Optimization of broadband omnidirectional antireflection coatings for solar cells

Broadband and omnidirectional antireflection coating is generally an effective way to improve solar cell efficiency, because the destructive interference between the reflected and incident light can maximize the light transmission into the absorption layer. In this paper, we report the incident quantum efficiency ηin, not incident energy or power, as the evaluation function by the ant colony algorithm optimization method, which is a swarm-based optimization method. Also, SPCTRL2 is proposed to be incorporated for accurate optimization because the solar irradiance on a receiver plane is dependent on position, season, and time. Cities of Quito, Beijing and Moscow are selected for two-and three-layer antireflective coating optimization over λ = [300,1100] nm and θ = [0°, 90°]. The ηin increases by 0.26%, 1.37% and 4.24% for the above 3 cities, respectively, compared with that calculated by other rigorous optimization algorithms methods, which is further verified by the effect of position and time dependent solar spectrum on the antireflective coating design.

Fabrication of flexible AlGaInP LED

Flexible light-emitting diodes(LEDs)are highly desired for wearable devices,flexible displays,robotics,biomedicine,etc.Traditionally,the transfer process of an ultrathin wafer of about 10–30μm to a flexible substrate is utilized.However,the yield is low,and it is not applicable to thick GaN LED chips with a 100μm sapphire substrate.In this paper,transferable LED chips utilized the mature LED manufacture technique are developed,which possesses the advantage of high yield.The flexible LED array demonstrates good electrical and optical performance.

Side ionic-gated perovskite/graphene heterojunction synaptic transistor with bipolar photoresponse for neuromorphic computing

By combining the good charge transport property of graphene and the excellent photo-carrier generation char-acteristic of perovskite nanocrystal,we propose and demonstrate an ionic-gated synaptic transistor based on CsPbBr_(3)∕graphene heterojunction for bipolar photoresponse.Controlling the potential barrier of the CsPbBr_(3)∕graphene heterojunction by the ionic-gate of the electrical double-layer effect can promote the sepa-ration of photogenerated carriers and effectively retard their recombination.Using the ionic-gate-tunable Fermi level of graphene and the pinning effect of perovskite nanocrystal,the bipolar photocurrent responses correspond-ing to the excitatory and inhibitory short-term and long-term plasticity are realized by adjusting the negative gate bias.A series of synaptic functions including logic operation,Morse coding,the optical memory and electrical erasure effect,and light-assisted re-learning have also been demonstrated in an optoelectronic collaborative path-way.Furthermore,the excellent optical synaptic behaviors also contribute to the handwritten font recognition accuracy of-95%in artificial neural network simulations.The results pave the way for the fabrication of bipolar photoelectric synaptic transistors and bolster new directions in the development of future integrated human ret-inotopic vision neuromorphic systems.

Impairment of autophagy promotes human conjunctival fibrosis and pterygium occurrence via enhancing the SQSTM1-NF-κB signaling pathway

Pterygium is a common ocular disease with a high recurrence rate,characterized by hyperplasia of subconjunctival fibrovascular tissue.Autophagy,an important process to maintain cellular homeostasis,participates in the pathogenic fibrosis of different organs.However,the exact role of autophagy in pterygium pathogenesis remains unknown.Here,we found that autophagic activity was decreased in human pterygium tissues compared with adjacent normal conjunctival tissues.The in vitro model of fibrosis was successfully established using human primary conjunctival fibroblasts(ConFB)treated with transforming growth factor-β1(TGF-β1),evidenced by increased fibrotic level and strong proliferative and invasive capabilities.The autophagic activity was suppressed during TGF-β1-or ultraviolet-induced fibrosis of ConFB.Activating autophagy dramatically retarded the fibrotic progress of ConFB,while blocking autophagy exacerbated this process.Furthermore,SQSTM1,the main cargo receptor of selective autophagy,was found to significantly promote the fibrosis of ConFB through activating the PKCι-NF-κB signaling pathway.Knockdown of SQSTM1,PKCι,or p65 in ConFB delayed TGF-β1-induced fibrosis.Overexpression of SQSTM1 drastically abrogated the inhibitory effect of rapamycin or serum starvation on TGF-β1-induced fibrosis.Collectively,our data suggested that autophagy impairment of human ConFB facilitates fibrosis via activating the SQSTM1-PKCι-NF-κB signaling cascades.This work was contributory to elucidating the mechanism of autophagy underlying pterygium occurrence.

A tutorial introduction to graphene-microfiber waveguide and its applications

Graphene-microfiber with the advantage of graphene material and the microfiber has been hailed as a wonderful waveguide in optics. A tutorial introduction to the graphene-microfiber （GMF） waveguides including the effect of graphene on waveguide, fabrication and applica- tions has been presented. Here, we reviewed recent progress in the graphene waveguides from mode-locking and Q-switching in fiber laser to gas sensing and optical modulation. A brief outlook for opportunities and challenges of GMF in the future has been presented. With the novel nanotechnology emerging, GMF could offer new possibilities for future-optic circuits, systems and networks.

Effect of SARS-CoV-2 infection in early pregnancy on placental development

Dear Editor,Since the COVID-19 pandemic, the potential risks associated with maternal SARS-CoV-2 infection and its effect on fetal development have been a subject of considerable public concern. Previous studies have shown that SARS-CoV-2 infection during pregnancy may increase the incidence of adverse outcomes.

角膜屈光手术中影响高阶像差的因素

角膜屈光手术目前主要分为表层角膜屈光手术、板层角膜屈光手术与飞秒激光透镜取出术3大类,均广泛应用于屈光不正的矫正。虽然大多数患者在术后能够获得理想的裸眼视力,但术后高阶像差的增大往往导致眩光、重影、夜视力下降等并发症的发生。角膜屈光手术中影响高阶像差的因素非常多,笔者就角膜屈光手术类别以及角膜瓣/帽、矫正度数高低、光学区直径大小、光学区偏心程度、不同准分子激光切削模式对术后高阶像差大小的影响进行综述。

Impact of damping on high speed 850 nm VCSEL performance

High speed VCSELs are important optical devices in short-reach optical communication links and interconnects because of their low cost and high modulation speeds. In this paper, the impact of damping on the their static and dynamic characteristics is analyzed and demonstrated. Through the shallow corrosion of the top layer DBR, the VCSELs with different damping is designed and fabricated. With the increase of the surface etch depth from 0 to ～55 nm for 9 μm oxide-aperture VCSEL, the K factor related with the damping is reduced from0.31 to 0.23 ns;. When the etch depth of the VCSEL with 9 μm oxide-aperture is decreased to ～25 nm,output power is increased from 4.03 to 4.70 mW and small signal modulation bandwidth is also increased from15.46 to 16.37 GHz. It shows that there is a tradeoff between damping and differential gain for improving modulation speed.

Wet nitrogen oxidation technology and its anisotropy influence on VCSELs

Vertical cavity surface emitting lasers（VCSELs） are widely used in optical communications and optical interconnects due to their advantages of low threshold, low power consumption and so on. Wet nitrogen oxidation technology, which utilizes H20 molecules to oxidize the Al;Ga;As, is used for electrical and optical mode confinement. In this paper, the effects of oxidation time, oxidation temperature and oxidation anisotropy on the oxidation rate are explored and demonstrated. The ratio of oxidation rate on [0-11] to [011] crystal orientation is defined as oxidation anisotropy coefficient, which decreases with the increase of oxidation temperature and oxidation time. In order to analyze the effect of the oxidation anisotropy on the VCSEL performance, an oxide-aperture of the VCSELs with two difference shapes is designed and then fabricated. The static performance of these fabricated VCSELs has been measured,whose threshold current ratio ～0.714 is a good agreement with that of the theoretical calculation value ～0.785. Our research on wet nitrogen oxidation and its anisotropy serves as an important reference in the batch fabrication of large-area VCSELs.

Underwater Bessel-like beams with enlarged depth of focus based on fiber microaxicon

Underwater optical wireless communication,which is useful for oceanography,environmental monitoring,and underwater surveillance,suffers the limit of the absorption attenuation and Mie–Rayleigh scattering of the lights.Here,Bessel-like beams generated by a fiber microaxicon is utilized for underwater wireless propagation.Underwater,the cone angle for generating Bessel-like beams starts from 46°,which is smaller than that in air for Bessel-like beams.When the cone angle of the fiber microaxicons is about 140°,the depth of focus underwater,which is four times as long as the depth of focus in air,has enlarged about 28μm,36.12μm,and 50.7μm for 470 nm,520 nm,and 632 nm visible lights.The transmission distance of the Bessel beams for visible lights has been simulated by using Henyey–Greenstein–Rayleigh phase function methods and spectral absorption by bio-optical model due to Monte Carlo methods.The results show that the propagation distance could reach 4000 m,which overcome the limit of the Mie–Rayleigh scattering and absorption attenuation underwater.