I dont think this is about light, its about heat. If you take a magnifying glass and focus the suns heat into something that produces steam, and or you take a satellite dish and focus the sun at a specific point, you can generate large amount of heat. this is already used elsewhere and is proven to work. Also Arizona land and climate isnt really suited for growing crops.
This is not true, many crops are successfully grown in the Arizona desert, usually irrigated out of the rivers. Agriculture is what made the Phoenix area grow in the early days. The land is fertile, the growing season is long- the only thing at issue is water. Areas that cannot be watered from the rivers tends to be the stark desert that most think of in Arizona but don't get the idea that Arizona is not a good place to farm. Of course farm land is being covered up with houses these days, but at one time a lot of food was grown in Arizona- and it still is an important part of Arizona's economy.
A lens is an optical device that focuses the light rays from the sun. The lens does not focus thermal energy, as from convection heating.
All the heat in concentrated on a boiler section which generates superheated steam, which runs turbines.
The mirrors track the sun and focus the heat on the boiler, like a magnifying lens on an ant.
I remember sending many of them up in smoke.
Easy technology, given today’s computer controlled tracking systems, and efficient motors moving the mirrors.
Freznel lens would help too.