| Photonic crystal sensor is widely used for lab-on-a-chip applications due to its advantages including high sensitivity,ultra-compact size,more suitable for multiple sensing and monolithic integration.When some suitably designed cavities are interlaced-coupled to a photonic crystal waveguide,we can detect several resonant wavelength dips so that a photonic crystal sensors array is designed.We can use photonic crystal sensors array to realize multiple detection,and it is essential for optical integrated circuit in the future.Low crosstalk between different photonic crystal sensors can be achieved by introducing radius-graded structure.To achieve photonic crystal cavities that possess smaller volume,higher quality factor and higher sensitivity,we focus on the study of 1-D photonic crystal nanobeam cavities and its combination with slot structures in this paper.The main work in this paper is shown as follows:Firstly,based on silicon substrate,we present a new optical 1-D photonic crystal nanobeam cavity and simulate its sensing properties.By simulating the bandgap and mirror strength of the 1-D photonic crystal nanobeam cavity,we can get the optimized air hole's radius and slot width.Then we introduce the air holes whose radius is parabolic tapered into a 1-D silicon waveguide to form the sensor structure.We use the stable first mode wavelength peak for sensing.Through the 3D-FDTD simulation of the sensor structure,we achieve a very high Q of?109,a small mode volume of 0.9(?/n)3,and a sensitivity of 109.3nm/RIU?Secondly,in order to enhance the light-matter interaction between 1-D photonic crystal nanobeam cavity,via combining the advantages between 1-D photonic crystal nanobeam cavities and slot structures,we present a novel optical nanosensor based on the design of a single 1-D photonic crystal slot nanobeam cavity.Thus the sensor structure can localize the maximum field to a region of lower refractive index and enhance the light-matter interaction,finally we obtain high sensitivity.In order to discuss the sensing performances of the proposed single 1-D photonic crystal slot nanobeam cavity influenced by the width of the slot,numerical 3D-FDTD simulations are calculated.Due to the trade-off between sensitivities and Q in label free optical sensors,in this paper we choose a trade-off value of the slot width(50 nm)to achieve ultra-high Q-factor(-2.67×107)while keep an attractive high sensitivity(750.89 nm/RIU)simultaneously.The performance advantages of the designed single 1-D photonic crystal slot nanobeam cavity make it a promising candidate for on-chip optical sensing.At last,we study the photonic crystal sensors arrays based on 2D photonic crystal substrates to improve the integration of optical sensing structures.We present two type of sensors array structure,including a temperature sensors array based on square lattice Si rods in air back-ground photonic crystal structure and a radius vertical graded nanoscale interlaced-coupled photonic crystal sensors array.The temperature sensors array structure is formed by introducing 9 cavities to a W1.15 waveguide,which adds the numbers of the sensors array and is more suitable for integrated system.Each cavity can be used for temperature sensing independently and the sensitivity of the sensors array can reach S=0.067 nm/?.The radius vertical graded nanoscale interlaced-coupled photonic crystal sensors array structure is formed by changing air holes'radius of six rows that are nearest to W1 waveguide,and then introducing 2 L3-cavities and 3 H1-cavities coupled to the waveguide.Through the optimization of the parameters of the cavities,we can achieve a sensors array which possesses high-Q,and makes it more suitable for optical integrated circuit.All the above studies offer new ideas in high sensitivity and high integration photonic crystal sensor design and applications.It has important reference significance and application value for the ultra-large scale sensor array in the future. |
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