Highly coherent mid-IR supercontinuum by self-defocusing solitons in lithium niobate waveguides with all-normal dispersion

Guo, Hairun; Zhou, Binbin; Zeng, Xianglong; Bache, Morten

doi:10.1364/oe.22.012211

Cited by 7 publications

(4 citation statements)

References 33 publications

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“…Thus, the cascaded nonlinear strength |γ casc | will not increase as fast as γ Kerr , and therefore the effective nonlinearity γ eff = γ casc + γ Kerr drops. This fact also evidences the dilemma of using strong confinement [27]: eventually γ eff becomes self-focusing, and one has to use QPM to regain selfdefocusing. We finally mention that using the 6.0 µm wide waveguide minimal spectral broadening was observed and only for high peak powers and long pump wavelengths: clearly in this case γ eff ≃ 0.…”

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confidence: 97%

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

et al. 2015

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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 µm 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. Supercontinuum generation (SCG) using stable ultrafast pulsed lasers in fibers and waveguides has found a wide range of applications in fields such as frequency metrology, optical coherence tomography and spectroscopy [1]. Especially soliton-induced SCG is efficient, which relies on balancing the material self-focusing Kerr nonlinearity with anomalous dispersion, i.e. pumping above the fiber zero-dispersion wavelength (ZDW). This obstacle was overcome in the near-IR through advanced silica fiber production technology, which allowed creating sophisticated photonic crystal fibers (PCFs) with strong waveguide dispersion so the waveguide ZDW could be shifted down to operating wavelengths of common ultrafast pulsed lasers. Current efforts target efficient and ultrafast mid-IR SCG sources [2], mainly motivated by the so-called molecular vibrational "fingerprint region" in the mid-IR. As mid-IR transparent glasses have ZDW well into the mid-IR, far from pump wavelengths of emerging mid-IR ultrafast lasers, a strong waveguide dispersion is needed here as well. However, to date only simple PCF designs have been made [3], and the most efficient fiber-based mid-IR SCG to date used a pump wavelength chosen to match the fiber dispersion [4].In contrast, for a self-defocusing nonlinearity soliton formation requires normal dispersion, i.e. pumping below the ZDW, so a self-defocusing waveguide is free from waveguide dispersion constraints. Uniquely, this is possible using cascaded nonlinearities in quadratic nonlinear crystals, where the crystal's intrinsic self-focusing nonlinearity (n 2,Kerr > 0) is counterbalanced by a selfdefocusing cascading nonlinearity n 2,casc < 0, leading to an effective self-defocusing effect n 2,eff ≡ n 2,casc + n 2,Kerr < 0. In bulk this has found numerous applications, e.g. for pulse compression and temporal soliton formation [5][6][7][8] and SCG [8][9][10][11]. Motivated by...

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confidence: 97%

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

et al. 2015

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“…H. Guo et al obtained the SC through the LiNbO 3 waveguide which supported the self‐defocusing soliton compression. [ 294 ] In the following reports, [ 296 ] the spectrum was broadened in the blue edge induced by the self‐defocusing nonlinearities, and the red‐edge frequency components were generated by the DW generation. Overall, the SCG in the LiNbO 3 ridge waveguide utilizes the interaction of self‐defocusing nonlinearity and Kerr nonlinearity.…”

Section: Supercontinuum Generation Based On Second‐order Nonlinearitymentioning

confidence: 99%

Recent Progress of Supercontinuum Generation in Nanophotonic Waveguides

Fang

Bao

et al. 2022

Laser & Photonics Reviews

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Supercontinuum (SC) has opened up possibilities for numerous applications in optical communications, signal processing, metrology, and spectroscopy. Supercontinuum generation (SCG) in the integrated nonlinear platforms has attracted much interest recently, due to its fundamental advantages in terms of complementary metal oxide semiconductor compatibility, low power consumption, compact size, and cost‐effectiveness. In this paper, the latest progress on various types of nanophotonic waveguides for SCG is reviewed. The material properties of silicon, germanium, silicon–germanium alloy, silicon nitride, silica, chalcogenide, III–V materials, lithium niobate, and other materials, which are used as nonlinear media for SCG are discussed. The wavelength‐dependent nonlinear Kerr index, material, and nonlinear loss of the waveguides are taken into account. This review mainly focuses on the SCG resulting from the cubic χ(3) nonlinearity processes pumped by the femtosecond pulse. The recent representative SCG works based on the integrated optical waveguides are summarized, and further classified according to the dispersion characteristics. Furthermore, different types of spectra broadening mechanisms in details according to the classifications are analyzed. Perspectives on the SC spectral coverage, the realization of various dispersion curves, and the novel materials, which are the key aspects of the SCG in nanophotonic waveguides are provided.

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“…In comparison with bulk crystals, periodically poled LN (PPLN) waveguides with strong light confinement ensure high-efficiency nonlinear frequency conversion over a long interaction path. Therefore, PPLN waveguides allow low-power near-infrared (NIR) laser systems to perform efficient nonlinear processes and scale their spectra to the MIR region [11][12][13][14] . MIR sources based on LN waveguides have small size and low power consumption, making them ideal for the construction of integrated MIR frequency comb equipment.…”

Section: Introductionmentioning

confidence: 99%

Compact mid-infrared dual-comb spectrometer over 3–4 μm via intra-pulse difference frequency generation in LiNbO₃ waveguides

Zhou,

Lou,

Deng

et al. 2024

High Pow Laser Sci Eng

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The mid-infrared optical frequency comb is a powerful tool for gas sensing. In this study, we demonstrate a simple midinfrared dual-comb spectrometer covering 3-4 µm in LiNbO 3 waveguides. Based on a low-power fiber laser system, the mid-infrared comb is achieved via intra-pulse difference frequency generation in the LiNbO 3 waveguide. We construct pre-chirp management before supercontinuum generation to control spatiotemporal alignment for pump and signal pulses. The supercontinuum is directly coupled into a chirped periodically poled LiNbO 3 waveguide for the 3-4 µm idler generation. A mid-infrared dual-comb spectrometer based on this approach provides a 100 MHz resolution over 25 THz coverage. To evaluate the applicability for spectroscopy, we measure the methane spectrum using the dualcomb spectrometer. The measured results are consistent with the HITRAN database, in which the root mean square of the residual is 3.2%. This proposed method is expected to develop integrated and robust mid-infrared dual-comb spectrometers on chip for sensing.

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Highly coherent mid-IR supercontinuum by self-defocusing solitons in lithium niobate waveguides with all-normal dispersion

Cited by 7 publications

References 33 publications

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Recent Progress of Supercontinuum Generation in Nanophotonic Waveguides

Compact mid-infrared dual-comb spectrometer over 3–4 μm via intra-pulse difference frequency generation in LiNbO₃ waveguides

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Highly coherent mid-IR supercontinuum by self-defocusing solitons in lithium niobate waveguides with all-normal dispersion

Cited by 7 publications

References 33 publications

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Supercontinuum generation in quadratic nonlinear waveguides without quasi-phase matching

Recent Progress of Supercontinuum Generation in Nanophotonic Waveguides

Compact mid-infrared dual-comb spectrometer over 3–4 μm via intra-pulse difference frequency generation in LiNbO3 waveguides

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Product

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Compact mid-infrared dual-comb spectrometer over 3–4 μm via intra-pulse difference frequency generation in LiNbO₃ waveguides