Covalent organic frameworks for optical applications

Linking molecules into extended crystalline networks to construct covalent organic frameworks(COFs)added in variety to the readily thriving research on moleculebased solid-state materials,featured by classic polymers and molecular crystals.Compared to the development of COFs for gas separation,energy storage,and conversion,where the porosity feature of COFs is utilized,the optical applications,such as fluorescence,white light emission,and photodynamic therapy,involving the molecular and crystalline feature of COFs,are much less explored.In this review,we focused on the optical properties of COFs,and how do these macroscopic properties correlate with the microscopic structure of COFs.Other than the influence from organic functional groups in previous reviews on COFs,here,three critical structure factors,the connection,orientation,and alignment of the molecular building blocks,are outlined and associated with the optical properties of COFs.We also analyze the properties of COFs from both energy and dynamic aspects in an attempt to provide further insight into the possible underlying mechanism.At the end of this review,we also discuss the remaining challenges and future directions for the design of COFs for optical applications,and unveil the potential of COFs toward this direction.

Optical applications of quantum dots in biological system

This review presents a simple introduction on the unique properties and general synthesis of quantum dots (QDs) in which we lay emphasis on the optical applications in the biological system. The detection of biological molecules such as DNA, protein and enzyme, the cell-based analysis and in vivo animal imaging are mainly discussed.

Polarization Insensitive Broadband Zero Indexed Nano-Meta Absorber for Optical Region Applications

Broadband response metamaterial absorber(MMA)remains a challenge among researchers.A nanostructured new zero-indexed metamaterial(ZIM)absorber is presented in this study,constructed with a hexagonal shape resonator for optical region applications.The design consists of a resonator and dielectric layers made with tungsten and quartz(Fused).The proposed absorbent exhibits average absorption of more than 0.8972(89.72%)within the visible wavelength of 450–600 nm and nearly perfect absorption of 0.99(99%)at 461.61 nm.Based on computational analysis,the proposed absorber can be characterized as ZIM.The developments of ZIM absorbers have demonstrated plasmonic resonance characteristics and a perfect impedance match.The incidence obliquity in typically the range of 0◦–90◦both in TE and TM mode with maximum absorbance is more than 0.8972(∼89.72%),and up to 45◦angular stability is suitable for solar cell applications,like exploiting solar energy.The proposed structure prototype is designed and simulated by studying microwave technology numerical computer simulation(CST)tools.The finite integration technique(FIT)based simulator CST and finite element method(FEM)based simulator HFSS also helps validate the numerical data of the proposed ZIM absorber.The proposed MMA design is appropriate for substantial absorption,wide-angle stability,absolute invisible layers,magnetic resonance imaging(MRI),color images,and thermal imaging applications.

Optical microfiber or nanofiber:a miniature fiber-optic platform for nanophotonics

An optical micro/nanofiber(MNF)is a quasi-one-dimensional free-standing optical waveguide with a diameter close to or less than the vacuum wavelength of light.Combining the tiny geometry with highrefractive-index contrast between the core and the surrounding,the MNF exhibits favorable optical properties such as tight optical confinement,strong evanescent field,and large-diameter-dependent waveguide dispersion.Meanwhile,as a quasi-one-dimensional structure with extraordinarily high geometric and structural uniformity,the MNF also has low optical loss and high mechanical strength,making it favorable for manipulating light on the micro/nanoscale with high flexibility.Over the past two decades,optical MNFs,typically being operated in single mode,have been emerging as a miniaturized fiber-optic platform for both scientific research and technological applications.In this paper,we aim to provide a comprehensive overview of the representative advances in optical MNFs in recent years.Starting from the basic structures and fabrication techniques of the optical MNFs,we highlight linear and nonlinear optical and mechanical properties of the MNFs.Then,we introduce typical applications of optical MNFs from nearfield optics,passive optical components,optical sensors,and optomechanics to fiber lasers and atom optics.Finally,we give a brief summary of the current status of MNF optics and technology,and provide an outlook into future challenges and opportunities.

Optical properties and applications for MoS_2-Sb_2Te_3-MoS_2 heterostructure materials

Two-dimensional(2D) materials with potential applications in photonic and optoelectronic devices have attracted increasing attention due to their unique structures and captivating properties. However, generation of stable high-energy ultrashort pulses requires further boosting of these materials' optical properties, such as higher damage threshold and larger modulation depth. Here we investigate a new type of heterostructure material with uniformity by employing the magnetron sputtering technique. Heterostructure materials are synthesized with van der Waals heterostructures consisting of MoS_2 and Sb_2Te_3. The bandgap, carrier mobility, and carrier concentration of the MoS_2-Sb_2Te_3-MoS_2 heterostructure materials are calculated theoretically. By using these materials as saturable absorbers(SAs), applications in fiber lasers with Q-switching and mode-locking states are demonstrated experimentally. The modulation depth and damage threshold of SAs are measured to be 64.17%and 14.13 J∕cm^2, respectively. Both theoretical and experimental results indicate that MoS_2-Sb_2Te_3-MoS_2 heterostructure materials have large modulation depth, and can resist high power during the generation of ultrashort pulses. The MoS_2-Sb_2Te_3-MoS_2 heterostructure materials have the advantages of low cost, high reliability, and suitability for mass production, and provide a promising solution for the development of 2D-material-based devices with desirable electronic and optoelectronic properties.

Nonlinear optical and optical limiting properties of new structures of organic nonlinear optical materials for photonic applications

The nonlinear optical （NLO） and optical limiting （OL） properties of three new structures of organic NLO guest host Poly（N-vinylcarbozole）/disperse orange 3 （PVK/DO3）, PVK/disperse orange 13 （PVK/DO13）. and PVK/disperse orange 25 （PVK/DO25） as a solution at different concentrations and as a thin-film sample are studied using continuous wave z-scan system at 532 nm. The open-aperture z-scan data of the NLO materials in the solution and thin-film samples displayed two-photon and saturable absorptions, respectively. The PVK/DO13 exhibites the largest and best values of the nonlinearities, such as n2, β, X（3） compared with those of PVK/DO3 and PVK/DO25. This nonlinearity increases as the concentration increases. Tile results indicate that these NLO materials are good candidates for optical switching and OL devices.

Special Polymer Optical Fibres and Devices for Photonic Applications

Remarkable progresses have been made in developing special polymer optical fibres and devices for photonic applications in recent years. This presentation will mainly report on the development of electro-optic, photosensitive and photorefractive polymer optical fibres and related devices.

Second-harmonic generation as a DNA malignancy indicator of prostate glandular epithelial cells

This paper first demonstrates second-harmonic generation （SHG） in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of 2.7 μm×2.7μm in cell nuclei, SHG signals produced from benign prostatic hyperplasia （BPH） and prostate carcinoma （PC） tissues （mouse model C57BL/6） have been investigated. Statistical analyses （t test） of a total of 405 measurements （204 nuclei from BPH and 201 nuclei from PC） show that SHG signals from BPH and PC have a distinct difference （p 〈 0.05）, suggesting a potential optical method of revealing very early malignancy in prostate glandular epithelial cells based upon induced biochemical and/or biophysical modifications in DNA.

Optical DE/MUX Components for Datacomunication Applications

This paper reviews the potential for WDM systems to be implemented within datacommunication systems, and indicates future network functions. Spectral and temporal multiplexing functions are reviewed, with particular focus being placed on 2DIO and amplifier based crosspoint components.

Long-period grating inscription on polymer functionalized optical microfibers and its applications in optical sensing

We demonstrated long-period grating(LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl methacrylate jackets and, thus, LPGs could be inscribed on optical microfibers via point-by-point ultraviolet laser exposure. For a 2 mm long microfiber LPG(MLPG) inscribed on optical microfibers with a diameter of 5.4 μm, a resonant dip of 15 d B at 1377 nm was observed. This MLPG showed a high sensitivity of strain and axial force, i.e.,-1.93 pm∕με and-1.15 pm∕μN, respectively. Although the intrinsic temperature sensitivity of the LPGs is relatively low, i.e.,-12.75 pm∕°C, it can be increased to be-385.11 pm∕°C by appropriate sealing. Benefiting from the small footprint and high sensitivity, MLPGs could have potential applications in optical sensing of strain,axial force, and temperature.

MEMS Torsion-Mirror Actuators for Optical Switching or Attenuating Applications

Novel MEMS torsion-mirror actuators with monolithically integrated fiber self-holding structures are fabricated, and investigated experimentally and theoretically. Their electromechanical and optical characteristics are acceptable for optical switching or attenuating applications.

Optical Negasensors and Prospects of Their Applications

The basic types of optical negasensors - sensors based on the application of negative resistance, negative inductance and negative capacitance, R, L, C-negatrons are presented. It is shown, that application of negative inductance and capacitance is not connected with stability decreasing as at application of negative resistance and allows to rise sensitivity of a optical sensor theoretically ad infinitum. The example design of multielement optical negasensor for airborne, underwater or biomedical imagin...

Adaptive Optics System and Its Application Predictions at 1.2m Telescope of Yunnan Observatory

A 61 element adaptive optical system has been preliminary tested in the Coudé path of the 1 2m telescope at the Yunnan observatory this year. The whole system will be fully operated next year. This paper describes the AO system performances and its first experiment results, and the possible astronomical research topics.

Study on the de-watermark algorithm based on grayscale text

When using the current popular text recognition algorithms such as optical character recognition(OCR)algorithm for text images,the presence of watermarks in text images interferes with algorithm recognition to the extent of fuzzy font,which is not conducive to the improvement of the recognition rate.In order to pursue fast and high recognition rate,watermark removal has become a critical problem to be solved.This work studies the watermarking algorithm based on morphological algorithm set and classic image algorithm in computer images.It can not only remove the watermark in a short time,but also keep the form and clarity of the text in the image.The algorithm also meets the requirements that the higher the clarity of image and text,the better the processing effect.It can process the Chinese characters with complex structure,complicated radicals or other characters well.In addition,the algorithm can basically process ordinary size images in 1 s,the efficiency is relatively high.

Tunable chiroptical application by encapsulating achiral lanthanide complexes into chiral MOF thin films

Chiral metal-organic frameworks(chirMOFs)have been widely considered on enantioselective adsorption/separation,asymmetric catalysis,biological and nonlinear optical applications.However,chirMOFs are facing a great challenge in development of chiroptical thin films with circularly polarized luminescence(CPL)property.Here,we first report CPL thin films by encapsulating achiral lanthanide complexes Ln(acac)_(3)(Ln=Eu_(a)Tb_(b)Gd_(c))into the pores of surface-coordinated chirMOF thin films(SURchirMOF)[Zn_(2)(cam)_(2)dabco]_(n) with layer by layer(Ibl)encapsulation strategy.Due to the unique combination of chiral porous MOF and adjustable luminescent complexes in the host-guest thin films,the obtained Ln(acac)_(3)@SURchirMOF possess strong and tunable CPL property with high dissymmetry factors.The compared CPL and fluorescent lifetime results show that the advantage of this preparation strategy can effectively achieve energy transfer from Ln(acac)_(3) to SURchirMOF,resulting in an excellent CPL performance.This study not only provides a novel strategy to develop new types of chiral thin films but also offers an efficient approach for tunable chiroptical applications.

13.5 mJ polarized 2.09μm fiber-bulk holmium laser and its application to a mid-infrared ZnGeP2 optical parametric oscillator

A high pulse repetition frequency（PRF）, high energy Ho：YAG laser directly pumped by a Tm-doped fiber laser and its application to a mid-infrared ZnGeP_2（ZGP） optical parametric oscillator（OPO） is demonstrated.The maximum polarized 2.09 μm laser pulse energy is 13.46 mJ at a PRF of 1 k Hz. The corresponding peak power reaches 504 kW. In a double-resonant ZGP-OPO, a maximum mid-infrared laser pulse energy of 1.25 m J,corresponding to a peak power of 79 kW, is accomplished at a PRF of 3 kHz. The nonlinear conversion efficiency reaches 41.7%. The nonlinear slope efficiency reaches 53.3%.

InN-Based Ill-Nitrides; A New Emerging Material System for Application in Optical Communications

The fact that InN has a direct bandgap of 0.75eV enables InN-based nitrides devices to cover the wavelength range from UV region to 1.8μm, therefore, emerging as a new material system for optical communication applications.

Toward mid-infrared nonlinear optics applications of silicon carbide microdisks engineered by lateral under-etching[Invited]

We report the fabrication and characterization of silicon carbide microdisks on top of silicon pillars suited for applications from near-to mid-infrared. We probe 10 μm diameter disks with different under-etching depths,from 4 μm down to 1.4 μm, fabricated by isotropic plasma etching and extract quality factors up to 8400 at telecom wavelength. Our geometry is suited to present high Q single-mode operation. We experimentally demonstrate high-order whispering-gallery mode suppression while preserving the fundamental gallery mode and investigate some requirements for nonlinear optics applications on this platform, specifically in terms of quality factor and dispersion for Kerr frequency comb generation.

Influence of Tm^(3+) ions on the amplification of Ho^(3+):~5I_7→~5I_8 transition in fluoride glass modified by Al(PO_3)_3 for applications in mid-infrared optics

In this work, we investigate a new type of fluoride glasses modified by Al（PO_3）_3 with various Tm^（3＋）∕Ho^（3＋） doping concentrations. The introduced PO_-~3 plays an effective role in improving the glass-forming ability and thermal stability. Besides, 1.47, 1.8, and 2.0 μm emissions originating from Tm^（3＋）and Ho^（3＋）, respectively, are observed.The spectroscopic properties and energy transfer mechanisms between Tm^（3＋）and Ho^（3＋）are analyzed as well. It is noted that the higher predicted spontaneous transition probability（118.74 s-1） along with the larger product of measured decay lifetime and the emission cross section（σemi×τ） give evidence of intense 2.0 μm fluorescence.