Yes I think you can, yout sperm, it just need harvesting, I read about this not that long ago. I think you need to in touch with a fertilty clinic to get more facts.
Good Luck
Talk to a urologist. In other words, you are saying, you don't want to reconnect the tubes, but would like to get your wife pregnant? I think (please ask the urologist) that it is possible to do this by putting a needle in and getting some sperm above the place where your tubes have been tied off. Not sure, though! So ask the doctor.