Superhybrid Mode-Enhanced Optical Torques on Mie-Resonant Particles.

Circularly polarized light carries spin angular momentum, so it can exert an optical torque on the polarization-anisotropic particle by the spin momentum transfer. Here, we show that giant positive and negative optical torques on Mie-resonant (gain) particles arise from the emergence of superhybrid modes with magnetic multipoles and electric toroidal moments, excited by linearly polarized beams. Anomalous positive and negative torques on particles (doped with judicious amount of dye molecules) are over 800 and 200 times larger than the ordinary lossy counterparts, respectively. Meanwhile, a rotational motor can be configured by switching the s- and p-polarized beams, exhibiting opposite optical torques. These giant and reversed optical torques are unveiled for the first time in the scattering spectrum, paving another avenue toward exploring unprecedented physics of hybrid and superhybrid multipoles in metaoptics and optical manipulations.

A Metalens with a Near-Unity Numerical Aperture.

The numerical aperture (NA) of a lens determines its ability to focus light and its resolving capability. Having a large NA is a very desirable quality for applications requiring small light-matter interaction volumes or large angular collections. Traditionally, a large NA lens based on light refraction requires precision bulk optics that ends up being expensive and is thus also a specialty item. In contrast, metasurfaces allow the lens designer to circumvent those issues producing high-NA lenses in an ultraflat fashion. However, so far, these have been limited to numerical apertures on the same order of magnitude as traditional optical components, with experimentally reported NA values of <0.9. Here we demonstrate, both numerically and experimentally, a new approach that results in a diffraction-limited flat lens with a near-unity numerical aperture (NA > 0.99) and subwavelength thickness (∼λ/3), operating with unpolarized light at 715 nm. To demonstrate its imaging capability, the designed lens is applied in a confocal configuration to map color centers in subdiffractive diamond nanocrystals. This work, based on diffractive elements that can efficiently bend light at angles as large as 82°, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated with the standard, phase mapping approach.

Noninterleaved Metasurface for (26-1) Spin- and Wavelength-Encoded Holograms.

Nanostructured metasurfaces demonstrate extraordinary capabilities to control light at the subwavelength scale, emerging as key optical components to physical realization of multitasked devices. Progress in multitasked metasurfaces has been witnessed in making a single metasurface multitasked by mainly resorting to extra spatial freedom, for example, interleaved subarrays, different angles. However, it imposes a challenge of suppressing the cross-talk among multiwavelength without the help of extra spatial freedom. Here, we introduce an entirely novel strategy of multitasked metasurfaces with noninterleaved single-size Si nanobrick arrays and minimalist spatial freedom demonstrating massive information on 6-bit encoded color holograms. The interference between electric dipole and magnetic dipole in individual Si nanobricks with in-plane orientation enables manipulating six bases of incident photons simultaneously to reconstructed 6-bit wavelength- and spin-dependent multicolor images. Those massively reconstructed images can be distinguished by pattern recognition. It opens an alternative route for integrated optics, data encoding, security encryption, and information engineering.

Resonant Light Guiding Along a Chain of Silicon Nanoparticles.

Subwavelength confined waveguiding is experimentally demonstrated with high refractive index dielectric nanoparticles with photon energy propagation at distances beyond 500 µm. These particles have naturally occurring electric and magnetic dipole resonances. When they are placed in a 1D chain, the magnetic resonances of adjacent elements couple to each other, providing a means to transport energy at visible or NIR wavelengths in a confined mode. Chains of nanoparticles made of silicon were fabricated and guided waves were measured with near-field scanning optical microscopy. Propagation loss is quantified at 34 dB/mm for 720 nm and 5.5 dB/mm for 960 nm wavelengths with 150 and 220 nm diameter particles, respectively. Simulations confirm the unique properties of this waveguiding in comparison with photonic crystals. The resonant nature of the waveguide lays a foundation for integrated photonics beyond nanowire waveguides of silicon and silicon nitride. This technology is promising for more compact and deeper photonic integration such as right angle bends, more compact modulators, slow light and interfacing with single photon emitters for photonic integrated circuits, quantum communications, and biosensing.

Asymmetric Nanoantennas for Ultrahigh Angle Broadband Visible Light Bending.

Wavefront manipulation in metasurfaces typically relies on phase mapping with a finite number of elements. In particular, a discretized linear phase profile may be used to obtain a beam bending functionality. However, discretization limits the applicability of this approach for high angle bending due to the drastic efficiency drop when the phase is mapped by a small number of elements. In this work, we discuss a novel concept for energy redistribution in diffraction gratings and its application in the visible spectrum range, which helps overcome the constraints of ultrahigh angle (above 80°) beam bending. Arranging asymmetric dielectric nanoantennas into diffractive gratings, we show that one can efficiently redistribute the power between the grating orders at will. This is achieved by precise engineering of the scattering pattern of the nanoantennas. The concept is numerically and experimentally demonstrated at visible frequencies using several designs of TiO2 (titanium dioxide) nanoantennas for medium (∼55°) and high (∼80°) angle light bending. Results show efficient broadband visible-light operation (blue and green range) of transmissive devices, reaching efficiencies of ∼90% and 50%, respectively, at the optimized wavelength. The presented design concept is general and can be applied for both transmission and reflection operation at any desired wavelength and polarization.

Printing Beyond sRGB Color Gamut by Mimicking Silicon Nanostructures in Free-Space.

Localized optical resonances in metallic nanostructures have been increasingly used in color printing, demonstrating unprecedented resolution but limited in color gamut. Here, we introduce a new nanostructure design, which broadens the gamut while retaining print resolution. Instead of metals, silicon nanostructures that exhibit localized magnetic and electric dipole resonances were fabricated on a silicon substrate coated with a Si3N4 index matching layer. Index matching allows a suppression of substrate effects, thus enabling Kerker's conditions to be met, that is, sharpened transitions in the reflectance spectra leading to saturated colors. This nanostructure design achieves a color gamut superior to sRGB, and is compatible with CMOS processes. The presented design could enable compact high-resolution color displays and filters, and the use of a Si3N4 antireflection coating can be readily extended to designs with nanostructures fabricated using other high-index materials.

Magnetic and electric hotspots with silicon nanodimers.

The study of the resonant behavior of silicon nanostructures provides a new route for achieving efficient control of both electric and magnetic components of light. We demonstrate experimentally and numerically that enhancement of localized electric and magnetic fields can be achieved in a silicon nanodimer. For the first time, we experimentally observe hotspots of the magnetic field at visible wavelengths for light polarized across the nanodimer's primary axis, using near-field scanning optical microscopy.

[Treatment of stage â ¡-â ¢ Kümmell disease with robot-assisted bone cement-augmented pedicle screw fixation].

OBJECTIVE: To evaluate the early clinical efficacy of robot-assisted percutaneous short-segment bone cement-augmented pedicle screw fixation in the treatment of stageⅡ-Ⅲ Kümmell disease. METHODS: The clinical data of 20 patients with stageⅡ-Ⅲ Kümmell's disease who underwent robot-assisted percutaneous bone cement-augmented pedicle screw fixation between June 2017 and January 2021 were retrospectively analyzed. There were 4 males and 16 females, aged from 60 to 81 years old with an average age of (69.1±8.3) years. There were 9 cases of stageⅡand 11 cases of stage Ⅲ, all of which were single vertebral lesions, including 3 cases of T11, 5 cases of T12, 8 cases of L1, 3 cases of L2, and 1 case of L3. These patients did not exhibit symptoms of spinal cord injury. The operation time, intraoperative blood loss, and complications were recorded. The position of pedicle screws and the filling and leakage of bone cement in gaps were observed using postoperative CT 2D reconstruction. The data of the visual analogue scale (VAS), Oswestry disability index (ODI), kyphosis Cobb angle, wedge angle of the diseased vertebra, and anterior and posterior vertebral height on lateral radiographs were statistically analyzed preoperatively, 1 week postoperatively, and at the final follow-up. RESULTS: Twenty patients were followed up for 10 to 26 months, with an average follow-up of (16.0±5.1) months. All operations were successfully completed. The surgical duration ranged from 98 to 160 minutes, with an average of (122±24) minutes. The intraoperative blood loss ranged from 25 to 95 ml, with an average of (45±20) ml. There were no intraoperative vascular nerve injuries. A total of 120 screws were inserted in this group, including 111 screws at grade A and 9 screws at grade B according to the Gertzbein and Robbins scales. Postoperative CT indicated that the bone cement was well-filled in the diseased vertebra, and cement leakage occurred in 4 cases. Preoperative VAS and ODI were (6.05±0.18) points and (71.10±5.37)%, respectively, (2.05±0.14) points and (18.57±2.77)% at 1 week after operation, and (1.35±0.11) points and (15.71±2.12) % at final follow-up. There were significant differences between postoperative 1 week and preoperative, and between final follow-up and postoperative 1 week(P<0.01). Anterior and posterior vertebral height, kyphosis Cobb angle, and wedge angle of the diseased vertebra were(45.07±1.06)%, (82.02±2.11)%, (19.49±0.77) °, and (17.56±0.94) ° preoperatively, respectively, (77.00±0.99)%, (83.04±2.02)%, (7.34±0.56) °, and (6.15±0.52) ° at 1 week postoperatively, and (75.13±0.86)%, (82.39±0.45)%, (8.38±0.63) °, and (7.09±0.59) ° at the final follow-up. CONCLUSION: Robot-assisted percutaneous short-segment bone cement-augmented pedicle screw fixation demonstrates satisfactory short-term efficacy in treating stageⅡ-Ⅲ Kümmell's disease as an effective minimally invasive alternative. However, longer operation times and strict patient selection criteria are necessary, and long-term follow-up is required to determine its lasting effectiveness.

A comparative study of robot-assisted and traditional surgeries in the treatment of thoracolumbar fractures based on 1-year follow-up observation.

BACKGROUND: There are conflicting results for robot-assisted (RA) pedicle screw fixation compared with freehand (FH) pedicle screw fixation. OBJECTIVE: This study was designed to retrospectively compare the accuracy and efficacy of RA percutaneous pedicle screw fixation and traditional freehand FH pedicle screw fixation in the treatment of thoracolumbar fractures. METHODS: A total of 26 cases were assigned to the RA group, and 24 cases were assigned to the FH group. The operation time, bleeding volume, and visual analog scale (VAS) score 1 day after the operation, and the anterior/posterior (A/P) vertebral height ratio of the injured vertebrae at 3 days and at internal fixation removal 1 year after the operation were compared between the two groups. Pedicle screw position accuracy was assessed according to Gertzbein criteria. RESULTS: The operation times of the RA group and FH group were 138.69 ± 32.67 minutes and 103.67 ± 14.53 minutes, respectively, and the difference was statistically significant. The intraoperative blood loss was 49.23 ± 22.56 ml in the RA group and 78.33 ± 23.90 ml in the FH group, and the difference was statistically significant. There was a significant difference in the A/P vertebral height ratio of the injured vertebrae 3 days after the operation compared with before the operation in both groups (P < 0.05). There was a significant difference in the A/P vertebral height ratio of the injured vertebrae 3 days after the operation compared with that at fixation removal in both groups (P < 0.05). CONCLUSION: The application of RA orthopedic treatment for thoracolumbar fractures can achieve good fracture reduction.

Low loss waveguiding and slow light modes in coupled subwavelength silicon Mie resonators.

Subwavelength light-guiding optical devices have gained great attention in the photonics community because they provide unique opportunities for miniaturization and functionality of the optical interconnect technology. On the other hand, high-refractive-index dielectric nanoparticles working at their fundamental Mie resonances have recently opened new venues to enhance and control light-matter interactions at the nanoscale while being free from Ohmic losses. Combining the best of both worlds, here we experimentally demonstrate low-loss slow light waveguiding in a chain of coupled silicon Mie resonators at telecommunication wavelengths. This resonant coupling forms waveguide modes with propagation losses comparable to, or even lower than those in a stripe waveguide of the same cross section. Moreover, the nanoparticle waveguide also exhibits slow light behaviour, with group velocities down to 0.03 of the speed of light. These unique properties of coupled silicon Mie resonator waveguides, together with hybrid coupler designs reducing the coupling loss from a bus waveguide, as also shown in this work, may open a path towards their potential applications in integrated photonics for light control in optical and quantum communications or biosensing, to mention some.

Highly Directive Hybrid Metal-Dielectric Yagi-Uda Nanoantennas.

A hybrid metal-dielectric nanoantenna promises to harness the large Purcell factor of metallic nanostructures while taking advantage of the high scattering directivity and low dissipative losses of dielectric nanostructures. Here, we investigate a compact hybrid metal-dielectric nanoantenna that is inspired by the Yagi-Uda design. It comprises a metallic gold bowtie nanoantenna feed element and three silicon nanorod directors, exhibiting high unidirectional in-plane directivity and potential beam redirection capability in the visible spectral range. The entire device has a footprint of only 0.38 λ2, and its forward directivity is robust against fabrication imperfections. We use the photoluminescence from the gold bowtie nanoantenna itself as an elegant emitter to characterize the directivity of the device and experimentally demonstrate a directivity of ∼49.2. In addition, we demonstrate beam redirection with our device, achieving a 5° rotation of the main emission lobe with a feed element displacement of only 16 nm. These results are promising for various applications, including on-chip wireless communications, quantum computing, display technologies, and nanoscale alignment.

[A case control study of perpendicular or parallel double plate for the treatment of young and middle-aged patients with type C fractures of distal humerus].

OBJECTIVE: To compare clinical outcomes of perpendicular or parallel double plate in treating type C fractures of distal humerus in adults. METHODS: From March 2009 and March 2013, 40 adult patients with type C distal humerus fractures were treated. The patients were divided into two groups according to fixed form. In perpendicular group(group A), there were 13 males and 9 females with a mean age of (37.56±9.24) years old(ranged 18 to 56);while in parallel plating group(group B), including 11 males and 7 females, with a mean age of (41.35±9.03) year old(ranged 20 to 53). All fractures were fresh and closed without blood vessels or nerve damaged. Incision length, operating time, blood loss, hospital stay, preoperative and postoperative radiological change, range of activity of elbow joint, Mayo score, flexor and extensor elbow strength, and postoperative complications were observed and compared. RESULTS: All incisions were healed well. One patient occurred myositis ossificans between two groups. Two patients in group A and 1 patient in group B occurred elbow joint stiffness. All fractures were obtained bone union. Group A were followed up from 20 to 36 months with an average of (25.2±7.1) months, while group B were followed up from 18 to 35 months with an average of(24.3±6.0) months. There were significant differences in blood loss and operative time, while there was no obvious meaning in incision length, hospital stay, muscle strength, fracture healing time, range of activity of elbow joint. Mayo score of group A was 82.27±10.43, 6 cases obtained excellent results, 12 good, 3 moderate and 1 poor;in group B was 81.94±12.02, 5 cases obtained excellent results, 9 good, 3 moderate and 1 poor;and there were no statistical significance between two groups. CONCLUSIONS: There was no significant differences in clinical effects between perpendicular and parallel double plate for adult patients with type C distal humerus fractures, while the operation should choose according to facture and proficiency of operator.

Quantum interference in the presence of a resonant medium.

Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting. We insert a sample in the Hong-Ou-Mandel interferometer and observe the modification of the two-photon interference pattern, which is driven by the coherent response of the medium, determined by the dephasing time. The dephasing time is then inferred from the observed pattern. This effect is distinctively different from the basic effect of spectral filtering, which was studied in earlier works. In addition to its ease of use, our technique does not require compensation of group velocity dispersion and does not induce photo-damage of the samples. Our technique will be useful for characterization of ultrafast phase relaxation processes in material science, chemistry, and biology.

Generalized Brewster effect in dielectric metasurfaces.

Polarization is a key property defining the state of light. It was discovered by Brewster, while studying light reflected from materials at different angles. This led to the first polarizers, based on Brewster's effect. Now, one of the trends in photonics is the study of miniaturized devices exhibiting similar, or improved, functionalities compared with bulk optical elements. In this work, it is theoretically predicted that a properly designed all-dielectric metasurface exhibits a generalized Brewster's effect potentially for any angle, wavelength and polarization of choice. The effect is experimentally demonstrated for an array of silicon nanodisks at visible wavelengths. The underlying physics is related to the suppressed scattering at certain angles due to the interference between the electric and magnetic dipole resonances excited in the nanoparticles. These findings open doors for Brewster phenomenon to new applications in photonics, which are not bonded to a specific polarization or angle of incidence.

Nonradiating anapole modes in dielectric nanoparticles.

Nonradiating current configurations attract attention of physicists for many years as possible models of stable atoms. One intriguing example of such a nonradiating source is known as 'anapole'. An anapole mode can be viewed as a composition of electric and toroidal dipole moments, resulting in destructive interference of the radiation fields due to similarity of their far-field scattering patterns. Here we demonstrate experimentally that dielectric nanoparticles can exhibit a radiationless anapole mode in visible. We achieve the spectral overlap of the toroidal and electric dipole modes through a geometry tuning, and observe a highly pronounced dip in the far-field scattering accompanied by the specific near-field distribution associated with the anapole mode. The anapole physics provides a unique playground for the study of electromagnetic properties of nontrivial excitations of complex fields, reciprocity violation and Aharonov-Bohm like phenomena at optical frequencies.

Directional visible light scattering by silicon nanoparticles.

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique optical properties arise because of simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Such behaviour is similar to Kerker's-type scattering by hypothetic magneto-dielectric particles predicted theoretically three decades ago. Here we show that directivity of the far-field radiation pattern of single silicon spheres can be strongly dependent on the light wavelength and the nanoparticle size. For nanoparticles with sizes ranging from 100 to 200 nm, forward-to-backward scattering ratio above six can be experimentally obtained, making them similar to 'Huygens' sources. Unique optical properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range metamaterials and nanoantenna devices.

Generating and manipulating higher order Fano resonances in dual-disk ring plasmonic nanostructures.

In this article, we investigate higher order (quadrupolar, octupolar, hexadecapolar, and triakontadipolar) Fano resonances generated in disk ring (DR) silver plasmonic nanostructures. We find that the higher order Fano resonances are generated when the size of the disk is reduced and falls into a certain range. With dual-disk ring (DDR) nanostructures, a rich set of tunable Fano line shapes is provided. More specifically, we report our observations on the optical behavior of the DDRs including asymmetric cases either in two disks with different sizes or their asymmetric locations inside the ring. In the case of symmetric dual-disk ring (SDDR) nanostructures, we demonstrate that the quadrupolar and the hexadecapolar Fano resonances are suppressed, which can reduce the cross-talk in spectroscopic measurements, while the octupolar and the triakontadipolar Fano resonances are enhanced. The potential of using the studied plasmonic nanostructures as biochemical sensors is evaluated with the figure of merit (FOM) and the contrast ratio (CR). The values of the FOM and the CR achieved using the triakontadipolar Fano resonance in the SDDR are 17 and 57%, respectively. These results indicate that the SDDRs could be developed into a high-performance biochemical sensor in the visible wavelength range.

[Curative effect comparison of two methods of treatment for distal tibial fractures].

OBJECTIVE: Evaluation of two different methods of treatment of distal tibial fractures of the clinical indications, complications and efficacy. METHODS: Forty-five cases of closed distal tibial fractures were assigned to two groups, 25 cases in group A included 18 males and 7 females, according to the AO/ASIF classification: 4 cases of type A, 14 cases of B, 7 cases of C, open reduction and anatomic plate fixation were used. Twenty cases in group B included 12 males and 8 females, 5 of type A, 9 of B, 6 of C, minimally invasive percutaneous locking compression plate osteosynthesis were used. Observed on the postoperative pain, skin necrosis of the incision, the incidence of deep infection and other complications, as well as the healing of fractures, ankle motor function for comparative study. RESULTS: All patients were followed up 10 to 15 months, according to the visual analogue scale (VAS) score, group A were moderate to severe in, group B were mild to moderate between. Bone healing time: group A averaged (16.0+/-4.2) weeks, group B averaged (13.0+/-3.2) weeks, the difference was significant (P<0.01). Postoperative complications of group A was more than that of group B (P<0.05), there were significant differences. Ankle function in accordance with the assessment criteria Kofoed, the good and excellent rate of group B was higher than that of group A (P<0.05), there were significant differences. CONCLUSION: Minimally invasive percutaneous locking compression plate osteosynthesis compared open reduction and anatomic plate fixation for distal tibial fractures with less trauma surgery, bone blood supply to the affected small, fracture healing faster, less complications, and ankle function better advantage of. It is consistent with the biomechanics of internal fixation, and is the treatment of tibial fractures ideal method.