Broadband mid-infrared phase retrieval for nonlinear microscopy.

Spectral phase characterization of ultrashort laser pulses is essential in nonlinear micro-spectroscopy. Whereas in many applications phases are determined for near-infrared (NIR) pulses, successful mid-infrared (MIR) phase retrieval is rare. The spectral phase of ultra-broadband MIR pulses is determined over more than 1000cm-1 in the presented work. This is accomplished by exploiting the d-scan method in two variants. Both allow for detecting high signals by using the interaction of the MIR and NIR pulses. The two variants differ in imprinting the dispersion. While the dual d-scan imprints phases on both pulses, the Xd-scan method disperses the NIR pulses solely.

Acousto-optic modulator based dispersion scan for phase characterization and shaping of femtosecond mid-infrared pulses.

Compression, shaping and characterization of broadband mid-infrared (MIR) pulses based on an acousto-optic modulator (AOM) pulse shaper is presented. Characterization of the spectral phase is achieved by an AOM-shaper based implementation of a dispersion scan (d-scan). The abilities of the setup are demonstrated by imprinting several test phases with increasing complexity on broadband MIR pulses centered at 3.2 µm and retrieval of the imprinted phases with the presented d-scan method. Phase characterization with d-scan in combination with an evolutionary algorithm allows us to compress the MIR pulses below 50 fs FWHM autocorrelation after the shaper.