Research On Nanolaser Based On BIC Mode

With the advancement of technology,photonic devices are becoming more and more miniaturized,so far the size of lasers can also reach the order of nanometers.In the research of photonic devices,especially the miniaturization and integration of nanolasers are constantly studied in depth.Confining light without absorbing it is a key problem for lasers.Conventional lasers use optical cavities that trap light using mirrors,total internal reflection or scattering in periodic microstructures such as photonic crystals.For these systems,the Q factor is limited and depends only weakly on the geometry of the cavity.In recent years,the bound state in the continuous state(“BIC”)has attracted the researching interest of various major groups because of its infinitely high Q factor and non-radiation state.The real BIC can only be generated in the ideal state of an infinite system,so the real BIC will be converted into a quasi-BIC under the constraints of materials and structures.Due to its high-Q factor and small radiation,quasi-BIC has attracted wide attention.It can be applied to sensors,lasers,filters and so on.At the same time,the quasi-BIC is a mode that effectively limits light and can generate ultra-high Q factors based on the geometry of the system.Based on these characteristics,it has great advantages in the lasering field,such as low threshold value and easy tunable lasering wavelength.In this paper,we have theoretically studied nanolaser based on quasi-BIC mode supported by all-dielectric nano-structure.The main research results are as follows:(1)The spectral characteristics of the eccentric ring are studied by using all-dielectric materials with a high refractive index.By adding an offset d,the spectral characteristics of the ring with or without d are compared.Due to symmetry protection,when d?0,a very sharp peak appears in the emission spectrum.The Q factors of each parameter structure are calculated,and the maximum Q factor can reach 9.6×10~4.High-Q factor makes the eccentric ring very suitable for laser.The lasering behavior of the eccentric ring is simulated by FDTD Solutions.The laser threshold is only6.46?J/cm~2.At the same time,the lasering wavelength and threshold can be adjusted by controlling the structural parameters of the eccentric nanoring.And the spectral characteristics and lasering behavior of eccentric ring with different materials are compared.(2)We propose a new nano-structure to study the spectral characteristics and lasering behavior of eccentric nano-spheres of all-dielectric materials.Similar to the study of eccentric nanorings,two very sharp peaks will appear in the reflection spectrum when d?0.The electric field distribution at one resonance peak is mainly distributed in the inner and outer spheres,and the electric field at the other peak is only distributed in the cavity of the nanospheres.We mainly discuss and study the first peak.When the asymmetry parameter is smaller,the Q factor is larger and the quasi-BIC is closer to the real BIC,and the local electric field value is very large.Based on these advantages,it is found that the lasering threshold of the eccentric sphere is very low,only 2.3?J/cm~2.