In this study, a white light generation device based on four different lenses is constructed according to the principle of white-light continuum generation and the different focusing characteristics of the achromatic lens and spherical lens at the focal position are discussed. Through theoretical simulation and experimental demonstration, it is concluded that: 1) a more blue-shifted white-light continuum can be achieved using an achromatic lens. When the beam is focused, the achromatic lens can considerably reduce the influence of dispersion, resulting in a smaller focal point radius and uniform photon distribution. When focusing on the sapphire crystal, the photon density at the focal spot is higher than that in the spherical lens at the same energy and the blue shift is visible. 2) Using a short focal lens will afford a blue shift and better spectral stability of the white-light continuum. For the same lens, different focal length affords different focal spot radii and depths at the focus position. When acting on sapphire crystal, the white-light continuum generated by a short focal lens has an obvious blue shift because the short focal lens can afford highly focused energy and uniform photons compared to a long focal lens. Because the short focal lens operating range is shorter and the monofilament channel created in the sapphire crystal is more stable, the white-light continuum has superior stability. The transient absorption of Rhodamine B was studied using four different types of white-light continuum-generating equipment. The blue-shifted white-light continuum is found to be more useful for measuring Rhodamine B's stimulated absorption signal. Therefore, in a transient absorption experiment, a short-focal achromatic lens can be used to assess Rhodamine B sample.