Conventional Device Structure Research Articles

Giant Colloidal Quantum Dot/α-Ga2O3 Heterojunction for High Performance UV-Vis-IR Broadband Photodetector.

Broadband optoelectronics, which extend from the UV to IR regions, are crucial for imaging, autonomous driving, and object recognition. In particular, photon detection efficiency relies significantly on semiconductor properties, such as absorption coefficients and electron-hole pair generation rate, which can be optimized by designing a suitable p-n junction. In this study, we devise giant PbS colloidal quantum dots (G-PbS CQDs) that exhibit high absorption coefficients and broadband absorption. To leverage these exceptional optical properties, we combine G-PbS CQDs with an ultrawide-bandgap semiconductor, α-Ga2O3, and create an efficient G-PbS CQD/α-Ga2O3 heterojunction photodetector that exhibits high performance across the UVC-vis-NIR spectrum range. The resultant heterojunction facilitates efficient electron-hole pair separation at the G-PbS CQD/α-Ga2O3 heterojunction. Furthermore, we utilize transparent graphene electrodes to overcome the limitations of conventional transistor-type device structures and the substantial optical losses induced by opaque metal electrodes. This strategy maximizes the light-collection area and results in an approximately 3-orders of magnitude higher responsivity (55.5 A/W) and specific detectivity (1.66 × 1013 Jones) compared to devices with opaque metal electrodes.

Performance optimisation of n-i-p type CH3NH3PbI3 based perovskite solar cells using SCAPS 1-D device simulation

Perovskite solar cells (PSCs) are emerging photovoltaic technologies with an efficiency of over 25%. PEDOT:PSS is the most commonly used hole transport material in the p-i-n type perovskite solar cell because the PEDOT:PSS dispersion is typically water-based material. Water-free PEDOT:PSS composites are used in the n-i-p architecture. The inverted PEDOT:PSS-based PSCs show 200 mV less open circuit voltage (VOC) as compared to conventional PSCs. Herein, the n-i-p type perovskite solar cell containing PEDOT:PSS as a hole transport layer is adopted to overcome the problem of open circuit voltage loss in an inverted solar cell. The design and analysis of n-i-p based perovskite solar cell is carried out using the 1D-Solar Cell Capacitance Simulator. The solar cell performance is improved by optimising the different parameters of perovskite solar cell. The optimised n-i-p structure solar cell has achieved the best power conversion efficiency of over 18% with 1.27 V open-circuit voltage for 350 nm thickness of the absorber layer. Therefore, the results provide a pathway to overcoming the voltage loss in PEDOT:PSS-based inverted PSCs by adopting a conventional device structure.

Effect of P-Type GaN Buried Layer on the Temperature of AlGaN/GaN HEMTs.

In this paper, a P-type GaN buried layer is introduced into the buffer layer of AlGaN/GaN HEMTs, and the effect of the P-type GaN buried layer on the device's temperature characteristics is studied using Silvaco TCAD software. The results show that, compared to the conventional device structure, the introduction of a P-type GaN buried layer greatly weakens the peak of the channel electric field between the gate and drain of the device. This leads to a more uniform electric field distribution, a substantial reduction in the lattice temperature of the device, and a more uniform temperature distribution. Therefore, the phenomenon of negative resistance caused by self-heating effect is significantly mitigated, while the breakdown performance of the device is also notably enhanced.

Demonstration of SiC Trench Gate MOSFETs with Narrow Cell Pitch Using Source Self-Aligned Process

The SiC trench gate MOSFET with narrow cell pitch is demonstrated using a process in which the n+ source is self-aligned to the trench gate. A minimum cell pitch of 1.6 μm, which is difficult to achieve using the conventional device structure, is easily fabricated by applying a deep n+ source and a buried interlayer dielectric structure. The cell pitch reduction indicates a beneficial trend that contributes to a decrease in the specific on-resistance and an increase in the breakdown voltage. The process and structure are promising for further improving SiC power device characteristics.

Mastering morphology of non-fullerene acceptors towards long-term stable organic solar cells

Despite the rapid progress of organic solar cells based on non-fullerene acceptors, simultaneously achieving high power conversion efficiency and long-term stability for commercialization requires sustainable research effort. Here, we demonstrate stable devices by integrating a wide bandgap electron-donating polymer (namely PTzBI-dF) and two acceptors (namely L8BO and Y6) that feature similar structures yet different thermal and morphological properties. The organic solar cell based on PTzBI-dF:L8BO:Y6 could achieve a promising efficiency of 18.26% in the conventional device structure. In the inverted structure, excellent long-term thermal stability over 1400 h under 85 °C continuous heating is obtained. The improved performance can be ascribed to suppressed charge recombination along with appropriate charge transport. We find that the morphological features in terms of crystalline coherence length of fresh and aged films can be gradually regulated by the weight ratio of L8BO:Y6. Additionally, the occurrence of melting point decrease and reduced enthalpy in PTzBI-dF:L8BO:Y6 films could prohibit the amorphous phase to cluster, and consequently overcome the energetic traps accumulation aroused by thermal stress, which is a critical issue in high efficiency non-fullerene acceptors-based devices. This work provides insight into understanding non-fullerene acceptors-based organic solar cells for improved efficiency and stability.

Double-Floating-Gate van der Waals Transistor for High-Precision Synaptic Operations

Two-dimensional materials and their heterostructures have thus far been identified as leading candidates for nanoelectronics owing to the near-atom thickness, superior electrostatic control, and adjustable device architecture. These characteristics are indeed advantageous for neuro-inspired computing hardware where precise programming is strongly required. However, its successful demonstration fully utilizing all of the given benefits remains to be further developed. Herein, we present van der Waals (vdW) integrated synaptic transistors with multistacked floating gates, which are reconfigured upon surface oxidation. When compared with a conventional device structure with a single floating gate, our double-floating-gate (DFG) device exhibits better nonvolatile memory performance, including a large memory window (>100 V), high on-off current ratio (∼107), relatively long retention time (>5000 s), and satisfactory cyclic endurance (>500 cycles), all of which can be attributed to its increased charge-storage capacity and spatial redistribution. This facilitates highly effective modulation of trapped charge density with a large dynamic range. Consequently, the DFG transistor exhibits an improved weight update profile in long-term potentiation/depression synaptic behavior for nearly ideal classification accuracies of up to 96.12% (MNIST) and 81.68% (Fashion-MNIST). Our work adds a powerful option to vdW-bonded device structures for highly efficient neuromorphic computing.

Conventional and Inverted Light-Emitting Diodes with 386 nm Emission Wavelength Based on Metal-Free Carbon Dots

Ultraviolet (UV) light-emitting diodes (LEDs) are of great concern due to wide applications in the fields of solid-state displays, photocommunication, and scientific and medical instruments. During the past 10 years, organic and inorganic semiconductors have made great breakthroughs in short-wavelength emission. Nowadays, carbon dots (CDs), which possess distinctive superiorities of high stability, nontoxicity, and low cost, are promising all-band emission materials for the next generation of LEDs. However, the fabrication of CD-based LEDs (CD-LEDs) with emission wavelengths below 400 nm is still a huge limitation in this field. Herein, we prepared UV emission CDs with the photoluminescence emission wavelength of 371 nm. The UV-CDs are perfectly compatible with both conventional and inverted device structures so as to realize the currently shortest electroluminescent emission wavelength of 386 nm for CD-LEDs. The conventional UV-CD-LEDs possess the optimum luminance of 268 cd m-2 (5427 W sr-1 m-2) with an external quantum efficiency (EQE) of 1.115%. Meanwhile, the inverted UV-CD-LEDs possess the optimum luminance of 132 cd m-2 (2673 W sr-1 m-2) with an EQE of 0.869%. This work paves a new road to manufacture carbon nanomaterial-based UV emission devices with high luminance, EQE, and stability.

Understanding the Composition of Layer‐by‐Layer Deposited Active Layer at Buried Bottom Surface

AbstractLayer‐by‐layer (LbL) coating is becoming a widely used method to fabricate nonfullerene active layer films for organic solar cells. However, the vertical compositional distribution of the LbL‐coated active layer, particularly at the buried bottom surface, is not clear yet. In common sense, it is believed that the LbL‐coating yields a donor–mixture–acceptor (D–m–A) vertical distribution in the active layer, i.e., a thin polymer donor layer at the bottom surface, a thin acceptor layer at the top surface and a donor‐acceptor mixture in the middle. In this study, it is shown that the LbL active layer vertically is an entire donor:acceptor mixture. A pure layer of polymer donor doesn't exist at the bottom surface. The LbL active layer delivers high performance in both conventional and inverted device structures. A thin polymer layer with different thicknesses (2, 6, 12 nm) is inserted at the bottom surface to study their effects on the device performance. Those inserted layers substantially deteriorate the device's performance. Furthermore, the assumption is further confirmed by X‐ray photoelectron spectroscopy measurement on the exposed “originally buried” surface. This study sheds light on understanding the vertical compositional distribution of active layer via layer‐by‐layer solution processing.

Silver decorated magnesium doped photoactive layer for improved collection of photo‐generated current in polymer solar cell

AbstractSilver doped magnesium (Ag:Mg) bimetallic nanoparticles (BMNPs) were successfully synthesized using wet chemical processing. The collection of enhanced photocurrents is possible through metal nanoparticles in the photoactive layer of a thin‐film organic solar cell (TFOSC). This investigation employed poly‐3‐hexylthiophene(P3HT) and [6‐6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) polymer blend solar absorbers in a conventional device structure. The solar cell performances were found to depend on the concentration of Ag:Mg BMNPs in the photoactive medium. Consequently, significant device performance was recorded for the solar cells containing Ag:Mg BMNPs at all doping levels compared to the un‐doped devices. Therefore, the highest power conversion efficiency (PCE) of 4.11% was achieved at a 1.5 wt% doping level with a high fill factor of 56% compared to the reference cell. The performance improvement in PCE constitutes a 79% improvement, which is much higher than undoped solar cells. This result was attributed to the occurrence of the localized surface plasmon resonance effect (LSPR), which is favorable for boosting the optical absorption and charge transport processes in TFOSC.

(Invited, Digital Presentation) Oxide TFTs Based on Semiconductors and Semimetals

Oxide semiconductors have opened a new era for large-area, flexible and transparent applications. Despite the progresses, a bottleneck issue of oxide thin-film transistors (TFTs) is the instability either under bias stress or when used as a current source. Furthermore, the carrier mobility and current driving capability need to be improved for high-spec displays. It is still hugely challenging to overcome both issues using the conventional device structure and oxide semiconductor materials.Here, we review our recent work on novel oxide TFTs that show a few desirable properties. Rather than using an ohmic metal contact as the source electrode, a high work-function Schottky source contact enables depletion around the TFT source region, which results in intrinsic immunity to the negative bias illumination stress, no obvious short channel effect, and superb current saturation over a wide range of drain voltage1. The flat saturation current gives rise to an extremely high voltage gain reaching 23,000, which is, to the best of our knowledge, the highest gain ever achieved by a solid-state transistor to date. The threshold voltage is also found to remain stable under different drain voltages, in contrast to standard TFTs, which may be useful in larger-area displays where the drain voltages of the drive TFTs can differ2. Furthermore, the depletion provided by the Schottky source electrode allows utilizing semi-metal ITO to replace IGZO as the TFT channel layer, which significantly enhances the carrier mobility and current driving capability. Other related work may also be discussed in the talk including oxide Schottky diodes operating beyond 10 GHz3, oxide TFTs operating beyond 1 GHz4, significantly enhanced carrier mobility by self-assembled monolayer treatment5,6, and CMOS-like oxide-based logic circuits7,8. References Extremely high-gain source-gated transistors, J Zhang, J Wilson, G Auton, Y Wang, M Xu, Q Xin, A Song, Proceedings of the National Academy of Sciences 116 (11), 4843-4848 (2019)Comparative Study of Short-Channel Effects Between Source-Gated Transistors and Standard Thin-Film Transistors, Zhenze Wang, Li Luo, Yiming Wang, Jiawei Zhang, and Aimin Song, IEEE Transactions on Electron Devices, 69(2), 561 - 566 (2022).Flexible indium–gallium–zinc–oxide Schottky diode operating beyond 2.45 GHz, J Zhang, Y Li, B Zhang, H Wang, Q Xin, A Song, Nature communications 6 (1), 1-7 (2015).Amorphous-InGaZnO thin-film transistors operating beyond 1 GHz achieved by optimizing the channel and gate dimensions, Y Wang, J Yang, H Wang, J Zhang, H Li, G Zhu, Y Shi, Y Li, Q Wang, Qian Xin, Zhongchao Fan, Fuhua Yang, Aimin Song, IEEE Transactions on Electron Devices 65 (4), 1377-1382 (2018).Significant Performance Improvement of Oxide Thin‐Film Transistors by a Self‐Assembled Monolayer Treatment, W Cai, J Zhang, J Wilson, J Brownless, S Park, L Majewski, A Song, Advanced Electronic Materials 6 (5), 1901421 (2020).Significant performance enhancement of very thin InGaZnO thin-film transistors by a self-assembled monolayer treatment, W Cai, J Wilson, J Zhang, J Brownless, X Zhang, LA Majewski, A Song, ACS Applied Electronic Materials 2 (1), 301-308 (2020).Complementary integrated circuits based on p-type SnO and n-type IGZO thin-film transistors, Y Li, J Yang, Y Wang, P Ma, Y Yuan, J Zhang, Z Lin, L Zhou, Q Xin, Aimin Song, IEEE Electron Device Letters 39 (2), 208-211 (2017).Thin Film Sequential Circuits: Flip-Flops and a Counter Based on p-SnO and n-InGaZnO, Y Yuan, J Yang, Y Wang, Z Hu, L Zhou, Q Xin, A Song, IEEE Electron Device Letters 42 (1), 62-65 (2020).

Improved efficiency of polymer solar cells via utilizing Alcohol-Soluble Small Molecules N-(2-Carboxyethyl)iminodi acetic acid as cathode interfacial layer

The cathode modification is vital for improving device performance of polymer solar cells (PSCs). Here, N-(2-Carboxyethyl)iminodiacetic acid (C7H11NO6) layers with different concentrations were deposited on the photoactive layer PTB7-Th:PC71BM film, and used as the cathode interface modification material for the conventional device structure of PSCs. By varying the concentration of C7H11NO6, the effect on the performance of PSCs was investigated. It was found that the efficiency of the photovoltaic device was reached as high as 8.86% at a C7H11NO6 concentration of 1 mg mL−1, which was about 56% higher than the performance of the reference device. Among them, the C7H11NO6 film acts as an effective cathode interface layers, forming an interfacial dipole on the surface of the PTB7-Th:PC71BM film to increase the built-in potential and promote photogenerated electron extraction and transport.

Power losses in conventional and inverted non-polymeric donor:fullerene bulk heterojunction solar cells - The role of vertical phase separation in BQR:PC71BM blends

The performance of bulk heterojunction (BHJ) organic solar cells can be affected by a range of factors including the materials combination, processing solvent, post deposition annealing, and/or whether they are used in a conventional or inverted architecture. In this study we compared conventional and inverted BHJ solar cells composed of a non-polymeric donor (5 Z ,5′ Z )‐5,5'‐[(5‴,5‴''''‐{4,8‐bis[5‐(2‐ethylhexyl)‐4‐ n -hexylthiophen‐2‐yl]benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl}bis{3′,3'',3‴‐trihexyl‐[2,2':5′,2'':5'',2‴‐quaterthiophene]‐5‴,5‐diyl})bis(methanylylidene)]bis[3‐ n -hexyl‐2‐thioxothiazolidin‐4‐one] (BQR) and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) as the acceptor. It was found that the conventional device structure had power conversion efficiencies nearly two and a half times that of the inverted device, 9.0% versus 4.0%. Through a combination of Shockley equivalent circuit fitting, optical modelling, and light intensity dependent photocurrent measurements we identified that the origin of the power losses for the inverted architecture relative to the conventional device structure arose from a larger component of bimolecular recombination. Neutron reflectometry measurements showed that the origin of the larger bimolecular recombination losses for the inverted device was due to the PC 71 BM phase separating, with a PC 71 BM rich layer located near the anode reducing the hole extraction efficiency. • BQR and PC 71 BM conventional and inverted BHJ solar cells are compared. • The conventional device structure was two and a half times more efficient. • Increased bimolecular recombination identified as the origin of the power losses for the inverted architecture. • A PC 71 BM rich layer near the anode reduced the hole extraction efficiency in inverted device.

Top Stack Optimization for Cu2BaSn(S, Se)4 Photovoltaic Cell Leads to Improved Device Power Conversion Efficiency beyond 6%

AbstractEarth‐abundant and air‐stable Cu2BaSnS4−xSex (CBTSSe) and related thin‐film absorbers are regarded as prospective options to meet the increasing demand for low‐cost solar cell deployment. Devices based on vacuum‐deposited CBTSSe absorbers have achieved record power conversion efficiency (PCE) of 5.2% based on a conventional device structure using CdS buffer and i‐ZnO/indium tin oxide (ITO) window layers, with open‐circuit voltage (VOC) posing the major bottleneck for improving solar cell performance. The current study demonstrates a >20% improvement in VOC (from 0.62 to 0.75 V) and corresponding enhancement in PCE (from 5.1% to 6.2% without antireflection coating; to 6.5% with MgF2 antireflection coating) for solution‐deposited CBTSSe solar cells. This performance improvement is realized by introducing an alternative successive ionic layer adsorption and reaction‐deposited Zn1−xCdxS buffer combined with sputtered Zn1−xMgxO/Al‐doped ZnO window/top contact layer, which offers lower electron affinities relative to the conventional CdS/i‐ZnO/ITO stack and better matching with the low electron affinity of CBTSSe. A combined experimental (temperature‐ and light intensity‐dependent VOC measurements) and device simulation (SCAPS‐1D) evaluation points to the importance of addressing relative band offsets for both the buffer and window layers relative to the absorber in mitigating interfacial recombination and optimizing CBTSSe solar cell performance.

Efficient InP/ZnSe/ZnS quantum dot shelling and the effect of a bi-layered organic-inorganic electron-transport layer on the performance of quantum dot light-emitting diode devices

We report the fabrication of red-emitting multi-shell InP quantum dots (QDs) via a two-pot synthesis method and their application to high-efficiency QD light-emitting diodes (QD-LEDs). We synthesized highly efficient and monodisperse deep-red-emitting InP/ZnSe/ZnS QDs with a photoluminescence quantum efficiency of 90% and a full width at half maximum of 49 nm using an eco-friendly phosphine precursor, tris(dimethylamino)phosphine. Furthermore, conventional QD-LED device structures in which metal oxide nanoparticles are used as the electron-transport layer (ETL) suffer from charge imbalance problems related to the charges injected from the cathode and anode. Therefore, in this study, we explored a new approach for efficiently balancing the electrons and holes, which involved the insertion of an additional organic layer of 2,2′,2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) between the inorganic zinc magnesium oxide (ZnMgO) as ETL and LiF as electron injection layer. The bi-layered organic-inorganic ETL reduced the electron mobility and modulated charge balance, thereby enhancing the properties of the conventional QD-LED device. The QD-LED device with the bi-layered ETL was 1.35 times and 1.36 times higher than those of the QD-LED device employing a mono-layered ZnMgO ETL, respectively.

Highly Stable SnO2-Based Quantum-Dot Light-Emitting Diodes with the Conventional Device Structure

ZnO-based electron-transporting layers (ETLs) have been universally used in quantum-dot light-emitting diodes (QLEDs) for high performance. The active surface chemistry of ZnO nanoparticles (NPs), however, leads to QLEDs with positive aging and unacceptably poor shelf stability. SnO2 is a promising candidate for ETLs with less reactivity, but NP agglomeration in nonionic solvents makes the conventional device structure abandoned, resulting in QLEDs with extremely low operational lifetimes. The large barrier for electron injection also limits the electroluminescence efficiency. Here, we report one solution to all the above-mentioned problems. Owing to the strong HO-SnO2 coordination and the steric effect provided by the hydrocarbon groups, tetramethylammonium hydroxide can stabilize SnO2 NPs in alcohol, while its intrinsic dipole induces a favorable electronic-level shift for charge injection. The SnO2-based devices, with the conventional structure, exhibit not only the most efficient electroluminescence among ZnO-free QLEDs but also an operational lifetime (T95) over 3200 h at 1000 cd m-2, which is comparable with that of state-of-the-art ZnO-based devices. More importantly, the superior shelf stability means that the TMAH-SnO2 NPs are promising to enable QLEDs with real stability.

Preparation of PdO-decorated NiO porous film on ceramic substrate for highly selective and sensitive H2S detection

This work is to develop high-performance thin film gas sensors on the alumina ceramic substrate. Here, porous NiO films of about 2 μm were obtained by the simple electrochemical deposition technique. The NiO gas sensing thin films obtained by the in-situ growth overcomes the disadvantages of great thickness, material agglomeration, and uneven size of the conventional device structure. The films exhibit good uniformity, consistency, and reproducibility. The composition of the films and their porous morphological characteristics were demonstrated by SEM, XRD, AFM, and XPS characterization. The doping of PdO significantly enhanced the sensitivity and specificity selection of the NiO films for H2S gas. 2 wt% PdO/NiO thin film sensor exhibited a high response (515.27) and fast dynamic process at 155 °C for 10 ppm H2S. The outstanding gas-sensing performance of the thin film sensor is due to the doping of PdO and the porous structure of the film.

Enhanced Electroluminescence via a Nanohybrid Material Consisting of Aromatic Ligand-Modified InP Quantum Dots and an Electron-Blocking Polymer as the Single Active Layer in Quantum Dot-LEDs.

Electron overcharge causes rapid luminescence quenching in the quantum dot (QD) emission layer in QD light–emitting diodes (QD–LEDs), resulting in low device performance. In this paper we describe the application of different aromatic thiol ligands and their influence on device performance as well as their behavior in combination with an electron blocking material (EBM). The three different ligands, 1–octanethiol (OcSH), thiophenol (TP), and phenylbutan–1–thiol (PBSH), were introduced on to InP/ZnSe/ZnS QDs referred to as QD–OcSH, QD–TP, and QD–PBSH. PBSH is in particular applied as a ligand to improve QD solubility and to enhance the charge transport properties synergistically with EBM probably via π–π interaction. We synthesized poly-[N,N-bis[4-(carbazolyl)phenyl]-4-vinylaniline] (PBCTA) and utilized it as an EBM to alleviate excess electrons in the active layer in QD–LEDs. The comparison of the three QD systems in an inverted device structure without the application of PBCTA as an EBM shows the highest efficiency for QD–PBSH. Moreover, when PBCTA is introduced as an EBM in the active layer in combination with QD–PBSH in a conventional device structure, the current efficiency shows a twofold increase compared to the reference device without EBM. These results strongly confirm the role of PBCTA as an EBM that effectively alleviates excess electrons in the active layer, leading to higher device efficiency.

Diamond Nanowire Transistor with High Current Capability

Carrier confinement in nanowire (NW) structures can offer a host of new material properties compared to bulk electronic devices. Diamond can be considered an ultimate semiconductor given its superlative electronic, physical, and optical properties. However, the development of diamond device technology has been hindered by doping problems in conventional device structures. Here, heavily doped diamond NWs, some 15 nm wide and only 1–2 nm deep overcome these issues and offer a significant advance in NW technology; transistor action can be induced with remote side gates alone, without the need for semiconductor junctions. Quasi‐ballistic transport is most‐likely responsible for extraordinary current handling capability of the NW transistors fabricated here at some 20 MA cm−2, being around 0.04 G0. This unipolar technology opens up a new paradigm in diamond nanoelectronic device technology.

Constructing all-solution-processed green phosphorescent organic light-emitting diodes based on zinc sulfide QDs as an electron injection layer

We have demonstrated an all-solution-processed multi-layer green phosphorescent organic light-emitting diodes(OLEDs) using zinc sulfide quantum dots (ZnS QDs) based electron injection layer (EIL) in the conventional device structure. The ZnS QDs EIL with proper work function offers efficient electron injection and retains the solvent resistance to the adjacent electron transportation layer. By inserting of a poly-ethyleneimine(PEI) interlayer between the emitting layer and electron transportation layer, solvent can be prevented from permeating through the emissive layers beneath and no additional injection barrier is formed. Thereby, the all-solution-processed OLED with a ZnS QDs EIL exhibits a highest current efficiency of 12.5 cd A−1 based on the PVK: Ir(ppy)3 emitter, achieving a 27.6% improvement in comparison to the reference without a ZnS QDs EIL. Our results provide a facile approach for the development of all-solution-processed OLEDs.

Ultra-Compact Mode-Division Multiplexed Photonic Integrated Circuit for Dual Polarizations

Polarization and mode division multiplexing are powerful tools for large-capacity parallel optical communications. Dual-polarization and mode-division multiplexed silicon photonic integrated circuit with ultra-small footprint is proposed and experimentally demonstrated. The circuits consist of a mode multiplexer, 3-dB power splitter and two demultiplexers which can simultaneously handle TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> mode. Compared with conventional device structure, the device footprint is scaled down via pixelated waveguide meta-structure. The mode multiplexer and the splitter have a footprint of only 6.8 μm × 6 μm and 6 μm × 5.25 μm, respectively. The fabrication tolerance on the nanohole size variations are studied, and the fabricated devices are systematically characterized. The measured insertion losses of the multiplexer and 3-dB power splitter are below 1.4 dB and 4.5 dB for all four modes within the wavelength range from 1530 nm-1570 nm. In the meantime, the measured maximum inter-mode cross talk is below -15 dB over a 30 nm bandwidth. The experimental results also indicate the power imbalance of the splitter is within 0.4 dB from 1530 nm-1570 nm. Since the demonstrated polarization and mode handling devices via pixelated meta-structures occupy significantly smaller chip area than conventional wisdoms, this work shows the potential for large scale and dense integration of polarization and mode division multiplexing system on photonic chip.