The Research On Extinction Properties Of α-MoO₃ Nanodisk

Phonon polariton is an electromagnetic oscillation wave generated on the surface of the crystal by the coupling of photons and optical phonons in polar crystals.Compared with the high loss characteristics of the plasmon polariton,the phonon polariton has the advantages of long propagation distance,low loss,etc.,and it has a stronger spatial confinement effect.The research of nanophotonic devices based on phonon polarions will have a great impact on the development of optoelectronic integrated devices.Based on the resonance phenomenon of the phonon polariton,the extinction characteristics of the α-MoO3 nanodisk will be studied in this paper by using the finite element method.In the mid-infrared region,the relationship between the dielectric constant of the aMoO3 nanodisk and the frequency of the excitation light is calculated,and the results show that the α-MoO3 nanodisk is anisotropic in the disk surface and in the thickness direction.By changing the polarization direction of the incident light,the influence of the polarization of the electric field on the extinction characteristics of the α-MoO3 nanodisk is studied.When the excitation light is perpendicular to the surface of the disk,due to the resonance of the phonon polariton,the components of the electric field along the x-axis and y-axis directions in the surface of the disk respectively excite a main extinction peak with different frequencies.As the polarization direction changes,two the intensity of the main extinction peak fluctuates from one to the other.When the excitation light is perpendicular to the side of the disk,that is,the wave vector is in the x-y plane and the electric field polarization direction is along the z-axis direction,a strong resonant extinction peak can also be excited.The influence of the structure of the aMo03 nanodisk on its extinction characteristics is also studied in this paper.The results show that as the diameter of the disk increases,the position of the extinction peak is red-shifted.As the height of the disk increases,the position of the extinction peak is blue-shifted.When the ratio of the disk diameter to the height is the same,the position of the extinction peak does not change.In summary,the extinction spectrum of the α-MoO3 nanodisk can be changed by changing the polarization direction of the incident light and the structural parameters of the α-MoO3 nanodisk.It provides the possibility to use the α-MoO3 nanodisk in the integrated optical path.