In spite of the success of fluorescence microscopes (such as STED, STORM and PALM) in biomedical field, which have realized nanometer scale imaging resolution and promoted the great development of bio-medicine, the super-resolution imaging method for non-fluorescent sample is still scarce, and the resolution still has a big gap to nanometer scale. Among existing methods, structured illumination microscopy, PSF engineering, super-oscillatory lens and microsphere assisted nanoscopy are more mature and widely applied. However, limited by the theory itself or engineering practice, the resolution of these approaches is hard to break through 50 nm, which restricts their application in many fields.
Enlightened by synthetic aperture technique, researchers proposed spatial frequency shift super-resolution microscopy through shifting and combining the spatial frequency spectrum of imaging target, which is a promising super-resolution imaging scheme as its resolution limit could be broken through continually. Currently, due to the restriction of the refractive index of optical materials, the wavelength of illumination evanescent wave is hard to be shorten when generated at prism surface via total internal reflection, which determines the highest resolution of this spatial frequency shift super-resolution imaging system. Another deficiency of this scheme is the difference of imaging resolution in different directions, as only in the direction along the wave vector of illumination evanescent wave, the image has the highest resolution; while in the direction perpendicular to it, the image has the lowest resolution, as same as that obtained by far-field illumination.
In order to solve the above thorny questions, a new model for evanescent wave generation has been proposed, which could generate omnidirectional evanescent wave with arbitrary wavelength based the phase modulation of nano-structure, and solve the both problem in imaging system at the same time. To verify the possibility of our scheme, we set up a complete simulation model for spatial frequency shift imaging scheme, which includes three parts:the generation of evanescent wave and its interaction with the nano-structures at imaging target, with could be simulated with FDTD algorithm; the propagation of light field from near-field to far-field, from the sample surface to the focal plane of objective lens, which could be calculated with angular spectrum theory; the propagation of light field from the focal place to the image plane, which could be calculated with Chirp-Z transform.
With this complete simulation model, we compared the resolution of microscopy illuminated by evanescent wave and propagating wave, firstly. The results verified the super-resolution imaging ability of evanescent wave illumination, and also demonstrated the influence of refractive index of prism, as higher refractive index makes shorter wavelength of evanescent wave and higher resolution of spatial frequency shift
surface are simulated by using molecular dynamics simulation at the atomic level. It finds that the dislocation loop direction, bulk temperature, depth, and helium atoms have great influence on the motion of the dislocation. This study shows that the 
dislocation loop (
is the Burgers vector, 
is the surface normal direction) tends to move towards the surface and the 
dislocation loops decompose into 
dislocations at elevated temperatures. Helium atoms impedes the migration of dislocation loop and increases its retention time. The existence of dislocation loops results in the uneven distribution of helium atoms under the W surface, and will potentially affect the surface morphology of tungsten.
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号