Adiabatic frequency converter as a custom octave-spanning dispersive element

Dispersion management is among the most challenging aspects of the design and realization of amplified laser systems possessing octave-spanning bandwidth and good compressed pulse quality. Here we demonstrate a new type of device for octave-spanning dispersion management. We combine the paradigm of chirped quasi-phase matching (QPM) for pulse shaping during frequency conversion with the robust, efficient, octave-spanning capability of an adiabatic frequency downconversion device. The result is a simple, monolithic device that can produce an octave-spanning infrared pulse with tailored dispersion – a technique that may be especially convenient for high-energy amplifier chains employing difference frequency generation and/or parametric amplification stages. The technique can also serve as a way to produce pulses of ~10 fs duration throughout the visible to mid-infrared spectrum for hyperspectral ultrafast spectroscopy. Adiabatic frequency conversion employs a slowly changing position-dependent poling frequency in a chirped QPM device to efficiently frequency shift photons over a wide bandwidth with a linear transfer function. In this work, we show that the frequency dependent localized conversion of the process allows tailoring of the total group-delay dispersion (GDD). We have demonstrated a first device with zero GDD, allowing efficient conversion of a few-cycle near-infrared input to a near-single-cycle mid-infrared output of the same duration (~12 fs, with bandwidth spanning 2.0-4.0 microns). We present additional designs for precise custom tailoring of the frequency-dependent group delay.