On-chip spatial mode operation, represented as mode-division multiplexing (MDM), can support high-capacity data communications and promise superior performance in various systems and numerous applications from optical sensing to nonlinear and quantum optics. However, the scalability of state-of-the-art mode manipulation techniques is significantly hindered not only by the particular mode-order-oriented design strategy but also by the inherent limitations of possibly achievable mode orders. Recently, metamaterials capable of providing subwavelength-scale control of optical wavefronts have emerged as an attractive alternative to manipulate guided modes with compact footprints and broadband functionalities. Herein, we propose a universal yet efficient design framework based on the topological metamaterial building block (BB), enabling the excitation of arbitrary high-order spatial modes in silicon waveguides. By simply programming the layout of multiple fully etched dielectric metamaterial perturbations with predefined mathematical formulas, arbitrary high-order mode conversion and mode exchange can be simultaneously realized with uniform and competitive performance. The extraordinary scalability of the metamaterial BB frame is experimentally benchmarked by a record high-order mode operator up to the twentieth. As a proof of conceptual application, an 8-mode MDM data transmission of 28-GBaud 16-QAM optical signals is also verified with an aggregate data rate of 813 Gb/s (7% FEC). This user-friendly metamaterial BB concept marks a quintessential breakthrough for comprehensive manipulation of spatial light on-chip by breaking the long-standing shackles on the scalability, which may open up fascinating opportunities for complex photonic functionalities previously inaccessible.
IntroductionHaving to adapt to a new environment with various other challenges while completing their studies, Chinese college students experience intense stress related to the study of the English language. However, there has been little research on the serial mediating mechanism of English-learning stress on English academic performance.MethodsPresent study recruited 1130 undergraduate students to finish self-report online questionnaire to collect the information about their English-learning stress, academic anxiety and burnout, English academic performance and grit. We constructed a moderated serial mediation model to test the effect of academic anxiety and academic burnout and explored whether grit can restrict the decrease in academic performance caused by English-learning stress.Results Results show that: (1) both academic anxiety and academic burnout mediate the relationship between English-learning stress and performance; (2) academic anxiety and academic burnout show a significant serial mediating role between academic pressure and English academic performance; and (3) grit significantly moderates the relationship between academic burnout and English academic performance.DiscussionThese results lead us to believe that cultivating the grit of Chinese college students may be an effective way to improve the academic performance of those experiencing high English-learning stress.
Internet addiction (IA) is a growing social problem with negative mental and social outcomes; the present study examined whether rejection sensitivity mediates the relationship between interparental conflict and adolescent IA and the moderating role of school connectedness. One thousand and seven adolescents (51.84% females; Meanage = 13.17; SD = 0.69) anonymously completed questionnaires to assess interparental conflict, school connectedness, rejection sensitivity, IA, and demographic information. The model results showed that: (1) the positive association between interparental conflict and adolescent IA was partially mediated by rejection sensitivity; (2) this indirect link was moderated by the school connectedness and was stronger for adolescents with high school connectedness. The results provide support for the attachment theory that high interparental conflict could increase adolescents’ rejection sensitivity, and high school connectedness plays a double-edged role that adolescents show more rejection sensitivity while reporting high interparental conflict and high school connectedness.
On-chip integrated mode-division multiplexing (MDM) has been emerging as a promising technology to further improve the link capacity and satisfy the continuously increasing bandwidth demand in data communications. One of the most important components in MDM and multimode photonics is a mode converter. While several configurations have been developed to realize on-chip mode converters, it is still very challenging to achieve versatile high-order mode converters with high performance in a generic way to reduce the R&D and prototyping costs. Here we initiate a breakthrough utilizing a simple yet universal generic building block concept with metasurface structures to implement programmable arbitrary highorder mode converters with competitive performance, high reliability and compact footprints. The building block, i.e., the TE0-TE2 mode converter is first introduced to illustrate the generic concept, which exhibits low insertion loss of 0.3 dB, low crosstalk of -10 dB across broad wavelength band of 250 nm with a footprint of 2.7×1.3 µ 2 m . All even-order and odd-order mode converters can be realized by directly programming multiple parallel basic building blocks and coarsely engineering the waveguide widths simply in a universal approach. The proposed mode converter building blocks for high-order mode conversion highlight features of uniform performance with broad bandwidth, low insertion loss, compact footprints and good fabrication tolerance, plus the uniquely simple and scalable generic fashion, making them extremely attractive for on-chip multimode optical interconnections.
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