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  • Optica Publishing Group  (192)
  • 2020-2024  (192)
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  • Optica Publishing Group  (192)
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  • 2020-2024  (192)
Year
  • 1
    Online Resource
    Online Resource
    Sweep frequency method with variance weight probability for temperature extraction of the Brillouin gain spectrum based on an artificial neural network
    Optica Publishing Group ; 2021
    In:  Optics Express Vol. 29, No. 18 ( 2021-08-30), p. 28994-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 18 ( 2021-08-30), p. 28994-
    Abstract: The development of optical fiber sensors has led to the possibility of accumulating vast, real-time databases of acoustic and other measurements throughout fiber networks, which brings even more widespread concern on improving the sampling effectiveness. In this paper, we present two kinds of sweep frequency methods based on using a neural network to extract temperature from the Brillouin gain spectrum (BGS). Gauss centralization and variance weight probability methods are proposed to compare with the uniform sweep frequency method. By analyzing formulas of the ideal BGS model, we find the gain near the peak of Brillouin gain spectrum has greater correlation with temperature extraction than other positions. Therefore, the Gaussian centralized sweep method is proposed. We further investigate the variation of the weights in the neural network and Brillouin data distribution in different positions and find that the variance is positively correlated with the weights in hidden layers. So, we propose the sweep frequency method based on variance weight probability and make a complement to interpret the rationality of this method in neural network. In all the aforementioned approaches, 281 points are obtained between the 9.07 GHz to 9.35 GHz range under the same condition. The data of each method is trained ten times and tested through the same neural network structure. All the RMSE of each test stage covers all data collecting the passage. The result shows that the RMSE of variance weight probability sweep frequency method is 0.5277, which is superior to the Gauss centralization sweep frequency method that was 0.6864 and the uniform sweep frequency method that was 0.9140.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.427998
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
    detail.hit.zdb_id: 1491859-6
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  • 2
    Online Resource
    Online Resource
    Elimination of the PMD related delay jitter in a fiber stretcher based ultra-stable microwave signal distribution system
    Optica Publishing Group ; 2021
    In:  Optics Express Vol. 29, No. 25 ( 2021-12-06), p. 41609-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 25 ( 2021-12-06), p. 41609-
    Abstract: We realize an ultra-stable microwave signal distribution system based on an optical phase-locked loop. The transmission delay jitter is accurately compensated with a piezoelectric fiber stretcher (PFS). For further eliminating the additional delay jitter originated from the polarization changes during the PFS stretching, we propose an orthogonal-polarized round-trip PFS structure. The transmission delay jitter of 24 GHz signals distributed to multiple remote ends using the proposed and the traditional PFS scheme are carefully compared and quantitively analyzed under various fiber types and lengths. With the proposed PFS structure, the relative delay jitter of two transmitted signals are decreased from 291.4 fs to merely 17.7 fs even via 200 m polarization maintaining fiber with considerable polarization mode dispersion, showing its remarkable superiority. This microwave signal distribution system can find its versatile applications in radio astronomy where multiple ultra-high relative stable microwave signals are highly desired in different locations.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.444199
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
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  • 3
    Online Resource
    Online Resource
    Optical system design for a hyperspectral imaging lidar using supercontinuum laser and its preliminary performance
    Optica Publishing Group ; 2021
    In:  Optics Express Vol. 29, No. 11 ( 2021-05-24), p. 17542-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 11 ( 2021-05-24), p. 17542-
    Abstract: To meet the urgent need for surveying and mapping using remote sensing instruments, a hyperspectral imaging lidar using a supercontinuum laser is proposed. This novel lidar system can solve the problem of the mismatching of the traditional lidar retrieved elevation data and hyperspectral data obtained by passive imaging instruments. The optical design of the lidar receiving system is described, developed, and tested in this study. An off-axis parabolic mirror is used as the receiving telescope of the system, and a transmissive grating is used to split the received hyperspectral light to each detection channel. A fiber array equipped with a micro-lens is used to guide the split light to the detectors. In practice, several fibers can be coupled to one detector according to the wavelength sensitivity of different objects. A reference laser is used to monitor the possible energy jitter of each transmitted laser pulse in real time. A spectrum calibration of the receiving system is accomplished in the laboratory, and radiation calibration is applied by receiving the backscattered light reflected by a standard white board. The spectral resolution of a single fiber is approximately 3 nm. An outdoor 500-m distance experiment was carried out for green and yellow leaves in day and evening settings. During the experiment, the wavelength of the laser was 460-900 nm. The reflection spectra collected by the lidar system in day and evening were consistent, indicating that the design of the optical receiving system is reliable and can be used for airborne hyperspectral imaging lidar.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.424748
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
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  • 4
    Online Resource
    Online Resource
    Field test of quantum key distribution over aerial fiber based on simple and stable modulation
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 16 ( 2023-07-31), p. 26301-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 16 ( 2023-07-31), p. 26301-
    Abstract: We have developed a simple time-bin phase encoding quantum key distribution system, using the optical injection locking technique. This setup incorporates both the merits of simplicity and stability in encoding, and immunity to channel disturbance. We have demonstrated the field implementation of quantum key distribution over long-distance deployed aerial fiber automatically. During the 70-day field test, we achieved approximately a 1.0 kbps secure key rate with stable performance. Our work takes an important step toward widespread implementation of QKD systems in diverse and complex real-life scenarios.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.494318
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 5
    Online Resource
    Online Resource
    Entangled qutrits generated in four-wave mixing without post-selection
    Optica Publishing Group ; 2020
    In:  Optics Express Vol. 28, No. 8 ( 2020-04-13), p. 11538-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 28, No. 8 ( 2020-04-13), p. 11538-
    Abstract: High-dimensional entangled states and quantum repeaters are important elements in efficient long-range quantum communications. The high-dimensional property associated with the orbital angular momentum (OAM) of each photon improves the bandwidth of the quantum communication network. However, the generation of high-dimensional entangled states by the concentration method reduces the brightness of the entangled light source, making extensions to these higher dimensions difficult. To overcome this difficulty, we propose to generate entangled qutrits in the OAM space by loading the pump light with OAM. Compared with the concentration method, our experimental results show that the rate of generation of photon pairs improves significantly with an observed 5.5-fold increase. The increased generation rate provides the system with the ability to resist the noise and improve the fidelity of the state. The S value of the Clauser–Horne–Shimony–Holt inequality increases from 2.48 ± 0.07 to 2.69 ± 0.04 under the same background noise, and the fidelity of the reconstructed density matrix improves from 57.8 ± 0.14% to 70 ± 0.17%. These achievements exhibit the enormous advantages of high-dimensional entanglement generation.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.383378
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
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  • 6
    Online Resource
    Online Resource
    Three-dimensional micropatterning of graphene by femtosecond laser direct writing technology
    Optica Publishing Group ; 2020
    In:  Optics Letters Vol. 45, No. 1 ( 2020-01-01), p. 113-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 45, No. 1 ( 2020-01-01), p. 113-
    Abstract: The reduction and patterning of graphene oxides (GOs) have broad applications in gene transfection, cell differentiation control, etc. However, two-dimensional (2D) photoreduction technologies (such as UV lithography) fail to realize the three-dimensional (3D) reduction and patterning of GO, limiting its applications in 3D electronic device interconnection and 3D graphene organ-on-a-chip. Here we developed 3D reduction and patterning of GO by femtosecond laser direct writing (FsLDW) technology. FsLDW has been adopted for 3D structure fabrication and 2D/3D micropatterning of reduced GOs on GO films. We deem that this technology will advance GO in the evolution of future electronics.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.45.000113
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
    detail.hit.zdb_id: 243290-0
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  • 7
    Online Resource
    Online Resource
    Optical memory for arbitrary perfect Poincaré states in an atomic ensemble
    Optica Publishing Group ; 2023
    In:  Optics Letters Vol. 48, No. 2 ( 2023-01-15), p. 477-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 48, No. 2 ( 2023-01-15), p. 477-
    Abstract: Inherent spin angular momentum (SAM) and orbital angular momentum (OAM), which manifest as polarization and spatial degrees of freedom (DOFs) of photons, hold a promise of large capability for applications in classical and quantum information processing. To enable these photonic spin and orbital dynamic properties strongly coupled with each other, Poincaré states have been proposed and offer advantages in data multiplexing, information encryption, precision metrology, and quantum memory. However, since the transverse size of Laguerre–Gaussian beams strongly depends on their topological charge numbers | l |, it is difficult to store asymmetric Poincaré states due to the significantly different light–matter interaction for distinct spatial modes. Here, we experimentally realize the storage of perfect Poincaré states with arbitrary OAM quanta using the perfect optical vortex, in which 121 arbitrarily selected perfect Poincaré states have been stored with high fidelity. The reported work has great prospects in optical communication and quantum networks for dramatically increased encoding flexibility of information.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.479915
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 243290-0
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  • 8
    Online Resource
    Online Resource
    Direct laser writing structural color for reversible encryption and decryption in different mediums
    Optica Publishing Group ; 2023
    In:  Optics Letters Vol. 48, No. 10 ( 2023-05-15), p. 2508-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 48, No. 10 ( 2023-05-15), p. 2508-
    Abstract: Structural color (SC) has enormous potential for improving the visualization and identification of functional micro/nano structures for information encryption and intelligent sensing. Nevertheless, achieving the direct writing of SCs at the micro/nano scale and the change of color in response to external stimuli simultaneously is rather challenging. To this end, we directly printed woodpile structures (WSs) utilizing femtosecond laser two-photon polymerization (fs-TPP), which demonstrated obvious SCs under an optical microscope. After that, we achieved the change of SCs by transferring WSs between different mediums. Furthermore, the influence of laser power, structural parameters, and mediums on the SCs was systematically investigated, and the mechanism of SCs using the finite-difference time-domain (FDTD) method was further explored. Finally, we realized the reversible encryption and decryption of certain information. This finding holds broad application prospects in smart sensing, anti-counterfeiting tags, and advanced photonic devices.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    URL: Article
    DOI: 10.1364/OL.486950
    DOI: 10.1364/OL.486950.v001
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 9
    Online Resource
    Online Resource
    Observation of robust edge mode and in-gap corner mode in Kagome surface-wave photonic crystals
    Optica Publishing Group ; 2023
    In:  Optics Letters Vol. 48, No. 11 ( 2023-06-01), p. 2825-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 48, No. 11 ( 2023-06-01), p. 2825-
    Abstract: Recent theory has demonstrated that Kagome photonic crystals (PCs) support first-order and second-order topological phenomena. Here, we extend the topological physics of the Kagome lattice to surface electromagnetic waves and experimentally show a Kagome surface-wave PC. Under the protection of first-order and second-order topologies, both robust edge modes and in-gap corner modes are observed. The robust transport of edge modes is demonstrated by high transmission through the waveguide with a sharp bend. The localized corner mode is found at the corner with one isolated rod when a triangle-shaped sample is constructed. Our work not only shows a platform to mimic the topological physics in classical wave systems, but also offers a potential application in designing high-performance photonic devices.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.488612
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 243290-0
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  • 10
    Online Resource
    Online Resource
    10-pm-order mechanical displacement measurements using heterodyne interferometry
    Optica Publishing Group ; 2020
    In:  Applied Optics Vol. 59, No. 27 ( 2020-09-20), p. 8478-
    Details
    In: Applied Optics, Optica Publishing Group, Vol. 59, No. 27 ( 2020-09-20), p. 8478-
    Abstract: In this paper, we present 10-pm-order mechanical displacement measurements using heterodyne interferometry. The measuring system includes a single-path heterodyne interferometer and a phase meter based on a phase-locked loop (PLL). It is not easy to measure a mechanical displacement of 10 pm or less owing to electronics and environmental noises in the interferometer. To solve this problem, the improvement of the noise floor is required for the phase meter. A PLL algorithm, which is programmed on a field-programmable gate array module, is used for efficient noise reduction of the phase meter. The interferometer combined with a stiff piezoelectric flexure stage is placed in a vacuum chamber. The measurement comparisons and the noise floor evaluations are performed between air and vacuum to evaluate effects from their environments. The interferometer has two spatially separated beams with different frequencies and two balanced optical arms. The measurement results demonstrate that the system combined with the above components is capable of measuring mechanical displacements of 11 pm in air and vacuum. A noise floor of 0.2 pm/ H z between 50 Hz and 100 Hz can be obtained in vacuum. In this paper, the setup of the interferometer, the signal processing of the PLL, experiments, and results are discussed.
    Type of Medium: Online Resource
    ISSN: 1559-128X , 2155-3165
    URL: Article
    DOI: 10.1364/AO.400682
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
    detail.hit.zdb_id: 207387-0
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