Ultra high resolution point spread function based on photonic crystal lens for 3D biomedical applications

Abstract

In this paper, a novel design of superlens based on photonic bandgap structure for high resolution point spread function (PSF) is reported at a wavelength of 3 μm. The lens is able to generate a non-diffraction Bessel beam with a number of focusing points with variant resolution limits. The optimized structure provides high resolution in both lateral and axial directions. The maximum achieved lateral resolution of PSF is down to ~ 0.27λ with corresponding axial resolution down to ~ 0.57λ attaining a FOM, the inverse of the product of both resolution limits, of ~ 6.49. Meanwhile, the maximum axial resolution is down to ~ 0.4λ with corresponding lateral resolution down to ~ 0.33λ with a FOM of ~ 7.34. In addition, the proposed design is able to generate a focusing point extended in space up to ~ 0.98 µm with a sub-diffraction lateral resolution down to ~ 0.47λ. Furthermore, the reported superlens demonstrates a sub-diffraction focusing in lateral direction along the range the bandgap wavelengths (from 2.4 to 3.6 µm) showing a significant increase of focal depth when decreasing the operating wavelength. Remarkably, a high focal depth up to ~ 1.77 µm is achieved at the operating wavelength of 2.6 µm. The suggested design has a tremendous potential in 3D biological imaging and biosensing applications.