Ferroelectrics are an important class of polar optoelectronic functional materials, exhibiting abundance of nonlinear optical, piezoelectric, pyroelectric, ferroelectric and photovoltaic properties. The essential feature is that spontaneous polarization reverses under the action of an external electric field. . In recent years, ferroelectric molecular compounds have received extensive attention and gradually developed into an important supplementary material for traditional inorganic ferroelectric ceramics. However, how to achieve rapid reversal of spontaneous polarization is an important issue that needs to be solved in current molecular ferroelectric materials research.
Luo Junhua, Research Fellow, “Inorganic Photoelectric Functional Crystal Materialsâ€, State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, National Natural Science, hosted by the National Outstanding Youth Fund, the Strategic Pilot Program of the Chinese Academy of Sciences, and Sun Zhihua, a researcher of the “100 Team†of the Haixi Research Institute Funded by the Excellent Youth Fund of the Fund Committee and the Outstanding Youth Fund of Fujian Province, an ion-type ferroelectric compound was designed and synthesized and a rapid reversal of the spontaneous polarization effect was achieved. It was found that the N-methylmorpholine cation and the trinitrophenol anion in the compound are connected by a strong NH...O hydrogen bond, and the two structural elements are ordered at a temperature of around 315 K. The change of order synergistically induces the spontaneous polarization effect of the compound; further, the ferroelectric phase transition of the compound is confirmed by second-order nonlinear optical effect, pyroelectricity, hysteresis loop and variable temperature solid-state magnetic spectroscopy. process. In addition, the spontaneous polarization of the material is easily reversed by the applied electric field, and the flip frequency is as high as 263 KHz. This work not only realizes the design and construction of ferroelectric molecular compounds, but also provides potential for further expansion of the application of such materials; the relevant research results were recently published in the form of communication in "German Applied Chemistry" (Angew. Chem., Int. Ed., 2018, doi:org/10.1002/ange.201805776). Due to the originality, novelty and importance of the work, the paper was highly praised by reviewers and was selected as the magazine's VIP (Very Important Paper) article. Sun Zhihua was the first author of the paper.
Recently, the team has made a series of advances in the design and synthesis of ferroelectric crystal materials and the photoelectric properties of related materials (J. Am. Chem. Soc., 2018, 140, 6806–6809; Angew. Chem., Int. Ed. , 2018, doi:org/10.1002/ange.201805776; Angew. Chem., Int. Ed., 2018, doi:org/10.1002/ange.201803716; Adv. Funct. Mater., 2018, 28, 1705467; Laser Photonics Rev., 2018, doi.10.1002/lpor.201800060).
Fiber optic adapters are typically used to connect two fiber optic cables together. They come in versions to connect single fibers together (simplex), two fibers together (duplex), or sometimes four fibers together (quad). Adapters are designed for multimode or single-mode cables. The single-mode adapters provide more precise alignment of the tips of the connectors and can be used to connect multimode cables. The reverse is not suggested as this might cause misalignment of the small single-mode fibers and loss of signal strength (attenuation).
Optical attenuators are commonly used in fiber-optic communications, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match transmitter and receiver levels. Sharp bends stress optic fibers and can cause losses. If a received signal is too strong a temporary fix is to wrap the cable around a pencil until the desired level of attenuation is achieved. However, such arrangements are unreliable, since the stressed fiber tends to break over time.
Types:
Optical attenuators can take a number of different forms and are typically classified as fixed or variable attenuators. What's more, they can be classified as LC, SC, ST, FC, MU, etc. according to the different types of connectors.
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