We present a novel and highly efficient temporal pulse shaping technique for the generation of flattop-like picosecond pulses in the deep UV. Using standard sum frequency generation (SFG) of a Ti:sapphire laser but with a pair of properly chirped beams prior to frequency-conversion, we were able to achieve picosecond pulses in the deep UV with a spectral width up to ten times larger than the non-linear crystal's acceptance bandwidth paired with an unprecedented high conversion efficiency of up to 15%. © 2011 IEEE.