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The noise equivalent temperature difference (NETD) indicates the minimum temperature difference resolvable by using an infrared detector. The lower the NETD, the better the sensor can register small temperature differences. In this work, we proposed a strategy to achieve a high temperature resolution using a superconducting nanowire single-photon detector (SNSPD) with ultra-high sensitivity. We deduced the model for calculating the NETD of a photon-counting-type detector and applied it to our SNSPD-based set-up. Experimentally, we obtained an NETD as low as 0.65 mK, which is limited by the background radiation of the environment, and the required infrared radiation power is calculated to be <1 pW. Furthermore, the intrinsic NETD of this SNSPD is estimated to be <0.1 mK. This work demonstrated a sub-mK temperature resolution when using the SNSPD, paving the way for future remote infrared thermal imaging with high temperature resolution. [ABSTRACT FROM AUTHOR]

Fluorescence of negative‐charged nitrogen‐vacancy centers in nanodiamond allows applications in quantum metrology, nanoscale sensor, and bioimaging, of utmost relevance to domains from nanotechnologies to biosensing. However, the low color center content and collection efficiency of photons are crucial issues. Although, several studies about coupling nanodiamond into optical waveguides have already been proposed, the search for the most appropriate substance and simplest, most effective method are of keys. In this study, we present a novel nontraditional way to incorporate nanodiamond with increased negative‐charged nitrogen‐vacancy content to 75.48% into tellurite germanate glass. The hybrid glass is stable in structure with predominant TeO4 trigonal bipyramid. Moreover, the fluorescence intensity is enhanced in composite. Such robust nanodiamond in tellurite germanate glass optical system has the potential to be used for nanoparticle sensing and quantum metrology. [ABSTRACT FROM AUTHOR]

The modulation of the required light wavefront polarization and phase based on the geometric phase encoding metasurface (GPEM) has recently become a hot topic. However, the transmission coefficient of a geometric phase metasurface is greatly decreased when the structure is rotated. To address this problem, a solution of adding a tapered antireflection layer to the substrate and design an all‐dielectric encoding metasurface composed of titanium dioxide and silicon dioxide in the visible light band with a transmission coefficient of 93.65%, is proposed. When circularly polarized light is incident on the designed encoding metasurfaces with rotating unit structures, the GPEM still maintain almost perfect transmission coefficient as with initial linearly polarized light is incident. By comparing the coded metasurface with and without conical structure, the coded metasurface with conical structure can greatly improve transmission efficiency. Importantly, the Fourier convolution theorem in digital signal processing is introduced on encoding metasurfaces. The scattering angle of transmission can be controlled arbitrarily by the all‐dielectric coded metasurface with Fourier convolution addition and subtraction operations. [ABSTRACT FROM AUTHOR]

All dielectric nanospheres with low loss and ultra‐compact characteristics can be effectively applied in nanophotonics in the visible and infrared ranges. The unidirectional forward scattering with azimuthally symmetry can be achieved by simple dielectric nanosphere. The physical origin of this directionality can be attributed to the interference effect of electric and magnetic resonances induced in nanoshperes. For the forward scattering of a single nanosphere the spectrally overlapping resonance of electric and magnetic quadrupoles can further enhance the directionality and magnitude of unidirectional forward scattering. For a nanosphere homodimers, the scattering pattern can also preserve the azimuthal asymmetry and the suppression of backscattering. But, the side scattering lobes occur due to the grating diffraction effect. Furthermore, the significant improvement of scattering magnitude and directionality can be achieved by a linear chain of nanospheres. These unique optical scattering of nanoshperes can be applied in the fields of nanoantennas, photovoltaics, and nanolasers in visible and near infrared ranges. [ABSTRACT FROM AUTHOR]

Fabry–Pérot interferometers (FPIs) are designed to work near and off the absorption resonance of an electro-optic (EO) polymer. The near-resonance EO activity (EO coefficient r13∼25.4 pm/V at ∼1086 nm) is enhanced over that off resonance (r13∼9.0 pm/V at ∼1526 nm). The full width at half maximum of the FPI transmission band is ∼16 nm near resonance compared to ∼22 nm off resonance. The modulation performance can, therefore, be improved with a modulation ratio increased to ∼78% near resonance (at 1064 nm) from ∼19% off resonance (at 1520 nm). The modulation speed is approximately megahertz and can be increased to greater than gigahertz with improved circuit design. [ABSTRACT FROM AUTHOR]