High Resolution through Graded-Index Microoptics

Abstract EN

By solving Helmholtz equations, relationships to describe propagating modes in an arbitrary graded-index planar waveguide are derived.

We show that in the quadratic- and secant-index waveguides a minimal mode width is 0.4λ/n, where λ is the wavelength in free space and n is the refractive index on the fiber axis.

By modeling in FullWAVE, we show that the high-resolution imaging can be achieved with half-pitch graded-index Mikaelian microlenses (ML) and Maxwell’s “fisheye” lenses.

It is shown that using a 2D ML, the point source can be imaged near the lens surface as a light spot with the full width at half maximum (FWHM) of 0.12λ.

This value is close to the diffraction limit for silicon (n=3.47) in 2D media FWHM=0.44λ/n=0.127λ.

We also show that half-pitch ML is able to resolve at half-maximum two close point sources separated by a 0.3λ distance.