Three-dimensional simulation of a nanophotonics device with use of fullwave software

Abstract

Using the FullWAVE software (www.rsoftdesign.com) that implements the finite-difference FDTD-method of solving Maxwell’s equations, we simulate the performance of a three-dimensional nanophotonics device comprising a sub-wavelength diffraction grating, a wide and a narrow planar waveguide, and a photonic crystal (PhC) Mikaelian lens located in a thin silicon film coated on a substrate containing a three-period Bragg mirror, with each period made up of silicon + silica layer. The device is intended to couple a focused laser beam with the focal spot of 3 × 4.6 μm2 and wavelength 1.55 μm into a planar waveguide of width 500 nm, resulting in a 125-fold “compression” of the input beam cross-section. The modeling has shown that the coupling efficiency amounts to 32% of the energy of the linearly polarized elliptic Gaussian beam focused onto the grating and 52% when a plane wave segment is incident onto the grating. For comparison, the grating-unaided coupling of light into the same device by the butt-coupling of light into the wide waveguide’s silicon film gives the efficiency as low as 8%.