Frequency-domain interferometric second-harmonic spectroscopy

We report a new spectroscopic technique to measure simultaneously the intensity and the phase of second-harmonic (SH) radiation over a broad spectral range without laser tuning. Temporally separated SH pulses from two sources, excited by the same broad-bandwidth 15-fs Ti:sapphire fundamental pulse, interfere in a spectrometer to yield frequency-domain interference fringes. We demonstrate the technique by measuring the strongly bias-dependent phase of SH radiation from a Si/SiO(2)/Cr metal-oxide-semiconductor capacitor in the spectral range of the SiE(1) critical point.     

Multipulse interferometric frequency-resolved optical gating: real-time phase-sensitive imaging of ultrafast dynamics

We demonstrate a powerful new tool for real-time single-shot imaging of ultrafast phase shifts based on multipulse interferometric frequency-resolved optical gating that can directly measure and display ultrafast-time-scale phase shifts without computation. In addition, this technique can, with the application of interferogram analysis and iterative phase-retrievial techniques, recover the intensity and phase of three pulses in a single shot and exhibits a linear sensitivity to the pulse field in the wings.     

Reflected fourth-harmonic radiation from a centrosymmetric crystal

We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001)- SiO(2)] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation.