A new approach was proposed and its role in improvement of the beam quality of high-power broad-area diode lasers was demonstrated, in which a composite arrow array and trench microstructure was used to suppress the beam waist and tailor the high order lateral modes. The beam waist shows a special shrinkage with increasing injection current resulting from the combined effect of mode tailoring and the thermal lens effect. A 58% improvement in lateral beam parameter product was realized compared with conventional broad-area diode lasers.