Fig. 3
From: Ultrafast perturbation maps as a quantitative tool for testing of multi-port photonic devices
Experimental investigation of a 1 × 4 MMI and comparison with predictions. a SEM image of the MMI. The design parameters are L = 29.4 μm and W = 8.0 μm but the SEM image shows fabricated length L = 30.2 μm and width W = 8.05 μm. b Calculated fieldmap of the design device for ingoing excitation by the fundamental mode of the input waveguide. c Experimental and theoretical perturbation maps for the transmittance between the input waveguide fundamental mode and the top and second top waveguides fundamental modes, showing a remarkable agreement in their details. The amplitude of the color bar is ±0.25 for the experimental maps and ±0.35 for the theoretical ones. d 2D maps of the correlation Γ for varying theoretical MMI region dimensions L and W, for the two considered output modes. The red dot and cross indicate the MMI design and SEM measured dimensions, respectively, and the contour lines indicate a 2% (solid), 10% (dash), and 20% (dot) decrease of the correlation with respect to the maximum correlation
