| 1. |
- Cao, Shun, et al.
(författare)
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Enhancing single photon emission through quasi-bound states in the continuum of monolithic hexagonal boron nitride metasurface
- 2021
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Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- A patterned structure of monolithic hexagonal boron nitride (hBN) on a glass substrate, which can enhance the emission of the embedded single photon emitters (SPEs), is useful for onchip single-photon sources of high-quality. Here, we design and demonstrate a monolithic hBN metasurface with quasi-bound states in the continuum mode at emission wavelength with ultrahigh Q values to enhance fluorescence emission of SPEs in hBN. Because of ultrahigh electric field enhancement inside the proposed hBN metasurface, an ultrahigh Purcell factor (3.3 x 10(4)) is achieved. In addition, the Purcell factor can also be strongly enhanced in most part of the hBN structure, which makes the hBN metasurface suitable for e.g. monolithic quantum photonics.
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| 2. |
- Cao, Shun, et al.
(författare)
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High-temperature ultra-broad UV–MIR high-efficiency absorber based on double ring-shaped titanium nitride resonators
- 2021
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Ingår i: Optics Communications. - : Elsevier B.V.. - 0030-4018 .- 1873-0310. ; 485
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Tidskriftsartikel (refereegranskat)abstract
- An ultrabroad absorber based on double-ring-shaped titanium nitride (TiN) nanoresonators, which can work in high temperatures, is proposed and numerically studied. The absorber with some optimal parameters exhibits an averaged absorption of 94.6% in the range of 200–4000 nm (from ultraviolet to mid-infrared) and a band from 200–3518 nm having an absorption > 90%. We have demonstrated in detail the physical mechanisms of the ultra-broad absorption, including the dielectric lossy property of TiN material itself in shorter wavelengths and plasmonic resonances caused by the metallic property of TiN nano-resonators in longer wavelengths. In addition, the absorber shows polarization independent and wide-angle acceptance. Another absorber with double TiN nano-rings of different heights has flatter and higher absorption efficiency (more than 95% absorption) at 200–2860 nm waveband. These properties make the proposed absorbers based on TiN has great potentials in many applications, such as light trapping, photovoltaics, thermal emitters.
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| 3. |
- Guo, Tingbiao, et al.
(författare)
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Thermal management with a highly emissive and thermally conductive graphite absorber
- 2019
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Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Thermal management on a variety of length scales is essential for many industrial, solar and computational systems. Here we explore the thermal properties of a nearly perfect graphite absorber with both high emissivity and thermal conductivity which is fabricated by simple one-step etching. The hemispherical reflectance of the absorber is around 1% in the visible range and the normal specular reflectance is less than 1% from 1.5 mu m to 10 mu m. The thermal conductivity of the absorber is measured above 630 Wm(-1) K-1, which is 2.5 times larger than the aluminum used in commercial heat sinks. Heat dissipation testing indicates that a device is 3.7 +/- 2 degrees cooler with the graphite absorber as the heat spreader than a pristine graphite sheet and 9.1 +/- 2 degrees cooler than an Au-coated graphite sheet, primarily due to improved radiation cooling. A theoretical analysis accounts for the results. Further analysis suggests that the radiative heat dissipation is more prominent in the low-convection environment, especially for a convection coefficient below 10 Wm(-2) K-1.
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| 4. |
- He, Nan, et al.
(författare)
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All-in-One Collimating Splitter Based on a Meta-Fiber Platform
- 2023
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- The use of array generators has become ubiquitous in various applications such as laser fabrication, face identification, and motion sensing. The Dammann grating, a diffractive optical element, is the mainstream approach for generating uniform spot arrays. However, its limited capability and the contradiction between the performance and the complexity of fabrication hinder its application. To address this issue, an all-in-one collimating splitter based on metasurfaces is theoretically proposed by synthesizing the phase of an inverse-optimized Dammann grating and a collimating lens. Leveraging both the diffraction effect of Dammann grating and the Fourier transformation of the collimating lens, the number of spot arrays can be largely increased with a single lenslet. The proposed design shows a large field of view of 62 degrees x 62 degrees ffi and a high uniformity of 1.29% in generating a spot array of 3 x 3 on a single-fiber platform, confirmed by both the scalar and full-wave simulation. Further, a larger spot array up to 15 x 15 is also derived in the far field by integrating the proposed metasurface on a 5 x 5 fiber array platform, confirmed by the scalar simulation. Our design may be transplanted to the vertical-cavity surface-emitting laser platform, and shows great potential in various applications including face identification and motion sensing.
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| 5. |
- He, Nan, et al.
(författare)
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High-Speed Duplex Free Space Optical Communication System Assisted by a Wide-Field-of-View Metalens
- 2023
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 10:9, s. 3052-3059
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Tidskriftsartikel (refereegranskat)abstract
- Free space optical communication (FSO) has gained significant attention due to the growing demand for a high information capacity. For FSO between multiple or moving targets, a receiver with a wide angle of acquisition capability is necessary. Traditionally, gimbals and fast steering mirrors have been used, but they are often difficult to make both compact and wide-angle. Here, a novel duplex FSO system is demonstrated, which utilizes a highly compact fiber coupling metalens to receive and transmit signals in a large field of view up to 80°. High coupling efficiency up to 48.8% at a wavelength of 1550 nm is experimentally achieved. The small coupling loss enables the user to modulate and direct the downstream power from the base station back along the same path, saving energy and leaving only one source in the FSO system. The low bit error rate and the open and clear eye diagram results validate the excellent downlink/uplink communication performance of a 10 Gbps FSO system empowered by the metalens. The system exhibits a large field of view, high data rate, compact size, and low power consumption, which meets the size, weight, and power requirement of smart devices.
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| 6. |
- Li, Chenxi, et al.
(författare)
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pH dependence of the chirality of nematic cellulose nanocrystals
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals produced by acid hydrolysis of native cellulose form a well-known chiral nematic liquid crystal phase. The mechanism involved in the formation of chirality has been the subject of a vigorous discussion. The pH and concentration dependence of the phase is studied using cellulose nanocrystal droplets within a silicon oil suspension, which allows for convenient real-time microscale manipulation of phase behaviors and properties. We demonstrate the existence of nematic phases at both low and high pH regions consistent with the Stroobants - Lekkerkerker - Odijk theory. Our results confirm electrostatic interactions play a critical role in controlling the strength of the chirality.
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| 7. |
- Li, Chenxi, et al.
(författare)
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Preparation and liquid crystal phase properties of discotic cellulose nanoparticles
- 2019
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Ingår i: Cellulose. - : SPRINGER. - 0969-0239 .- 1572-882X. ; 26:18, s. 9543-9552
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the behavior of fluids with inhomogeneous structural properties is critical for many industrial and biological materials. Sulfuric acid hydrolysis of cotton with ultrasonic treatment and low-speed centrifugation during purification yields "spiky" discotic cellulose particles. Amorphous cellulose remained in solution and forms discotic units which may be nucleated by crystalline rods. Scanning electron microscope and transmission electron microscope images confirm the discotic nature of the cellulose. High speed centrifugation could recover rod-like cellulose nanocrystals from the discotic cellulose nanoparticle solution. 3.6 wt% discotic cellulose nanoparticles formed the typical nematic phase and the liquid crystal texture became more structured with increasing concentration. Our results showed that spontaneous structuring of amorphous cellulose can lead to phase behavior that cannot be achieved using just rod-like cellulose nanocrystals. Graphic abstract Mixtures containing amorphous and crystalline cellulose can form discotic cellulose nanoparticles. These solutions can form nematic phase (A), a structured columnar-like phase (B), and a glassy phase [GRAPHICS] .
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| 8. |
- Li, Chenxi, et al.
(författare)
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Preparation of optical waveplates from cellulose nanocrystal nematics on patterned polydimethylsiloxane substrates
- 2019
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Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 9:12, s. 4614-4623
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Tidskriftsartikel (refereegranskat)abstract
- Optical waveplates play an essential role in controlling polarization in various applications. We show the feasibility of facile production of optical waveplates from plant-based cellulose nanocrystal (CNC) nematics. We align CNC nematic liquid crystals doped with polyethylene glycol on periodically patterned polydimethylsiloxane substrates on large scale by shearing forces and prepare a 1/4 lambda and a 1/2 lambda CNC waveplates for 530 nm by bonding two slices of CNC nematic films with half-period displacement. The optical performance of the CNC waveplates is investigated by Mueller matrix analysis and is examined by measuring the transmission spectra of the waveplate between two polarizers, and optical extinction and birefringence of CNCs are extracted from the measured spectra. Our CNC waveplates of arbitrary phase difference are flexible and can be tailored into any desirable shape conveniently.
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| 9. |
- Lin, Zijian, et al.
(författare)
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Low-cost, high-speed multispectral imager via spatiotemporal modulation based on a color camera
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:25, s. 42613-42623
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Tidskriftsartikel (refereegranskat)abstract
- Spectral imaging is a powerful tool in industrial processes, medical imaging, and fundamental scientific research. However, for the commonly used spatial/spectral-scanning spectral imager, the slow response time has posed a big challenge for its employment in dynamic scenes. In this paper, we propose a spatiotemporal modulation concept and build a simple, low-cost spectral imager by combining a liquid crystal (LC) cell with a commercial color camera. By the synergic effect of temporal modulation of the LC materials and spatial modulation of the Bayer filter in a color camera, high-quality multispectral imaging is successfully demonstrated with a high rate of 8 Hz, far beyond the counterparts. Experimental results show that even with three tuning states of the LC material, optical signals with a 10-nm band can be resolved in the range between 410 and 700 nm by this method, overcoming the tradeoff between spectral resolution and time resolution. As a proof of demonstration, we present its potential usage for metamerism recognition, showing superiority over traditional color cameras with more spectral details. Considering its low cost, miniaturization and monolithic-integration ability on color sensors, this simple approach may bring the spectral imaging technology closer to the consumer market and even to ubiquitous smartphones for health care, food inspection and other applications.
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| 10. |
- Liu, Zhenchao, et al.
(författare)
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Guided Mode Induced Surface Phase Mutation for Enhanced SPR Biosensor with Dual-Parameters Interrogation
- 2023
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 10:34
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Tidskriftsartikel (refereegranskat)abstract
- Ongoing research on the sensitivity and integration of refractive index-based biosensors has resulted in significant advancements. Here, the study presents an enhanced surface plasmon resonance biosensor that integrates imaging technology and features dual-parameter interrogation (intensity and phase) with guided mode coupling. By depositing a silica-waveguide-layer on a metal-layer, two-mode coupling is established to generate a high Q resonance and induce a phase mutation. The sensing performance experiment demonstrated a phase sensing sensitivity of 1.1 × 105 degree RIU−1, Q-value of the resonant peak up to 314, and figure of merit of 300 RIU−1, superior to most standard plasmonic sensors. An in-line phase-polarization modulation scheme combined with imaging technology is proposed to extract the resonant phase carrying refractive index information. Additionally, a pair-prism module is designed to optimize the sensing system configuration. Meanwhile, dual-parameters interrogation including the intensity and phase are demonstrated, which offers potential for complementary and multi-sensing fusion applications. The intensity interrogation also shows a considerable sensitivity of 7.2 × 104 a.u. RIU−1. Furthermore, it is combined with microfluidic chip to detect of alpha-synuclein protein closely related to Parkinson's disease, and the limit of detection can reach 300 pg mL−1 level, which indicated a considerable potential for high-throughput diagnosis application.
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| 11. |
- Liu, Zhenchao, et al.
(författare)
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Phase Interrogation Sensor Based on All-Dielectric BIC Metasurface
- 2023
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 23:22, s. 10441-10448
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Tidskriftsartikel (refereegranskat)abstract
- The low performance of sensors based on an all-dielectric metasurface limits their application compared to metallic counterparts. Here, for the first time, an all-dielectric BIC (bound states in the continuum) metasurface is employed for highly sensitive phase interrogation refractive index sensing. The proposed sensor is well analyzed, fabricated, and characterized. Experimentally, a high-performance BIC-based microfluidic sensing chip with a Q factor of 1200 is achieved by introducing symmetry breaking. A refractive index sensor with high figure of merit of 418 RIU-1 is demonstrated, which is beneficial to the phase interrogation. Notably, we measure a record phase interrogation sensitivity of 2.7 x 10(4) deg/RIU to the refractive index, thus enabling the all-dielectric BIC to rival the refractive index detection capabilities of metal-based sensors such as surface plasmon resonance. This scheme establishes a pivotal role of the all-dielectric metasurface in the field of ultrahigh sensitivity sensors and opens possibilities for trace detection in biochemical analysis and environment monitoring.
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| 12. |
- Sun, Yuwei, et al.
(författare)
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Enhancing Circularly Polarized Emission by a Planar Chiral Dielectric Metasurface
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 11:14
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Tidskriftsartikel (refereegranskat)abstract
- Circularly polarized emission (CPE) has attracted great interest in optoelectronics, biosensing, etc. Here, a resonant planar chiral dielectric metasurface that can be constructed to provide a preferable way for CPE is demonstrated. The planar metasurface is easy to fabricate, and the corresponding far-field circular polarization degree is extremely high and angle-insensitive. The designed metasurface is made of a periodic array of in-plane mirror-asymmetric silicon pillar dimers and supports a low-leakage chiral band-edge mode. Experimentally, the photoluminescence of a thin film of PbS/CdS quantum dots coated on such a metasurface is enhanced by 57 times with the far-field degree of circular polarization as high as 0.74. The planar platform provides a flexible and efficient way for manipulating CPE, in which other periodic coupling effects may also be adopted to enhance the light–matter interaction, such as quasi-bound states in the continuum and lattice resonance.
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| 13. |
- Tian, Jiahan, et al.
(författare)
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Wide-field-of-view auto-coupling optical antenna system for high-speed bidirectional optical wireless communications in C band
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:20, s. 33435-33448
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Tidskriftsartikel (refereegranskat)abstract
- Due to a great many superior features of infrared light communication (ILC), like high capacity and strong privacy, ILC is considered a potential candidate for serving the high demands of beyond fifth-generation/sixth-generation (B5G/6 G) communication systems. However, the terminal's limited field-of-view (FOV) induces great difficulty in establishing line-of-sight (LoS) link between the transceiver and the terminal. In this paper, we propose a wide-FOV auto-coupling optical antenna system that utilizes a wide-FOV telecentric lens to collect incident infrared beams and automatically couple them into a specific single-mode-fiber (SMF) channel of fiber array and optical switch. The performance of this optical antenna system is assessed through simulation and manual alignment operation, and validated by automatic alignment results. A coupling loss of less than 10.6 dB within a FOV of 100(degrees )for both downstream and upstream beams in C band is demonstrated by the designed system. Furthermore, we establish a bidirectional optical wireless communications (OWC) system employing this antenna and a fiber-type modulating retro-reflector (MRR) system in the terminal. Both 10-Gbps on-off keying (OOK) downstream and upstream transmissions are successfully realized with the FOV of up to 100(degrees) in C band where the measured bit-error-rate (BER) is lower than 3.8 x 10-3. To the best of our knowledge, this is a brand-new auto-coupling optical antenna system with the largest FOV in ILC automatic alignment works in terminals that have ever been reported.
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| 14. |
- Tian, Jiahan, et al.
(författare)
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Wide-Field-of-View Modulating Retro-Reflector System Based on a Telecentric Lens for High-Speed Free-Space Optical Communication
- 2023
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- Modulating retro-reflector (MRR) free-space optical (FSO) communication technology presents a bright future for realizing the small size, weight, and power (SWaP) design of one end of the optical link, facilitating the further application of the FSO communication to the small platforms. However, the limited field-of-view (FOV) of MRR impedes its wide employment. In this article, a novel wide-FOV MRR using an image space telecentric lens is proposed and a bidirectional FSO communication system is experimentally demonstrated using this MRR with a single light source. The performance of the telecentric lens between the transceiver and terminal is assessed by simulation and also validated by experimental results, with a coupling loss less than 9.1 dB within a FOV of 110 degrees. Both 10-Gbit/s on-off keying (OOK) downstream and upstream signals for free space communication at different incident angles are successfully realized using this designed wide-FOV MRR. The experimental results validate the proposed MRR has a FOV of up to 110 degrees where the measured bit error rate (BER) is lower than 3.8 x 10-3 for both downstream and upstream signals. To the best of our knowledge, this is the largest FOV ever reported for MRRs in high-speed bidirectional FSO communication systems.
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| 15. |
- Zhang, Zhi, et al.
(författare)
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Customized Structural Color Filters by Pixel-Level Electrothermal Regulation
- 2023
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Ingår i: Laser & Photonics reviews. - : Wiley. - 1863-8880 .- 1863-8899. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- Reflective structural colors have backlight-free supremacy and can provide energy-efficient and environmental-friendly color production for many applications. However, they are hindered by the complex process and incorrect colors after fabrication. Here, a pixelated electrothermal oxidation technique is proposed that can precisely tailor and produce reflective structural colors covering the entire visible range, providing the possibility for customized structural color filter arrays from a titanium canvas. Furthermore, as a demonstration, a photonic-firework-like color filter array is achieved in a single step via thermal engineering. Based on this one-step-forming color array, a computational spectrometer is also realized featuring a resolvability of 10 nm and operating bandwidth covering the whole visible range. Considering its compactness and mass production capability, this method has numerous potential applications in, e.g., imaging, anti-counterfeiting, printing, color display, and spectroscopy.
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