Multiplexing Applications Research Articles

Ultra-compact and -broadband integrated plasmonic waveplates with high efficiency

Ultra-compact and -broadband integrated gold plasmonic half-wave and quarter-wave plates (HWP and QWP) based on the mode interference mechanism are proposed with applications in magneto-photonics, mode- and polarization-division multiplexing. The numerical simulations based on a finite element method reveals that the proposed HWP offers a maximum polarization conversion efficiency of 99.6% at a wavelength of lambda _0 = 1.55 mum with a 1 dB bandwidth of 140 nm (lambda _0 = 1.47–1.61 mum), covering 82% of the S to L telecommunication bands. In this wavelength range, HWP has an insertion loss below 2.3 dB and an extinction ratio between 9 and 24 dB, respectively. The presented QWP functions over the C telecommunication band (lambda _0 = 1.53–1.565 mum), where the transmission contrast between its transverse magnetic and electric modes is 0±0.04. Moreover, QWP offers a polarization rotation angle in the range of 45±5^circ over the same wavelength range. Finally, this paper illustrates that the proposed waveplates have a robust tolerance to fabrication errors.

Application of a dense SNP PCR multiplex for high throughput kinship determination using Next Generation Sequencing (NGS)

The need to identify large numbers of missing persons from mass disasters, armed conflicts and human rights abuses has become increasingly prevalent. The ForenSeq® Kintelligence Library Prep Kit together with NGS (sometimes called massively parallel sequencing), has been designed to interrogate 10,230 SNPs for the purpose of solving cold cases, including missing persons identification. The kit allows up to 3 samples per sequencing run in order to call sufficient SNPs for detecting relationships up to 5th degree when searching direct to consumer DNA databases, such as GEDmatch PRO™. For missing persons cases with high numbers of post-mortem (P.M.) and ante-mortem (A.M.) samples from the deceased and their family members, respectively, a higher throughput solution is required. In this report, we present the feasibility of increasing sequencing plexity for PM to 12 and AM to 32 samples using the Kintelligence kit and workflow. This generates sufficient SNP calls for kinship determination up to 3rd order. DNA was extracted from bones and dental remains, as well as artificially degraded and low input DNA to simulate P.M. samples. DNA from diverse populations was typed to simulate A.M. samples. We determined the number of called SNPs overlapping between A.M. and P.M samples from these high-plexity sequencing runs and showed the impact on two methods of estimating kinship: kinship coefficients and likelihood ratios (LR). LR and kinship coefficient decrease as fewer SNPs are called (i.e., in more challenging samples) or for more distant relationships. However, filtering on both values achieved high sensitivity and specificity out to 3rd degree. Furthermore, relationship identification out to 3rd degree was robust to loss of heterozygosity in the samples. Overall, increasing plexity can facilitate higher throughput DNA analysis of missing persons cases, without severe loss in kinship estimation.

Magnetically Tunable Micro-Ring Resonators for Massive Magneto-Optical Modulation in Dense Wavelength Division Multiplexing Systems.

We demonstrate, numerically, a new concept for on-chip magneto-optical (MO) modulation in dense wavelength division multiplexing (DWDM) applications. Our idea uses materials and mechanisms that are compatible with current silicon-on-insulator fabrication and CMOS technologies for monolithic integration. The physics behind our idea stems in the exploitation of the enhanced MO activity of a micro-ring, made of cerium substituted yttrium iron garnet (Ce:YIG) material, to actively manipulate the resonance wavelengths of an adjacent micro-ring resonator (MRR) of silicon (Si). This active manipulation of the latter MO-MRR structure is used to modulate the optical signal traveling through a side-coupled Si bus waveguide. Moreover, by proper tailoring multiple MO-MRRs (side-coupled to the single Si bus waveguide) to match wavelength channels in DWDM across the entire C-band optical communications spectrum, we extend our proposal to massive and dynamic MO modulation in DWDM applications. Significantly, we noticed that the active MO shifting of the resonant wavelength (used for MO modulation here) can be used for improvements in the spectrum utilization efficiency in future elastic optical networks (EONs).

Versatile software and hardware combo enabling photon counting acquisition and real-time display for multiplexing, 2D and continuous 3D two-photon imaging applications.

.Significance: rPySight brings a flexible and highly customizable open-software platform built around a powerful multichannel digitizer; combined, it enables performing complex photon counting-based experiments. We exploited advanced programming technology to share the photon counting stream with the graphical processing unit (GPU), making possible real-time display of two-dimensional (2D) and three-dimensional (3D) experiments and paving the road for other real-time applications.Aim: Photon counting improves multiphoton imaging by providing better signal-to-noise ratio in photon-deprived applications and is becoming more widely implemented, as indicated by its increasing presence in many microscopy vendor portfolios. Despite the relatively easy access to this technology offered in commercial systems, these remain limited to one or two channels of data and might not enable highly tailored experiments, forcing most researchers to develop their own electronics and code. We set to develop a flexible and open-source interface to a cutting-edge multichannel fast digitizer that can be easily integrated into existing imaging systems.Approach: We selected an advanced multichannel digitizer capable of generating 70M tags/s and wrote an open software application, based on Rust and Python languages, to share the stream of detected events with the GPU, enabling real-time data processing.Results: rPySight functionality was showcased in real-time monitoring of 2D imaging, improved calcium imaging, multiplexing, and 3D imaging through a varifocal lens. We provide a detailed protocol for implementing out-of-the-box rPySight and its related hardware.Conclusions: Applying photon-counting approaches is becoming a fundamental component in recent technical developments that push well beyond existing acquisition speed limitations of classical multiphoton approaches. Given the performance of rPySight, we foresee its use to capture, among others, the joint dynamics of hundreds (if not thousands) of neuronal and vascular elements across volumes, as is likely required to uncover in a much broader sense the hemodynamic transform function.

The Utilization of Tunable Transducer Elements Formed by the Manipulation of Magnetic Beads with Different Sizes via Optically Induced Dielectrophoresis (ODEP) for High Signal-to-Noise Ratios (SNRs) and Multiplex Fluorescence-Based Biosensing Applications.

Magnetic beads improve biosensing performance by means of their small volume and controllability by magnetic force. In this study, a new technique composed of optically induced dielectrodphoresis (ODEP) manipulation and image processing was used to enhance the signal-to-noise ratio of the fluorescence for stained magnetic beads. According to natural advantages of size-dependent particle isolation by ODEP manipulation, biomarkers in clinical samples can be easily separated by different sizes of magnetic beads with corresponding captured antibodies, and rapidly distinguished by separated location of immunofluorescence. To verify the feasibility of the concept, magnetic beads with three different diameters, including 21.8, 8.7, and 4.2 μm, were easily separated and collected into specific patterns in the defined target zone treated as three dynamic transducer elements to evaluate fluorescence results. In magnetic beads with diameter of 4.2 μm, the lowest signal-to-noise ratio between stained and nonstained magnetic beads was 3.5. With the help of ODEP accumulation and detection threshold setting of 32, the signal-to-noise ratio was increased to 77.4, which makes this method more reliable. With the further optimization of specific antibodies immobilized on different-size magnetic beads in the future, this platform can be a potential candidate for a high-efficiency sensor array in clinical applications.

Planar liquid crystal optics for simultaneously surface displaying and diffraction-limited focusing.

Planar optical elements have attracted widespread attentions because of their precise light modulation. Liquid crystals (LCs) are well known for their applications in the current displaying field, and show great potential in planar optical elements with the development and innovation of LC micro-operation technology. However, previous researches on LC elements mainly involved only one type of optical manipulation, which inevitably limited the functional diversity. In this work, we propose a multifunctional LC element which integrates the surface display into a binary-phase focusing lens by controlling the complex amplitude of the incident light. The light modulation of the anisotropic LC molecule satisfies a sinusoidal variation, which can be regarded as the combination of a continuous amplitude modulation and a binary phase modulation. The element with millimeter size is then fabricated, and the experimental measurements agree well with our design with a high-definition surface pattern and high-quality optical focusing/imaging performance. Furthermore, as the complex amplitude modulation changes from sine to cosine function after rotating the sample by 45°, a bifocal lens with two different focal lengths is also demonstrated. We expect the proposed multifunctional LC elements can find applications in information multiplexing, image displaying, etc.

Numerical analysis of strongly coupled multicore photonic crystal fibres for multiplexer and de-multiplexer applications

In this study, the coupling properties of multicore photonic crystal fibers (MCPCFs) are analyzed numerically using COMSOL Multiphysics 5.5, based on the finite element method. The dependence of the coupling properties on the structure of the MCPCFs and the wavelength are investigated to realize applications such as multiplexers-demultiplexers for wavelength division multiplexing. The effective mode indexes and transverse electric field distributions of multiple cores are evaluated for different spatial configurations of identical and non-identical cores. A slight change in the central core diameter relative to adjacent cores leads to non-identical cores that lead to wavelength-dependent coupling properties, such as the coupling lengths and strength of the coefficients. The results show that the coupling lengths become longer and the strength coefficients become smaller as the wavelength decreases for non-identical cores than the identical cores. The introduction of anisotropy to all core diameters shows that the coupling lengths become longer and the strength of the coefficients become smaller as the wavelength decreases as well, and both values become lower than the ones for non-identical cores. These results prove that coupling lengths of MCPCF couplers are significantly shorter in μm compared to conventional multicore optical fiber couplers.

Photonic crystal analysis for multiplexer and de-multiplexer applications

In our present work, we have made an investigation of several theoretical tools using the finite element method depending on the COMSOL MULTIPHYSICS program, for intuitive insight into the optical properties of the optical crystal. Analysis of the bandgap of a two-dimensional periodic photonic crystal with square lattice, evaluate the photonic band structure by the eigenfrequency of the unit cell of the first Brillouin zone. Moreover, creating defect mode inside the bandgap of photonic crystal, such as a resonant cavity, waveguide defect, narrowband filter, sharp drop filter, channel drop filter, waveguide bends, waveguide splitter promises us to a platform to design devices that includes a certain optical range of wavelengths. The transmission, as a result, the influence of the light localized in the defect area of the periodic structure of the photonic crystal. This study is important for producing photonic integrated circuits based on photonic crystals for future advanced optical communication.

Low-Loss Silicon Photonic 16 × 16 Cyclic AWGR Based on SOI Platform

We experimentally demonstrate a low-loss and low-crosstalk 16-channel 200 GHz-channel-spacing arrayed waveguide grating router (AWGR) with a size of 0.67 × 0.37 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , targeting for C-band wavelength division multiplexing (WDM) interconnect routing applications. As a result, the AWGR features a channel spacing of 200±10 GHz, a free spectral range of 25.62 nm and a 3 dB channel bandwidth of 0.9 nm. Based on comprehensive optimal design, the measured characterization revealed 5.55 dB maximum channel loss non-uniformity with 1.13 dB best-case channel insertion loss. Besides, the fabricated device exhibits good cyclic-frequency operation for all 16 × 16 port combinations with channel crosstalk of –15.11 dB.

Demonstration of an all-fiber cladding-pumped FM-EDFA with low differential modal gain

An all-fiber few mode erbium doped fiber amplifier (FM-EDFA) with low differential modal gain (DMG) is theoretically and experimentally demonstrated. Firstly, a double-cladding six-mode EDF (6M-EDF) with triple-layer erbium ion doping is designed and fabricated. Then, based on the homemade 6M-EDF, an all-fiber cladding-pumped FM-EDFA is implemented with high modal fidelity. Our experimental results show that the DMG is less than 2.65 dB in the wavelength range of 1535–1570 nm, the modal gains for the 6 modes are higher than 19 dB, and the noise figures are about 4.61–7.66 dB. The all-fiber FM-EDFA with low DMG offers a cost-effective and stable alternative for high-integrated all-fiber long-haul spatial division multiplexing applications.

Experimental demonstration of robust nanophotonic devices optimized by topological inverse design with energy constraint

In this paper, we present the experimental results for integrated photonic devices optimized with an energy-constrained inverse design method. When this constraint is applied, optimizations are directed to solutions that contain the optical field inside the waveguide core medium, leading to more robust designs with relatively larger minimum feature size. We optimize three components: a mode converter (MC), a 1310 nm/1550 nm wavelength duplexer, and a three-channel C-band wavelength demultiplexer for coarse wavelength division multiplexing (CWDM) application with 50 nm channel spacing. The energy constraint leads to nearly binarized structures without applying independent binarization stage. It also reduces the appearance of small features. In the MC, well-binarized design, improved insertion loss, and cross talk are obtained as a result. Furthermore, the proposed constraint improves the robustness to fabrication imperfections as shown in the duplexer design. With energy constraint optimization, the corresponding spectrum shifts for the duplexer under ± 10 nm dimensional variations are reduced from 105 nm to 55 nm and from 72 nm to 60 nm for the 1310 nm and 1550 nm channel, respectively. In the CWDM demultiplexer, robustness toward ± 10 nm fabrication error is improved by a factor of 2. The introduction of the energy constraint into topological optimization demonstrates computational gain with better-performing designs.

Computational Soliton Modulated Nonlinear Microring Add-drop Multiplexer and Potential Applications

This paper proposed the design of the multiplexer node for the free-space transmission link. Various soliton modulated signal categories are numerically studied. The proposed system is a modified micro-optical add-drop multiplexer. The cross phase modulated signals induced into the main ring by the two side rings can give more signal complexity, which can lead to having the securely transmitted signal requirement. The high optical power obtained from the soliton aspect can give long-distance communication, where the required frequency band can be improved and suitable for the required applications. For an instant, the use for the side road connection of the vehicle-to-everything (V2X) can be implemented in either cable or wireless(free-space) connection. The results obtained have shown promising applications such as free-space transmission link in both above and underground nodes, quantum cryptography, and communication security based on nonlinear aspects. Moreover, the electro-optic conversion can also be used by the stacked layers of silicon-graphene-gold, in which the signal conversion can be applied suitably.

Efficient mode coupling between a few-mode fiber and multi-mode photonic chip with low crosstalk.

The mode-division multiplexing technology has been developing slowly in the field of fiber-chip-fiber optical interconnects, mainly limited by the inefficient mode coupling between few-mode fiber and multi-mode photonic chip. Here we propose and design a multi-mode coupler composed of tapered few-mode fiber and silicon integrated multistage waveguide tapers, which allows the direct coupling between high-order fiber modes and high-order waveguide modes with high coupling efficiency and low crosstalk. Based on the edge coupling scheme, the six linear polarization modes (LP01x/y, LP11a x/y, LP11bx/y) in few-mode fiber are firstly coupled into the integrated waveguide with low insertion loss, then the input modes are converted to the desired waveguide modes (TE0, TE1, TE2, TM0, TM1, TM2) with low mode crosstalk relying on the mode evolution principle. The obtained results show that the coupling efficiency is higher than 87%, while for the mode conversion process, the efficiency is higher than 99% and the mode crosstalk is lower than -25 dB. The favorable performance achieved may open new perspectives for diverse mode-division multiplexing applications, enabling efficient capacity scaling in fiber-chip-fiber optical interconnects and optical communication systems.

Compact silicon-based polarization-independent 1.55/2 μm wavelength diplexer based on a multimode interference coupler with multiple shallow grooves

Faced with the rapid growth of internet traffic demand, which has posed a huge challenge to the current fiber-based communications systems, expanding the telecommunications bands from traditional near-infrared (NIR) region to mid-infrared (MIR) region is emerging as an attractive solution. And on-chip wavelength division multiplexing (WDM) application for NIR/MIR wavelengths is an essential element in future optical telecommunication systems. Here, we propose a compact silicon-based polarization-independent wavelength diplexer for the NIR/MIR wavelengths of 1.55/2 μm, where multiple rectangular grooves are shallowly etched on the silicon MMI waveguide for introducing the refractive-index perturbations on the MMI waveguide eigenmodes. And this refractive-index perturbation scheme provides a simple and scalable method to manipulate the four beat lengths of the two wavelengths at TE- or TM-polarization in a single waveguide via self-imaging effect, leading to a compact footprint. By optimizing the structural parameters, both NIR/MIR wavelength demultiplexing and polarization independence, for the first time, are obtained simultaneously in the present single device. From the results, the proposed diplexer is only 21.6 μm in length, and shows a wide bandwidth of ∼ 100/120 nm around the wavelength of 1.55/2 μm for insertion loss (IL) < 1 dB and extinction ratio (ER) > 15 dB. Moreover, we also realize a compact and polarization-independent wavelength diplexer for 1.31/2 μm by flexibly changing the dimensions, showing the flexibility and extensibility of our refractive-index perturbation scheme. Besides, fabrication tolerances are analyzed and mode propagation profiles are also demonstrated.

2:1 Multiplexer Design Using Lector, LCnmos, LCpmos Power Reduction Techniques with 45nm, 90nm, 180nm CMOS Technology

Today’s modern communication requires high data transmission rate and low power consumption. One of the most common concept of data transmission can be achieved by Multiplexers. The Multiplexers are the logic designs where data can be transmitted by n number of inputs over transmission path based on the selection line producing the single input. The application of Multiplexers is more active in communications system. AlsoLow power consumption and high-speed result is the major concern for choosing the digital circuits [1,2]. Here we designed 2:1 Multiplexer using CMOS technology with 45nm, 90nm, 180nm. Since CMOS offers less power consumption, we can till reduce the power consumed by using power reduction techniques. In this paper we designed and compared the 2:1 Multiplexer using Lector, LCnmos and LCpmos power reduction techniques.

Emission colour tuning of Mn, Yb, Er-NaGdF4 upconverting nanoparticles by energy density variation and pulse modulation

We describe, for the first time, the effects of Mn co-doping on the upconversion emission of Yb, Er - NaGdF4 nanoparticles using an ns pulsed laser with variable energy density and pulse width modulation. Unlike cw excitation that leaves unchanged the emission colour with power density, ns pulsed excitation induced a remarkable green to orange colour tuning with the increase of the energy density from 3 to 70 mJ/cm2. Pulse width modulation from 0.02 to 5 ms determines green to yellow colour tuning for 10% Mn, which is well-correlated with the built and decay stages of Er green and red emissions. Our study gives new insights into Mn role in colour tuning of Mn, Yb, Er - NaGdF4 nanoparticles and highlights the potential of these systems for anti-counterfeiting, bioimaging and lifetime multiplex applications.

Degree of Polarization of High-Power Laser Diodes: Modeling and Statistical Experimental Investigation

A statistical experimental investigation of the characteristic changes associated with the degree-of-polarization reduction of high-power laser diodes is reported. A simple model accounting for the stress-induced degree-of-polarization changes through the photoelastic effect is introduced to qualitatively support the experimental results. Functional characteristics addressed in the investigation are the threshold current, the slope efficiency, the polarization-resolved far field and near field, and the beam parameter product. Model outcomes and measured parameters related to different degree-of-polarization values have proven very useful for device optimization aimed to polarization multiplexing applications.

Design of 31 and 37 cores trench-assisted and air-hole assisted multi-core fibre for high-density space-division multiplexing

In this paper, we have designed two multi-core fibres (MCFs) structures with 31 and 37 trench-assisted and air-hole-assisted cores with reduced inter-core crosstalk (XT). The air-hole pairs and triplets are placed between adjacent trench-assisted cores in order to further suppress modal field overlap. The XT analysis of the 31-core design underlines the significance of enclosing the outer cores with the air-hole structure. The effect of core pitch on the XT is also investigated. Placing the low-index air-hole shield closer to the trench enhances the modal confinement within relatively large trench-assisted core structures. As a result, the lowest possible core-pitch MCF (air-holes touching outer trench boundaries) yielded a minimum inter-core XT of between −60 dB and −70 dB for 100 km of fibre length. Therefore, our 37-core MCF design is suitable for high-density space-division multiplexing applications.

Rotational Multiplexing Method Based on Cascaded Metasurface Holography

AbstractSince the emergence of optical metasurfaces, their outstanding wavefront modulation ability and numerous degrees of freedom (DOFs) have motivated many multiplexing methods, and many unprecedented functionalities and impressive advances have been achieved. However, the number of DOFs of single‐layer metasurfaces is intrinsically limited. To further explore the innovative multiplexing dimensions and application scenarios of metasurfaces, multilayer and cascaded metasurfaces are proposed. Inspired by the alignment sensitivity of cascaded metasurface holography, here the authors use the in‐plane rotation between two cascaded metasurfaces as an additional design DOF to introduce the concept of the rotational multiplexing method. An iterative gradient optimization scheme based on a machine learning method is developed to obtain the phase profiles. Dual working modes can be achieved, and both single‐layer and rotational cascaded holography can be reconstructed in the far‐field. Such versatile configurations may provide promising solutions for optical encryption, data storage, and dynamic display.

Investigation on Ultra-Compact 2DPC Coarse Wavelength Division Demultiplexer

A two dimensional Photonic Crystal (2DPC) based eight-channel wavelength division de-multiplexer is proposed and designed for Coarse Wavelength Division Multiplexing (CWDM) applications. The circular ring resonator, channel selector, circulator rod, L bend waveguide and linear bus waveguide are essential parts of the proposed system. The system’s functional parameters such as Transmission efficiency, resonant wavelength, spectral width, channel spacing, Quality factor and crosstalk investigated this paper. The eight different wavelengths of channels are filtered out by altering the size of channel selector rod, setting the radius of the circle shaped cavity and relative refractive index of circulator rod. Initially the Photonic Band gap (PBG) is manipulated by applying Plane Wave Expansion (PWE) method of the 2DPC structure. The functional parameters are analysed by Finite Difference Time Domain (FDTD) method in periodic and non-periodic structure of the proposed system to arrive normalized transmission spectrum. The resonant wavelengths of designed eight paths of the device are varying from 1420nm to 1460nm with average spectral width and channel spacing are 5.8nm, 5.6nm respectively. The footprint of the device is 286.84μm2. Hence, this small device can be implemented for CWDM systems in Photonic Integrated Circuits (PIC)