Optical tuning of an epitaxial, all‐semiconductor optical interference filter is reported. The filter is a high reflector composed of alternating, strained layers of GaP (360 Å) and GaAs0.2P0.8 (360 Å) grown by metalorganic chemical vapor deposition. With low optical power, these reflectors exhibit reflectances up to 90% at 510 nm over a 10‐nm bandwidth. With absorbed optical pulses of energy density 3 mJ/cm2, this high‐reflectance zone can be blue shifted by 20 Å. As a result, very large changes in reflectance can be produced. The effect is interpreted as a plasma‐induced refractive index depression in a semiconductor superlattice. Furthermore, the layer strain enhances the optically induced index change of the high reflector compared to that in bulk materials.