Search

This study was conducted to evaluate the application value of a degradable liquid fiducial marker (LFM) in image-guided radiotherapy. In vitro experiment: using a solid fiducial marker (SFM) as a reference, the visibility, artifact, and optimal injection volume of an LFM under different cone beam CT tube voltage conditions were evaluated. In vivo experiment: using the SFM as a reference, the stability and degradation status of the LFM in nude mice were evaluated. Nude mice implanted with tumor cells were randomly divided into four groups: single fraction radiotherapy group (16 Gy/fraction) without LFM injection, single fraction radiotherapy group (16 Gy/fraction) with LFM injection, 2 fractions radiotherapy group (8 Gy/fraction) with LFM injection, and 4 fractions radiotherapy group (4 Gy/fraction) with LFM injection. The impact of LFM on tumor growth was evaluated based on the irradiation results. Compared with SFM, the LFM artifacts were significantly smaller (all p

Benefiting from their large second‐order nonlinear coefficients and high integration capabilities, crystalline lithium niobate (LN) films have shown great application prospects in the field of nonlinear metasurfaces. It is necessary to endow LN metasurfaces with optical resonances to further boost nonlinear optical responses. Among these optical resonances, anapole resonances carried by LN metasurfaces have been predicted to efficiently enhance second harmonic generations (SHG) but have never been experimentally realized. Anapole resonance requires ideal nanostructures to have steep sidewalls and a high filling ratio, but the intrinsic hardness and inert chemical properties of LN materials pose great challenges for the fabrication of LN nanostructures. Here, a multi‐gas component dry‐etching technique is proposed to prepare various LN nanostructures, achieving typical LN nanopillar arrays with a sidewall angle of ≈85° at a depth of 300 nm and a filling ratio of 52%. Importantly, nanostructured LN metasurfaces are designed and fabricated to experimentally realize anapole resonances at a fundamental wavelength of ≈800 nm, demonstrating a ≈30‐fold enhancement in second harmonic generation compared with bare LN films. The work provides promising strategies for the versatile fabrication of LN nanostructures and their applications in nonlinear meta‐optics. [ABSTRACT FROM AUTHOR]

Two-hierarchical nanostructures, characterized by two distinct configurations along the height direction, exhibit immense potential for applications in various fields due to their significantly enhanced controllable degree compared to single-order structures. However, due to the limitations imposed by planar technology, the realization of two-hierarchical nanostructures encounters huge challenges. In this work, we developed a one-step etching method based on inductively coupled plasma reactive ion etching for two-hierarchical nanostructures. Thanks to the shrinking effect of the Cr mask and the generation of a passivation layer during etching, the target materials experienced two different states from vertical etching to shrink etching. Consequently, the achieved two-hierarchical nanostructure configuration features a cross-section of an upper triangle and a lower rectangle, showing higher controllable degrees compared to the one-order ones. Both the mask pattern and etching parameters play crucial roles, by which two-hierarchical structures with diversiform shapes can be constructed controllably. This method for two-hierarchical nanostructures offers advantages including excellent control over structural properties, high processing efficiency, uniformity across large areas, and universality in materials. This developed strategy not only presents a simple and rapid nanofabrication platform for realizing optoelectronic devices, but also provides innovative ideas for designing the next generation of high-performance devices. [ABSTRACT FROM AUTHOR]

Dark excitons are fascinating for condensed matter physics, quantum information processing, and optoelectronics due to their long lifetimes. However, direct optical access to dark excitons is still challenging due to the violation of the spin selection rule. Here, a new scheme for the brightening of spin‐forbidden dark exciton in WS2 monolayers by creating artificial out‐of‐plane shear strain that induces an effective in‐plane pseudo‐magnetic field is proposed. To reveal dark excitons, low‐temperature magneto‐photoluminescence experiments on the strained WS2 monolayers are performed. It is found that the dark excitons appear at 59 meV below the bright ones and exhibit an asymmetric magnetic field dependence, which is in agreement with the model taking into account the effect of the out‐of‐plane shear strain on spin‐flip processes of exciton states. The fieldless scheme has great potential in the application of dark excitons for new quantum information processing devices. [ABSTRACT FROM AUTHOR]

Manipulating light polarization is of fundamental importance in the modern photonic applications such as spectroscopy, laser science, optical communication, quantum information processing, chemical and biological sensing. Polarization control of light is typically achieved by natural chiral or birefringent materials with macroscopic volume due to the weak light–matter interaction. Here, a folded eta‐shaped metamaterial that is capable of generating gigantic optical chirality and spectrally breaking the spin degeneracy of optical transmission at multiband is experimentally demonstrated. The intrinsic chiral configuration is achieved by folding the eta‐shaped metasurface along the vertical direction to break the mirror symmetries. A remarkable circular dichroism approaching unity is experimentally achieved, with the maximum transmittance exceeding 93%. This is the record high value demonstrated to date for single‐layer metasurfaces without diffraction in infrared region. The folded metamaterial provides a straightforward strategy for achieving intrinsic 3D chirality and has great potential for applications in photon‐spin selective devices and chiral biomolecule identification. [ABSTRACT FROM AUTHOR]

The metamaterials (MMs) with planar metal arrays of split ring resonators were fabricated on quartz and silicon substrates; the influences of substrate permittivity and metal conductance on the magnetic responses of in the terahertz region were investigated. The electromagnetic (EM) responses of the metamaterials were characterized by terahertz time-domain spectroscopy. The experimental result reveals that there is a 0.39 THz redshift in the transmission spectra for the magnetic response when the substrate changes from quartz to silicon, which is in consistence with the finite-difference time-domain (FDTD) simulation. Based on the simulation and experimental results, and taking into account the EM properties of substrate materials, a modified L-C model is presented to understand the MM system in terahertz domain. [ABSTRACT FROM AUTHOR]