What is the pump wavelength range? How do we make the pump and the probe beams to have different wavelengths?

The pump wavelength range is determined by the OPA and/or the Harmonics Generator.

There are several options for modifying the laser wavelength in a transient absorption experiment. One is to use an optical parametric amplifier (OPA) for sample excitation. An OPA is essentially a broadly tunable ultrafast pulse source, which is pumped by an amplified ultrafast laser. Using an OPA allows for selecting various wavelengths (from UV to IR) for the pump beam. Another way for modifying the excitation wavelength is using a harmonics generator to generate the second (TiSa: 400 nm, Yb: 515 nm), the third (TiSa: 267 nm, Yb: 355 nm), and the fourth (Yb: 267 nm) harmonics of the fundamental laser output. It is also possible to use an OPA as a probe light source. This approach is sometimes used when probing in the SWIR spectral range.