Design Of Tunable Optical Biosensor Based On Metamaterials

Optical biosensors have an increasing attraction in the field of biomedical detection.Designs of sensors based on surface plasmonic metamaterials are of great importance in detecting the change of refractive index of gas molecules or biomedical solutions,owing to its high sensitivity to metal nanostructures on the surface and surrounding medium.As artificial materials,metamaterials have unique optical properties,and the structure is usually small and light after fabricating,which is convenient in integration.Traditional optical metamaterials can not adjust its optical properties once the processing is completed,greatly limiting its application in the actual environment.This paper designs two optical biosensors based on phase change material VO₂ and anisotropic two-dimensional material?-Mo O₃with different working principles at visible range.The first is a tunable hyperbolic metamaterial biosensor based on Brewster modes,which can be excited from free space.The multilayered HMM takes VO₂ as dielectric medium and the Brewster angle is calculated using the TMM.An abrupt change of phase can be observed at the Brewster angle and the corresponding Goos-H?nchen shift is calculated.The calculated refractive index sensitivity of this proposed biosensor reaches a maximum of6.75?10⁶ nm RIU^-1 before transition and 350nm RIU^-1after transition.The highly sensitive and flexible optical biosensor can flexibly tune its two working states responding to the needs of different measurement ranges by applying energy from the outside to change the state of VO₂.The second is a tunable MIM biosensor based on?-Mo O₃.The dielectric constant in the x and y crystal directions are different.As a result,there is no need to apply energy from the outside to tune the biosensor when the polarization state of the incident light is changed or the sensor platform is rotated.The Finite difference time domain calculation software FDTD Solutions is used to calculate the electromagnetic field of the structure.The designed MIM structure has an obvious characteristic absorption peak in the visible range,and can be shifted by changing the polarization state of the incidence.Changing the thickness of the dielectric layer to optimize the absorption peak of the MIM sensor at visible range,the peak becomes more sensitive to the change of the environmental refractive index.The highest sensitivity of460nmRIU^-1 can be achieved in the application of detecting solution RI.By tuning the polarization angle of the incidence,the working wavelength can be adjusted about 5nm.The two designed optical biosensors can be tuned by applying energy from the outside and changing the polarization angle of the incidence respectively.The max sensitivity of two biosensors can reach6.75?10⁶ nm RIU^-1 and 460nm RIU^-1 at visible range.It provides new ideas for the future research and application in design of optical biosensors,and plays a major role in medical diagnosis and fixed-point care.