The interaction of intense ultrashort laser pulses with matter in the strong-field regime of nonlinear optics enables the study of electron excitations with high temporal resolution. We report on the development a two-colour nonlinear interferometer which coherently combines the laser field with its third harmonic frequency for tailoring the nonlinear optical response of solids in the strong-field regime.
The newly introduced spectral interferometry technique enables the measurement of the emission delay of high harmonic photons from the sample on attosecond time scale.