A scheme is investigated that laser with wavelength λf is produced by backscattering of incident laser with wavelength λi and an incident electron beam with its velocity v0 passing through a magnetic field with its period λw . The characteristics of the scheme are as follows. Provided that v0 is large enough, λi-λf.When superconductivity sheets with their gaps cover the waggle magnets, or when incident laser is strong enough, the longitudinal length of effective backscattering region s can markedly decrease. Thus, the laser with its wavelength λf can be realized. A laser resonator parallel with the incident electron beam can produce incident laser with high enough intensity. It is possible that the power of an outputting laser beam is larger than that of an incident laser beam, although the number of the photons of the outputting laser beam is less than that of the incident laser beam.