We demonstrate an all polarization-maintaining (PM) fiber mode-locked laser seeded, hybrid fiber/solid-slab picosecond pulse laser system which outputs $40~\unicode[STIX]｛x03BC｝\text｛J｝$, 10 ps pulses at the central wavelength of 1064 nm. The beam quality factors $M^｛2｝$ in the unstable and stable directions are 1.35 and 1.31, respectively. $15~\unicode[STIX]｛x03BC｝\text｛J｝$ picosecond pulses at the central wavelength of 355 nm are generated through third harmonic generation (THG) by using two $\text｛LiB｝_｛3｝\text｛O｝_｛5｝$ (LBO) crystals, in order to get better processing efficiency on polycrystalline diamonds. The high pulse energy and beam quality of these ultraviolet (UV) picosecond pulses are confirmed by latter experiments of material processing on polycrystalline diamonds. This scheme which combines the advantages of the all PM fiber mode-locked laser and the solid-slab amplifier enables compact, robust and chirped pulse amplification-free amplification with high power picosecond pulses.