Improved method to obtain wavelength-dependent radius and chromatic dispersion of a supercontinuum laser beam

Supercontinuum lasers are important for nonlinear optics, spectroscopy, microscopy, optical communication, frequency comb, biomedicine, and so on. However, very little research has focused on the measurement of their wavelength-dependent diameters and chromatic dispersion, which are significant parameters. Based on an improved knife-edge technique, we built a home-made setup to measure the chromatic dispersion of a supercontinuum laser over the wavelength range of 500-755 nm. The setup is based on two integrating spheres, two spectrometers, and two motorized linear translation stages. The beam waist and focal point position for each wavelength of the laser beam are successfully obtained using this setup, from which the chromatic dispersion of the laser is determined. Our measurement technique and analysis method may prove a useful and widely applicable characterization tool for nonlinear optics, metrology, biomedical imaging, and diagnostics based on supercontinuum light.