| The optomechanical system has attracted many interests because of the crossover control of mechanical and optical degrees of freedom therein.Most of the current optomechanical systems are made of silicon,gallium arsenide,silicon nitride,etc.,where the eigen frequency,decay rate,and optomechanical coupling rate,are determined experimentally and used by most theorists.Recently,many emerging materials,such as 2D materials,have been considered as potential candidates for optomechanical applications.Due to high mechanical and optical quality factors originated from the atomically flat surface,transition metal dichalcogenides can be used in optomechanical systems.In this thesis,the key optomechanical parameters and absorption of optomechanical crystal cavities based on TMDC have been studied systematically,including:The first principles method is used to study the electronic structure,mechanical properties,optical properties and photoelastic properties of TMDC bulk materials.The photoelastic properties reflect the change of materials’ refractive index under strain.The research results show that when the same strain is applied to TMDC,the refractive index changes much more in the out-of-plane direction than that in the in-plane direction,which leads to greater photoelastic strength.In addition to the photoelastic effect,the moving boundary effect can also cause optomechanical coupling.We have studied the contributions of these two effects separately.The finite element method is used to simulate the optical and mechanical fields of optomechanical crystal cavity based on TMDCs.Simulation results show that with the increase of anion atomic number,the eigenfrequencies of cavity and resonator decrease,the quality factor of cavity increases,the quality factor of resonator decreases,and the absolute value of optomechanical coupling rate increases.When the light field propagates in the in-plane or outof-plane direction of the TMDC,the mechanical resonator appears to be stretched or compressed.The absorption properties of the optomechanical crystal cavity are studied when light propagates in the in-plane and out-of-plane directions of the TMDC.It is shown that obvious optomechanical induced transparency is manifested in the optomechanical system when light propagates in the in-plane direction.However,it exhibits optomechanical induced amplification when the light propagates in the out-of-plane.This phenomenon can be attributed to the lower quality factor of the cavity and higher decay rate of the optical field,which leads to the reduction of the critical power for inducing transparency.In summary,TMDC-based optomechanical systems have excellent optomechanical properties and have potential applications for detecting the properties of TMDC via optomechanical coupling. |
