A D-shaped photonic crystal fiber (PCF) based plasmonic sensor for detection of a wider range of low refractive indexes operating at near to mid-infrared wavelengths is presented in this paper. Using finite element method (FEM) on the basis of y-polarized transverse electric (TE) mode TEy, wavelength sensitivity, amplitude sensitivity and resolution of the proposed sensor have been investigated numerically. Plasmonic material Gold (Au) and sensing layer are placed outside the fiber for attaining practically feasible detection mechanism. A thin layer of titanium dioxide (TiO2) is employed as an adhesive layer in order to attach the plasmonic material with silica glass. In the sensing range of 1.00 to 1.37, maximum sensitivities of 20000 nm/RIU and 811 refractive index unit (RIU)^-1 are obtained with resolutions of 5×10^-6 and 1.43×10^-5 RIU using wavelength and amplitude interrogation method, respectively. Therefore, it would be a suitable candidate for environmental monitoring, pharmaceutical inspection, organic chemical sensing, and other analytes detection.