Electro-Optic Polymer Integrated Optic Devices and Future Applications

Recent developments in electro-optic polymer materials and devices have led to new opportunities for integrated optic devices in numerous applications. The results of numerous tests have indicated that polymer materials have many properties that are suitable for use in high-speed communications systems, various sensor systems, and space applications. These results, coupled with recent advances in device and material technology, will allow very large bandwidth modulators and switches with low drive voltages, improved loss, long-term stability, and integration with other microelectronic devices such as MEMS. Low drive voltage devices are very important for space applications where power consumption scales as the square of the modulator half-wave voltage. In addition, we have demonstrated novel dual polymer modulators for mixing RF signals to produce sum and difference frequency modulation on an optical beam. This novel approach allows the suppression of the modulation at the two input RF signals, and only the mixing signals remain superposed on the optical beam. The dual modulator can be used for various encoding/decoding and frequency conversion schemes that are frequently used for both terrestrial and space communications. Another application of polymer integrated optics is in the field of optical sensing for high-frequency (GHz) electric fields.     

Electro-Optic Polymer Integrated Optic Devices and Future Applications

Recent developments in electro-optic polymer materials and devices have led to new opportunities for integrated optic devices in numerous applications. The results of numerous tests have indicated that polymer materials have many properties that are suitable for use in high-speed communications systems, various sensor systems, and space applications. These results, coupled with recent advances in device and material technology, will allow very large bandwidth modulators and switches with low drive voltages, improved loss, long-term stability, and integration with other microelectronic devices such as MEMS. Low drive voltage devices are very important for space applications where power consumption scales as the square of the modulator half-wave voltage. In addition, we have demonstrated novel dual polymer modulators for mixing RF signals to produce sum and difference frequency modulation on an optical beam. This novel approach allows the suppression of the modulation at the two input RF signals, and only the mixing signals remain superposed on the optical beam. The dual modulator can be used for various encoding/decoding and frequency conversion schemes that are frequently used for both terrestrial and space communications. Another application of polymer integrated optics is in the field of optical sensing for high-frequency (GHz) electric fields.     

Graphene integrated photodetectors and opto-electronic devices — a review

Graphene and other two-dimensional materials have recently emerged as promising candidates for next-generation,high-performance photonics. In this paper, the progress of research into photodetectors and other electro-optical devices based on graphene integrated silicon photonics is briefly reviewed. We discuss the performance metrics, photo-response mechanisms, and experimental results of the latest graphene photodetectors integrated with silicon photonics. We also lay out the unavoidable performance trade-offs in meeting the requirements of various applications. In addition, we describe other opto-electronic devices based on this idea. Integrating two-dimensional materials with a silicon platform provides new opportunities in advanced integrated photonics.     

Ultra-Compact and Efficient Integrated Multichannel Mode Multiplexer in Silicon for Few-Mode Fibers

Space-division multiplexing (SDM) is one of the key enabling technologies to increase the capacity of fiber communication systems. However, implementing SDM-based systems using multimode fiber has been challenging with the need for compact, low-cost, and scalable mode de/multiplexer (DE/MUX). Here a novel integrated mode MUX for few-mode fibers (FMFs) is presented which can launch up to eight spatial and polarization channels. The new design is composed of a 2D multimode grating coupler (MMGC), highly compact spot size converters (SSCs), and adiabatic directional couplers (ADCs). Eight data lanes in FMFs can be selectively launched with integrated optical phase shifters. Experimental results reveal efficient chip-to-fiber coupling with peak efficiencies of −3.8, −5.5, −3.6, and −4.1 dB for LP₀₁, LP_11a, LP_11b, and LP_21b modes, respectively. Thanks to the use of an integrated subwavelength Mikaelian lens for mode-independent field size conversion with loss ≤−0.25 dB, the total footprint of the MMGC and SSCs is only 35×35 µm². The proposed design shows great potential for densely integrated photonic circuits in future SDM applications.     

Ultra‐low loss waveguide platform and its integration with silicon photonics

Planar waveguides with ultra‐low optical propagation loss enable a plethora of passive photonic integrated circuits, such as splitters and combiners, filters, delay lines, and components for advanced modulation formats. An overview is presented of the status of the field of ultra‐low loss waveguides and circuits, including the design, the trade‐off between bend radius and loss, and fabrication rationale. The characterization methods to accurately measure such waveguides are discussed. Some typical examples of device and circuit applications are presented. An even wider range of applications becomes possible with the integration of active devices, such as lasers, amplifiers, modulators and photodetectors, on such an ultra‐low loss waveguide platform. A summary of efforts to integrate silicon nitride and silica‐based low‐loss waveguides with silicon and III/V based photonics, either hybridly or heterogeneously, will be presented. The approach to combine these integration technologies heterogeneously on a single silicon substrate is discussed and an application example of a high‐bandwidth receiver is shown.     

Polyacrylamide Nanoparticles with Visible and Near‐Infrared Autofluorescence

Nowadays, self‐fluorescent materials such as quantum dots are widely studied and applied in biomedical field. However, the biggest obstacle is biocompatibility. Here, a novel autofluorescent nanoparticle is constructed by crosslinking polyacrylamide nanoparticles (PAANPs) that contain ε‐poly‐l ‐lysine with glutaraldehyde (named fPAANPs). The nanoparticle has a mean size of about 16 nm, a zeta potential of about +16 mV, and strong visible and near‐infrared autofluorescence. The nanoparticle can be efficiently internalized into cells with high biocompatibility, the LC50 of which in RAW264.7, HepG2, and Hepa1‐6 cells is 6, 9, and 7.5 mg mL^?1, respectively. The nanoparticle shows no visible impact on the mice vitality even at a high intravenously administered dose (126 mg kg^?1). The autofluorescence of fPAANPs shows high stability, persistence, allowing long‐term dynamic imaging for 25 d in subcutaneous injections and 18 d in xenograft tumors in mice. The nanoparticle thus provides a self‐traceable nanomaterial that can be exploited as drug carrier and potential photodynamic therapy photosensitizer.     

Integrated all‐optical switch with 10 ps time resolution enabled by ALD

Abstract The potential of GaAs‐based photonic crystals for fast all‐optical switching in the telecom spectral range is exploited by controlling the surface recombination and, thereby, the carrier relaxation dynamics. The structure is entirely coated with a layer of aluminium oxide using atomic layer deposition. This results in a carrier lifetime of about 10 ps, as determined by spectrally resolved pump–probe measurements. We show that the nonlinear response of the resonator is optimized when it is excited with a few‐picoseconds pulse. This dynamics is perfectly captured by our model accounting for the carrier diffusion with an impulse response function. Moreover, the suppression of photo‐induced oxidation is revealed to be crucial to demonstrate all‐optical operation at GHz rates with average coupled pump power of 0.5 mW (hence 100 fJ/bit). The switching window is 12 ps wide (1/e), as resolved by homodyne pump–probe measurements. The devices respond to a sequence of closely spaced pump pulses demonstrating a gating window close to 10 ps, with a contrast as high as 7 dB.

     

Co3O4 Hollow Nanoparticles and Co Organic Complexes Highly Dispersed on N‐Doped Graphene: An Efficient Cathode Catalyst for Li‐O2 Batteries

Rechargeable Li‐O₂ batteries are promising candidates for electric vehicles due to their high energy density. However, the current development of Li‐O₂ batteries demands highly efficient air cathode catalysts for high capacity, good rate capability, and long cycle life. In this work, a hydrothermal‐calcination method is presented to prepare a composite of Co₃O₄ hollow nanoparticles and Co organic complexes highly dispersed on N‐doped graphene (Co–NG), which acts as a bifunctional air cathode catalyst to optimize the electrochemical performances of Li‐O₂ batteries. Co–NG exhibits an outstanding initial discharge capacity up to 19 133 mAh g^?1 at a current density of 200 mA g^?1. In addition, the batteries could sustain 71 cycles at a cutoff capacity of 1000 mAh g^?1 with low overpotentials at the current density of 200 mA g^?1. Co–NG composites are attractive as air cathode catalysts for rechargeable Li‐O₂ batteries.     

Room Temperature Ferromagnetism in Graphene/SiC(0001) System Intercalated by Fe and Co

The utilization of graphene on silicon carbide (SiC) substrates holds substantial promise for advancements in spintronics and nanoelectronics. Furthermore, incorporating magnetic metals provides an optimal framework for probing fundamental physical phenomena. The approach to developing such systems is in situ intercalation of graphene with magnetic metals. Herein, the electronic structure is analyzed and the magnetic properties of the system are synthesized by the thermal decomposition of 6H-SiC(0001) surface and subsequent intercalation of graphene with cobalt (Co) and iron (Fe) atoms. X-ray photoemission spectroscopy and low-energy electron diffraction are employed to control the synthesis and metal intercalation processes. The morphological characteristics of the synthesized system are studied by means of atomic force microscopy. The findings derived from magneto-optic Kerr effect measurements reveal a homogeneous ferromagnetic ordering at room temperature. Angle-resolved photoemission spectroscopy is used to ascertain the impact of intercalation on graphene's electronic structure. The results of this study are essential for the development of graphene-based spintronics and nanoelectronic devices as well as for fundamental studies in magnetic graphene systems.     

Controllable Formation of Niobium Nitride/Nitrogen‐Doped Graphene Nanocomposites as Anode Materials for Lithium‐Ion Capacitors

Niobium nitride/nitrogen‐doped graphene nanosheet hybrid materials are prepared by a simple hydrothermal method combined with ammonia annealing and their electrochemical performance is reported. It is found by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the as‐obtained niobium nitride nanoparticles are about 10–15 nm in size and homogeneously anchored on graphene. A non‐aqueous lithium‐ion capacitor is fabricated with an optimized mass loading of activated carbon cathode and the niobium nitride/nitrogen‐doped graphene nanosheet anode, which delivers high energy densities of 122.7–98.4 W h kg^?1 at power densities of 100–2000 W kg^?1, respectively. The capacity retention is 81.7% after 1000 cycles at a current density of 500 mA g^?1. The high energy and power of this hybrid capacitor bridges the gap between conventional high specific energy lithium‐ion batteries and high specific power electrochemical capacitors, which holds great potential applications in energy storage for hybrid electric vehicles.     

Atomic spectroscopy and quantum optics in hollow‐core waveguides

Atomic spectroscopy is a well‐established, integral part of the physicist's toolbox with an extremely broad range of applications ranging from astronomy to single atom quantum optics. While highly desirable, miniaturization of atomic spectroscopy techniques on the chip scale was hampered by the apparent incompatibility of conventional solid‐state integrated optics and gaseous media. Here, the state of the art of atomic spectroscopy in hollow‐core optical waveguides is reviewed The two main approaches to confining light in low index atomic vapors are described: hollow‐core photonic crystal fiber (HC‐PCF) and planar antiresonant reflecting optical waveguides (ARROWs). Waveguide design, fabrication, and characterization are reviewed along with the current performance as compact atomic spectroscopy devices. The article specifically focuses on the realization of quantum interference effects in alkali atoms which may enable radically new optical devices based on low‐level nonlinear interactions on the single photon level for frequency standards and quantum communication systems.     

光纤中的集成光学与离散光学

光纤集成光学和离散光学有望成为光子学集成的一个新分支。这种集成技术可以通过离散的方法方便地在一根光纤中控制和操纵光波,也为集成光学与离散光学的研究提供了一个灵活方便的平台,为微光子器件和系统集成提供了一种有效的方法和手段。文章简要总结了在光纤内实现光学器件集成和微光学系统集成的主要思想和关键技术,探讨了离散光学需要考虑的核心内容,为该方向的进一步发展提供了若干前期的研究基础。     

Development of Novel Graphene/g‐C3N4 Composite with Broad‐Frequency and Light‐Weight Features

In this study, a novel graphene/g‐C₃N₄ microwave absorber is developed to solve the electromagnetic wave interference problem. Graphene/g‐C₃N₄ composite is synthesized by loading g‐C₃N₄ nanosheets on graphene through a simple liquid‐phase approach. High‐performance electromagnetic absorption performance can be achieved. The optimal reflection loss value is up to ?29.6 dB under a thin coating layer of 1.5 mm. At the same time, the corresponding absorption bandwidth of this composite can reach 5.2 GHz (12.8–18 GHz). Excellent electromagnetic absorption property may be attributed to the current attenuation theory which has been proven by replacing graphene with porous graphene or graphene oxide. The results reveal that free electron numbers and loading mass of g‐C₃N₄ on graphene play the key roles in the intensity of current attenuation and resistance value.     

Graphene and Graphene‐Based Materials in Biomedical Science

Graphene and its composite materials are very important in many disciplines of science and have been used enormously by researchers since their discovery in 2004. These are a new group of compounds, and are also wonderful model systems for quantum behavior studies. Their properties like exceptional conductivity, biocompatibility, surface area, mechanical strength, and thermal properties make them rising stars in the scientific community. Graphene and its composite compounds are utilized widely in different medical applications, for example, biosensing of biological compounds responsible for disease development, bioimaging of various cells, tissues, microorganisms, animal models, etc. In addition, they are used for enhancing and supporting the stem cell differentiation, i.e., regenerative medicine for regeneration studies of various human organs, tissue engineering in biology for the development of carrier materials, as well as in bone reformation. This review focuses on the modification procedure involved in the fabrication of graphene‐based biomaterials for various applications and recent developments in research related to graphene and graphene‐based materials in biosensing, optical sensing, gas sensing, drug, gene, protein delivery, tissue engineering, and bioimaging. In addition, the potential toxicological effects of graphene‐based biomaterials are discussed.