Efficient supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Abstract

Efficient supercontinuum generation (SCG) requires excitation of solitons at the pump laser wavelength. Quadratic nonlinear waveguides may support an effective self-defocusing nonlinearity so solitons can directly be generated at common ultrafast laser wavelengths without any waveguide dispersion engineering. We here experimentally demonstrate efficient SCG in a standard lithium niobate (LN) waveguide without using quasi-phase matching (QPM). By using femtosecond pumps with wavelengths in the $1.25-1.5\mu \mathrm{m}$ range, where LN has normal dispersion and thus supports self-defocusing solitons, octave-spanning SCG is observed. An optimized mid-IR waveguide design is expected to support even broader spectra. The QPM-free design reduces production complexity, allows longer waveguides, limits undesired spectral resonances and effectively allows using nonlinear crystals where QPM is inefficient or impossible. This result is important for mid-IR SCG, where QPM-free self-defocusing waveguides in common mid-IR nonlinear crystals can support solitons directly at mid-IR ultrafast laser wavelengths, where these waveguides have normal dispersion.

To appear in Optics Letters

References in corpus (3)

• Nonlocal explanation of stationary and nonstationary regimes in cascaded soliton pulse compression
• Limits to compression with cascaded quadratic soliton compressors
• Scaling laws for soliton pulse compression by cascaded quadratic nonlinearities

Cited by in corpus (1)

• Energetic mid-IR femtosecond pulse generation by self-defocusing soliton-induced dispersive waves in a bulk quadratic nonlinear crystal