Extending on-chip supercontinuum generation in Si3N4 throughout the blue wavelength range

The broad coherent optical spectra obtained by supercontinuum generation (SCG) are of significant importance for applications in, e.g., spectroscopy, biology and precision metrology. Of particular interest is SCG using integrated optical waveguides fabricated from stoichiometric silicon nitride (Si3N4) with low-pressure chemical vapor deposition because this provided, so far, the broadest supercontinuum on a chip [1], reaching down into the blue wavelength range at 470 nm, using infrared pump lasers [2]. We investigate the extension of this percontinuum further toward the ultraviolet via dispersion engineering and shorter pump wavelengths. In current experiments, we use the waveguides without their SiO2 top cladding for reshaping the generated spectra. The goal is to shift the zero-dispersion wavelength to below 800 nm, such that a femtosecond Ti:Sa laser can be used as a pump.