Shaping the spectra of a second-harmonic laser by spatial focusing
Phys. Rev. A 114, 043538 – Published 30 October, 2026
DOI: https://doi.org/10.1103/zs48-ypcc
Abstract
Accurately controlling the spectral width of second-harmonic generation (SHG) is critical in applications such as nonlinear microscopy, ultrafast spectroscopy, and quantum optics, where tailored spectral properties are required. Although it is known that the focal length of the lens used to focus the pump beam influences the SHG spectrum, a simple and precise theoretical understanding of this effect has been lacking. Here, we develop a theoretical model to describe how pump-focusing conditions affect SHG spectral broadening and experimentally validate the model using beta barium borate crystals with lenses of 50 mm and 200-mm focal lengths. Our results establish a practical method for engineering the SHG spectral width through pump focusing, providing valuable guidance for designing nonlinear optical systems with specific spectral requirements.
