Recent Advances of Light Propagation in Surface Plasmon Enhanced Quantum Dot Devices

Surface plasmons are of particular interest recently as their performance is approaching the enhancement of light emission efficiencies, after synthesized close to the vicinity of solid state materials, i.e., semiconductor structure. As other scientific works have been proposed to improve the light-emitting efficiency, such as the use of resonant cavities, photon recycling, and thin-light emitting layers with periodic surface texturing, surface plasmon possesses a promising way to the light enhancement, due to the energy coupling effect between the emitted photons from the semiconductor and the metallic nanoparticles fabricated by nanotechnology. The usual pathway of plasmon enhanced light emitting devices is the use of Ag/Au nanoparticles coating the surface of semiconductor quantum dot (QD) or quantum well (QW) structures. However, apart from efforts to extract as much light as possible from single-driven surface plasmon-QD/QW, it is possible to enhance the light emission rate with double optical-excitations. This approach is based on the quantum interference between the external lasers and the localized quantum light, and promised to stimulate the development of plasmon-enhanced optical sensors. In this review, we describe the quantum properties of light propagation in hybrid nanoparticle and semiconductor materials, i.e., quantum dot or nanomechanical resonator coupled to Ag/Au nanoparticles, driven by two optical fields. Distinct with single excitation, plasmon-assisted complex driven by two optical fields, exhibit specific quantum interference characteristics that can be used as sensitive all-optical devices, such as the slow light switch, nonlinear optical Kerr modulator, and ultra-sensitive mass sensing. We summarize the recent advances of light propagation in surface plasmon-enhanced quantum dot devices, driven by two optical fields, which would stimulate the development of novel optical materials, deeper theoretical insights, innovative new devices, and plasmonic applications with potential for significant technological and societal impact.     

Organic materials in future integrated optoelectronic circuits

During the last two decades, lithium niobate has been extensively studied for applications in integrated optical circuits. However, it is difficult to integrate lithium niobate optical devices with semiconductor electronic devices because the materials are incompatible. In recent years, semiconductor materials have been emerging as the main contenders in applications; these materials have the advantage of allowing both optical and electronic devices to be integrated. Further, the semiconductor technology has advanced rapidly, allowing us to engineer device parameters very precisely. In semiconductor optoelectronic devices, that is, bulk and quantum well structures, electroabsorption has mainly been used for amplitude modulation of light. The electrorefraction effect is the most useful for devices employing phase-modulation techniques, but this effect cannot be effectively utilized in semiconductors since the strongest electrorefraction effect is near the absorption edge of the material. Recently, organic materials have been shown to have electro-optic coefficients equal to or larger than that of lithium niobate. There are major advantages of organic materials: (1) the organics can be deposited on semiconductor substrates, and therefore both electronic and optical circuits can be integrated; (2) in organic materials the electrorefraction can be effectively utilized to obtain both amplitude and phase modulation; (3) the organic material composition can be adjusted to satisfy some device requirements. In this paper, a comparison of these material systems are made in terms of device applications.     

Two-dimensional materials for ultrafast lasers

As the fundamental optical properties and novel photophysics of graphene and related two-dimensional(2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches(or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out.     

用于下一代传感和光源的新型材料、光纤及器件

制造技术与复杂模型、设计工具的进步使微纳结构光学器件的实现成为可能。微纳结构光学器件可用于导光与光的相互作用,液态或气态新型光源和传感器件。IPAS致力于新型光学材料研究与开发,将玻璃工艺和光纤开发有机结合,重点研究微纳结构光纤,光纤表面功能处理和器件开发。介绍了IPAS的研究实力和近年的发展概况,其中包括中红外光学材料、纳米粒子嵌入玻璃材料、新型化学和生物传感器(适用于超低量样本及/或体内样本)、激光器件,以及用于光数据处理的新型高非线性光纤。     

Two-dimensional materials-decorated microfiber devices for pulse generation and shaping in fiber lasers

Two-dimensional(2D) materials have been regarded as a promising nonlinear optical medium for fabricating versatile optical and optoelectronic devices. Among the various photonic applications, the employment of 2D materials as nonlinear optical devices such as saturable absorbers for ultrashort pulse generation and shaping in ultrafast lasers is one of the most striking aspects in recent years. In this paper, we review the recent progress of 2D materials based pulse generation and soliton shaping in ultrafast fiber lasers, and particularly in the context of 2D materials-decorated microfiber photonic devices. The fabrication of 2D materials-decorated microfiber photonic devices, high performance mode-locked pulse generation, and the nonlinear soliton dynamics based on pulse shaping method are discussed. Finally, the challenges and the perspective of the 2D materials-based photonic devices as well as their applications are also discussed.     

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.     

Photodetectors based on two-dimensional materials and organic thin-film heterojunctions

High-performance photodetectors are expected to open up revolutionary opportunities in many application fields, such as environment monitoring, military, optical communication and biomedical science. Combining two-dimensional materials(which have tunable optical absorption and high carrier mobility) with organic materials(which are abundant with low cost, high flexibility and large-area scalability) to form thin-film heterojunctions, high-responsivity photodetectors could be predicted with fast response speed in a wide spectra region.In this review, we give a comprehensive summary of photodetectors based on two-dimensional materials and organic thin-film heterojunctions, which includes hybrid assisted enhanced devices, single-layer enhanced devices, vertical heterojunction devices and tunable vertical heterojunction devices. We also give a systematic classification and perspectives on the future development of these types of photodetectors.     

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.     

Development of organic light‐emitting diodes for electro‐optical integrated devices

Organic light‐emitting diodes (OLEDs) are discussed for electro‐optical integrated devices that are used for optical signal transmission. Organic optical devices including polymeric optical fibers are used for optical communication applications to realize polymeric electro‐optical integrated devices. The OLEDs were fabricated by vacuum process, i.e. the organic molecular beam deposition (OMBD) technique or a solution process on a polymeric or a glass substrate, for comparison. Optical signals faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing rubrene doped in 8‐hydoxyquinolinum aluminum (Alq₃), as an emissive layer. OLEDs fabricated by solution process utilizing rubrene doped in carrier‐transporting materials have also discussed. OLEDs utilizing polymeric materials by solution process are also fabricated and discussed. Moving‐picture signals are transmitted utilizing both vacuum‐ and solution‐processed OLEDs, respectively.     

Nonunity permeability in metamaterial-based GaInAsP/InP multimode interferometers

We demonstrated an InP-based optical multimode interferometer (MMI) combined with metamaterials consisting of minute split-ring resonators (SRRs) arrayed on the MMI. The MMI could operate at an optical fiber communication wavelength of 1.5 μm. Magnetic resonance occurred between the SRR metamaterial and light at 1.5 μm, and the relative permeability of the metamaterial increased to 2.4 around this wavelength. This result shows that it is possible to use new materials with nonunity permeability to construct semiconductor-based photonic devices.     

Modulation of the second-harmonic generation in MoS_2 by graphene covering

Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterization,and optical imaging.Investigating and manipulating the nonlinear optical response of target materials lead us to reveal hidden physics and develop applications in optical devices.Here,we report the realization of facile manipulation of nonlinear optical responses in the example system of MoS₂ monolayer by van der Waals interfacial engineering.We found that,the interfacing of monolayer graphene will weaken the exciton oscillator strength in MoS₂ monolayer and correspondingly suppress the second harmonic generation(SHG)intensity to 30%under band-gap resonance excitation.While with off-resonance excitation,the SHG intensity would enhance up to 130%,which is conjectured to be induced by the interlayer excitation between MoS₂ and graphene.Our investigation provides an effective method for controlling nonlinear optical properties of two-dimensional materials and therefore facilitates their future applications in optoelectronic and photonic devices.     

Transformation Optics: From Classic Theory and Applications to its New Branches

In the modern world, the ability to manipulate and control electromagnetic waves has greatly changed people's lives. Novel optical and electromagnetic phenomena and devices will lead to new scientific trends and techniques in the future. The exploration of new theories of optical design and new materials for optical engineering has attracted great attention in recent years. Transformation optics (TO) provides a new way to design optical devices with extraordinary predesigned functions such as invisibility cloaks and electromagnetic wormholes. As the development of artificial electromagnetic media (e.g. metamaterials and metasurfaces) progresses, many of these novel optical devices designed by TO have been experimentally demonstrated and used in specific applications. Starting from the basic theory of transformation optics, we review its applications, extensions, new branches and recent developments in this paper.     

SiP monolayers: New 2D structures of group IV–V compounds for visible-light photohydrolytic catalysts

Because of graphene and phosphorene, two-dimensional (2D) layered materials of group IV and group V elements arouse great interest. However, group IV–V monolayers have not received due attention. In this work, three types of SiP monolayers were computationally designed to explore their electronic structure and optical properties. Computations confirm the stability of these monolayers, which are all indirect-bandgap semiconductors with bandgaps in the range 1.38–2.21 eV. The bandgaps straddle the redox potentials of water at pH = 0, indicating the potential of the monolayers for use as watersplitting photocatalysts. The computed optical properties demonstrate that certain monolayers of SiP 2D materials are absorbers of visible light and would serve as good candidates for optoelectronic devices.     

Fabrication of microgratings on the ends of standard optical fibers by the electrostatic self-assembly monolayer process

The electrostatic self-assembly monolayer process has been utilized for what is believed to be the first time to deposit quarter-wavelength stacks on the end faces of cleaved and polished optical fibers. Standard multimode optical fibers as well as single-mode optical fibers were used as substrates with different coating materials to fabricate broadband filters, and the experimentally measured spectral responses of these devices are shown. These optical filter structures were employed to develop chemical sensors that use an unperturbed reference wavelength to normalize the output signal.     

BOR-FDTD analysis of nonlinear Fiber Bragg grating and distributed Bragg resonator

Recently, nonlinear materials have attracted a great deal of attention because of their importance in designing new devices to meet a need range of optical systems. An intense investigation of the possibility of using these materials for all optical ultrafast applications is achieved by allowing their dielectric characteristics to be varied in such a way that a periodic perturbation of their refractive index along the length of the waveguide will be formed. The Finite-Difference Time-Domain (FDTD) method, on the other hand, has been proven to be one of the most powerful numerical techniques that are usefully applied to a wide range of optical devices. In this paper, a FDTD technique, developed for nonlinear structures, is used to analyze a nonlinear waveguide and periodic nonlinear structures that exhibit attractive properties that make them suitable for novel devices with wavelength tunable characteristics. More specifically, the Bodies of Revolution (BOR) FDTD numerical simulation method will be used to model the fiber Bragg Grating (FBG) and the direct integration method will be employed to include the effect of Self Phase Modulation (SPM) in this model. The combination of these techniques will result in a model that is used to analyze two different types of periodic nonlinear structure, FBG and Distributed Bragg Resonator (DBR). The nonlinear effect provides the designer an added degree of design flexibility for devices with wavelength tunable characteristics, for example, in the design of tunable filters, WDM systems and optical sensors.     

Construction of Two-Dimensional Waveguides in Insulating Optical Materials by Means of Ion Beam Implantation for Photonic Applications: Fabrication Methods and Research Progress

Ion beam implantation has been used not only to modify some properties of the bulk materials but also to construct waveguide structures in many optical substrates by accurate control the refractive index in selected regions. This paper reviews the recent development of ion beam implantations on fabrication of two-dimensional (2D) optical waveguides, i.e., in cases of channel or ridge configurations, in diverse insulating optical materials by giving detailed fabrication methods and research progress obtained to date. Future prospects of practical applications in photonics are also discussed briefly. Another aim of this work is to show the challenging task of this field, that is, to create practical 2D waveguide devices applicable in any existing insulating optical materials.     

Photodetecting and light-emitting devices based on two-dimensional materials

Two-dimensional(2D) materials, e.g., graphene, transition metal dichalcogenides(TMDs), and black phosphorus(BP), have demonstrated fascinating electrical and optical characteristics and exhibited great potential in optoelectronic applications. High-performance and multifunctional devices were achieved by employing diverse designs, such as hybrid systems with nanostructured materials, bulk semiconductors and organics, forming 2D heterostructures. In this review,we mainly discuss the recent progress of 2D materials in high-responsive photodetectors, light-emitting devices and single photon emitters. Hybrid systems and van der Waals heterostructure-based devices are emphasized, which exhibit great potential in state-of-the-art applications.     

Strained 2D Layered Materials and Heterojunctions

2D layered materials and heterojunctions with excellent ductility and controllable atomic‐layer thicknesses have shown promise for use in advanced electronics and optical functional devices. Tailoring of nanoscale configurations and physical properties is essential and required for bespoke fabrication of advanced devices based on 2D materials. Due to the high strain tolerance of 2D layered materials, strain engineering is an effective method to tune their behaviors of electrons and phonons. A wide variety of 2D materials are available with tunable bandgaps from interface coupling effects, making 2D layered heterojunctions a versatile platform for understanding fundamental physical issues. Most physical properties and functional applications can be tailored by applying strain to 2D layered materials and heterostructures to realize a scheduled target in carrier concentration, mobility, and barrier height. Herein, the latest research on the roles of strain in modulating the physical properties of 2D layered materials and heterojunctions is introduced, focusing on the physical properties behind strain modulation in 2D materials. Understanding and manipulating strain in 2D layered materials and heterojunctions is important and beneficial for creating tunable electronic and optoelectronic constructions with advanced components, including functional flexible and wearable devices.     

Transformation devices with optical nihility media and reduced realizations

Starting from optical nihility media (ONM), we design several intriguing devices with transformation optics method in two dimensions, such as a wave splitter, a concave lens, a field rotator, a concentrator, and an invisibility cloak. Though the extreme anisotropic property of ONM hinders the fabrication of these devices. We demonstrate that those devices could be effectively realized by simplified materials with Fabry–Pérot resonances (FPs) at discrete frequencies. Moreover, we propose a reduced version of simplified materials with FPs to construct a concentrator and a rotator, which is feasible in experimental fabrications. The simulations of total scattering cross-sections confirm their functionalities.     

Laser beam manipulation by composite material electro-optic devices

Liquid crystals are anisotropic materials whose optical properties can be easily controlled applying an electric field. For this reason, they are widely used in electro-optical devices. Besides other applications, liquid crystals electro-optical devices are suitable for laser beam manipulation. In this paper, we present some devices developed or studied in our laboratory: a twisted nematic liquid crystal (TN-LC) polarization rotator, a TN-LC protected light sensor, a polymer dispersed liquid crystal (PDLC) light modulator, a PDLC optoelectronic polarizer and a polymer liquid crystal (PoLiCryst) light modulator.