Starting physics concepts, but more for beginners:
http://www.physicsclassroom.com/Class/Youtube has some cool vids, but ussually only on general science. Ted ed, however can get a little more advanced. Some other channels i watch are vsauce, sci show, asap science, big think, and 1veritasium.
Also online college stuff like Udacity and EDX have awesome science courses. Some electronics, but no photonics or nano tech it seems
Although you can check out MIT open cour ware, they have EVERYTHING.
Nice topic btw, im really interested in all the things you mentioned, and have been looking for more specialized sources.