I've listened to some presentations by an engineer from a local company that is the premier supplier of submarine periscopes to the US and allies.
Quite a bit of technology that goes into a $15 million periscope - apparently the new units no longer penetrate the hull.
http://www.eo.kollmorgen.com
I'm planning to take a course in optoelectronics as a senior elective.
Downloaded the class-notes for a previous section and it seems like an intense course.
Can't wait!