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  • Optica Publishing Group  (26)
  • 1
    Online Resource
    Online Resource
    Optica Publishing Group ; 2018
    In:  Optics Express Vol. 26, No. 17 ( 2018-08-20), p. 21403-
    In: Optics Express, Optica Publishing Group, Vol. 26, No. 17 ( 2018-08-20), p. 21403-
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2018
    detail.hit.zdb_id: 1491859-6
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  • 2
    Online Resource
    Online Resource
    Optica Publishing Group ; 2023
    In:  Optics Letters Vol. 48, No. 7 ( 2023-04-01), p. 1750-
    In: Optics Letters, Optica Publishing Group, Vol. 48, No. 7 ( 2023-04-01), p. 1750-
    Abstract: Photothermal microscopy (PTM) was developed to image non-fluorescent objects. In the past two decades, PTM has reached single-particle and single-molecule sensitivity and has been used in the fields of material science and biology. However, PTM is a far-field imaging method whose resolution is restricted by the diffraction limits. This Letter reports a resolution improvement approach for photothermal microscopy called modulated difference PTM (MD-PTM), which utilizes Gaussian and doughnut formalism heating beams that are modulated at the same frequency but are of opposite phase to generate the photothermal signal. Furthermore, the opposite phase characteristics of the photothermal signals are applied to determine the objective profile from the PTM magnitude, and this helps to improve the lateral resolution of PTM. The lateral resolution is related to the difference coefficient between the Gaussian and doughnut heating beams; an increase in the difference coefficient causes a larger sidelobe of the MD-PTM amplitude, which readily forms an artifact. A pulse-coupled neural network (PCNN) is employed for phase image segmentations of MD-PTM. We experimentally study the micro-imaging of gold nanoclusters and crossed nanotubes using MD-PTM, and the results indicate that MD-PTM has merit in terms of improving the lateral resolution.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 243290-0
    detail.hit.zdb_id: 1479014-2
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  • 3
    Online Resource
    Online Resource
    Optica Publishing Group ; 2024
    In:  Optics Letters Vol. 49, No. 8 ( 2024-04-15), p. 1957-
    In: Optics Letters, Optica Publishing Group, Vol. 49, No. 8 ( 2024-04-15), p. 1957-
    Abstract: In the past two decades, photothermal microscopy (PTM) has achieved sensitivity at the level of a single particle or molecule and has found applications in the fields of material science and biology. PTM is a far-field imaging method; its resolution is restricted by the diffraction limits. In our previous work, the modulated difference PTM (MDPTM) was proposed to improve the lateral resolution, but its resolution improvement was seriously constrained by information loss and artifacts. In this Letter, a deep learning approach of the cycle generative adversarial network (Cycle GAN) is employed for further improving the resolution of PTM, called DMDPTM. The point spread functions (PSFs) of both PTM and MDPTM are optimized and act as the second generator of Cycle GAN. Besides, the relationship between the sample’s volume and the photothermal signal is utilized during dataset construction. The images of both PTM and MDPTM are utilized as the inputs of the Cycle GAN to incorporate more information. In the simulation, DMDPTM quantitatively distinguishes a distance of 60 nm between two nanoparticles (each with a diameter of 60 nm), demonstrating a 4.4-fold resolution enhancement over the conventional PTM. Experimentally, the super-resolution capability of DMDPTM is verified by restored images of Au nanoparticles, achieving the resolution of 114 nm. Finally, the DMDPTM is successfully employed for the imaging of carbon nanotubes. Therefore, the DMDPTM will serve as a powerful tool to improve the lateral resolution of PTM.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2024
    detail.hit.zdb_id: 243290-0
    detail.hit.zdb_id: 1479014-2
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  • 4
    Online Resource
    Online Resource
    Optica Publishing Group ; 2023
    In:  Optical Materials Express Vol. 13, No. 7 ( 2023-07-01), p. 1921-
    In: Optical Materials Express, Optica Publishing Group, Vol. 13, No. 7 ( 2023-07-01), p. 1921-
    Abstract: With the rapid development of high-speed THz communications, there has been a growing interest in exploring the potential of the orbital angular momentum (OAM) of electromagnetic waves. In this study, we propose a cross-polarized reflective broadband metasurface operating in the THz band to harness the benefits of OAM in the optical field. We quantitatively analyze the reflection amplitude and phase characteristics of the metasurface elements, which supports the design of a reflective broadband element surface array with an ordered arrangement of 3-bit elements. By combining the 3-bit metasurface elements in an array, linearly polarized waves can effectively be converted into vortex beams in the operating frequency range of 0.6THz-1.3THz. The simulation results demonstrate that the designed metasurface element structure can achieve not only efficient cross-polarization reflection amplitude but also effective phase control by adjusting the size parameters. Our proposed metasurface is able to convert linearly polarized waves into vortex beams with an efficiency exceeding 85% and can achieve high-purity OAM beam acquisition. Furthermore, the metasurface structure is simple to implement and can be easily integrated with photoelectric circuits, making it ideal for use in ultrahigh-speed THz communications.
    Type of Medium: Online Resource
    ISSN: 2159-3930
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 2619914-2
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  • 5
    In: Photonics Research, Optica Publishing Group, Vol. 9, No. 5 ( 2021-05-01), p. 734-
    Abstract: In this work, a self-powered GaN-based metal-semiconductor-metal photodetector (MSM PD) with high responsivity has been proposed and fabricated. The proposed MSM PD forms an asymmetric feature by using the polarization effect under one electrode, such that we adopt an AlGaN/GaN heterojunction to produce the electric field, and by doing so, an asymmetric energy band between the two electrodes can be obtained even when the device is unbiased. The asymmetric feature is proven by generating the asymmetric current-voltage characteristics both in the dark and the illumination conditions. Our results show that the asymmetric energy band enables the self-powered PD, and the peak responsivity wavelength is 240 nm with the responsivity of 0.005 A/W. Moreover, a high responsivity of 13.56 A/W at the applied bias of 3 V is also achieved. Thanks to the very strong electric field in the charge transport region, when compared to the symmetric MSM PD, the proposed MSM PD can reach an increased photocurrent of 100 times larger than that for the conventional PD, even if the illumination intensity for the light source becomes increased.
    Type of Medium: Online Resource
    ISSN: 2327-9125
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
    detail.hit.zdb_id: 2724783-1
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  • 6
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 18 ( 2022-08-29), p. 32333-
    Abstract: A low-numerical aperture (NA) confined-doped long-tapered (LCT) Yb-doped fiber is proposed and fabricated by modified chemical vapor deposition combined with solution doping technique. The LCT fiber owns the core NA of ∼0.05 and the gain dopant doping diameter ratio of ∼77%, with a core/cladding diameter of 25/400 µm at both ends and 37.5/600 µm in the middle. The laser performance is demonstrated by a bidirectional pumping all-fiber amplifier, of which a 4.18-kW single-mode (M 2 factor ∼1.3) laser output is achieved with a slope efficiency of ∼82.8%. Compared with the conventional fiber, the co-pumped and counter-pumped transverse mode instability thresholds and beam quality of the LCT fiber are remarkably enhanced. Throughout the continuous operation, the LCT fiber amplifier presents high power stability with fluctuation of 〈 1%. These results indicate that LCT fiber has great potential in power scaling remaining excellent beam quality.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 1491859-6
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  • 7
    Online Resource
    Online Resource
    Optica Publishing Group ; 2021
    In:  Applied Optics Vol. 60, No. 23 ( 2021-08-10), p. 6989-
    In: Applied Optics, Optica Publishing Group, Vol. 60, No. 23 ( 2021-08-10), p. 6989-
    Abstract: To determine the methods of color measurement and color-difference calculation for holographic prints with light pillars, 94 pairs of holographic prints constituted by 17 different products were collected. A set of color-difference comparison experiments was organized by 64 observers with normal color vision, and a total of 86 groups of visual judgments were gathered. The CIELAB and CIEDE2000 color-difference values were calculated on the basis of the analysis of the microstructures of gratings distributed on the holographic paper. The performances of the original formulas were evaluated in terms of the standardized residual sum of squares index, and then they were optimized considering the power function effects ( a , b factors) together with a contribution from lightness ( k L factor). Meanwhile, the color-difference threshold of the holographic prints was estimated with a goal to minimize the number of wrong decision in the visual experiment; therefore, the values were set as 2.50 and 2.00 for the original CIELAB and CIEDE2000 with the consistency of 91.5% and 98.9%, respectively. The results can also provide guidance to evaluate the color quality of the holographic prints with light pillars in the packaging and printing industries.
    Type of Medium: Online Resource
    ISSN: 1559-128X , 2155-3165
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
    detail.hit.zdb_id: 207387-0
    detail.hit.zdb_id: 1474462-4
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  • 8
    Online Resource
    Online Resource
    Optica Publishing Group ; 2022
    In:  Applied Optics Vol. 61, No. 26 ( 2022-09-10), p. 7608-
    In: Applied Optics, Optica Publishing Group, Vol. 61, No. 26 ( 2022-09-10), p. 7608-
    Abstract: An asymmetric double-image encryption scheme based on chaotic random phase encoding (CRPE) is proposed. In this proposed encryption scheme, two grayscale images to be encrypted are first Fresnel transformed and combined into a complex image. Then, the amplitude and phase components are obtained by conducting phase–amplitude truncation on the complex image. Finally, the amplitude component is again Fresnel transformed and encrypted into a noise-like pattern by the CRPE in the Fresnel domain. Since the initial values and control parameters of the chaotic map can replace the random phase masks to serve as secret keys, the management and transmission of secret keys will become more convenient in the proposed encryption scheme. Furthermore, the Fresnel transform parameters and phase keys derived from the complex image’s phase component can also act as secret keys during the decryption process. Numerical simulations have demonstrated the feasibility, security, and robustness of the proposed encryption scheme.
    Type of Medium: Online Resource
    ISSN: 1559-128X , 2155-3165
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 207387-0
    detail.hit.zdb_id: 1474462-4
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  • 9
    In: Optics Express, Optica Publishing Group, Vol. 22, No. S4 ( 2014-06-30), p. A1093-
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2014
    detail.hit.zdb_id: 1491859-6
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  • 10
    Online Resource
    Online Resource
    Optica Publishing Group ; 2016
    In:  Optics Express Vol. 24, No. 2 ( 2016-01-25), p. A44-
    In: Optics Express, Optica Publishing Group, Vol. 24, No. 2 ( 2016-01-25), p. A44-
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2016
    detail.hit.zdb_id: 1491859-6
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