Can't wait.
The Greek word, "photizo," means illuminate, bring to light, make evident, or reveal. Whatever it was they had been "once enlightened" something had been brought to light to them, revealed to them. It's the same word the author of Hebrews used when he wrote,
Hebrews 10:31-33
It is a terrifying thing to fall into the hands of the living God. But remember the former days, when, after being enlightened, you endured a great conflict of sufferings, partly by being made a public spectacle through reproaches and tribulations, and partly by becoming sharers with those who were so treated.
and the same word Paul used when he wrote,
Ephesians 1:15-21
For this reason I too, having heard of the faith in the Lord Jesus which exists among you and your love for all the saints, do not cease giving thanks for you, while making mention of you in my prayers; that the God of our Lord Jesus Christ, the Father of glory, may give to you a spirit of wisdom and of revelation in the knowledge of Him. I pray that the eyes of your heart may be enlightened, so that you will know what is the hope of His calling, what are the riches of the glory of His inheritance in the saints, and what is the surpassing greatness of His power toward us who believe. These are in accordance with the working of the strength of His might which He brought about in Christ, when He raised Him from the dead and seated Him at His right hand in the heavenly places, far above all rule and authority and power and dominion, and every name that is named, not only in this age but also in the one to come.
Both passages are about saved people. I cannot find an example of enlightenment in the epistles applied to the unsaved.