Investigation of PPLN Waveguide Uniformity via Second Harmonic Generation Spectra

Gray, Alan C.; Berry, Sam A.; Carpenter, Lewis G.; Gates, James C.; Smith, Peter G. R.; Gawith, C.B.E.

doi:10.1109/lpt.2019.2957199

Cited by 8 publications

(1 citation statement)

References 16 publications

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“…Eqs. 3 and 4 also do not account for SHG spectral changes caused by imperfections in waveguide fabrication, which can cause asymmetry in the side lobes and a departure from the expected symmetrical SHG intensity profile [5,21,22].…”

Section: Shg Spectral Narrowingmentioning

confidence: 99%

CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm

Carpenter¹,

Berry²,

Gray³

et al. 2020

Opt. Express

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Periodically poled lithium niobate (PPLN) waveguides are a proven and popular means for efficient wavelength conversion. However, conventional PPLN waveguides typically have small mode field diameters (MFD) (≲6 µm) or significant insertion and/or propagation losses, limiting their ability to operate at multi-watt power levels. In this work we utilise zinc indiffused PPLN ridge waveguides that have a larger MFD, favourable pump/SHG modal overlap, and low insertion losses. Here for the first time, we have demonstrated continuous wave (CW) spectral narrowing from a PPLN waveguide; both with high efficiency and multi-watt second harmonic generation (SHG). 2.5 W of 780 nm has been produced by SHG of an amplified 1560 nm telecom laser with a device efficiency of 58% in a 4.0 cm-long ridge waveguide. We have modelled conversion efficiency and applied experimentally measured waveguide parameters to show excellent agreement to the SHG spectra. Spectral narrowing of the full width half maximum (FWHM) of 35.7% has been measured as the nonlinear drive is increased. This work demonstrates that single-pass, multi-watt, CW SHG at 780 nm is feasible from our PPLN waveguide in the large conversion regime.

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Section: Shg Spectral Narrowingmentioning

confidence: 99%

CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm

Carpenter¹,

Berry²,

Gray³

et al. 2020

Opt. Express

Self Cite

View full text Add to dashboard Cite

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Unveiling the origins of quasi-phase matching spectral imperfections in thin-film lithium niobate frequency doublers

Zhao,

Li,

et al. 2023

APL Photonics

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Thin-film lithium niobate (TFLN) based frequency doublers have widely been recognized as an essential component for both classical and quantum optical communications. Nonetheless, the efficiency (unit: %/W) of these devices is hindered by imperfections present in the quasi-phase matching (QPM) spectrum. In this report, we present a thorough experimental study of spectral imperfections in TFLN frequency doublers with varying lengths, ranging from 5 to 15 mm. A non-destructive diagnostic method based on scattered light imaging is proposed and employed to identify the waveguide sections and primary waveguide parameters contributing to the imperfections in the QPM spectrum. By applying this method, we obtain the evolution of the QPM spectrum along the waveguide’s length. Correlating this information with the measurements of the relevant geometric parameters along the waveguides suggests that the TFLN film thickness variation is the primary source for the measured spectral distortions. Furthermore, we numerically reproduce the QPM spectra with the mapped TFLN film thickness across the entire waveguiding regions. These findings align with and complement the simulation results from previous numerical studies, providing further evidence of the effectiveness of the developed diagnostic method. This comprehensive investigation offers valuable insights into the identification and mitigation of spectral imperfections in TFLN-based frequency doublers, paving the way for the realization of nonlinear optical devices with enhanced efficiency and improved spectral fidelity.

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Zinc-indiffused MgO:PPLN waveguides for blue/UV generation via VECSEL pumping

Gray¹,

Woods²,

Carpenter³

et al. 2020

Appl. Opt.

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We present the design and characterization of a zinc-indiffused periodically poled lithium-niobate ridge waveguide for second-harmonic generation of ∼ 390 n m light from 780 nm. We use a newly developed, broadband near-infrared vertical external-cavity surface-emitting laser (VECSEL) to investigate the potential for lower-footprint nonlinear optical pump sources as an alternative to larger commercial laser systems. We demonstrate a VECSEL with an output power of 500 mW, containing an intracavity birefringent filter for spectral narrowing and wavelength selection. In this first demonstration of using a VECSEL to pump a nonlinear waveguide, we present the ability to generate 1 mW of ∼ 390 n m light with further potential for increased efficiency and size reduction.

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Investigation of PPLN Waveguide Uniformity via Second Harmonic Generation Spectra

Cited by 8 publications

References 16 publications

CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm

CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm

Unveiling the origins of quasi-phase matching spectral imperfections in thin-film lithium niobate frequency doublers

Zinc-indiffused MgO:PPLN waveguides for blue/UV generation via VECSEL pumping

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