waveguide (trace guiding type) inscription condition inside yb3+ doped phosphate bulk glass was investigated under irradiating of 50 khz repetition rate volume ultrafast lasers. we processed single trace and multi-core ones inside the bulk material, the captured near field mode pattern confirmed that both structures perform good guiding properties. beam shaping technique was adopted during fabrication of the single trace in order to obtain a relative symmetric waveguide cross section. waveguide lasing was achieved in the single line trace with a linear cavity configuration. the maximum laser output of 11 mw was obtained under mono-directional of 980 nm space light pumping, with similar to 2% corresponding slope efficiency. guiding mode could be manipulated in the expanded-core waveguide (ecw) by extra design freedom in the structure parameter, and ecw generally support larger effective mode area light transporting.