> Light from the Sun isn't coherent, and you can't focus it with mirrors very far away. Lasers have many orders of magnitude less divergence when talking about distances measured in light-years.
To expand on your point, those characteristics become even more important when using the light received to decelerate at your destination, though it is worth noting that there are alternative means of deceleration that don't have the same requirements (eg. electric and magnetic sails).
To expand on your point, those characteristics become even more important when using the light received to decelerate at your destination, though it is worth noting that there are alternative means of deceleration that don't have the same requirements (eg. electric and magnetic sails).