Visible part of spectrum does not get involved to nucleus. Maybe electrons. Which can only make plasma or increase pressure if it is constrained in a cube. If pressure can reach the critical level, then deuterium can be used for fusion(like pressurizing through lazer bombardment).
So, you need sudden increase of pressure right(to increase probability of tunneling and imploding of D-T pellet)? Which also needs high temperatures.
http://en.wikipedia.org/wiki/Radiation_pressure says on earth, 9.15 N per kilometer-square
Deuterium pellet initiating pressure is http://link.springer.com/article/10.1023%2FA%3A1020858108669#page-1
http://www.wolframalpha.com/input/?i=150+MPa 150MN per meter square so you need :
16,393,442,622,950 meter-square of lightened area. 16 Tera Meter Square
This number is for 1-meter-squared area target. Deuterium pellet is micro-meter sized so there are 1,000,000,000,000 pellets on 1m² area, which means only 16meter-square is enough to just to pressurize one of pellets.
Then, if you want to also increase the temperature by a great deal(maybe to heat 1micro-meter pellet to 100M Kelvin), you would need %3 of earth surface.
For 100M Kelvin, you may need to multiply the result maybe by a million.
Focused and concentrated LASER array is just more applicable for now.
If what you think was applicable, scientists would have used that already.