We have microfabricated two-dimensional ͑2D͒ photonic band gap structures in a thin slab of dielectric material to define reflectors and high-Q microresonators. By selectively omitting holes from the 2D photonic crystal, optical microcavities, and in-plane microresonator switches can be defined. We have designed this structure with a finite difference time domain approach, and demonstrate the effect of lithographic 2D band gap tuning on the emission spectra of InGaAs/ InGaAsP multiple quantum well material emission wavelength of 1.55 m.