How can I get or make gems above the "Star" level?

I maxed out my jeweler (level 10) and "Star" jewels are the best he can make, though the Auction House shows listings for Flawless, Perfect, and Radiant Star gems (higher levels than "Star"). Are these gems dropped in Inferno or somewhere else? If not, how can I make them? Do "plans" exist for these gem levels somewhere? If so, where can I find them?

The highest level gem plans are dropped items. You can see all the jeweler recipies here.

Unfortunately, I'm not aware of any specific place that has a higher chance of dropping them than anywhere else, so the standard diablo answer of "go to a level appropriate area, and kill things".

They are plans. From the Battle.net site you can see each gem and what it takes. You will see in the bottom of the picture that it says you get it from a Design. I suspect that since it takes tombs of secrets to create that it only drops in Inferno.