Infrared photodetectors have been used extensively in biomedicine, surveillance, communication and astronomy. However, state of the art technology based on III-V and II-VI compounds still lacks ...excellent performance for high-temperature operation. Surface plasmon polaritons (SPPs) have demonstrated their capability in improving the light detection from visible to infrared wave range due to their light confinement in subwavelength scale. Advanced fabrication techniques such as electron-beam lithography (EBL) and focused ion-beam (FIB), and commercially available numerical design tool like Finite-Difference Time-Domain (FDTD) have enabled rapid development of surface plasmon (SP) enhanced photodetectors. In this review article, the basic mechanisms behind the SP-enhanced photodetection, the different type of plasmonic nanostructures utilized for enhancement, and the reported SP-enhanced infrared photodetectors will be discussed.
Computer-assisted detection (CADe) is a promising technologic advance that enhances adenoma detection during colonoscopy. However, the role of CADe in reducing missed colonic lesions is uncertain. ...The aim of this study was to determine the miss rates of proximal colonic lesions by CADe and conventional colonoscopy.
This was a prospective, multicenter, randomized, tandem-colonoscopy study conducted in 3 Asian centers. Patients were randomized to receive CADe or conventional white-light colonoscopy during the first withdrawal of the proximal colon (cecum to splenic flexure), immediately followed by tandem examination of the proximal colon with white light in both groups. The primary outcome was adenoma/polyp miss rate, which was defined as any adenoma/polyp detected during the second examination.
Of 223 patients (48.6% men; median age, 63 years) enrolled, 7 patients did not have tandem examination, leaving 108 patients in each group. There was no difference in the miss rate for proximal adenomas (CADe vs conventional: 20.0% vs 14.0%, P = .07) and polyps (26.7% vs 19.6%, P = .06). The CADe group, however, had significantly higher proximal polyp (58.0% vs 46.7%, P = .03) and adenoma (44.7% vs 34.6%, P = .04) detection rates than the conventional group. The mean number of proximal polyps and adenomas detected per patient during the first examination was also significantly higher in the CADe group (polyp: 1.20 vs .86, P = .03; adenoma, .91 vs .61, P = .03). Subgroup analysis showed that CADe enhanced proximal adenoma detection in patients with fair bowel preparation, shorter withdrawal time, and endoscopists with lower adenoma detection rate.
This multicenter trial from Asia confirmed that CADe can further enhance proximal adenoma and polyp detection but may not be able to reduce the number of missed proximal colonic lesions. (Clinical trial registration number: NCT04294355.)
Optics-based sensing platform working under unpolarized light illumination is of practical importance in the sensing applications. For this reason, sensing platforms based on localized surface ...plasmons are preferred to their integrated optics counterparts for their simple mode excitation and inexpensive implementation. However, their optical response under unpolarized light excitation is typically weak due to their strong polarization dependence. Herein, the role of rotational symmetry for realizing robust sensing platform exhibiting strong optical contrast and high sensitivity is explored. Specifically, gammadion and star-shaped gold nanostructures with different internal and external rotational symmetries are fabricated and studied in detail, from which their mode characteristics are demonstrated as superposition of their constituent longitudinal plasmons that are in conductive coupling with each other. We demonstrate that introducing and increasing internal rotational symmetry would lead to the enhancement in optical contrast up to ~3x under unpolarized light illumination. Finally, we compare the sensing performances of rotationally symmetric gold nanostructures with a more rigorous figure-of-merit based on sensitivity, Q-factor, and spectral contrast.
Aluminum is a promising candidate for light at the nanoscale in the ultraviolet (UV); however, the realization of magnetic resonance in the UV range remains challenging due to stringent dimensional ...requirements arising from the intrinsic loss caused by the interband transition. Here, the mode interaction with the aluminum interband transition and preferential excitation of the hybrid magnetic–electric mode, as discovered in ultrasmall Al resonators, are reported.
This study investigated the behavior of a 38-m deep twin circular peanut-shaped cofferdam interconnected with a rectangular section for cut-and-cover tunnel construction using distributed fiber-optic ...sensors (DFOSs) based on optical frequency domain reflectometry (OFDR). The distributed sensors revealed that temperature changes on the two sides of the diaphragm wall were different upon its exposure by excavation, while the measured strains were used to evaluate the wall deflection and bending moments. The high spatial resolution achieved by DFOS measurements revealed unique aspects of the wall response, which are difficult to obtain by conventional types of instrumentation. In particular, the strains along vertical and lateral directions of the wall panels were measured, the latter of which indicated eccentric compression in the concrete panels that arises from the distinctive peanut-shaped geometry. Developments of hoop forces and circumferential bending moments in the panels at various construction stages are discussed, with particular focus on the release of such during partial demolition of a temporary cross wall to facilitate the assembly and launching of tunnel boring machines. The mechanisms of stress developments and release were simulated using three-dimensional finite-element models that, together with the field measurements, enhance the understanding of the behavior of multicell cofferdams.
Non‐Invasive Super‐Resolution Speckle Fluctuation Imaging
Sub‐diffraction‐limit visualization of an object behind scattering media is possible with the non‐invasive super‐resolution speckle ...fluctuation imaging (NISSFI) technique. By analysing multiple speckle patterns from a fluctuating object within the optical memory effect region, high order cumulants of a fluctuating object are computed to reconstruct an image with reduced noise and diffraction‐limit‐breaking resolution. NISSFI promises broader applications, potentially enabling nanometer‐level resolution imaging of biological samples, tissues, bacteria or viruses under skin. For more details, see article number 2300712 by Sujit Kumar Sahoo, Cuong Dang, and co‐workers.
Engineering the spectral lineshape of plasmonic modes by various electromagnetic couplings and mode interferences enables significant improvements for plasmonic sensing. However, bulk and surface ...sensitivities remain constrained by a trade-off arising from their respective dependence on the interaction volume and decay length of the plasmonic mode, making higher bulk sensitivity realized at the expense of reduced surface sensitivity. We propose a new approach to overcome this trade-off by combining near-field and far-field coupling in an intercalated 3-disk plasmonic crystal, where ∼10× higher figure of merit (FoM) and ∼2× higher surface sensitivity can be achieved, in comparison with those achievable by localized surface plasmons. A plasmonic mode with a
Q
-factor up to ∼110 is demonstrated based on gold 3-disk arrays in the visible spectrum, with a bulk FoM of ∼24 and a surface sensitivity prefactor of ∼13.56. The design and fabrication simplicity of the 3-disk structure highlight its potential for a robust plasmonic sensing platform with a high figure of merit.
Hybridized surface lattice mode in an intercalated 3-disk plasmonic lattice for overcoming an inherent trade-off in plasmonic sensing.
Integration of photonic nanostructures with optoelectrical semiconductors offers great potential of developing high sensitivity and multifunctional photodetectors enabled by enhanced light–matter ...interactions. Split ring resonator (SRR) array which resonates at different resonant modes, including fundamental magnetic mode (m0), high order magnetic mode (m1), and electric (e) mode has been investigated because of the high potential for different applications. In this work, we study photodetection enhancement of these resonant modes of U-shape SRR arrays in the mid-infrared (2–5 μm) range and report, for the first time, the strong enhancement of photodetection by superimposition of m1 and e modes in an integrated photodetector consisting of a U-shape SRR array and an InAsSb-based heterojunction photodiode. We observe that the m1 mode in the SRR array shows the strongest enhancement of photocurrent, sequentially followed by the e and m0 modes. Using superimposed m1 and e modes, about an order of enhancement in room temperature detectivity (to about 2.0 × 1010 Jones) is achieved under zero-power-supply without sacrificing the response speed. In addition, polarization-resolved photoresponse between m1 and e modes and tunable enhancement of photoresponse are also demonstrated. The remarkable enhancement makes mid-infrared photodetection possible to operate at room temperature.
PDF
