http://www.thorlabs.com/thorProduct.cfm?partNumber=CPS180

I bought this laser diode from Thorlabs today to try the current modulation trick Phil and I discussed last Friday. 

That is:

1. Accept that there will be interference fringes on the Hartmann sensor probe beam with a laser diode source (especially if the probe beam is the retro-reflection from a Michelson interferometer with a macroscopic arm length difference)
2. Modulate the current of the laser diode source to vary its wavelength by a few hundreds on nm. Do this on a time scale that is much faster than the exposure time for a Hartmann sensor measurement
3. The contrast of the interference fringes should average out and the exposure should appear to be the sum of two incoherent beams.