scispace - formally typeset
Search or ask a question

Showing papers in "IEEE Journal of Selected Topics in Quantum Electronics in 2021"


Journal ArticleDOI
TL;DR: Current AV sensor challenges are highlighted, and the strengths and weaknesses of the perception sensor currently deployed are analyzed, and current factors hindering the affirmation of silicon photonics OPAs and their future research directions are discussed.
Abstract: This paper aims to review the state of the art of Light Detection and Ranging (LiDAR) sensors for automotive applications, and particularly for automated vehicles, focusing on recent advances in the field of integrated LiDAR, and one of its key components: the Optical Phased Array (OPA). LiDAR is still a sensor that divides the automotive community, with several automotive companies investing in it, and some companies stating that LiDAR is a ‘useless appendix’. However, currently there is not a single sensor technology able to robustly and completely support automated navigation. Therefore, LiDAR, with its capability to map in 3 dimensions (3D) the vehicle surroundings, is a strong candidate to support Automated Vehicles (AVs). This manuscript highlights current AV sensor challenges, and it analyses the strengths and weaknesses of the perception sensor currently deployed. Then, the manuscript discusses the main LiDAR technologies emerging in automotive, and focuses on integrated LiDAR, challenges associated with light beam steering on a chip, the use of Optical Phased Arrays, finally discussing current factors hindering the affirmation of silicon photonics OPAs and their future research directions.

101 citations


Journal ArticleDOI
TL;DR: A review of recent progress in structured light in turbulence, first with a tutorial style summary of the core concepts, before highlighting the present state of the art in the field, and with new experimental studies that reveal which types of structured light are best in turbulence.
Abstract: Optical communication is an integral part of the modern economy, having all but replaced electronic communication systems. Future growth in bandwidth appears to be on the horizon using structured light, encoding information into the spatial modes of light, and transmitting them down fibre and free-space, the latter crucial for addressing last mile and digitally disconnected communities. Unfortunately, patterns of light are easily distorted, and in the case of free-space optical communication, turbulence is a significant barrier. Here we review recent progress in structured light in turbulence, first with a tutorial style summary of the core concepts, before highlighting the present state-of-the-art in the field. We support our review with new experimental studies that reveal which types of structured light are best in turbulence, the behaviour of vector versus scalar light in turbulence, the trade-off of diversity and multiplexing, and how turbulence models can be exploited for enhanced optical signal processing protocols. This comprehensive treatise will be invaluable to the large communities interested in free-space optical communication with spatial modes of light.

65 citations


Journal ArticleDOI
TL;DR: In this paper, an ultra-wide detection range refractive index sensor based on surface plasmon resonance (SPR) with photonic crystal fiber (PCF) is designed and discussed.
Abstract: An ultra-wide detection range refractive-index sensor based on surface plasmon resonance (SPR) with photonic crystal fiber (PCF) is designed and discussed. The central air-hole of the fiber is injected with the analyte. The properties of refractive-index sensor are investigated with different structure parameters. Simulation results show that the proposed sensor has an ultra-wide detection range from 1.29 to 1.49. The refractive index sensitivities of x-polarized and y-polarized core mode are −4156.82 nm/RIU and −3703.64 nm/RIU respectively, and the corresponding linear fitting degrees are 0.99598 and 0.99236. The designed refractive-index sensor with ultra-wide detection range has a great potential in the fields of biology, chemistry, environment and medicine.

55 citations


Journal ArticleDOI
TL;DR: In this article, an antibody modified terahertz (THz) metamaterial biosensor is proposed to detect the concentration of carcinoembryonic antigen (CEA), which has four metal split-ring-resonators in a unit cell.
Abstract: An antibody modified terahertz (THz) metamaterial biosensor is proposed to detect the concentration of carcinoembryonic antigen (CEA). The biosensor has four metal split-ring-resonators (SRR) in a unit cell. The finite integration time domain (FITD) method is used to design and optimize the structure. The simulation shows that the biosensor is insensitive to incident angles and the sensitivity reaches to 76.5 GHz/RIU (Refractive Index Unit). The sample is manufactured using a surface micromachining process and characterized by a THz time domain spectroscopy (THz-TDS) system. The experimental results indicate that the resonant frequency of the biosensor decreases with the increase of the concentration of analytes on the surface. After that, the biosensor is modified with anti-CEA and used to detect the concentration of the CEA. Interestingly, the response of the biosensor depends heavily on the concentration of the Anti-CEA modified on the surface of the biosensor. When the concentration of Anti-CEA is 20 ng/ml, the resonant frequency shift shows good linearity to the concentration of CEA and the limit of detection (LOD) reaches to 0.1 ng/ml. This study paves a new way for sensitively detection of biomolecules, cancer biomarkers and immune responses, which is important for early stage diagnosis of cancers.

49 citations


Journal ArticleDOI
TL;DR: In this article, the authors theoretically and numerically demonstrate a polarization-controlled dynamically tunable electromagnetically induced transparency-like (EIT-like) effect based on graphene metasurfaces.
Abstract: In this paper, we theoretically and numerically demonstrate a polarization-controlled dynamically tunable electromagnetically induced transparency-like (EIT-like) effect based on graphene metasurfaces. The unit cell of metasurface is composed of a rectangular graphene ring placed between two parallel graphene strips, which can achieve tunable spectral responses in different polarization directions. And when the polarization angle of the incident light changes gradually from 0° to 90°, the number of transparent windows can be switched between 1 and 2. The theoretical calculations based on the coupled Lorentz oscillator models have an excellent agreement with the simulation results. The mechanism of the dynamical modulation is attributable to the near field coupling of resonator units. Moreover, we can significantly adjust the transparency windows of the EIT-like by changing the asymmetry parameter and the Fermi level of graphene. Also, the strong dispersion and tunable group delay accompanied with the transparency window can be achieved for slow light application. Our proposed graphene metasurface architecture provides a new platform of multi-controlled EIT-like system for applications in slow light, optical sensor and selective filter.

42 citations


Journal ArticleDOI
TL;DR: The aim is the development of scalability on the platform, to point the way to ever-closer integration, toward silicon quantum photonic systems-on-a-chip.
Abstract: Quantum technology is poised to enable a step change in human capability for computing, communications and sensing. Photons are indispensable as carriers of quantum information—they travel at the fastest possible speed and readily protected from decoherence. However, the system requires thousands of near-transparent components with ultra-low-latency control. To be implemented, a new paradigm photonic system is required: one with in-built coherence, stability, the ability to define arbitrary circuits, and a path to manufacturability. Silicon photonics has unparalleled density and component performance, which, with CMOS compatible fabrication, place it in a strong position for a scalable quantum photonics platform. This paper is a progress report on silicon quantum photonics, focused on developments in the past five years. We provide an introduction on silicon quantum photonic component and the challenges in the field, summarise the current state-of-the-art and identify outstanding technical challenges, as well as promising avenues of future research. We also resolve a conflict in the definition of Hong-Ou-Mandel interference visibility in integrated quantum photonic experiments, needed for fair comparison of photon quality across different platforms. Our aim is the development of scalability on the platform, to which end we point the way to ever-closer integration, toward silicon quantum photonic systems-on-a-chip.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a plasmonic pixel composed of a metallic nanoantenna covered by a thin oxide layer, and a conductive oxide, e.g., ITO, for use in a reflectarray metasurface is proposed.
Abstract: Controlling the phase and amplitude of light emitted by the elements ( i.e. , pixels) of an optical phased array is of paramount importance to realizing dynamic beam steering for LIDAR applications. In this paper, we propose a plasmonic pixel composed of a metallic nanoantenna covered by a thin oxide layer, and a conductive oxide, e.g. , ITO, for use in a reflectarray metasurface. By considering voltage biasing of the nanoantenna via metallic connectors, and exploiting the carrier refraction effect in the metal-oxide-semiconductor capacitor in the accumulation and depletion regions, our simulations predict control of the reflection coefficient phase over a range $>330^{\circ }$ with a nearly constant magnitude. We discuss the physical mechanism underlying the optical response, the effect of the connectors, and propose strategies to maximize the magnitude of the reflection coefficient and to achieve dual-band operation. The suitability of our plasmonic pixel design for beam steering in LIDAR is demonstrated via 3D-FDTD simulations.

35 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the evolution of various kinds of mode-locked laser from a scientific toy to a robust industrial tool, and the utilization benefits of high-average power, high-pulse-repetition-rate ultra-short pulse laser are closely related to beam shaping and manipulation techniques.
Abstract: Ultra-short pulse lasers, generating coherent light pulses with pulse durations in the picosecond and femtosecond range, are becoming popular in precision laser microfabrication. They are benefiting not only from well-predicted laser ablation with the suppressed heat-affected zone but also by opening new processing opportunities, especially in transparent materials, due to enhanced non-linear interaction with the material. In this review, the evolution of various kinds of mode-locked lasers from a scientific toy to a robust industrial tool is reviewed. The utilization benefits of high-average-power, high-pulse-repetition-rate ultra-short pulse laser are closely related to beam shaping and manipulation techniques. Fast beam scanning with galvanometric and polygon scanners as well as multi-beam parallel processing methods were developed. Some hot applications areas are briefly described. The efficient use of photons from ultra-short pulse lasers pushed the development of optimization methods in the ablation process. Efforts toward upscaling the process by increasing the average power of mode-locked lasers made feedback to laser developers, and burst regime became a necessity as well as high-speed beam scanning devices. Unique opportunities of ultra-short pulses are successfully exploited in machining transparent materials, with glass separation being the leading application.

33 citations


Journal ArticleDOI
TL;DR: In this article, the use of Fabry-Perot (FP) lasers as potential neuromorphic computing machines with parallel processing capabilities was introduced for signal equalization in 25 Gbaud intensity modulation direct detection optical communication systems.
Abstract: We introduce the use of Fabry-Perot (FP) lasers as potential neuromorphic computing machines with parallel processing capabilities. With the use of optical injection between a master FP laser and a slave FP laser under feedback we demonstrate the potential for scaling up the processing power at longitudinal mode granularity and perform real-time processing for signal equalization in 25 Gbaud intensity modulation direct detection optical communication systems. We demonstrate the improvement of classification performance as the number of modes multiplies the number of virtual nodes and offers the capability of simultaneous processing of arbitrary data streams. Extensive numerical simulations show that up to 8 longitudinal modes in typical Fabry-Perot lasers can be leveraged to enhance classification performance.

28 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a simple method for fast and label-free identification of early stage cervical cancerous tissues using a metamaterial (MM) terahertz (THz) biosensor with two resonant absorption frequencies at 0.286 THz and 0.850 THz, respectively.
Abstract: We propose a simple method for fast and label-free identification of early-stage cervical cancerous tissues using a metamaterial (MM) terahertz (THz) biosensor with two resonant absorption frequencies at 0.286 THz and 0.850 THz, respectively. Because the two resonant absorption frequencies are very sensitive to the ambient change of dielectric properties, the cervical cancerous tissues can be distinguished from the normal tissues by analyzing the resonant frequency shift. The calculated sensitivity of the low resonant frequency and that of the high resonant frequency are 29 and 74 GHz/RIU, respectively. In the experiment, the cervical cancerous tissue samples were taken from different patients, and the cancerous and normal parts were determined by hematoxylin-eosin (HE) stain. Compared with the traditional method of directly detecting cancer tissue without the sensor, this method has the advantages of being simple, label free and fast. In addition, compared with biosensors which have a single resonant absorption frequency, the biosensors with double resonant absorption frequencies have higher accuracy. This method potentially can be applied for the detection and diagnosis of many other cancer tissues.

27 citations


Journal ArticleDOI
TL;DR: The photonic spike timing dependent plasticity (STDP) is applied to design a hardware-friendly biologically plausible supervised learning algorithm for a multi-layer photonic SNN, which is capable of solving the classical XOR problem.
Abstract: We propose a framework for hardware architecture and learning algorithm co-design of multi-layer photonic spiking neural network (SNN). The vertical-cavity surface-emitting laser with an embedded saturable absorber (VCSEL-SA) which contains two polarization-resolved modes is employed as a spiking neuron. The connection between two identical polarization modes is considered as the excitatory synapse, whereas the connection between two orthogonal polarization modes is regarded as the inhibitory synapse. The physical model of the photonic spiking neuron is derived based on the combination of spin-flip model and Yamada model. The photonic spike timing dependent plasticity (STDP) is applied to design a hardware-friendly biologically plausible supervised learning algorithm for a multi-layer photonic SNN. Thanks to the polarization mode competition effect in the VCSEL-SA, the proposed neuromorphic network is capable of solving the classical XOR problem. The effect of physical parameters of photonic neuron on the training convergence is also considered. We further extend the multi-layer photonic SNN to realize other logic learning tasks. To the best of our knowledge, such a modified supervised learning algorithm dedicated for a multi-layer photonic SNN has not yet been reported, which is interesting for spiking learning of neuromorphic photonics.

Journal ArticleDOI
TL;DR: In this paper, the authors presented the first CMOS SPAD with performance comparable or better than that of the best custom SPADs, to date, achieving a peak PDP of 55% at 480nm with a very broad spectrum spanning from NUV to NIF and a normalized DCR of 0.2cps/m2, both at 6V of excess bias.
Abstract: In this paper, we present the first CMOS SPAD with performance comparable or better than that of the best custom SPADs, to date. The SPAD-based design, fully integrated in 180 nm CMOS technology, achieves a peak PDP of 55% at 480nm with a very broad spectrum spanning from NUV to NIF and a normalized DCR of 0.2cps/m2, both at 6V of excess bias. Thanks to a dedicated CMOS pixel circuit front-end, an afterpulsing probability of about 0.1% at a dead time of3ns were achieved. We designed three SPADs with a diameter of 25, 50, and 100m to study the impact of size on the timing jitter and to create a scaling law for SPADs. For these SPADs, a SPTR of 12.1ps, 16ps, and 27ps was achieved at 6V of excess bias, respectively. The SPADs operate in a wide range of temperatures, from -65C to 40C, reaching a normalized DCR of 1.6 mcps/m2 at 6V of excess bias. The proposed SPADs are ideal for a wide range of applications, including LiDAR, super-resolution microscopy, QRNGs, QKD, fluorescence lifetime imaging, time-resolved Raman spectroscopy, to name a few.

Journal ArticleDOI
TL;DR: The protein dissociation rate obtained for colorectal tissues was approximately 3 times higher in pathological than in normal mucosa and the kinetics of diffuse reflectance in the UV allowed to estimate the diffusion coefficient for water in gingival mucosa at glycerol action as (1.78 ± 0.26) × 10−6 cm2/s.
Abstract: In this paper, we describe the combination of ultraviolet (UV) spectroscopy with the optical clearing technique to induce new tissue windows, evaluate their efficiency, study the diffusion properties of agents and discriminate cancer. The use of highly concentrated glycerol solutions has induced high efficiency clearing effects in the UV, both in human colorectal and gingival tissues. The protein dissociation rate obtained for colorectal tissues was approximately 3 times higher in pathological than in normal mucosa and the kinetics of diffuse reflectance in the UV allowed to estimate the diffusion coefficient for water in gingival mucosa at glycerol action as (1.78 ± 0.26) × 10−6 cm2/s.

Journal ArticleDOI
TL;DR: This study presents a hardware-friendly deep learning architecture with one-dimensional convolutional neural networks (1D CNN) for fast analyzing fluorescence lifetime imaging (FLIM) data and shows that 1D CNNs have great potential in various real-time FLIM applications.
Abstract: We present a hardware-friendly deep learning architecture with one-dimensional convolutional neural networks (1D CNN) for fast analyzing fluorescence lifetime imaging (FLIM) data. A 1D CNN shows unparalleled advantages; they are more straightforward, quicker to train, and faster than high dimensional CNNs. 1D CNNs can be easily applied to multi-exponential fluorescence decay models. Compared with traditional least-square methods, superior performances of 1D CNNs on fluorescence lifetime image reconstruction have been validated using simulated data. We also employ the proposed 1D CNN to analyze two-photon FLIM images of functionalized gold nanoprobes in Hek293 and human prostate cancer cells. The results further demonstrate that 1D CNNs are fast and can accurately extract lifetime parameters from fluorescence signals. Our study shows that 1D CNNs have great potential in various real-time FLIM applications.

Journal ArticleDOI
TL;DR: In this paper, the radiation characteristics of a THz antenna made of a circular dielectric rod decorated with conformal graphene strip and illuminated by the field of a line magnetic current are investigated.
Abstract: In this article, we consider the radiation characteristics of a THz antenna made of a circular dielectric rod decorated with conformal graphene strip and illuminated by the field of a line magnetic current. The strip has arbitrary angular size and location and its surface impedance is characterized with Kubo theory. Our mathematically accurate analysis uses a dedicated hypersingular integral equation for the current induced on the strip. Discretization of this equation is carried out by the Nystrom-type method, which has a guaranteed convergence. We study the dependences of the powers radiated and absorbed in this configuration and also the directivity of antenna emission, in wide frequency range from 0 to 10 THz. They show very interesting interplay between the broadband inverse photonic-jet effect of lens-like dielectric rod and two types of resonances: on the moderate-Q plasmon modes of graphene strip and on the extremely high-Q whispering-gallery modes of the circular rod.

Journal ArticleDOI
TL;DR: In this paper, the design of grating-based micro-antennas with perfectly vertical emission in the 300-nm silicon-on-insulator platform is presented, which leverage a methodology combining adjoint optimization and machine learning dimensionality reduction to efficiently map the multiparameter design space of the antennas, analyse a large number of relevant performance metrics, carry out the required multiobjective optimization, and discover high performance designs.
Abstract: Compact and efficient optical antennas are fundamental components for many applications, including high-density fiber-chip coupling and optical phased arrays. Here we present the design of grating-based micro-antennas with perfectly vertical emission in the 300-nm silicon-on-insulator platform. We leverage a methodology combining adjoint optimization and machine learning dimensionality reduction to efficiently map the multiparameter design space of the antennas, analyse a large number of relevant performance metrics, carry out the required multi-objective optimization, and discover high performance designs. Using a one-step apodized grating we achieve a vertical upward diffraction efficiency of almost 92% with a 3.6 $\mu {}$ m-long antenna. When coupled with an ultra-high numerical aperture fiber, the antenna exhibits a coupling efficiency of more than 81% (−0.9 dB) and a 1-dB bandwidth of almost 158 nm. The reflection generated by the perfectly vertical antenna is smaller than −20 dB on a 200-nm bandwidth centered at $\lambda$ = 1550 nm.

Journal ArticleDOI
TL;DR: In this paper, an integrated device based on microring resonator (MRR) assisted Mach-Zehnder interferometer (MZI) preceded by a tunable MZ coupler for nonlinear optical signal processing is introduced.
Abstract: We introduce an integrated device based on microring resonator (MRR) assisted Mach-Zehnder interferometer (MZI) preceded by a tunable MZ coupler for nonlinear optical signal processing The novel structure of this device provides both high programmability and switching contrast These desirable features suggest its potential use as a multi-purpose optical processor providing different high-performance functionalities We experimentally demonstrate two functionalities using the same device fabricated on a silicon-on-insulator substrate One functionality is an all-optical thresholder enabling 40× signal contrast improvement, and the other functionality is clock-less pulse carving technique that converts long-pulse signals to short-pulse signals With these functionalities, we discuss system-level applications of our device in optical interconnects and photonic neural networks

Journal ArticleDOI
TL;DR: This paper highlights certain optical signal processing functions that can be achieved when using optical frequency combs, and explores the following general topics: tailoring a comb for enhanced usability in OSP, and enabling various transmission and networking functions, such as multicasting, format conversion, and dynamic bandwidth allocation.
Abstract: This paper highlights certain optical signal processing (OSP) functions that can be achieved when using optical frequency combs. An optical frequency comb can provide many narrow-linewidth, mutually coherent, and equidistant optical carriers, making it a potentially useful tool for facilitating efficient signal processing functions. In this paper, we explore the following general topics: (a) tailoring a comb for enhanced usability in OSP, such as inserting more lines, generating Nyquist pulse trains, and regenerating a comb at a distance; (b) achieving a tunable linear and nonlinear filter for correlation, equalization, and Volterra filtering, and (c) enabling various transmission and networking functions, such as multicasting, format conversion, and dynamic bandwidth allocation.

Journal ArticleDOI
TL;DR: This paper theoretically investigate, assess and demonstrate the feasibility of implementing all-optically multiple logic gates (AND, NOR, OR, NOT) at 160 Gb/s by means of a single quantum-dot semiconductor optical amplifier and a concatenated optical filter.
Abstract: All-optical logic gates are indispensable modules for executing exclusively by means of light fundamental Boolean operations. Despite intense research in this field, most efforts have not treated these gates in a joint design and operating manner. This causes waste of hardware resources and lack of versatility. In this paper, we theoretically investigate, assess and demonstrate the feasibility of implementing all-optically multiple logic gates (AND, NOR, OR, NOT) at 160 Gb/s by means of a single quantum-dot semiconductor optical amplifier (QD-SOA) and a concatenated optical filter. We follow a methodical approach and conduct a thorough numerical study to derive rules for the selection of the critical operating parameters so that appropriate performance criteria defined for each gate are made acceptable. The intersection of the permissible bounds allows us to specify a combination of parameters’ values which is the same for all gates and guarantees the execution of the corresponding Boolean functions with logically correct and high quality outcome. The proposed scheme can be reconfigured to realize the different gates at 160 Gb/s without changes in its basic setup or driving conditions. This is achieved simply by detuning the optical filter according to the design guidelines of each gate.

Journal ArticleDOI
TL;DR: In this article, the state of the art in four-wave mixing-based parametric amplification, and wavelength conversion in silicon fibers that have been tapered to improve the material quality, and engineer the dispersion profile is described.
Abstract: Silicon core fibers represent a versatile platform for all-fiber integrated nonlinear optical applications. This paper describes the state of the art in four-wave mixing-based parametric amplification, and wavelength conversion in silicon fibers that have been tapered to improve the material quality, and engineer the dispersion profile. Fibers with submicron core dimensions have been fabricated, and used to demonstrate high gain parametric amplification in the C-Band, and broadband wavelength conversion extending out to the S-, and L-bands. The potential to use these fibers for all-optical signal processing of $20\,$ Gbit/s data signals has also been demonstrated, with a robust all-fiber coupling scheme presented to improve the efficiency, and practicality of these devices. These results highlight the potential of silicon core fibers for use in nonlinear signal processing within future telecommunication systems.

Journal ArticleDOI
TL;DR: In this paper, a time-of-flight based indoor positioning system for LiFi is presented based on the ITU -T recommendation G.9991, which can reach an average distance error of a few centimeters in three dimensions.
Abstract: Precise position information is considered as the main enabler for the implementation of smart manufacturing systems in Industry 4.0. In this article, a time-of-flight based indoor positioning system for LiFi is presented based on the ITU - T recommendation G.9991. Our objective is to realize positioning by reusing already existing functions of the LiFi communication protocol which has been adopted by several vendors. Our positioning algorithm is based on a coarse timing measurement using the frame synchronization preamble, similar to the ranging, and a fine timing measurement using the channel estimation preamble. This approach works in various environments and it requires neither knowledge about the beam characteristics of transmitters and receivers nor the use of fingerprinting. The new algorithm is validated through both, simulations and experiments. Results in an $\text{1}\;{\rm{m}} \times \text{1}\;{\rm{m}} \times \text{2}\;{\rm{m}}$ area indicate that G.9991-based positioning can reach an average distance error of a few centimeters in three dimension. Considering the common use of lighting in indoor environments and the availability of a mature optical wireless communication system using G.9991, the proposed LiFi positioning is a promising new feature that can be added to the existing protocols and enhance the capabilities of smart lighting systems further for the benefit of Industry 4.0.

Journal ArticleDOI
Fan Zhang1, Lei Zhang1, Xiaoke Ruan1, Fan Yang1, Hao Ming1, Yanping Li1 
TL;DR: In this article, the basic design of a typical carrier-depletion-based dual-drive traveling-wave Mach-Zehnder modulator (TW-MZM) is studied by simulation based on an all-silicon TW-MzM, and the transmission experiments of high baud rate single sideband 4-ary pulse amplitude modulation (PAM-4) signals with linear equalization and artificial neural network based equalization, respectively, are reported.
Abstract: We review high baud rate operation of silicon photonic modulators with emphasis on short-reach and metro-haul applications The current status of both devices and digital signal processing are discussed The basic design of a typical carrier-depletion-based dual-drive traveling-wave Mach-Zehnder modulator (TW-MZM) is studied by simulation Based on an all-silicon TW-MZM, we report the transmission experiments of high baud rate single sideband 4-ary pulse amplitude modulation (PAM-4) signals with linear equalization and artificial neural network based equalization, respectively Our work indicates all-silicon modulators can address the requirements of future optical communication systems operating at 100 Gbaud

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an all-dielectric metasurface and conduct a comprehensive analysis of the multi-Fano resonances in the structure with high Figure of Merit for the near-infrared regime.
Abstract: At present, many refractive index sensors based on plasmonic structures are inefficiency in practical applications due to the presence of metal ohmic losses. Here we propose an all-dielectric metasurface and conduct a comprehensive analysis of the multi-Fano resonances in the structure with high Figure of Merit for the near-infrared regime. The structure is composed of two silicon elliptical cylinders with asymmetric minor axe on silica substrate coated graphene. The finite-difference time-domain method for three-dimensional model is utilized for investigating the transmission spectra and electromagnetic field distributions. The results show the Fano resonances are arising from the interactions between a radiant mode and a non-radiative dark mode by adding asymmetric parameter. Four sharp Fano peaks can be observed which the maximum Q-factor can exceed 104. According to the electromagnetic field distributions, we analyze the resonant modes of the four peaks in detail and investigate the influence of geometry parameters on the resonances. Furthermore, we find that the Fano resonances are very sensitive to the background refractive index. The results show that the sensitivity of the structure can achieve 400 nm/RIU and the corresponding figure of merit can reach 3074. The proposed structure has potential application as refractive index sensor.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a robust and broadband integrated in-plane terahertz (THz) coupler based on the surface plasmon polaritons (SPPs) waveguides, conducted with the quantum engineering - Stimulated Raman Adiabatic Passage (STIRAP).
Abstract: The in-plane terahertz (THz) surface plasmon polaritons (SPPs) coupler is a key element of THz information transmission and processing. However, existing parallel coupler based on two SPPs waveguides is not robust against perturbations of geometric parameters (arising due to fabrication imperfections) and are limited by the single frequency of operation. In this work, we propose a robust and broadband integrated THz coupler based on the in-plane SPPs waveguides, conducted with the quantum engineering – Stimulated Raman Adiabatic Passage (STIRAP). Our coupler consists of two asymmetric specific curved corrugated metallic structures working as the input and output SPPs waveguides, and one straight corrugated metallic structure functioning as the middle SPPs waveguide. From the theoretical and simulated results, we demonstrate that the SPPs can be efficiently transferred from the input to the output waveguides. Our device is robust against the perturbations of geometric parameters, and meanwhile it manifests broadband performance (from 0.5 THz to 0.8 THz) with a high transmission rate over 70 ${\%}$ . This work represents a step forward for significant improvements in THz sensing, THz imaging, on-chip THz signal processing, and other next-generation THz photonic device.

Journal ArticleDOI
Baoluo Yan1, Zehui Lu1, Jinyao Hu1, Tianxu Xu1, Hao Zhang1, Wei Lin1, Yang Yue1, Haifeng Liu1, Bo Liu1 
TL;DR: In this paper, the authors demonstrate one kind of asymmetric spatial modes, namely Lommel-Gaussian (LMG) mode carrying orbital angular angular momentum (OAM) for optical communications, which possesses higher channel capacity through orthogonal multiplexing process.
Abstract: Unlike traditional symmetrical vortex beams, we demonstrate one kind of asymmetric spatial modes, namely Lommel-Gaussian (LMG) mode carrying orbital angular momentum (OAM) for optical communications, which possesses higher channel capacity through orthogonal multiplexing process. Some unique properties, such as better detection probabilities of high-order modes compared with low-order modes, are experimentally observed and well explained using theoretical models based on Rytov approximation method. An efficient scheme to generate LMG superposition states for OAM mode multicasting and multiplexing is proposed. Also, some critical issues, such as mode mismatching, still need further investigations. This work inspires us to explore more spatial multiplexing approaches, whose distinctive properties may open up new prospects for future communications systems.

Journal ArticleDOI
TL;DR: The role of plasmon resonance on the optical efficiency of nanoantennas for tip-enhanced Raman spectroscopy (TERS) is reviewed in this article.
Abstract: The role of plasmon resonance on the optical efficiency of nanoantennas for tip-enhanced Raman spectroscopy (TERS) is reviewed. Technical details on surface plasmon polaritons (SPP), localized surface plasmon resonance (LSPR), and the plasmon gap mode are provided. Nanotechnology engineering is necessary to adequate the nanoantenna's size, shape and composition to match resonance conditions with the exciting radiation source. Computational simulation guides the development of new types of plasmonic nanoantennas with different materials and morphologies, specially designed to reach target applications. An overview on a recently developed nanoantenna composed by a truncated micropyramidal body with a nanopyramid end is presented. The characteristic length $L$ of the nanopyramid tip is dimensioned to fine-tune LSPR modes, giving rise to the so-called plasmon-tunable tip pyramid (PTTP). The plasmonic properties of this type of probe were investigated by electron energy loss spectroscopy and computational simulations, reveling that PTTPs act as monopole nanoantennas. TERS results obtained with the PTTPs demonstrate the achievement of unprecedent levels of field enhancement mediated by LSPR with excellent reproducibility rate.

Journal ArticleDOI
TL;DR: This work investigates hybrid device architectures utilizing semiconductor and metallic properties of the graphene for ultrafast and energy-efficient electro-optic phase modulators on semiconductors and dielectric platforms.
Abstract: The atomic layer thin geometry and semi-metallic band diagram of graphene can be utilized for significantly improving the performance matrix of integrated photonic devices. Its semiconductor-like behavior of Fermi-level tunability allows graphene to serve as an active layer for electro-optic modulation. As a low loss metal layer, graphene can be placed much closer to active layer for low voltage operation. In this work, we investigate hybrid device architectures utilizing semiconductor and metallic properties of the graphene for ultrafast and energy-efficient electro-optic phase modulators on semiconductor and dielectric platforms. (1) Directly contacted graphene-silicon heterojunctions. Without the oxide layer, the carrier density of graphene can be modulated by direct contact to silicon layer, while silicon intrinsic region stays mostly depleted. With doped silicon as electrodes, carriers can be quickly injected and depleted from the active region in graphene. The ultrafast carrier transit time and small RC constant promise ultrafast modulation speed (3 dB bandwidth of 67 GHz) with an estimated Vπ·L of 1.19 V·mm. (2) Graphene integrated lithium niobite modulator. As a transparent electrode, graphene can be placed close to integrated lithium niobate waveguide for improving coupling coefficient between optical mode profile and electric field with minimal additional loss (4.6 dB/cm). Numerical simulation indicates a 2.5× improvement of electro-optic field overlap coefficient, with an estimated Vπ of 0.2 V.

Journal ArticleDOI
Shihao Sun1, Mingbo He1, Mengyue Xu1, Shengqian Gao1, Siyuan Yu1, Xinlun Cai1 
TL;DR: In this article, the authors discuss the technologies for realizing hybrid LN/SiPh platform and analyze the configuration and key metrics of hybrid MZM in detail, and derive functional devices derived from the Mach-Zehnder interferometer (MZI) configuration.
Abstract: Hybrid Lithium Niobate (LN) and Silicon photonic (SiPh) integration platform has emerged as a promising candidate to combine the scalability of silicon photonics with the excellent modulation performance of LN. Mach-Zehnder modulators (MZMs) based on this platform exhibit outstanding performance with low insertion loss, low drive voltage, and large bandwidth. In this paper, we discuss the technologies for realizing hybrid LN/SiPh platform. The configuration and key metrics of LN/SiPh MZM are analyzed in detail. Furthermore, various functional devices derived from the Mach-Zehnder interferometer (MZI) configuration are also reviewed.

Journal ArticleDOI
TL;DR: In this article, a phase-shift-amplified optical fiber interferometry based on microwave photonics (MWP) was proposed for sensing applications with substantially improved sensitivity, which combines a destructive interference-based phase shift amplification technique with optical carrier-based microwave interFERometry (OCMI).
Abstract: This paper proposes phase-shift-amplified optical fiber interferometry based on microwave photonics (MWP) for sensing applications with substantially-improved sensitivity. The principal idea of the system combines a destructive interference-based phase-shift amplification technique with optical carrier-based microwave interferometry (OCMI). The phase sensitivity of the OCMI system is significantly improved due to the phase amplifier, and more importantly, can be adjusted by simply varying the amplitude ratio of the two beams used in the interferometer. The amplification of the phase sensitivity is numerically investigated and experimentally demonstrated using a Mach-Zehnder interferometer for temperature and strain measurements. The measurement results accurately match theoretical predictions. Moreover, we demonstrate that light-scattering dots in the optical fiber core, created by tightly-focused femtosecond laser pulses, can be used to precisely tune the amplitude ratio of the two-beam interferometer. We postulate that amplification of several orders of magnitude in phase sensitivity can be achieved in the OCMI system by employing micromachining methods.

Journal ArticleDOI
TL;DR: In this article, a beam steering by fiber-fed passive diffractive beam steering modules and wavelength-tunable transceivers located in a separate controller location enables readily scalable connectivity to many devices and their nomadic mobility.
Abstract: By means of narrow 2D-steerable infrared beams, interference-free individual wireless connections to densely-spaced devices in industry 4.0 settings can be made. Beam steering by fiber-fed passive diffractive beam steering modules and wavelength-tunable transceivers located in a separate controller location enable readily scalable connectivity to many devices and their nomadic mobility. To accommodate the dynamics in industry 4.0 settings, self-calibrating localization of the devices by means of retro-reflecting corner cube foils and beam scanning is demonstrated, and a low-complexity broadband wide field-of-view optical wireless receiver is presented, based on a matrix of photodiodes.