Design And Application Of Optical Microsensor Based On VCSEL

With the rapid development of the Internet of Things,optical sensors are more and more widely used in people's daily lives.Among them,laser sensors have attracted tremendous attention due to their ultra-fast response speed and very high sensitivity.In the field of laser sensing,vertical cavity surface emitting laser(VCSEL)is an important light source and sensing detection device attribute to its advantages such as low power consumption,small size,and easy integration.However,the VCSEL device is not sensitive to the environment and the miniaturization of VCSEL is not enough,which increases the manufacturing difficulty of on-chip integrated laser sensor,so it needs to be improved in structure design to be better applied in the sensing field.Therefore,through the integration of high contrast grating(HCG)and VCSEL,the structure can be improved to make the device size more compact,and the interaction between the resonator and the environment can be increased to improve the sensitivity.In this paper,based on the linear and nonlinear gain materials,we have designed the resonant cavity and analyzed the sensing principle.The optical microsensor design of grating feedback VCSEL is proposed and its sensing characteristics are simulated.The main research work of this paper is summarized as follows:(1)Firstly,the development and structure of VCSEL are introduced,and the structure of grating feedback VCSEL is proposed.Then the diffraction theory of grating and guided mode resonance theory are expounded,and we have explained the sensing principle based on grating feedback VCSEL.In addition,the numerical simulation method that is finite-difference time-domain(FDTD)algorithm and FDTD Solution used in this paper are introduced.(2)The structure design of 850 nm VCSEL based on grating feedback is proposed.The 3D simulation of the device is carried out using FDTD Solution,the spectrum and field distribution characteristics of HCG-VCSEL are studied.Finally,the single-mode HCG-VCSEL with narrow line-width is obtained.Then based on HCG-VCSEL,the refractive index of the grating and the refractive index of the simulated environment are changed to study the sensor characteristics.(3)Ultra-compact grating feedback organic VCSEL is proposed and its potential application in gas sensing field is discussed.Firstly,we simulate the dye gain Rhodamine 6G and the device in FDTD Solution,and a grating feedback organic VCSEL with a central wavelength of 568 nm and a threshold of 12.22?J/cm² are obtained.Then,the background refractive index of the simulation region is changed to simulate the gas environment to study its sensing characteristics.The results show that the laser spectrum have a linear shift,the approached bulk sensitivity and figure of merit(FOM)reaches to 26.5 nm/RIU and 441/RIU,respectively.Its detection resolution is at the level of10^-3.The laser sensor designed by us can accurately detect the changes in the gas environment.