Fig. 1

MAIM theory. a Two opposite evanescent waves are generated when two light beams are incident from both sides of the optical axis at an angle beyond the critical angle θ_c, which can interfere with each other to modulate the sample frequencies. b The position of the light focus at the back focal plane (BFP) of the objective determines whether or not the TIRF will appear. The larger the angle of incidence is, the closer the focal point is to the edge of the BFP and the shallower the penetration depth of the evanescent wave is. By changing the incident angle, we can obtain a series of images at different depths of the sample. c Simulated relationships between the incident angle and the penetration depth and normalized intensity of the evanescent wave at z = 0. d Simulated intensity distribution of the evanescent wave as a function of the incident angle and the sample depth