I'm trying to couple 654nm laser light from a 4/125um SM fiber into a rectangular optical waveguide (0.5um wide by 0.35um high) on an integrated circuit.
I've been using simple end-fire coupling, with a cleaved fiber brought close to the waveguide, but the coupling efficiency is horrible - on the order of 1%.
I've tried using ground and tapered fibers, but they keep breaking on me.
Some other things I've thought of, but haven't yet gotten around to trying are:
- Attaching a small lens to the cleaved tip of a fiber, and using that to focus the light into the WG.
- Using a microscope objective "in reverse", so to speak, to collimate and focus light into the WG. (I'm not sure if I physically have enough room for something like this.)
- Similar to the above, using some free space optics to collimate and then focus the laser light into the WG.
Does anybody have another, hopefully better, ideas?
Note that any solution needs to be capable of fine translations. It wouldn't be much good to focus the beam down to a 1um or less spot size, but not be able to project the spot onto the end facet of the WG. (i.e. "Damn - the spot's 10um to the left of the WG. Now I have to tear everything down and move it over 10um!")
Does anybody have any suggestions for vendors of solutions, or solution components? (Beyond the "usual suspect", that is - ThorLabs, Melles Griot, et al.)
Thanks in advance for any suggestions!
Bob Pownall