A method of manufacturing a wavelength conversion element including a periodic polarization inversion structure, includes: forming the periodic polarization inversion structure by alternately forming polarization inversion portions and non-polarization inversion portions on a ferroelectric substrate; etching a surface of the ferroelectric substrate provided with the periodic polarization inversion structure, to form level differences between the polarization inversion portions and the non-polarization inversion portions; forming a joining layer having a first thickness on the ferroelectric substrate provided with the level differences; polishing a surface of the joining layer to cause the joining layer to have a second thickness; and joining a support substrate to the polished surface of the joining layer.

A broadband radiation source device configured for generating a broadband output radiation upon receiving pump radiation, the device including: a hollow-core photonic crystal fiber (HC-PCF) including at least one structurally varied portion having at least one structural parameter of the HC-PCF varied with respect to one or more main portions of the HC-PCF, wherein the at least one structurally varied portion includes at least a structurally varied portion located downstream of a position along the length of the HC-PCF where the pump radiation will be spectrally expanded by a modulation instability dominated nonlinear optical process, and wherein the at least one structurally varied portion is configured and located such that the broadband output radiation includes wavelengths in the ultraviolet region.

A system for generating a supercontinuum comprising a frequency comb generator and a waveguide structure coupled to the frequency comb generator. The waveguide structure comprises distinct sections: an untapered input section with specified first cross-sectional outer dimensions, a down-taper transition section leading to a taper waist section with second cross-sectional outer dimensions that are smaller than the first cross-sectional outer dimensions, followed by an up-taper transition section extending to an untapered output section which reverts to third cross-sectional outer dimensions that are larger than the second cross-sectional outer dimensions.