The use of harmonics to achieve coherent short wavelengths

Harmonics of the fundamental radiation are generated through both linear and nonlinear interactions during the self-amplified spontaneous emission (SASE) process. Ultimately the nonlinear harmonics dominate over those generated through the linear process. It has been shown that at saturation the power levels in the first few nonlinear harmonics can reach significant, useful values. The nonlinear harmonics are driven by the fundamental radiation producing microbunching with a strong harmonic content. As such, these harmonics are dominated by the fundamental interaction; therefore, beam requirements to achieve these wavelengths are relaxed and are predominately driven by the needs of the fundamental. Here we explore the use of these harmonics in achieving coherent short wavelengths and discuss the beam requirements and output power levels as compared to presently proposed next-generation light source experiments such as the Linac Coherent Light Source (LCLS).