Photochromic spiropyran in guided wave mode geometry was used to demonstrate the performance of an ultrafast molecular photonics system utilizing femtosecond (fs) white light as a probe and fs blue light as a pump. Specific and reversible changes were observed by photochromism in fs white light for dip wavelength and/or dip reflectance depending on the incident angle. The present system will contribute a great deal to future ultrafast all-optical processing in a broad wavelength region.