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Jiang W, Wang J, Yang Y, Bu Y. A Review of Microsphere Super-Resolution Imaging Techniques. SENSORS (BASEL, SWITZERLAND) 2024; 24:2511. [PMID: 38676128 PMCID: PMC11053913 DOI: 10.3390/s24082511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/07/2024] [Accepted: 04/12/2024] [Indexed: 04/28/2024]
Abstract
Conventional optical microscopes are only able to resolve objects down to a size of approximately 200 nm due to optical diffraction limits. The rapid development of nanotechnology has increased the demand for greater imaging resolution, with a need to break through those diffraction limits. Among super-resolution techniques, microsphere imaging has emerged as a strong contender, offering low cost, simple operation, and high resolution, especially in the fields of nanodevices, biomedicine, and semiconductors. However, this technology is still in its infancy, with an inadequate understanding of the underlying principles and the technology's limited field of view. This paper comprehensively summarizes the status of current research, the advantages and disadvantages of the basic principles and methods of microsphere imaging, the materials and preparation processes, microsphere manipulation methods, and applications. The paper also summarizes future development trends.
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Affiliation(s)
- Wenbo Jiang
- School of Electrical Engineering and Electronic Information, Xihua University, Chengdu 610039, China; (J.W.); (Y.Y.); (Y.B.)
- Sichuan Provincial Key Laboratory of Signal and Information Processing, Xihua University, Chengdu 610039, China
| | - Jingchun Wang
- School of Electrical Engineering and Electronic Information, Xihua University, Chengdu 610039, China; (J.W.); (Y.Y.); (Y.B.)
- Sichuan Provincial Key Laboratory of Signal and Information Processing, Xihua University, Chengdu 610039, China
| | - Yidi Yang
- School of Electrical Engineering and Electronic Information, Xihua University, Chengdu 610039, China; (J.W.); (Y.Y.); (Y.B.)
- Sichuan Provincial Key Laboratory of Signal and Information Processing, Xihua University, Chengdu 610039, China
| | - Yun Bu
- School of Electrical Engineering and Electronic Information, Xihua University, Chengdu 610039, China; (J.W.); (Y.Y.); (Y.B.)
- Sichuan Provincial Key Laboratory of Signal and Information Processing, Xihua University, Chengdu 610039, China
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Karamehmedović M, Glückstad J. Phase-only steerable photonic nanojets. OPTICS EXPRESS 2023; 31:27255-27265. [PMID: 37710804 DOI: 10.1364/oe.497469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/23/2023] [Indexed: 09/16/2023]
Abstract
We demonstrate numerically the feasibility of axial and angular control of the position of a photonic nanojet (PNJ) by lossless phase-only modulation of a fixed Gaussian beam illuminating a fixed 2D circular homogeneous dielectric micro-lens. We furthermore demonstrate that our phase-only modality can be used to calibrate and improve the confinement of PNJ generation.
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Xu C, Ye R, Zou P, Yang T, Melinte S, Wang Z, Zuo C. Focusing light with a metal film coated patchy particle. OPTICS EXPRESS 2023; 31:10894-10904. [PMID: 37157625 DOI: 10.1364/oe.484060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Microsphere-assisted super-resolution imaging is a promising technique that can significantly enhance the resolution of conventional optical microscopes. The focus of a classical microsphere is called photonic nanojet, which is a symmetric high-intensity electromagnetic field. Recently, patchy microspheres have been reported to have superior imaging performance than pristine microspheres, and coating microspheres with metal films leads to the formation of photonic hooks, which can enhance the imaging contrast of microspheres. Understanding the influence of metal patches on the near-field focusing of patchy particles is important for the rational design of a nanostructured microlens. In this work, we theoretically and experimentally showed that the light waves can be focused and engineered using patchy particles. When coating dielectric particles with Ag films, light beams with a hook-like structure or S-shaped structure can be generated. Simulation results show that the waveguide ability of metal films and the geometric asymmetry of patchy particles cause the formation of S-shaped light beams. Compared with classical photonic hooks, S-shaped photonic hooks have a longer effective length and a smaller beam waist at far-field region. Experiments were also carried out to demonstrate the generation of classical and S-shaped photonic hooks from patchy microspheres.
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Karamehmedović M, Scheel K, Listov-Saabye Pedersen F, Villegas A, Hansen PE. Steerable photonic jet for super-resolution microscopy. OPTICS EXPRESS 2022; 30:41757-41773. [PMID: 36366644 DOI: 10.1364/oe.472992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
A promising technique in optical super-resolution microscopy is the illumination of the sample by a highly localized beam, a photonic jet (also called photonic nanojet). We propose a method of computation of incident field amplitude and phase profiles that produce photonic jets at desired locations in the near field after interaction with a fixed micro-scale dielectric lens. We also describe a practical way of obtaining the incident field profiles using spatial light modulators. We expect our photonic jet design method to work for a wide range of lens shapes, and we demonstrate its application numerically using two-dimensional micro-lenses of circular and square cross-sections. We furthermore offer a theoretical analysis of the resolution of photonic jet design, predicting among other that a larger lens can produce a narrower photonic jet. Finally, we give both theoretical and numerical evidence that the waist width of the achieved designed jets is increasing linearly and slowly over a large interval of radial distances. With uniform plane wave illumination, the circular two-dimensional micro-lens produces a similar-sized jet at a fixed radial distance, while the square lens does not form a jet at all. We expect our steerable optical photonic jet probe to enable highly localized adaptive real-time measurements and drive advances in super-resolution optical microscopy and scatterometry, as well as fluorescence and Raman microscopy. Our relatively weak peak jet intensity allows application in biology and health sciences, which require high resolution imaging without damaging the sample bio-molecules.
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Shi R, Wang Z, Hung ST, Hellmann C, Wyrowski F. Numerical analysis of tiny-focal-spot generation by focusing linearly, circularly, and radially polarized beams through a micro/nanoparticle. OPTICS EXPRESS 2021; 29:2332-2347. [PMID: 33726430 DOI: 10.1364/oe.415576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 12/28/2020] [Indexed: 06/12/2023]
Abstract
Obtaining a tiny focal spot is desired for super resolution. We do a vectorial numerical analysis of the linearly, circularly, and radidally polarized electromagnetic fields being focused through a dielectric micro/nanoparticle of size comparable to the wavelength. We find tiny focal spots (up to ∼0.05 λ2) can be obtained behind micro/nanoparticles of various shapes, e.g. spherical, disk-shaped, and cuboid micro/nanoparticles. Furthermore, we also investigate the influence of the misalignment of a real lens system on the tiny focal spots. We find that tiny focal spots can still be generated even though they are distorted due to the misalignment.
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Wen Y, Yu H, Zhao W, Li P, Wang F, Ge Z, Wang X, Liu L, Li WJ. Scanning Super-Resolution Imaging in Enclosed Environment by Laser Tweezer Controlled Superlens. Biophys J 2020; 119:2451-2460. [PMID: 33189683 DOI: 10.1016/j.bpj.2020.10.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/29/2020] [Accepted: 10/30/2020] [Indexed: 10/23/2022] Open
Abstract
Super-resolution imaging using microspheres has attracted tremendous scientific attention recently because it has managed to overcome the diffraction limit and allowed direct optical imaging of structures below 100 nm without the aid of fluorescent microscopy. To allow imaging of specific areas on the surface of samples, the migration of the microspheres to specific locations on two-dimensional planes should be controlled to be as precise as possible. The common approach involves the attachment of microspheres on the tip of a probe. However, this technology requires additional space for the probe and could not work in an enclosed environment, e.g., in a microfluidic enclosure, thereby reducing the range of potential applications for microlens-based super-resolution imaging. Herein, we explore the use of laser trapping to manipulate microspheres to achieve super-resolution imaging in an enclosed microfluidic environment. We have demonstrated that polystyrene microsphere lenses could be manipulated to move along designated routes to image features that are smaller than the optical diffraction limit. For example, a silver nanowire with a diameter of 90 nm could be identified and imaged. In addition, a mosaic image could be constructed by fusing a sequence of images of a sample in an enclosed environment. Moreover, we have shown that it is possible to image Escherichia coli bacteria attached on the surface of an enclosed microfluidic device with this method. This technology is expected to provide additional super-resolution imaging opportunities in enclosed environments, including microfluidic, lab-on-a-chip, and organ-on-a-chip devices.
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Affiliation(s)
- Yangdong Wen
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China; University of the Chinese Academy of Sciences, Beijing, China
| | - Haibo Yu
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China.
| | - Wenxiu Zhao
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China; University of the Chinese Academy of Sciences, Beijing, China
| | - Pan Li
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China; University of the Chinese Academy of Sciences, Beijing, China
| | - Feifei Wang
- Department of Chemistry, Stanford University, Stanford, California
| | - Zhixing Ge
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China; University of the Chinese Academy of Sciences, Beijing, China
| | - Xiaoduo Wang
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China
| | - Lianqing Liu
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Shenyang, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, China
| | - Wen Jung Li
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China.
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Du B, Zhang H, Xia J, Wu J, Ding H, Tong G. Super-Resolution Imaging with Direct Laser Writing-Printed Microstructures. J Phys Chem A 2020; 124:7211-7216. [PMID: 32786979 DOI: 10.1021/acs.jpca.0c05415] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dielectric microstructures coupled with a conventional optical microscope have been proven to be a successful way to achieve super-resolution imaging. However, a limitation of such super-resolution imaging is the microstructure fabrication ability, which generally provides natural structures (such as spherical, hemispherical, superhemispherical microlenses, and so on). Meanwhile, the influences of microstructures with complex shapes on the super-resolved imaging still remain unknown. In this paper, direct laser writing (DLW) lithography is used to produce a series of complex microstructures, which are capable of achieving super-resolution imaging in the optical far-field region. Cylinder, truncated cone, hemisphere, and protruding hemisphere microstructures are successfully fabricated by this 3D printing technology, allowing us to resolve features as small as 100 nm under classical microscopy. Moreover, different microstructures lead to different photonic nanojet (PNJ) illuminations and collection efficiencies, resulting in a critical role in super-resolved imaging. The microstructures with spherical surfaces can easily collect the light scattered by the object and convert the high-spatial-frequency evanescent waves into propagating waves.
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Affiliation(s)
- Bintao Du
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
| | - Hao Zhang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
| | - Jun Xia
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
| | - Jun Wu
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
| | - Haibo Ding
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
| | - Guodong Tong
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
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Abstract
Microsphere-assisted microscopy currently benefits from a considerable interest in the microscope-research community. Indeed, this new imaging technique enables the lateral resolution of optical microscopes to reach around λ/5 through a full-field and a far-field acquisition while being label-free. Despite the photonic jet clearly not being a relevant concept to justify the super-resolution phenomenon, we show here how it can be used to predict imaging formation and performance such as the image position and the microsphere magnification. This study allows a better understanding of the experimental measurements that have been observed over the last decade and that will be observed in coming years, through numerical simulations using different optical and geometrical parameters.
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Aakhte M, Abbasian V, Akhlaghi EA, Moradi AR, Anand A, Javidi B. Microsphere-assisted super-resolved Mirau digital holographic microscopy for cell identification. APPLIED OPTICS 2017; 56:D8-D13. [PMID: 28375382 DOI: 10.1364/ao.56.0000d8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper, we use a glass microsphere incorporated into a digital holographic microscope to increase the effective resolution of the system, aiming at precise cell identification. A Mirau interferometric objective is employed in the experiments, which can be used for a common-path digital holographic microscopy (DHMicroscopy) arrangement. High-magnification Mirau objectives are expensive and suffer from low working distances, yet the commonly used low-magnification Mirau objectives do not have high lateral resolutions. We show that by placing a glass microsphere within the working distance of a low-magnification Mirau objective, its effective numerical aperture can be increased, leading to super-resolved three-dimensional images. The improvement in the lateral resolution depends on the size and vertical position of microsphere, and by varying these parameters, the lateral resolution and magnification may be adjusted. We used the information from the super-resolution DHMicroscopy to identify thalassemia minor red blood cells (tRBCs). Identification is done by comparing the volumetric measurements with those of healthy RBCs. Our results show that microsphere-assisted super-resolved Mirau DHMicroscopy, being common path and off-axis in nature, has the potential to serve as a benchtop device for cell identification and biomedical measurements.
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Lai HSS, Wang F, Li Y, Jia B, Liu L, Li WJ. Super-Resolution Real Imaging in Microsphere-Assisted Microscopy. PLoS One 2016; 11:e0165194. [PMID: 27768774 PMCID: PMC5074592 DOI: 10.1371/journal.pone.0165194] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 10/08/2016] [Indexed: 11/18/2022] Open
Abstract
Microsphere-assisted microscopy has received a lot of attention recently due to its simplicity and its capability to surpass the diffraction limit. However, to date, sub-diffraction-limit features have only been observed in virtual images formed through the microspheres. We show that it is possible to form real, super-resolution images using high-refractive index microspheres. Also, we report on how changes to a microsphere's refractive index and size affect image formation and planes. The relationship between the focus position and the additional magnification factor is also investigated using experimental and theoretical methods. We demonstrate that such a real imaging mode, combined with the use of larger microspheres, can enlarge sub-diffraction-limit features up to 10 times that of wide-field microscopy's magnification with a field-of-view diameter of up to 9 μm.
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Affiliation(s)
- Hok Sum Sam Lai
- Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong
| | - Feifei Wang
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang, 110016, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yi Li
- Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong
| | - Boliang Jia
- Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong
| | - Lianqing Liu
- State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang, 110016, China
| | - Wen Jung Li
- Mechanical and Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong
- * E-mail:
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Gu G, Zhou R, Xu H, Cai G, Cai Z. Subsurface nano-imaging with self-assembled spherical cap optical nanoscopy. OPTICS EXPRESS 2016; 24:4937-4948. [PMID: 29092321 DOI: 10.1364/oe.24.004937] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Frequently-used subsurface nano-imaging techniques have limitations in interference, stability, complexity, timeliness and cost reduction on account of the combination of excited ultrasound signal or probed cantilever tip. Though some improved optical methods can directly and visually obtain subsurface nanofeatures, the high refractive index difference (RID) between introduced superlens and subsurface object will inevitably degenerate the image quality. In this paper, a simple and reliable experimental technique is presented to self-assemble spherical cap optical nanoscopy (SCON) subsurface nano-imaging system (SNIS) with two low RID materials. By using SCON-SNIS, subsurface objects with a spacing as small as 0.16 times of illumination wavelength, and involving wider field of views (nearly one-half of SCON's great-circle diameter in the direction of the equator) and deeper depth (several micrometers) can be imaged. In order to get insights into the imaging mechanism, a finite element simulation and a ray-optics analytical study are performed, in which the imaging process is elucidated both theoretically and experimentally. This non-invasive, label-free and real-time subsurface nano-imaging paradigm could be a promising tool in life, material, biology and engineering sciences.
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Ding C, Wei J. Far-field optical imaging with subdiffraction resolution enabled by nonlinear saturation absorption. Sci Rep 2016; 6:18845. [PMID: 26727415 PMCID: PMC4698740 DOI: 10.1038/srep18845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/27/2015] [Indexed: 11/10/2022] Open
Abstract
The resolution of far-field optical imaging is required to improve beyond the Abbe limit to the subdiffraction or even the nanoscale. In this work, inspired by scanning electronic microscopy (SEM) imaging, in which carbon (or Au) thin films are usually required to be coated on the sample surface before imaging to remove the charging effect while imaging by electrons. We propose a saturation-absorption-induced far-field super-resolution optical imaging method (SAI-SRIM). In the SAI-SRIM, the carbon (or Au) layers in SEM imaging are replaced by nonlinear-saturation-absorption (NSA) thin films, which are directly coated onto the sample surfaces using advanced thin film deposition techniques. The surface fluctuant morphologies are replicated to the NSA thin films, accordingly. The coated sample surfaces are then imaged using conventional laser scanning microscopy. Consequently, the imaging resolution is greatly improved, and subdiffraction-resolved optical images are obtained theoretically and experimentally. The SAI-SRIM provides an effective and easy way to achieve far-field super-resolution optical imaging for sample surfaces with geometric fluctuant morphology characteristics.
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Affiliation(s)
- Chenliang Ding
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, People's Republic of China.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Jingsong Wei
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, People's Republic of China
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Wang F, Lai HSS, Liu L, Li P, Yu H, Liu Z, Wang Y, Li WJ. Super-resolution endoscopy for real-time wide-field imaging. OPTICS EXPRESS 2015; 23:16803-16811. [PMID: 26191692 DOI: 10.1364/oe.23.016803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Resolving subcellular structures in vitro beyond optical diffraction barrier by a light microscope has achieved significant development since the advancement of super-resolution fluorescence microscopes, such as stimulated emission depletion (STED) microscopy, stochastic optical reconstruction microscopy (STORM) and photoactivated localization microscopy (PALM). However, the resolution of observation in deep and dense in vivo tissues is still confined to cellular level presently, and hence, exploring image details at subcellular level or even beyond organelle level in vivo has continued to attract much research attention. Currently, endoscopy provides an effective way to achieve in vivo observations and is compatible with mature optical microscopy technologies, but its resolution is usually confined to ~1 µm. Here we report a new endoscopy method by functionalizing graded-index (GRIN) lens with microspheres for real-time white-light or fluorescent super-resolution imaging. The capability of resolving objects with feature size of ~λ/5, which breaks the diffraction barrier of traditional GRIN lens based endoscopes by a factor of two, has been demonstrated by using this super-resolution endoscopy method. Further development of such a super-resolution endoscopy technique may provide new opportunities for in vivo life sciences studies.
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Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies. Sci Rep 2015; 5:11131. [PMID: 26053074 PMCID: PMC4459103 DOI: 10.1038/srep11131] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 05/14/2015] [Indexed: 11/21/2022] Open
Abstract
A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green’s function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments.
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Gu G, Zhou R, Chen Z, Xu H, Cai G, Cai Z, Hong M. Super-long photonic nanojet generated from liquid-filled hollow microcylinder. OPTICS LETTERS 2015; 40:625-8. [PMID: 25680166 DOI: 10.1364/ol.40.000625] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Photonic nanojet (PNJ) from liquid-filled hollow microcylinder (LFHM) under a liquid immersion condition is numerically investigated based on the finite element method and physically analyzed with ray optics. Simulation and analysis results show that, by simultaneously introducing the immersed liquid and filled liquid, the propagation beam is greatly flattened, and super-long PNJs with decay length more than 100 times the illumination wavelengths are obtained in the outer near-field region of the LFHM. With the variation of the refractive index contrast between the filled and immersed-liquids, the properties of the PNJs, such as the focal distance, decay length, full width at half-maximum, and maximum light intensity can be flexibly tuned.
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