I am trying to simulate a nanotaper and a fiber (SM-400) for designing an edge coupler. As a part of the simulation, I am trying to make an overlap calculation between these two by the built-in overlap integral function in the mode solver. The mode profile of the nanotaper tip and fiber tip looks quite different yet I am getting an overlap of 81%. Could you please tell me, is it the correct way or not?
Also, the modal area of these two modes are different by a factor of 2, so having an overlap of 81% seems quite questionable. In the application library, I saw the edge coupler simulation was done in this way.
Please note that, the nanotaper has a dimension of 125 nm*30nm while the fiber has core of 1.5 µm and cladding of 20 µm.