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Broadband frequency comb generation through cascaded quadratic nonlinearity remains experimentally untapped in free-space cavities with bulk χ(2)materials mainly due to the high threshold power and restricted ability of dispersion engineering. Thin-film lithium niobate (LN) is a good platform for nonlinear optics due to the tight mode confinement in a nano-dimensional waveguide, the ease of dispersion engineering, large quadratic nonlinearities, and flexible phase matching via periodic poling. Here we demonstrate broadband frequency comb generation through dispersion engineering in a thin-film LN microresonator. Bandwidths of 150 nm (80 nm) and 25 nm (12 nm) for center wavelengths at 1560 and 780 nm are achieved, respectively, in a cavity-enhanced second-harmonic generation (doubly resonant optical parametric oscillator). Our demonstration paves the way for pure quadratic soliton generation, which is a great complement to dissipative Kerr soliton frequency combs for extended interesting nonlinear applications.
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Efficient on-chip green light generation via frequency upconversion in SiN–transfer-printed LN hybrid waveguides
We demonstrate efficient on-chip green light generation via frequency upconversion in silicon nitride–thin-film lithium niobate (SiN-TFLN) hybrid waveguides, obtained by transfer printing LN coupons on selected areas of photonic integrated circuits (PICs). By utilizing modal phase matching (MPM), our devices achieve a high normalized conversion efficiency of 42.5% W−1cm−2in a single-pass, 2.4-mm-long waveguide configuration. The SiN–LN transition in the waveguide inherently facilitates mode conversion, transforming a higher-order second-harmonic mode into a fundamental TE mode, ensuring coherent, narrow-linewidth, green light emission. Our waveguide platform gives rise to a wavelength shift of ∼1 nm for every 10 nm of waveguide width variation and temperature-induced wavelength tuning of ∼0.02 nm/°C.
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- Award ID(s):
- 2310869
- PAR ID:
- 10625251
- Publisher / Repository:
- Optica
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 50
- Issue:
- 10
- ISSN:
- 0146-9592
- Page Range / eLocation ID:
- 3281
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1364/OL.560034
