using the wavelength interrogation method at Au layer thickness of 40 nm, the offered sensor displays maximum wavelength sensitivity of 15000 nm/RIU in the detecting range between 1.42 RIU to 1.46 RIU. • Using the amplitude interrogation method at Au layer thickness of 40 nm, the offered sensor displays maximum amplitude sensitivity of 230 RIU−1 in the detecting range between 1.42 RIU to 1.46 RIU. • A maximum sensor wavelength resolution of 6.67 × 10−6 RIU, amplitude resolution 4.348 × 10−5 RIU and Figure of merit (FoM) are obtained. • A relative review is executed comparing the amplitude and wavelength sensitivity parameters of the offered sensor with existing sensors. In this paper, a proper concept of a kind of photonic crystal fiber known as D-shaped PCF sensor based on SPR or Surface Plasmon Resonance phenomenon has been discussed. The analysis has been performed numerically using FEM or Finite Element Method and PML (Perfectly Matched Layer) boundary conditions. Modal analysis has been performed keeping the smallest mesh as possible. The main mechanism of the sensor is the interaction between the core guided light beam and the metal layer surface that generates free electrons. The proposed sensor shows a refractive index detection range of 1.42–1.46 RIU, with a metal thickness variation of 35 nm-45 nm and a pitch variation of 1.8 μm–2.0 μm. The sensor obtained the highest sensitivity of 15000 nm/RIU with a maximum 6.67 × 10 - 6 RIU resolution, using the wavelength interrogation method. Average spectral sensitivity is 8000 nm/RIU. The amplitude interrogation method found a maximum sensitivity of 230 RIU−1 with a resolution of 4.348 × 10 - 5 RIU. The sensor also shows high linearity fitting and Figure of Merit (FoM). For ease of design, high detection range, high wavelength and amplitude sensitivity, less fabrication complexity, high linearity and stability, the sensor can be a great competitor of the PCF sensors previously proposed. [ABSTRACT FROM AUTHOR]

• To illustrate a High Sensitivity circular Shaped Hollow Core Photonic Crystal Fiber. • The proposed structure is demonstrated consisting of all circular air holes with an external coating of Silver (Ag) and sensing layer. • To investigate Sensing characteristics with the modal analysis. • To obtain that the maximum amplitude and wavelength sensitivity. This article numerically offers and analyses a hollow core circular shaped photonic crystal fiber-based surface plasmon resonance (CH-PCF-SPR) biosensor. The biosensor sensitivity is analyzed with applying a mode solver built finite element method (FEM) incorporating multi-physics software " COMSOL ". A nano film of silver is coated as sensing layer on the external surface for easy sensing and more practical realization. The biosensor unveils the highest wavelength sensitivity valued 21000 nm/RIU and amplitude sensitivity valued 2456 RIU−1, and corresponding wavelength resolution of 4.76 × 10−6 RIU and amplitude resolution of 4.07 × 10−6 RIU, respectively, using wavelength interrogation technique (WIT) and technique of amplitude interrogation (AIT), in detecting effective refractive index range 1.33 RIU and 1.42 RIU. Besides, the consequence of changing structural parameters like – pitch, diameter of air hole, various plasmonic metals and silver (Ag) layer thickness are also resulted in results section. The sensitivity of the offered sensor is analyzed to examine the means of spectral loss depth, resolution and amplitude sensitivity. In arrears to the modest scheme, highly sensitive and resolution nature, the offered design can be precisely applied in detection of bio molecular analytes [ABSTRACT FROM AUTHOR]