PD Array Research Articles

Overlapping Signals Separation for Two Light Sources Based on Mode-Mixed PD Arrays

Overlapping Signals Separation for Two Light Sources Based on Mode-Mixed PD Arrays

Optical Integrated Sensing and Communication System Based on Combination of OIRS and PD Array for Mobile Scenarios

Optical Integrated Sensing and Communication System Based on Combination of OIRS and PD Array for Mobile Scenarios

Compact OWC Receiver: Micro-Lens and PD Array on Glass Interposer

In this paper, we propose a compact optical wireless receiver based on micro-lens and photodiode array flip-chipped on a glass interposer. With simulation models and experiments, we verify the performance of two optical wireless communication receivers assembled based on this structure with gigabit and high-speed photodiodes. First, co-integrated gigabit photodiodes and micro-lenses indicate that micro-lenses can deliver a 3.5 dB gain of light collection efficiency to the gigabit photodiode array while keeping the field of view larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 18 degrees. Besides, a 5.5 Gbps maximum throughput has been verified by this optical wireless communication receiver with discrete multitone modulation. Moreover, co-integrated high-speed photodiodes and micro-lenses prove that micro-lenses realize a 26.6 dB improvement in light collection efficiency, enabling a 10 Gbps error-free connection using as little as -0.5 dBm transmission power. Those results conclude that the co-integration of micro-lenses on the photodiode array can enhance the light collection efficiency of the photodiode array while keeping a larger field of view, providing a high-performance, low-cost solution for the receiver of optical wireless links.

Highly Sensitive SPAD-Based Receiver for Dimming Control in LiFi Networks

Visible light communication (VLC) is an emerging mode of wireless communication that supports both illumination and communication. One essential function of VLC systems is the dimming control, which requires a sensitive receiver for low-light conditions. The use of an array of single-photon avalanche diodes (SPADs) is one promising approach to enhancing receivers’ sensitivity in a VLC system. However, because of the non-linear effects brought on by the SPAD dead time, an increase in the brightness of the light might degrade its performance. In this paper, an adaptive SPAD receiver is proposed for VLC systems to ensure reliable operation under various dimming levels. In the proposed receiver, a variable optical attenuator (VOA) is used to adaptively control the SPAD’s incident photon rate according to the instantaneous received optical power so that SPAD operates in its optimal conditions. The application of the proposed receiver in systems with various modulation schemes is investigated. When binary on–off keying (OOK) modulation is employed due to its good power efficiency, two dimming control methods of the IEEE 802.15.7 standard based on analogue and digital dimming are considered. We also investigate the application of the proposed receiver in the spectral efficient VLC systems with multi-carrier modulation schemes, i.e., direct current (DCO) and asymmetrically clipped optical (ACO) orthogonal frequency division multiplexing (OFDM). Through extensive numerical results, it is demonstrated that the suggested adaptive receiver outperforms the conventional PIN PD and SPAD array receivers in terms of bit error rate (BER) and achievable data rate.

High-Power and High-Speed Ge/Si Traveling-Wave Photodetector Optimized by Genetic Algorithm

We experimentally demonstrate a 4-stage and an 8-stage Ge/Si distributed traveling-wave photodetectors (TWPDs) with high RF output powers and large bandwidths. The genetic algorithm is utilized to synergistically optimize multiple relevant design parameters, including the dimension of the coplanar waveguide electrode and the aperiodic arrangement of the PD array. After the genetic algorithm optimization, the 3dB bandwidth of the 4-stage TWPD is improved from 46 GHz to 54 GHz under the constraint that the bandwidth of the unterminated single PD element is 50 GHz. Meanwhile, the 3dB bandwidth of the 8-stage TWPD is improved from 33 GHz to 40 GHz. A good agreement between measured and calculated frequency responses is obtained. The measured maximum RF output powers of the aperiodic 4-stage and 8-stage TWPDs at 30 GHz are 2.5 dBm and 6.3 dBm, respectively. Furthermore, the effectiveness of our design methodology is verified by measurement results of devices fabricated at different silicon photonics foundries.

Investigation on the hemispherical array structure for VLC transceiver

To achieve high quality, strong adaptability, and stability of visible light communication system, this paper plans to study the hemispherical array structure to realize the alignment of the light path. The structured surface covers multiple LED and PD detection arrays according to the longitude and weft direction, realizing the bidirectional sending and receiving model. It is demonstrated that the effective light intensity ratio of the hemispherical array is higher than that of the planar array, and the interference between channels of the hemispherical array is less than that of the planar array under the same conditions. In addition, the influence mechanism of optical mechanism parameters (transceiver hemisphere array radius, LED tilt angle, and PD tilt angle) on beam scattering is established, and the influence of relative position changes between LED array and PD array on communication performance is clarified.

Atomic Heterointerface Boosts the Catalytic Activity toward Oxygen Reduction/Evolution Reaction

AbstractInterface engineering is an efficient strategy to enhance the electrocatalytic activity of hybrid materials by taking advantage of the synergistic effect of double or even multiple active sites. Here, the rational design of a Pd/NiO atomic interface with well patterned Pd arrays imbedded into NiO thin films are reported to boost the catalytic activity toward the oxygen reduction/evolution reaction. Theoretical analysis elucidates that the Pd (111)/NiO (111) interface with minimized lattice mismatch effectively adsorbs intermediates (OH*, LiO2*, Li2O2*, and Li2O*) and induces the growth/decomposition of electrochemical reaction products, which greatly lowers the Gibbs energy barrier of crucial steps and boosts the reaction kinetics. As expected, such hybrid thin films exhibit high catalytic activity for both the oxygen reduction reaction and oxygen evolution reaction, with performance comparable to the benchmarked Pt/C and RuO2 catalysts. Moreover, favorable performance is also achieved in both aqueous Zn–air batteries and aprotic Li–air batteries with an overpotential of only 0.69 and 0.50 V, respectively. This work suggests the great potential of such particularly morphological hybrid thin films in the development of high‐performance catalysts for energy storage and conversion.

A sponge like Pd arrays on Ni foam substrate: Highly active non-platinum electrocatalyst for methanol oxidation in alkaline media

In order to commercialize direct methanol fuel cells (DMFCs), the selection of the appropriate catalysts for the replacement of platinum is a basic factor. Herein, we report a sponge like Pd arrays on Ni foam (NF) substrate which is successfully synthesized by a template method. The surface of NF is covered with patterned mesoporous silica (NF-PMS) through electro-assisted self-assembly (EASA) method and Pd nanoparticles are deposited on NF-PMS via the galvanic replacement reaction. After template removal, the synthesized catalyst viz. Pd2/NF-PMS is used for electrocatalytic oxidation of methanol in the alkaline media. The efficiency of template method is proved with the comparison between electrocatalytic activity of Pd2/NF-PMS and Pd2/NF. The synthesized catalyst show more than 5 times higher mass activity and significantly lower onset potential for methanol oxidation as compared with the state-of-the-art Pt/C as well as high antipoisoning property. The excellent results propose Pd2/NF-PMS as an excellent candidate anode for electrocatalytic oxidation of methanol.

Multisensor Systems by Electrochemical Nanowire Assembly for the Analysis of Aqueous Solutions.

The development of electrochemical multisensor systems is driven by the need for fast, miniature, inexpensive, analytical devices, and advanced interdisciplinary based on both chemometric and (nano)material approaches. A multicomponent analysis of complex mixtures in environmental and technological monitoring, biological samples, and cell culture requires chip-based multisensor systems with high-stability sensors. In this paper, we describe the development, characterization, and applications of chip-based nanoelectrochemical sensor arrays prepared by the directed electrochemical nanowire assembly (DENA) of noble metals and metal alloys to analyze aqueous solutions. A synergic action of the electrode transducer function and electrocatalytic activity of the nanostructured surface toward analytes is achieved in the assembled metal nanowire (NW) sensors. Various sensor nanomaterials (Pd, Ni, Au, and their multicomponent compositions) can be electrochemically assembled on a single chip without employing multiple cycles of photolithography process to realize multi-analyte sensing applications as well as spatial resolution of sensor analysis by this single-chip multisensor system. For multi-analyte electrochemical sensing, individual amperometric signals of two or more nanowires can be acquired, making use of the specific electrocatalytic surface properties of the individual nanowire sensors of the array toward analytes. To demonstrate the application of a new electrochemical multisensor platform, Pd-Au, Pd-Ni, Pd, and Au NW electrode arrays on a single chip were employed for the non-enzymatic analysis of hydrogen peroxide, glucose, and ethanol. The analytes are determined at low absolute values of the detection potentials with linear concentration ranges of 1.0 × 10−6 − 1.0 × 10−3 M (H2O2), 1.5 × 10−7 − 2.0 × 10−3 M (glucose), and 0.7 × 10−3 − 3.0 × 10−2 M (ethanol), detection limits of 2 × 10−7 M (H2O2), 4 × 10−8 M (glucose), and 5.2 × 10−4 M (ethanol), and sensitivities of 18 μA M−1 (H2O2), 178 μA M−1 (glucose), and 28 μA M−1 (ethanol), respectively. The sensors demonstrate a high level of stability due to the non-enzymatic detection mode. Based on the DENA-assembled nanowire electrodes of a compositional diversity, we propose a novel single-chip electrochemical multisensor platform, which is promising for acquiring complex analytical signals for advanced data processing with chemometric techniques aimed at the development of electronic tongue-type multisensor systems for flexible multi-analyte monitoring and healthcare applications.

Batch fabrication of nanogap electrodes arrays with controllable cracking for hydrogen sensing

Hydrogen sensor based on Pd nanogap arrays was fabricated using the swelling induced cracking method. The square hole Pd array is patterned on the polymer to define the position of the nanogaps. We discuss the influence of the size and the shape of the holes on the formed nanogaps. The structural and morphological characteristics of the metal array and the nanogaps were investigated using laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). To illustrate an application of the nanogap structure, the Pd nanogap array was deposited on epoxy and polyimide (PI) substrate and used as H2 sensor, showing a good sensitivity and stability at room temperature. Moreover, the performance of the nanogap array on PI substrate remains stable after annealing at 80–180 °C. This effect is attributed to the high thermal stability of the PI substrate. The effective fabrication method, good sensitivity and the high stability of the Pd nanogap arrays show promising application for H2 sensing.

Contiguous multiple π-coordination of π-conjugated polyenes: bonding nature and charge delocalization behaviour of polyene-(palladium chain) sandwich clusters.

The contiguous multiple π-coordination (CMπC) bonds are formed at the molecular interface between the extended π-conjugated sp2-carbon framework and metal-metal moieties. However, the static properties including the bonding nature of the CMπC bonds have not been well-understood. Here we report the charge delocalization behavior and bonding nature of the polyene-(palladium chain) sandwich clusters. We observed the chain-length dependent 13C NMR chemical shifts of the terminal phenyl groups in [Pdm{Ph(CH[double bond, length as m-dash]CH)m+1Ph}2][B(ArF)4]2 (m = 3, 4, 5, 6), showing the efficient delocalization of positive charge over the polyene ligands. Furthermore, the detailed molecular orbital analysis of several model clusters provides insights into the bonding nature of the μ-η2:(η2:)nη2- and μ-η3:(η2:)nη3-poylene palladium chain sandwich clusters, where the former type is attributed to the corner-sharing Pd array and the latter to the edge-sharing/corner-sharing hybrid Pd array. The analogy of the μ-η3:(η2:)nη3-type with the carbonyl-bridge coordination is discussed. The Pd string in each mode of sandwich chain clusters has a weak M-M bonding interaction.

4 channel × 10 Gb/s bidirectional optical subassembly using silicon optical bench with precise passive optical alignment.

We demonstrate an advanced structure for optical interconnect consisting of 4 channel × 10 Gb/s bidirectional optical subassembly (BOSA) formed using silicon optical bench (SiOB) with tapered fiber guiding holes (TFGHs) for precise and passive optical alignment of vertical-cavity surface-emitting laser (VCSEL)-to-multi mode fiber (MMF) and MMF-to-photodiode (PD). The co-planar waveguide (CPW) transmission line (Tline) was formed on the backside of silicon substrate to reduce the insertion loss of electrical data signal. The 4 channel VCSEL and PD array are attached at the end of CPW Tline using a flip-chip bonder and solder pad. The 12-channel ribbon fiber is simply inserted into the TFGHs of SiOB and is passively aligned to the VCSEL and PD in which no additional coupling optics are required. The fabricated BOSA shows high coupling efficiency and good performance with the clearly open eye patterns and a very low bit error rate of less than 10-12 order at a data rate of 10 Gb/s with a PRBS pattern of 231-1.

Magnetization-Switching Study of fcc Fe–Pd Nanowire and Nanowire Arrays Studied by In-Field Magnetic Force Microscopy

Using electrodeposition into anodic aluminum oxide (AAO) membranes, we have successfully fabricated near-equiatomic Fe48±3Pd52±3 nanowires (NWs) with the diameter of $\approx 200$ nm and the length of $\approx 3.5~\mu{\rm m}$ . X-ray diffraction and transmission electron microscopy/selected-area electron diffraction analyses revealed that the as-deposited NWs are isotropic and polycrystalline with an average crystal size of 5 nm and have an fcc crystal structure. Magnetic force microscopy (MFM) on a single Fe–Pd NW revealed its single-domain behavior with the easy axis of magnetization along the long axis of the NW. The magnetizationswitching behavior of a single Fe–Pd NW studied with the MFM suggested a square-shaped magnetization curve $(M/Ms = 1)$ with $H_{C\Vert} \approx 3.2$ kA/m. In addition, using in-field MFM techniques, the effects of dipolar interactions in an Fe–Pd array of NWs still embedded in the AAO were determined. It was found that the dipolar interactions greatly reduce the parameters of the magnetization hysteresis loop, such as the coercivity, the remanence, and the switching-field distribution of the Fe–Pd NW array.

A 40 Gb/s Optical Bus for Optical Backplane Interconnections

Optical technologies have received large interest in recent years for use in board-level interconnects. Polymer multimode waveguides in particular, constitute a promising technology for high-capacity optical backplanes as they can be cost-effectively integrated onto conventional printed circuit boards (PCBs). This paper presents the first optical backplane demonstrator based on the use of PCB-integrated polymer multimode waveguides and a regenerative shared bus architecture. The backplane demonstrator is formed with commercially-available low-cost electronic and photonic components onto conventional FR4 substrates and comprises two opto-electronic (OE) bus modules interconnected via a prototype regenerator unit. The system enables interconnection between the connected cards over four optical channels, each operating at 10 Gb/s. Bus extension is achieved by cascading OE bus modules via 3R regenerator units, overcoming therefore the inherent limitation of optical bus topologies in the maximum number of cards that can be connected to the bus. Details of the design, fabrication, and assembly of the different parts of this optical bus backplane are presented and related optical and data transmission characterisation studies are reported. The optical layer of the OE bus modules comprises a four-channel three-card waveguide layout that is compatible with VCSEL/PD arrays and ribbon fibres. All on-board optical paths exhibit insertion losses below 13 dB and intra-channel crosstalk lower than -29 dB. The robustness of the signal distribution from the bus inputs to all respective bus output ports in the presence of input misalignment is demonstrated, while 1 dB input alignment tolerances of approximately ±10 μm are obtained. The electrical layer of the OE bus modules comprises the essential driving circuitry for 1×4 VCSEL and PD arrays and the corresponding control and power regulation circuits. The interface between the optical and electrical layers of the bus modules is achieved with simple OE connectors that enable end-fired optical coupling into and out of the on-board polymer waveguides. The backplane demonstrator achieves error-free (BER <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) 10 Gb/s data transmission over each optical channel, enabling therefore, an aggregate interconnection capacity of 40 Gb/s between any connected cards.

Low Cost, Precision, Passive-Alignment Technique for 100 Gb/s DP-QPSK Receiver

We propose and develop a passive alignment technique of 4 output waveguides of PLC-based 90° OH and a 1×4 PD array. This alignment technique only uses an infrared CCD camera and an infrared light.

Terabit/Sec VCSEL-Based 48-Channel Optical Module Based on Holey CMOS Transceiver IC

We report here on the design, fabrication and characterization of 48-channel parallel optical transceivers demonstrating terabit/sec data transfer rate. The 0.48 Tb/s transmit plus 0.48 Tb/s receive throughput was achieved using a second-generation single-chip holey CMOS transceiver IC. In addition to 24 receiver (RX) and 24 laser diode driver circuits, the 5.2 mm × 5.8 mm single CMOS chip incorporates 48 through-substrate optical vias (holes), one for each transmitter (TX) and RX channel. A complete holey Optochip is formed following direct flip-chip attachment of 24-channel 850-nm VCSEL and PD arrays. The 48 optical vias enable optical access to the 24 VCSELs and 24 PDs. The holey Optochip concept provides a dense chip-scale package which is fully compatible with industry-standard top emitting/detecting 850-nm VCSELs/PDs providing optimized high-speed performance through close integration of the optoelectronic (OE) devices with their drive electronics. Furthermore, the optical vias and OE devices are arranged in a 4 × 12 array on 250 μm × 250 μ m pitch to facilitate direct fiber-coupling to a standard 4 × 12 multi-mode fiber array. The Optochips are packaged into complete modules by flip-chip soldering to high-density, high-speed organic carriers. A pluggable connector soldered to the bottom of the carrier provides all module electrical I/O. The 18 mm × 18 mm overall module area is dictated by the 0.8 mm-pitch ball grid array (BGA) of the organic carrier and connector. Fully functional holey Optomodules with 24 TX and 24 RX channels operate up to 20 Gb/s/ch achieving efficiencies (including both TX and RX) of 7.3 pJ/bit. The terabit/sec data rate (480 Gb/s TX + 480 Gb/s RX) is highest reported for single-chip CMOS transceiver modules.

The fabrication of palladium hollow sphere array and application as highly active electrocatalysts for the direct oxidation of ethanol

SiO 2 opals template was prepared on Au substrate with vertical deposition technique from highly monodispersed SiO 2 particles. After that, Pd was electrodeposited on the SiO 2 spheres to fabricate the Pd hollow sphere array after the removal of the SiO 2 template with HF solution. The prepared Pd array had a highly ordered structure with huge surface area and exhibited excellent electrocatalytic activity, stability and anti-poison capability for ethanol electrooxidation in alkaline media, which showed that the Pd hollow sphere array could be used as effective electrocatalysts for direct alcohol fuel cells.

Transcriptome analysis of HTLV-1-infected cells in comparison to the normal and Tax-expressing T cells

The transactivator protein of HTLV, Tax, is required for the activity of viral promoter LTR (long terminal repeat) and is capable of regulating both virus and host transcription. Tax is known to interact with several cellular factors including CREB/ATF, NF-κB and those involved in chromatin remodeling, cell cycle and DNA damage/repair. However, the process of Tax-mediated transactivation of chromosomally integrated LTR is not fully understood. Therefore, we have performed an extensive Protein/DNA transcription factor array (PD array I, Panomics) analysis on the HTLV-1 infected cells (MT-2) in comparison to the Tax-expressing cells (C8166) and normal T cells (Jurkat). Besides known factors, significant changes were observed in several new nuclear and cytoplasmic factors such as RxR, AP-1, AP-2, in both MT-2 and C8166 cells as compared to Jurkat indicating an overlap with viral replication and Tax-activity. Interestingly, MT-2 cells demonstrated the down-regulation of majority of the factors analyzed while several nuclear (NF-E1, NF-E2, TFIID) and cytoplasmic (MEF-1, RAR) factors were upregulated in C8166 suggesting Tax activity independent of viral replication. Overall, this data suggest that more scrutiny on nuclear and cytoplasmic factors associated with Tax transactivation process is needed to clearly elucidate the mechanism underlying adult-T-cell leukemia and tropical spastic paraparesis associated with HTLV-1 infection.

Steering Epitaxial Alignment of Au, Pd, and AuPd Nanowire Arrays by Atom Flux Change

We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO(3) substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations.

Low-cost high-efficiency optical coupling using through-silicon-hole in parallel optical transceiver module

We present a cost-efficient parallel optical transceiver module based on a 1×4 VCSEL array, a 1×4 PD array, and a 12-wide multimode fiber ribbon for very-short-reach application. A passive alignment technique using through-silicon-hole (TSH) has been developed to realize high-efficient butt-coupling between optoelectronic arrays and multimode fibers. In this paper, the detail optical coupling structure, misalignment tolerance, micro-assembly process, and measurement results are mainly discussed. Finally, lensed multimode fibers formed by chemical etching are proposed, which exhibit a great potential for further improvement of coupling performance.