Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Hairun Guo, Binbin Zhou, Michael Steinert, Frank Setzpfandt, Thomas Pertsch, Hung-ping Chung, Yen-Hung Chen, Morten Bache

    Research output: Contribution to journalJournal articleResearchpeer-review


    Supercontinuum generation (SCG) is most efficient when the solitons can be excited directly at the pump laser wavelength. Quadratic nonlinear waveguides may induce an effective negative Kerr nonlinearity, so temporal solitons can be directly generated in the normal (positive) dispersion regime overlapping with common ultrafast laser wavelengths. There is no need for waveguide dispersion engineering. Here, we experimentally demonstrate SCG in standard lithium niobate (LN) waveguides without quasi-phase matching (QPM), pumped with femtosecond pulses in the normal dispersion regime. The observed large bandwidths (even octave spanning), together with other experimental data, indicate that negative nonlinearity solitons are indeed excited, which is backed up by numerical simulations. The QPM-free design reduces production complexity, extends the maximum waveguide length, and limits undesired spectral resonances. Finally, nonlinear crystals can be used where QPM is inefficient or impossible, which is important for mid-IR SCG. QPM-free waveguides in mid-IR nonlinear crystals can support negative nonlinearity solitons, as these waveguides have a normal dispersion at the emission wavelengths of mid-IR ultrafast lasers. © 2015 Optical Society of America
    Original languageEnglish
    JournalOptics Letters
    Issue number4
    Pages (from-to)629-632
    Publication statusPublished - 2015


    • Waveguides
    • Supercontinuum generation
    • Ultrafast nonlinear optics
    • Pulse propagation and temporal solitons


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