  We reiterate, in more details, our previous proposal of using quasi-particle
interference to determine the pairing form factor in iron-based
superconductors. We also present our functional renormalization group(FRG)
results on LaFePO and Fe(Se,Te) superconductors. In particular we found that
the leading pairing channel in LaFePO is nodal s$_{\pm}$, with nodes on
electron Fermi surfaces. For Fe(Se,Te) system we found fully gapped s$_{\pm}$
pairing, with substantial gap anisotropy on electron Fermi surfaces, and large
gap is concentrated in regions with dominant $xy$ orbital character. We further
fit the form factor obtained by FRG to real space orbital basis pairing
picture, which shows more clearly the differences between different iron-based
superconductors.
