Ultrabroadband chirped pulse second-harmonic spectroscopy: measuring the frequency-dependent second-order response of different metal films.

ABSTRACT

We introduce a spectroscopic method for measuring the frequency-dependent second-order response using ultrabroadband strongly chirped laser pulses. The dispersion suppresses nonlinear frequency mixing, hence the second-order response of a material can be unambiguously retrieved. We demonstrate this method by measuring the frequency-dependent second-harmonic (SH) response of the metals gold, aluminium, silver, and copper in the wavelength range of about 900-1150 nm and compare the results to classical SH spectroscopy. The SH spectra indicate that interband transitions in the metals influence the overall nonlinear optical response.