| 1. |
- Gao, Yan, 1995, et al.
(författare)
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Compact lithium niobate microring resonators in the ultrahigh Q/V regime
- 2023
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 48:15, s. 3949-3952
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Tidskriftsartikel (refereegranskat)abstract
- Lithium niobate (LN) is a promising material for future complex photonic-electronic circuits, with wide applications in such fields as communications, sensing, quantum optics, and computation. LN took a great stride toward compact photonic integrated circuits (PICs) with the development of partially etched LN on insulator (LNOI) waveguides. However, integration density is still limited for future highly compact PICs, owing to the partial etching nature of their waveguides. Here, we demonstrate a fully etched LN PIC platform, which, for the first time to our knowledge, simultaneously achieves ultralow propagation loss and compact circuit size. The tightly confined fully etched LN waveguides with smooth sidewalls allow us to bring the bending radius down to 20 μm (corresponding to 1 THz free spectral range). We have achieved compact high Q microring resonators with Q/V of 8.7 × 104 μm−3, almost one order of magnitude larger than previous demonstrations. The statistical mean propagation losses of our LN waveguides is 8.5 dB/m (corresponding to a mean Q factor of 4.9 × 106), even with a small bending radius of 40 μm. Our compact and ultralow-loss LN platform shows great potential in future miniaturized multifunctional integration systems. As complementary evidence to show the utility of our platform, we demonstrate soliton microcombs with an ultrahigh repetition rate of 500 GHz in LN.
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| 2. |
- Gao, Yan, 1995, et al.
(författare)
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Low-loss compact lithium niobate photonic integrated circuits
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023.
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Konferensbidrag (refereegranskat)abstract
- Lithium niobate (LN) is a promising material among integrated photonics, with applications like high-speed EO modulators, frequency combs, frequency converters, and photon-pair sources [1]. Increasing the system complexity of LN integrated circuits requires large-scale arrays of photonic components [2]. Therefore, an ideal integrated LN waveguide platform should allow dense integration, low propagation losses, and exhibit low fabrication complexity.
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| 3. |
- Lei, Fuchuan, 1987, et al.
(författare)
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Hyperparametric Oscillation via Bound States in the Continuum
- 2023
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 130:9
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Tidskriftsartikel (refereegranskat)abstract
- Optical hyperparametric oscillation based on the third-order nonlinearity is one of the most significant mechanisms to generate coherent electromagnetic radiation and produce quantum states of light. Advances in dispersion-engineered high-Q microresonators allow for generating signal waves far from the pump and decrease the oscillation power threshold to submilliwatt levels. However, the pump-to-signal conversion efficiency and absolute signal power are low, fundamentally limited by parasitic mode competition and attainable cavity intrinsic Q to coupling Q ratio, i.e., Qi/Qc. Here, we use Friedrich-Wintgen bound states in the continuum (BICs) to overcome the physical challenges in an integrated microresonator-waveguide system. As a result, on-chip coherent hyperparametric oscillation is generated in BICs with unprecedented conversion efficiency and absolute signal power. This work not only opens a path to generate high-power and efficient continuous-wave electromagnetic radiation in Kerr nonlinear media but also enhances the understanding of a microresonator-waveguide system - an elementary unit of modern photonics.
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| 4. |
- Lei, Fuchuan, 1987, et al.
(författare)
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Power-efficient hyperparametric oscillation via bound states in the continuum
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023.
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Konferensbidrag (refereegranskat)abstract
- Optical hyperparametric oscillation (h-OPO) emerges in a driven Kerr cavity because of modulation instability. Two pump photons are converted into a pair of two correlated photons at new wavelengths. For many realistic applications, efficient operation of h-OPO is required, especially at high-power regime. Currently, the pump-to-signal conversion efficiency is fundamentally limited mainly by two factors: parasitic mode competition [1] and attainable cavity intrinsic Q (Qi) to coupling Q (Qc) ratio [2].
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| 5. |
- Lei, Fuchuan, 1987, et al.
(författare)
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Self-injection-locked optical parametric oscillator based on microcombs
- 2024
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Ingår i: Optica. - 2334-2536. ; 11:3, s. 420-426
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Tidskriftsartikel (refereegranskat)abstract
- Narrow-linewidth yet tunable laser oscillators are one of the most important tools for precision metrology, optical atomic clocks, sensing, and quantum computing. Commonly used tunable coherent oscillators are based on stimulated emission or stimulated Brillouin scattering; as a result, the operating wavelength band is limited by the gain media. Based on nonlinear optical gain, optical parametric oscillators (OPOs) enable coherent signal generation within the whole transparency window of the medium used. However, the demonstration of OPO-basedHertz-level linewidth and tunable oscillators has remained elusive. Here, we present a tunable coherent oscillator based on a multimode coherent OPO in a high-Q microresonator, i.e., a microcomb. Single-mode coherent oscillation is realized through self-injection locking (SIL) of one selected comb line. We achieve coarse tuning up to 20 nm and an intrinsic linewidth down to sub- Hertz level, which is three orders of magnitude lower than the pump. Furthermore, we demonstrate that this scheme results in the repetition rate stabilization of the microcomb. These results open exciting possibilities for generating tunable coherent radiation where stimulated emission materials are difficult to obtain, and the stabilization of microcomb sources beyond the limits imposed by the thermorefractive noise in the cavity.
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