Research On Optical Readout Thermal Detection Technology Based On Thermo-optic Effect

At present,there are two major categories of infrared detectors,one is the photodetector,the other is the thermal detector,while both of them are restricted by the readout circuit noise.The optical readout scheme is not restricted by the readout circuit,but the existing optical readout technology is limited by the readout mechanism and the optical system.Therefore,new optical readout mechanism and implementation method are urgently needed.In this paper,a scheme is proposed to read out infrared light using scattering spectra of metallic nanostructure that is controlled by thermal-optic effects of microcavity dielectric based on a combination of local surface plasmon resonance(LSPR)and Fabry-Perot(F-P)microcavity,and the feasibility of that is approved according to the principles of simulation,experiment and optical testing.The main content of this paper is including but not limited to:(1)Researching on LSPR characteristics of nanostructure in different material,shape and size by finite-difference time-domain(FDTD)algorithm,analyzing the reflective properties and figuring out the limitation of dielectric F-P cavities,and concluding the best material and structure for this optical readout scheme.(2)Researching on the LSPR scattering properties of nanoparticle-coupled microcavity structure,analyzing its principles and temperature sensing characteristics and coming up with a plan to read out infrared light by scattering visible light based on that.(3)Designing and fabricating thermal-optic modulation unit,the core in optical readout scheme.The unit consists of two layers of Ti O₂ film with high refractive index as cavity wall,and high thermal-optic coefficient polymer NOA73 as interlayer.The cavity surface contains Al disk nanostructure array as scattering particle.The parameters of fabricating high-quality Ti O₂ films and Al disk nanostructure arrays were investigated.It was found that the Ti O₂ films fabricated at high temperature,high sputtering power and low pressure had better quality.(4)Making optical tests of the thermal-optic modulation unit.Verifying that the thermal-optic modulation have more than 95%of absorptivity for 3.39?m medium-wave infrared light and temperature sensitivity is 0.24 nm/?in range of 605?640 nm spectrum.Verifying the feasibility of the optical readout scheme for 3.39?m infrared radiation and laying a foundation for implementation of optical readout detection and imaging of infrared light.