Tonicization" is what secondary dominants do. It is a cadence (as I understand the term), that's the point.
It's NOT a modulation to a new key - because that would mean the secondary dominant becomes the primary (of the new key)!
Tonicization just means strengthening a move to any of the diatonic chords (other than I). I can't quite see how this is possible without using a secondary dominant, because a V-I move is what we need to get a "tonicization" effect.
There are such things as secondary subdominants and secondary supertonics