In the present study, the concentration of potassium chloride in their aqueous solution is investigated using optical sensor. Optical sensor is realized by 2D photonic crystal structure (PCS), which is made up of silicon materials (background/substrate) consisting of 8×8 air holes containing aqueous potassium chloride solution. The principle of measurement is based on logarithmic variation of photonic band gap (PBG) with respect to different concentrations of potassium chloride. The PBG is found by using PWE method. An experimental set up is designed to measure the output voltages with respect to same concentrations of potassium chloride. Simulation result revealed that the potential measured at photo-detector varies logarithmically with respect to potassium chloride concentration leading to an accurate measurement of potassium chloride concentration in aqueous solution. It was concluded that both PBG of PCS and potential at photo-detector varies logarithmically with respect to potassium chloride concentration.Keywords: Photonic crystal structure, photonic band gap, plane wave expansion, potassium chloride
