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We demonstrate dramatic parametric amplifier conversion efficiency enhancement simply by arranging for simultaneously phase-matched idler second-harmonic generation, with 44% pump-to-signal energy conversion (68% pump depletion) in a 48-dB-gain bulk-crystal mid-IR amplifier stage with Gaussian beams. 

For as widely used a tool as nonlinear optical frequency conversion is for both science and industry, it remains widely limited in eciency and bandwidth (and ultimately also in cost) due to the fundamental problem of backconversion in the nonlinear evolution dynamics. This review paper covers new developments and capabilities in frequency conversion devices, including optical up- and down-converters and ampli ers, based on nonlinear evolution dynamics in which back-conversion is suppressed. One such approach is adiabatic frequency conversion, in which the dynamics of rapid adiabatic passage replace the regular cyclic conversion evolution in phase-matched sum- and dierence-frequency generation. This approach has enabled devices far surpassing the conventional eciency-bandwidth trade-o. For example, in chirped quasi-phase matched quadratic crystals, microjouleenergy single-cycle mid-infrared pulses were generated with arbitrary pulse shaping capability, presenting a source with unique features for nonlinear spectroscopy and strong- eld physics applications. We review new developments in the use of optical bers as a cubic nonlinear platform for the same concept, utilizing a tapered core diameter or a pressure gradient to allow up- and down-conversion with ultra-wide bandwidth and high eciency. We also review a newly introduced concept for high eciency optical parametric ampli cation, via a novel approach for suppressing back-conversion in optical parametric ampli cation by simultaneously phasematching the idler wave for second harmonic generation. Keywords: Adiabatic wave mixing, ecient optical parametric ampli cation, octave-spanning