25-terahertz-bandwidth all-optical temporal differentiator.

An all-optical temporal differentiator with a record operation bandwidth of 25 THz (200 nm, at least one order of magnitude larger than any previously reported temporal differentiation technology) is experimentally demonstrated based on a simple and compact all-fiber wavelength-selective directional coupler. The fabricated directional coupler can be used to process optical signals with time features as short as a few tens of femtosecond. A Gaussian-like optical pulse with a time-width of 250-fs is experimentally differentiated with a processing error of 2.1%. As an application example, a chirp-free flat-top pulse with a time-width of 540-fs is also successfully generated.