Mirror reflective interference axial-narrowing super-resolution microscopy

The axial resolution of conventional confocal microscopy is usually larger than 600 nm. In super-resolution microscopy, although Stimulated emission depletion (STED) microscopy offers lateral resolution beyond the optical diffraction limit [1, 2], the axial resolution often remains the same, unless a special set of phase modulation is employed. With two opposing objectives in 4Pi microscopy, the interference of confocal excitation light can confine the axial excitation field to ~ 100nm [3]. But, 4Pi requires the precise alignment of two diffraction-limited focal spots by two opposite microscope setups.