Basic High Frequency S-Parameters

This is my first time using COMSOL so this may be too basic of a question. I just downloaded COMSOL 5.2 and ran a few basic tests to make sure I was setting up the S-Parameters correctly. I chose the electromagnetic frequency domain and subsequent frequency analysis for my 3D model. First I made a 300nm x 300 nm block of air, with user defined e, u, and o of 1, 1, and 0 respectively. I set the PMC sides to be in the y direction, the PEC sides to be in the x direction, and ports to be in the z direction. I turned excitation on for port 1, the bottom, power to 1 Watt and an initial E-field in the x direction. I also set the same E-field with no excitation for port 2. After defining my frequency analysis range to be from 100 THz to 200 THz I ran my study. I ran an identical test with a box that was half n=1 half n=3. Both tests yielded the same result; S11 at 0dB throughout, S21 hovering around -260dB throughout.

This is not what I would expect. My question is, am I forgetting to set something rather basic? Is there something fundamentally wrong with my test?