This light did not simply "appear", but is part of the Creation. Nor does this "light" refer to Jesus Christ. If you say that this "light", is Jesus Christ, then Jesus is part of the Creation.
This light is indeed YHWH [later to be revealed as Christ Jesus] -
YHWH came into the realm of space and time [our four dimensions] to manage the creation process upon the Earth.
Let there be light is God coming into our universe to continue the process of creation upon the Earth culminating in the creation of human beings.
And Jesus is about life - both naturally and spiritually.
His appearance brought supernatural light upon the virgin world before the creation of our Sun and Moon - plants were already in existence before this.
2Cor 4:6 For God, who said, “Let light shine out of darkness,” has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ.
1Tim 6:15 which in his own seasons he, the blessed and only Potentate, shall show, the King of kings, and Lord of lords;
16 who alone hath immortality,
dwelling in light unapproachable; whom no man hath seen, nor can see: to whom be honour and power eternal. Amen.
Exodus 33:18 Moses said, “Please show me your glory.”
19 And he said, “I will make all my goodness pass before you and will proclaim before you my name ‘The LORD.’ And I will be gracious to whom I will be gracious, and will show mercy on whom I will show mercy.
20 But,” he said, “you cannot see my face, for man shall not see me and live.”
21 And the LORD said, “Behold, there is a place by me where you shall stand on the rock,
22 and while my glory passes by I will put you in a cleft of the rock, and I will cover you with my hand until I have passed by.