Research On Narrowband Absorption And Its Application Based On Metasurface

Narrowband metamaterial absorbers have gained lots of attention in recent years.They have a great potential in narrowband thermal emitters,narrowband photonic detectors and high-sensitive sensors.This research is mainly carried out on the application of narrowband absorption in thermal emission,refraction index sensing and humidity sensing by using the angle-insensitive narrowband structure,ultrahigh directional absorption structure and grating FP cavity coupling absorption structure.It’s difficult for an absorber to realize narrowband absorption and angle-insensitivity at the same time.A high Q local resonant mode is used to realize such an angle-insensitive narrowband absorption.And it can be used as a angle-insensitive narrowband thermal emitter.The absorber has a higher Q factor compared to other local resonances with the same metal material.By slotting the top structure to enhance the coupling between the resonant cavity and free space,this narrowband absorption mode can work at a lower frequency.To realize an ultrahigh directional thermal emission,we have designed an ultrahigh directional narrowband absorber by using the two opposite effects of diffraction.To the best of our knowledge,there are no other absorbers which have such a high directional absorption.These effects exist for the incidence of TE wave and TM wave and are fit for most local resonances.The research also finds that the narrowband absorber is very sensitive to environment refraction index.It is lack of research for metasurfaces in the application of humidity sensing.At present,the optical method of humidity sensing mainly adopts optical fiber.We find the FP effect can almost completely inhibit the absorption of metal grating.The obtained structure is sensitive to the thickness of the middle dielectric layer.The high sensitivity of humidity can be achieved by replacing the middle dielectric layer to the vapour absorbing material such as PVA.