The power imbalance between different waveguide outputs is compensated by manipulating the dispersion of the guided propagation in the multimode interference (MMI) region. This is attainable using a tapered region at the beginning of the MMI region that has been verified through simulation and experiment. From this, the fabrication tolerance for the diameters of holes in a tapered 1 × 3 photonic crystal waveguide (PhCW) splitter is relaxed up to a range of at least 27nm. The output power is well-balanced to within 1 dB. The effective bandwidth of the splitters shifts only around 13nm, for a reduction of 10nm in the diameter of the PhCW holes. The optimized component is an outstanding ultracompact 1 × 3 splitter for the photonic integrated circuit (PIC). © 2011 Optical Society of America.