Reb Avraham:
The droplet yearns
For the source.
The spark craves
The great fire.
I can bear no longer
The darkness of the world
Let us plunge
Into the sea of Nothingness
Let the grains of our existence
Melt within
His infinite being
Reb Zalman:
He who first
Carved my spark
From His blaze
Desires not
The extinction of my candle
Within his flame
Rather He seeks
The searing tremor of my soul
Longing
From afar, from the dark
Towards His light.

What is the source for the two opinions expressed by R' Avraham and the Alter Rebbe in this poem? Is there a story behind it, or a specific teaching?
Thank you so much
Yes, see Likutei Sichos Vol 27 pg. 267 ff. (273-4 specifically)
See also footnote 49 for earlier sources of this story.