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  • NRN113 - Engineering Near-field Focusing of a Microsphere Lens with Pupil Masks

    Science Direct

    • Sensors and Devices, 
    • Knowledge Transfer

    Recent researches have shown small dielectric microspheres can perform as super-resolution lens to break optical diffraction limit for super-resolution applications. In this paper, we show for the first time that by combining a microsphere lens with a pupil mask, it is possible to precisely control the focusing properties of the lens, including the focusing spot size and focal length.

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  • NRN113 - Photonic nanojet of cylindrical metalens assembled by hexagonally arranged nanofibers for breaking the diffraction limit

    The Optical Society of America

    • Sensors and Devices, 
    • Knowledge Transfer

    In this Letter, we seek the combination of the metamaterial concept with a photonic nanojet. The idea is to use nanofibers as building blocks to create a microsized artificial metalens. By varying the compositional nanofiber diameter, we shall be able to tune the focusing property of the metalens according to our needs.

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  • NRN113 - Microsphere Super-resolution Imaging

    Royal Society of Chemistry

    • Sensors and Devices, 
    • Knowledge Transfer

    Recently, it was discovered that microsphere can generate super-resolution focusing beyond diffraction limit. This has led to the development of an exciting super-resolution imaging technique – microsphere nanoscopy – that features a record resolution of 50 nm under white lights.

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  • NRN141 - Frictional Fluid Dynamics and Plug Formation in Multiphase Millifluidic Flow

    Physical Review Letters

    • Materials

    We study experimentally the flow and patterning of a granular suspension displaced by air inside a narrow tube. The invading air-liquid interface accumulates a plug of granular material that clogs the tube due to friction with the confining walls. The gas percolates through the static plug once the gas pressure exceeds the pore capillary entry pressure of the packed grains, and a moving accumulation front is reestablished at the far side of the plug. The process repeats, such that the advancing interface leaves a trail of plugs in its wake. Further, we show that the system undergoes a fluidization transition—and complete evacuation of the granular suspension—when the liquid withdrawal rate increases beyond a critical value. An analytical model of the stability condition for the granular accumulation predicts the flow regime.

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  • NRN097 - Characterization of polymer fiber Bragg grating with ultrafast laser micromachining

    IEEE Xplore

    • Sensors and Devices, 
    • Modelling, 
    • Knowledge Transfer, 
    • Materials

    We report that the main photosensitive mechanism of poly(methyl methacrylate)-based optical fiber Bragg grating (POFBG) under ultraviolet laser micromachining is a complex process of both photodegradation and negative thermo-optic effect. We found experimentally the unique characteristics of Bragg resonance splitting and reunion during the laser micromachining process providing the evidence of photodegradation, while the mean refractive index change of POFBG was measured to be negative confirming further photodegradation of polymer fiber. The thermal-induced refractive index change of POFBG was also observed by recording the Bragg wavelength shift. Furthermore, the dynamic thermal response of the micromachined-POFBG was demonstrated under constant humidity, showing a linear and negative response of around -47.1 pm/°C.

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