Design And Research Of The Pressure Sensor Based On Two-dimensional Photonic Crystal

Photonic crystal is a new kind of optical micro structure with a low-loss periodic dielectric medium.Photonic crystal can control the flow of photons just like semiconductor controls the flow of electron.The most important characteristic of photonic crystal is photonic bandgap.By introducing defects into the structure,optical waveguide and resonant cavity can be made.In this thesis,point defect and line defect are introduced into the photonic crystal in order to get a narrow-band filter.The design of the structure and the optical characteristic are simulated by COMSOL Multiphysics 5.0.In the meantime Rsoft2013 is used to analyze the bandgap of the photonic crystal.Then pressure is introduced and transmission spectrum is analyzed.An obvious red-shift linear relationship can be observed between resonant wavelength and pressure,allowing linear measurements of the pressure.Four sensors are designed and simulated in this paper based on GaAs substrate.The sensor with square lattice GaAs rods is studied first.The lattice constant is 580 nm and the radius of the rods is 130 nm.By removing two rows of rods,waveguide can be achieved.The radius of one rod in the centre of the structure is change to 0.3r in order to achieve resonant cavity.By optimizing the structure,the quality factor reaches 31257 and the sensitivity reaches 8.7nm/GPa.The sensor with triangular lattice GaAs rods is also studied.The lattice constant equals 540 nm and the radius of the rods is 130 nm.Waveguide can also be achieved by removing two rows of rods.Resonant cavity is made by removing one rod in the centre and adding two rods which the radius is 0.3r into the structure.By optimizing the structure,the quality factor reaches 1500 and the sensitivity reaches 13.9nm/GPa.The sensitivity is much higher than the structure with square lattice.The sensor with GaAs rods has high sensitivity but the structure cannot stand high pressure and it costs high,so the sensor with air holes should be studied in order to overcome these disadvantages.The sensor with square lattice air holes is studied first.The lattice constant is 450 nm and the radius of the air holes is 0.34 a.By removing two rows of air holes,waveguide can be achieved.By removing one air hole,resonant cavity is made.By optimizing the structure,the quality factor reaches 4579 and the sensitivity reaches 13.6nm/GPa.The sensor with triangular lattice air holes has the best performance.Waveguide can also be achieved by removing two rows of air holes.The resonant cavity is made by removing one air holes and moving two air holes in the centre of the structure.The quality factor of the sensor is 37688 and the sensitivity reaches 14.7nm/GPa.