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In this work we provide a numerical simulation for doped silicon nanosphere with a validation using 3D FDTD commercial kit (Lumerical). We have calculated the absorption efficiency of silicon microspheres of different doping concentration based on Mie resonance. Meanwhile, filling the surrounding medium with specific gases which have absorption in the MIR region changes the calculated spectrum. The input parameters for this simulation were the radius of the sphere, the complex refractive index of the sphere’s material and the host gas, and the targeted wavelength range. The absorption spectra were calculated for a silicon microsphere of radius 0.5 microns and different doping concentrations. In each case, the microsphere is surrounded with air and then with Methane. There is no peak shift between the two curves. However, there is an oscillation in the curve of Methane in the wavelength range where the absorption region of Methane lies. Increasing the doping concentration of silicon makes the absorption curve of sphereair shift to the left (blue shifted). This in turn makes this oscillation more visible, especially at doping concentration of 5×1020 cm-3. This can be explained that, increasing the doping concentration makes the silicon sphere more metal alike and increases in turn the surface plasmonic effect. That opens the door for multitude of sensing applications using the concept of Mie resonance.
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