Through the control of laser energy and chirp, continuous wavelength tuning of high-order harmonics was achieved without sacrificing spectral sharpness. This process was implemented after the amplification stage in a chirped-pulse amplification Ti:sapphire laser, without changing laser spectrum. It opens a new pathway for the realization of a continuously tunable, coherent, femtosecond x-ray source, i.e., a tabletop synchrotron.

• Received 24 April 2002

DOI:https://doi.org/10.1103/PhysRevA.67.051801