Two-photon generated color-center gratings in KBr: Proposed picosecond pulsewidth measuring technique for the ultraviolet

Two-photon generated color centers in the alkali halides are proposed as a picosecond pulsewidth measuring technique for the ultraviolet. Measurements in KBr using the XeCI laser show that the color-center density varies as I^1.5and that intensities less than 10 MW/cm²are sufficient for color-center generation. Two-photon generated color-center gratings were produced by a UV interference pattern and were used to measure the diffusion distance of the electrons before becoming color centers. The measured diffusion distance of 25μ limits the minimum resolvable pulsewidth to about 0.25 ps.