Third time: That's the top of the motor, that turns the DVD. That's why it spins! This has nothing to do with a diode.
There are two diodes in the sled, and the sled is the part in your second picture.
Your second picture is showing the sled from the middle, where the focusing rig is - a lens floating on some steel wires between some magnets. (There are coils around those magnets. When current is applied, the amount of it determines how the focus will change.)
This lens does the focusing for both the IR and the red diode, which are mounted into the sled from the sides. You can not see the diode untill you dig it out. The can will probably be the IR, and the red will most likely be a flat square thing in a piece of metal for heatsinking. You won't see them, untill you dig them out.
It's possible the red flat chip's heatsink may be held in place with screws. You need to get the diodes out, but unfortunatelly, you would have to build a collimating assembly from scratch, as you won't be able to stick that diode into an AixiZ module. It's still theoretically possible, but i wouldn't recommend trying. If you still can, you should reassemble this drive, put it in a computer, and buy a Sony NEC Optiarc 7190 for harvesting, because it has a powerfull open can, like the one Chido posted.
EDIT: If you never saw a diode in person, you may overestimate it's size. You wouldn't be the first one. They are incredibly tiny. They just look big in the macro pictures. Maybe that's why you're confusing the spindle with the diode?