Dual-Wavelength Delay

The delay of spectra can also be achieved by two monochromators, as already pointed out in Sec. 3.3.2. 

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The dual-wavelength (two-color) extension of the standard Z-scan technique [19,20] has been used to measure the nondegenerate nonlinear susceptibility at the (weak) laser probe frequency a>p due to the presence of a (strong) excitation beam at frequency This technique has been further used to time resolve the dynamics of a nonlinear process by introducing a temporal delay between the pump and probe beams [21-23]. 

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