| 1. |
- Chang, Jin, et al.
(författare)
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Efficient mid-infrared single-photon detection using superconducting NbTiN nanowires with high time resolution in a Gifford-McMahon cryocooler
- 2022
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Ingår i: Photonics Research. - : Optica Publishing Group. - 2327-9125. ; 10:4, s. 1063-1070
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Tidskriftsartikel (refereegranskat)abstract
- Shortly after their inception, superconducting nanowire single-photon detectors (SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency, high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons (<0.8 eV) with high efficiency and low timing jitter has remained a challenge. To achieve unity internal efficiency at mid-infrared wavelengths, previous works used amorphous superconducting materials with low energy gaps at the expense of reduced time resolution (close to a nanosecond), and by operating them in complex milliKelvin (mK) dilution refrigerators. In this work, we provide an alternative approach with SNSPDs fabricated from 5 to 9.5 nm thick NbTiN superconducting films and devices operated in conventional Gifford-McMahon cryocoolers. By optimizing the superconducting film deposition process, film thickness, and nanowire design, our fiber-coupled devices achieved >70% system detection efficiency (SDE) at 2 mu m and sub-15 ps timing jitter. Furthermore, detectors from the same batch demonstrated unity internal detection efficiency at 3 mu m and 80% internal efficiency at 4 mu m, paving the road for an efficient mid-infrared single-photon detection technology with unparalleled time resolution and without mK cooling requirements. We also systematically studied the dark count rates (DCRs) of our detectors coupled to different types of mid-infrared optical fibers and blackbody radiation filters. This offers insight into the trade-off between bandwidth and DCRs for mid-infrared SNSPDs. To conclude, this paper significantly extends the working wavelength range for SNSPDs made from polycrystalline NbTiN to 1.5-4 mu m, and we expect quantum optics experiments and applications in the mid-infrared range to benefit from this far-reaching technology. Published by Chinese Laser Press under the terms of the Creative Commons Attribution 4.0 License.
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| 2. |
- Jo, Gaehun, 1992-, et al.
(författare)
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Wafer-level hermetically sealed silicon photonic MEMS
- 2022
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Ingår i: Photonics Research. - : Optical Society of America. - 2327-9125. ; 10:2, s. A14-A21
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Tidskriftsartikel (refereegranskat)abstract
- The emerging fields of silicon (Si) photonic micro–electromechanical systems (MEMS) and optomechanics enable a wide range of novel high-performance photonic devices with ultra-low power consumption, such as integrated optical MEMS phase shifters, tunable couplers, switches, and optomechanical resonators. In contrast to conventional SiO2-clad Si photonics, photonic MEMS and optomechanics have suspended and movable parts that need to be protected from environmental influence and contamination during operation. Wafer-level hermetic sealing can be a cost-efficient solution, but Si photonic MEMS that are hermetically sealed inside cavities with optical and electrical feedthroughs have not been demonstrated to date, to our knowledge. Here, we demonstrate wafer-level vacuum sealing of Si photonic MEMS inside cavities with ultra-thin caps featuring optical and electrical feedthroughs that connect the photonic MEMS on the inside to optical grating couplers and electrical bond pads on the outside. We used Si photonic MEMS devices built on foundry wafers from the iSiPP50G Si photonics platform of IMEC, Belgium. Vacuum confinement inside the sealed cavities was confirmed by an observed increase of the cutoff frequency of the electro-mechanical response of the encapsulated photonic MEMS phase shifters, due to reduction of air damping. The sealing caps are extremely thin, have a small footprint, and are compatible with subsequent flip-chip bonding onto interposers or printed circuit boards. Thus, our approach for sealing of integrated Si photonic MEMS clears a significant hurdle for their application in high-performance Si photonic circuits.
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| 3. |
- Kornienko, Vassily, et al.
(författare)
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Simultaneous multiple time scale imaging for kHz-MHz high-speed accelerometry
- 2022
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Ingår i: Photonics Research. - 2327-9125. ; 10:7, s. 1712-1722
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Tidskriftsartikel (refereegranskat)abstract
- Fast transient events, such as the disintegration of liquid bodies or chemical reactions between radical species, involve various processes that may occur at different time scales. Currently, there are two alternatives for monitoring such events: burst- or high-speed imaging. Burst imaging at ultrahigh speeds (∼100 MHz to THz) allows for the capture of nature's fastest processes but only for a narrowly confined period of time and at a repetition rate of ∼10 Hz. Monitoring long lasting, rapidly evolving transient events requires a significantly higher repetition rate, which is met by existing ∼kHz to 1 MHz high-speed imaging technology. However, the use of such systems eliminates the possibility to observe dynamics occurring on the sub-microsecond time scale. In this paper, we present a solution to this technological gap by combining multiplexed imaging with high-speed sensor technology, resulting in temporally resolved, high-spatial-resolution image series at two simultaneous time scales. We further demonstrate how the collection of such data opens up the tracking of rapidly evolving structures up to MHz burst rates over long durations, allowing, for the first time, to our knowledge, the extraction of acceleration fields acting upon the liquid bodies of an atomizing spray in two dimensions at kHz frame rates.
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| 4. |
- Tian, Ke, et al.
(författare)
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Blue band nonlinear optics and photodarkening in silica microdevices
- 2022
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Ingår i: Photonics Research. - 2327-9125. ; 10:9, s. 2073-2080
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Tidskriftsartikel (refereegranskat)abstract
- There are extensive studies to date on optical nonlinearities in microcavities at the near and mid-IR wavelengths. Pushing this research into the visible region is equally valuable. Here, we demonstrate a directly pumped, blue band Kerr frequency comb and stimulated Raman scattering (SRS) at 462 nm in a silica nanofiber-coupled whispering gallery microcavity system. Notably, due to the high optical intensities achieved, photodarkening is unavoidable and can quickly degrade the optical quality of both the coupling optical nanofiber and the microcavity, even at very low pump powers. Nonetheless, stable hyperparametric oscillation and SRS are demonstrated in the presence of photodarkening by taking advantage of in-situ thermal bleaching. This work highlights the challenges of silica-based, short wavelength nonlinear optics in high-quality, small mode volume devices and gives an effective method to overcome this apparent limitation, thus providing a baseline for optics research in the blue region for any optical devices fabricated from silica.
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| 5. |
- Xu, Ze-Sheng, et al.
(författare)
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Direct measurement of topological invariants in photonic superlattices
- 2022
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Ingår i: PHOTONICS RESEARCH. - : Optica Publishing Group. - 2327-9125. ; 10:12, s. 2901-2907
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Tidskriftsartikel (refereegranskat)abstract
- Since the discovery of topological insulators, topological phases have generated considerable attention across the physics community. The superlattices in particular offer a rich system with several degrees of freedom to explore a variety of topological characteristics and control the localization of states. Albeit their importance, characterizing topological invariants in superlattices consisting of a multi-band structure is challenging beyond the basic case of two-bands as in the Su-Schreifer-Heeger model. Here, we experimentally demonstrate the direct measurement of the topological character of chiral superlattices with broken inversion symmetry. Using a CMOS-compatible nanophotonic chip, we probe the state evolving in the system along the propagation direction using novel nano -scattering structures. We employ a two-waveguide bulk excitation scheme to the superlattice, enabling the iden-tification of topological zero-energy modes through measuring the beam displacement. Our measurements reveal quantized beam displacement corresponding to 0.088 and -0.245, in the cases of trivial and nontrivial photonic superlattices, respectively, showing good agreement with the theoretical values of 0 and-0.25. Our results provide direct identification of the quantized topological numbers in superlattices using a single-shot approach, paving the way for direct measurements of topological invariants in complex photonic structures using tailored excitations with Wannier functions.
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