Research On Photonic Crystal Sensor In The Near-infrared Band

The photonic crystal is an artificial microstructure proposed by John and Yablonovitch at the same time in 1987.Different from the function of total reflection to guide and transmit photons,the photonic crystal provides a new type of light guiding mechanism,which guide and control the light transmission through the existence of photonic band gap formed by periodically arranging the dielectrics.Owing to their unique photonic band gap,photonic crystals are used in various kinds of all-optical functional devices,including waveguides,filters,fibers,lasers,beam splitters,and sensors,etc.The photonic crystal sensor has attracted great attention in the sensing field due to its advantages of short response time,strong anti-interference ability,small size,easy integration,and so on.We employed the finite-difference time-domain method to construct different kinds of defects based on the two-dimensional quasi-periodic and periodic photonic crystals,and studied their spatial mode profiles of defects,the difference among them was also compared,finally the concentration-gradient sensor and the protein-attaching sensor based on the twelve-fold quasi-periodic photonic crystal were proposed respectively.The multi-channel slotted air hole photonic crystal sensors based on the silicon and germanium background materials are also proposed.The proposed concentration gradient sensor and the protein adsorption sensor are based on the twelve-fold quasi-periodic photonic crystal consisting of silicon pillars arranged in a free-flowing liquid environment.Through designing different defect bodies,their sensitivities reach the highest value under different working conditions,respectively.The detection limit of the concentration gradient sensor is 8.75×10-5 RIU for the alteration of the background refractive index,and the detection limit of the protein adsorption sensor is 5 nm for the alteration of the protein layer's thickness.Air slots are introduced between the air holes connecting the defect bodies of the silicon-based and germanium-based multi-channel photonic crystal sensors,and make the electromagnetic field energy limited within the slots,which enhanced the light-matter interaction,and the sensitivities of the sensors are increased.By studying the effect of the defect body's parameters on the defect modes,the sensors are multiplexed and optimized.The sensitivity of the silicon-based slotted air hole photonic crystal sensor can be larger than 720 nm/RIU,and the germanium-based slotted air holes structure photonic crystal sensor can be larger than 810 nm/RIU.