First observation of self-amplified spontaneous emission at 1.064 μm

We report evidence of self-amplified spontaneous emission at 1064 nm. Single pass, on-axis microwiggler emissions into a 25 nm bandwidth have been recorded as a function of beam charge, and show a clear enhancement over spontaneous emission after threshold. These are the first measurements of SASE at such a short wavelength, and employ the smallest period wiggler used to date in a successful SASE experiment. The experiment has been performed with the MIT microwiggler at the Accelerator Test Facility at BNL. A single micropulse at 34 MeV with a variable charge of 0-1 nC and < 5 ps bunch length is passed through the microwiggler and emissions into a limited solid angle and bandwidth, selected by an aperture and interference filter, are focused onto a silicon photodiode. Enhancement of the emissions from 2 to 6 times the spontaneous emission level is observed at the highest charges.