Amylkie, if you remove the τε, or insert a τὸ (which means "the") before γέλασμα, you destroy the metrical scheme, the rhythm if you will, of Prometheus' utterance. Are you sure you want to do that? In any case, the definite article doesn't have the same standing in Aeschylean poetry that it does in prose. You can easily translate γέλασμα as "the laughter," without worrying about whether or not a τὸ is present.