Frequency multiplication conversion device and ultraviolet femtosecond laser

The utility model discloses a frequency multiplication conversion device and an ultraviolet femtosecond laser. The frequency multiplication conversion device comprises an adjusting unit, a frequency multiplication unit and a beam splitting unit. The adjusting unit is used for adjusting the spot size of the fundamental frequency light; the frequency doubling unit is in coupling connection with the adjusting unit, the frequency doubling unit sequentially comprises a frequency doubling crystal, a compensating plate and a frequency tripling crystal in the light path propagation direction, the frequency doubling crystal is used for converting fundamental frequency light into frequency doubling light, the compensating plate is used for reducing the group velocity difference generated by the fundamental frequency light and the frequency doubling light in the frequency doubling crystal, and the frequency tripling crystal is used for generating frequency tripling light. The frequency tripling crystal is used for conve