By taking into consideration what is only One, the « second » cannot exist, because in accordance with the Haqiqa, nothing exists but The One who is at the origin of Existence. Allah is now as He ever was, and nothing exists but Him.
First of all, nothing forbid us to do dhikr with the Name "Allah" neither in Allah's book nor in the Sunnah of the Messenger of Allah ﷺ. Another argument is the fact that the companions did not practice this kind of dhikr.
It is the visible expression of The One who is Named. The Name (Al Ism) is the basis of all His Names and in the same time it gathers them together. It is the founding principle of all the meanings and their secrets.
Monotheistic religions that have an esoteric tradition like Christianity and Islam, have long time ago spoken explicitly about the divine light and its experiencing through spiritual vision.