I think so, as long as you know how far away your target is (the focal point) to position the sender, and you need a way to send the signals at the right angles "skimming" the sun at the right distance. (note: armchair amateur, this is just conjecture / thought experiments)
But why? Sending signal this way does not amplify the signal. Just point lasers directly at that point.
Protector by Larry Niven (1973) also features a gravity-powered telescope.