Study On Photoacoustic Properties Of Metal Nanostructures

Photoacoustic effect refers to the phenomenon that acoustic signals can be generated when objects are excited by light with periodically changing intensity.With the development and integration of biomedicine,material science and applied physics in recent years,photoacoustic effect has been applied into many fields such as photoacoustic imaging,photoacoustic spectroscopy as well as photoacoustic drive and so forth,in which how to use photoacoustic effect to produce ultrasonic signal with high intensity has become a key issue.In this context,the physical process of photoacoustic effect is explored in this paper.And new materials for photoacoustic conversion are designed by combining metal nanomaterials with thermal expansion materials.To begin with,the research advances and applications of photoacoustic effect and metal photoacoustic conversion materials are introduced.The theory of photoacoustic effect is analyzed from the physical and numerical simulation aspect.Then COMSOL Multiphysics software are used to explore the photoacoustic properties of different metal nanostructures.Through simulation analysis,the metal-insulator-metal(MIM)structure can achieve nearly 100%optical absorption in the resonance band due to the localized plasmon resonance effect,and can significantly improve the intensity of the photoacoustic signal.In addition,Cr-PDMS-Cr film structure which can achieve high optical absorption in visible band is proposed.Laser light with different wavelengths are used to excite the photoacoustic signal.The experimental results show that this kind of film structure can effectively improve the photoacoustic signal when compared with metal films.And the intensity of the photoacoustic signal is related to both its optical absorption and the thickness of the PDMS layer.Due to its simple structure and easy fabrication process,this structure can be applied as photoacoustic conversion material into photoacoustic imaging,sonic scalpel,ultrasound generator and many other fields.In the end,the content of this thesis is summarized and several future research directions of metal photoacoustic materials are proposed.