RESUMEN
Nanodomain engineering in lithium niobate on insulator (LNOI) is critical to realize advanced photonic circuits. Here, we investigate the tip-induced nanodomain formation in x-cut LNOI. The effective electric field exhibits a mirror symmetry, which can be divided into preceding and sequential halves according to the tip movement. Under our configuration, the preceding electric field plays a decisive role rather than the sequential one as in previous reports. The mechanism is attributed to the screening field formed by the preceding field counteracting the effect of the subsequent one. In experiment, we successfully fabricate nanodomain dots, lines, and periodic arrays. Our work offers a useful approach for nanoscale domain engineering in x-cut LNOI, which has potential applications in integrated optoelectronic devices.
RESUMEN
Nasopharyngeal cancer is a rare cancer with unique ethnic and geographic distribution. Since nasopharyngeal cancer often originates from the pharyngeal crypt, early symptoms are not obvious. They are difficult to detect in time, and the disease is usually diagnosed and treated only when it has progressed to an advanced-stage. Since angiogenesis is essential for the growth and invasion of solid tumors, antiangiogenic therapy has become a common treatment strategy for many solid tumors, and it has also achieved remarkable results in the treatment of nasopharyngeal carcinoma, which is prone to recurrence and distant metastasis. In this paper, we review the latest research progress of antiangiogenic drugs for nasopharyngeal carcinoma and their antiangiogenic mechanism of action and further propose some promising antiangiogenic therapeutic targets.
RESUMEN
Nonlinear beam shaping refers to spatial reconfiguration of a light beam at a new frequency, which can be achieved by using nonlinear photonic crystals (NPCs). Direct nonlinear beam shaping has been achieved to convert second-harmonic waves into focusing spots, vortex beams, and diffraction-free beams. However, previous nonlinear beam shaping configurations in one-dimensional and two-dimensional (2D) NPCs generally suffer from low efficiency because of unfulfilled phase-matching condition. Here, we present efficient generations of second-harmonic vortex and Hermite-Gaussian beams in the recently-developed three-dimensional (3D) lithium niobate NPCs fabricated by using a femtosecond-laser-engineering technique. Since 3D χ(2) modulations can be designed to simultaneously fulfill the requirements of nonlinear wave-front shaping and quasi-phase-matching, the conversion efficiency is enhanced up to two orders of magnitude in a tens-of-microns-long 3D NPC in comparison to the 2D case. Efficient nonlinear beam shaping paves a way for its applications in optical communication, super-resolution imaging, high-dimensional entangled source, etc.
RESUMEN
Metasurfaces are two-dimensional metamaterials composed of a carefully designed series of subwavelength meta-atom (antenna or aperture) arrays. These surfaces can manipulate the phase, amplitude and polarization of output light by changing the shapes and orientations of the meta-atoms on a subwavelength scale. Using these properties, we experimentally demonstrate variable meta-axicons composed of rectangular nano-apertures arranged in several concentric rings that can focus left circularly polarized (LCP) light into a real Bessel beam and defocus right circular polarized (RCP) light to form a virtual beam. A desired phase discontinuity in cross-polarized transmitted light is introduced along the interface by controlling the orientations of the nano-apertures. In addition, the meta-axicons can generate Bessel beams of arbitrary orders by suitable design of the phase profile along the surface. The meta-axicons demonstrate broadband optical properties that can switch the wavelength of the incident light from 690 nm to 1050 nm. These variable meta-axicons open a path towards the development of new applications using integrated beam shaping devices.
RESUMEN
We report on the extraordinary optical transmission (EOT) of an orbital angular momentum (OAM) state of light in the paraxial approximation. The OAM state transmits through a subwavelength metal hole array with a square structure, and then is analyzed by using a Mach-Zehnder interferometer. In the experiment, the transmitted light well conserves the OAM information while the transmission efficiency of the OAM mode is much greater than 1 (i.e., EOT works). Further study shows that the OAM mode has no significant influence on the transmission spectrum of the EOT paraxial process under our experimental configuration. Our work can be useful for future plasmon-based OAM devices.
RESUMEN
The luminescence properties of high color rendering white LED depending on the proportions of mixed phosphor powders were investigated by adopting green and red phosphors stimulated by a 440 nm InGaN/GaN based blue LED. The results show that when the proportion of A/B type silica gels and green/red phosphor powders is 0.5 : 0.5 : 0.2 : 0.03, two luminance bands are stimulated and their wavelength peaks are 535 and 643 nm, respectively. The minimum color temperature can reach 3 251 K, while the color rendering is as high as 88. 8. Compared with the traditional white LED fabricated by yellow YAG-phosphors-coated high efficiency 460 nm blue LED, the color temperature is lower and the color rendering index can be increased by almost 26%.
