CORDIS - EU research results

Cascaded Optical Pulse Compressor

Final Report Summary - COPULCO (Cascaded Optical Pulse Compressor)

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In this project we studied cascaded quadratic soliton compressions (CQSC) in quadratic nonlinear waveguides. Formation and interaction of few-cycle solitons in a lithium niobate channel waveguide are numerically investigated and experimentally demonstrated. Quadratic (nonlinear) waveguides are well known not only inherit to the nonlinear properties from the material, but also have optical waveguide structures that could provide good guidance and confinement on the laser light beam. Basically the light is guided and propagated inside the channel waveguide to suppress the effects of light spatial diffractions and increase the pulsed laser intensities. Therefore, laser pulses with nano-joule (nJ) energy and high repetition rate can be operated, which are complementary solutions to CQSCs in bulk materials that operate high-energy, large-beam-size pulsed lasers.
The solitons are created through a cascaded phase-mismatched second-harmonic generation process, which induces a dominant self-defocusing Kerr-like nonlinearity on the pump pulse. The inherent material self-focusing Kerr nonlinearity is overcome over a wide wavelength range, and self-defocusing solitons are supported from 1100 to 1900 nm, covering the whole communication band. Single cycle self-compressed solitons and supercontinuum generation spanning 1.3 octaves are observed when pumped with femtosecond nanojoule pulses at 1550 nm.
On the other hand, the dispersion engineering is possible through the design on the waveguide structure. We obtain an understanding of soliton spectral tunneling (SST) effect and use novel nonlinear phenomena to extend the conversion regimes. With a more extreme dispersion engineering, the normal dispersion range can be largely extended towards long wavelengths beyond the material zero dispersion wavelength (ZDW) and even an all-normal dispersion profile can be achieved, which could extend the CQSC into the near-infrared range (near-IR) and mid-infrared range (mid-IR), since the overall self-defocusing nonlinearity is always broadband far beyond the material ZDW.