The Research On Application Of Photonic Crystal Bandgap Theory In Solution Concentration Measurement

Photonic crystal is a new kind of photonic material in which the substance’s dielec-tric constants is distributed periodically. Since the 2d photonic crystal, photonic crystal fiber and photonic crystal waveguide have porous microstructer it is easy to detecting and measuring and via filling with gas and solution. Therefore, the photonic crystal de-tecting/measuring technology became a hot topic in measuring gas density, environmen-tal pollution, biodetector, molecular density and solution concentration etc. This thesis studied the method of measuring solution concentration such as copper chloride, copper nitrate, methanol, active acid, ethanol, based on the band gap width of photonic crys-tal and photonic crystal transmittance. Firstly, using the planewave expansion method studied the band gap structure of quadratic lattice photonic crystal, triangular lattice photonic crystal, honeycomb lattice photonic crystal and diamond structured photonic crystal. We find that in the scope of bigger dielectric constant, the honeycomb lattice has wider photonic band gap and photonic band gap will change according to dielectric constant. The diamond structured photonic crystal also has wider photonic band gap and the change of band gap structure is very sensitive to dielectric constant. Based on these informations, we studied the relation between the molarity and honeycomb band gap width under the condition like copper nitrate and copper chloride. Through data analy-ses we find that there exists linear relation between concentration and band gap, and get the linear fitting equation and fitting rate and propose the concentration measurement method based on the honeycomb lattice photonic crystal band gap width. Studied the relation between the band gap width of diamond structured photonic crystal and con-centration of methanol. Calculation results again show that there exists linear relation between the concentration and the band gap width. Secondly, based on the finite element time domain method, obtain the transmission spectrum quadratic lattice photonic crystal with the help of Meep software.Through simulation,get the relation of the concentration and transmission using ethanol,methanol,respectively.We find that the transmission is proportional to the concentration.Then we get it’s linear fitting function and fitting rate, propose the measuring method based on the above results.