Reconfigurable Mode Research Articles

Reconfigurable mode converter based on a Sb2Se3 phase change material and inverse design

In this paper, we combine the inverse design with a silicon-Sb2Se3 hybrid platform to design an on-chip mode converter that converts basic modes to higher-order modes. Firstly, we present a 1 × 2 mode converter with dimensions of 4.8 × 2.7 µm2 that enables TE0 mode input, TE0 or TE1 output in the C-band (1530 nm to 1565 nm) with an insertion loss (IL) of less than 0.8 dB and a crosstalk (CT) of less than -13 dB. Secondly, the device is extended to a 1 × 3 switchable three-mode converter. Using two controllable phase change regions as drivers, it can flexibly control the switching from TE0 mode input to three modes of TE0, TE1, or TE2 outputs, which enables mode switching and signal routing. The device can be switched between three modes and has broad application potential in broadband optical signal processing for mode division multiplexing systems, as well as optical interconnections. Finally, the device is extended to a 1 × 2 controllable (mode and power) beam splitter, which can control the power ratio between output modes. By modulating the crystallinity of Sb2Se3, the simulation achieves a multilevel switching of 36 levels (> 5-bit). These devices pave the way for high integration densities in future photonic chips.

Compact multichannel reconfigurable mode demultiplexer enabled by phase change material

The reconfigurable mode demultiplexer is a crucial component for flexibly routing modes into different channels in on-chip multimode photonic systems with enhanced information processing capabilities. In this paper, we present a multichannel reconfigurable mode demultiplexer enabled by ultralow-loss phase-changing Sb2Se3. By harnessing the phase-change-mediated mode coupling in asymmetric directional couplers (ADCs), one or more of the higher-order modes including TE1, TE2 and TE3 modes could be selectively dropped from the bus waveguide with low losses. With an optimized ADCs structure, the proposed mode demultiplexer demonstrates insertion loss less than 0.227 dB in the ON (amorphous) state and the extinction ratios large than 23.28 dB over the C-band. By coupling the access waveguides of the higher-order mode in parallel on both sides of the bus waveguide, the device size can be compact with a footprint of ∼ 7 × 75 µm2, and this design approach can be further extended to enable more higher-order mode multiplexing.

Mode multicasting without parasitic wavelength conversion.

Optical multicasting, which involves delivering an input signal to multiple different channels simultaneously, is a key function to improve network performance. By exploiting individual spatial modes as independent channels, mode-division-multiplexing (MDM) can solve the capacity crunch of traditional standard single-mode fiber (SSMF) transmission system. In order to realize mode multicasting with high flexibility in future hybrid wavelength-division-multiplexing (WDM) and MDM networks, we propose a mode multicasting scheme without parasitic wavelength conversion, based on the inter-modal four-wave mixing (FWM) arising in the few-mode fiber (FMF). The operation mechanism including nonlinear phase shift for efficient mode multicasting is analytically identified. Then, based on the derived operation condition, we numerically investigate the impact of the dual-pump power and the FMF length on the performance of mode multicasting. By properly setting the pump wavelength and the dual-pump power, mode multicasting performance, in terms of mode multicasting efficiency, 3-dB bandwidth, and destination wavelength, can be tuned according to various application scenarios. After the performance optimization, mode multicasting of 25-Gbaud and 100-Gbaud 16-quadratic-amplitude modulation (16-QAM) signals is numerically demonstrated. The proposed reconfigurable mode multicasting is promising for future WDM-MDM networks.

Broadband and compact reconfigurable polymeric thermo-optic mode converter based on cascaded Y-junctions

We propose and demonstrate experimentally a thermo-optically reconfigurable mode converter based on cascaded Y-junctions on a polymer waveguide platform. The proposed device, which can achieve reconfigurable mode conversion between the LP01 and LP11a modes, features compact, broadband, and low-power. Our typical fabricated mode converter has a footprint of 1.5 mm × 66.2 μm. The power consumptions of each heater for achieving the LP01-to-LP11a and LP11a-to-LP01 mode conversions are 32 mW and 28 mW, respectively. The mode crosstalks are as low as −20.7 dB and −18.9 dB for the x- and y-polarized LP01 modes over the wavelength range of 1530–1600 nm, respectively. Our proposed mode converter could find applications in reconfigurable mode-division multiplexing optical communication systems.

Chip-to-chip optical multimode communication with universal mode processors

The increasing amount of data exchange requires higher-capacity optical communication links. Mode division multiplexing (MDM) is considered as a promising technology to support the higher data throughput. In an MDM system, the mode generator and sorter are the backbone. However, most of the current schemes lack the programmability and universality, which makes the MDM link susceptible to the mode crosstalk and environmental disturbances. In this paper, we propose an intelligent multimode optical communication link using universal mode processing (generation and sorting) chips. The mode processor consists of a programmable 4 × 4 Mach Zehnder interferometer (MZI) network and can be intelligently configured to generate or sort both quasi linearly polarized (LP) modes and orbital angular momentum (OAM) modes in any desired routing state. We experimentally establish a chip-to-chip MDM communication system. The mode basis can be freely switched between four LP modes and four OAM modes. We also demonstrate the multimode optical communication capability at a data rate of 25 Gbit/s. The proposed scheme shows significant advantages in terms of universality, intelligence, programmability and resistance to mode crosstalk, environmental disturbances, and fabrication errors, demonstrating that the MZI-based reconfigurable mode processor chip has great potential in long-distance chip-to-chip multimode optical communication systems.

Design and Test of Embedded Reconfigurable Mode Converter Based on Spontaneous Deformable Materials.

The mode converter, as a passive mode conversion device in transmission lines, is well-investigated and widely implemented in various electromagnetic systems. However, most traditional mode converters can only realize a single conversion mode. Thus, a mode converter achieving multiple controllable output modes is urgently needed. In this paper, a reconfigurable mode converter operating in the microwave range is achieved by embedding a deformable all-dielectric material with quadrilateral shape into a rectangular waveguide based on coupled-mode theory. It can achieve different target modes with controllable output for the same input by exciting the deformable all-dielectric material. The design principle of the mode converter is expounded concretely and simulation is carried out using HFSS software 2022 R2. Experimental results, consisting of the simulation results, demonstrate that the proposed mode converter can achieve various mode conversions with mode purity higher than 95%. This article innovatively applies deformable materials to waveguide mode conversion, expanding the application of deformable memory materials in electromagnetic devices.

Inverse design of deformed Sb2Se3 stripes in silicon waveguide for reconfigurable mode converters

Reconfigurable photonic devices integrated with silicon waveguides are important building blocks for future on-chip photonic circuits. In this paper, we focus on the mode order conversion in silicon waveguides with non-volatile reconfigurable capability. Deformed phase change material Sb2Se3 (antimony triselenide) stripes are introduced at the edges of the functional region to provide the refractive index difference required by mode conversions. The shapes of stripes are inversely designed by a gradient-based iterative optimization strategy with 57 (19) iterations for TE0-to-TE1 (TE0-to-TE2) mode converter. The footprint of the functional region is as compact as square center wavelength. In the crystalline phase, TE0-to-TE1 and TE0-to-TE2 mode conversions are realized with conversion efficiencies of 98.5% and 96.3% at a center wavelength of 1550 nm, respectively. While in the amorphous phase, the input TE0 mode directly passes through the functional region with efficiencies of 93.0% and 92.4%, respectively. The output mode can be reconfigured by changing the phase of Sb2Se3 stripes. Moreover, after introducing ±10 nm geometrical deviations to the perfect Sb2Se3 stripe design, corresponding red and blue shifts of conversion efficiency spectra can be observed, and the simulation results reflect the reasonable robustness of the proposed mode converters.

A planar UWB-MIMO antenna with high isolation and reconfigurable single band-elimination characteristics

A compact ultra-wideband (UWB) triple mode frequency reconfigurable multiple-input multiple-output (MIMO) antenna with electronically controllable single band elimination properties is presented in this work. The reported antenna comprises of two rotationally symmetric identical modified circular radiators each having tapered microstrip feed lines and separate partial defected ground structures (DGS). The slotted radiating patches consist of C-shaped parasitic strips placed at their centers. Two PIN diode switches were utilized to join and detach the C-shaped strip and slotted circular radiator, and thus total four PIN diodes are employed in the dual-port MIMO configuration to achieve switchable operation between UWB and single band-notched UWB characteristics. The recommended antenna possesses ultrawide bandwidth with Snn ≤ −10 dB except at the rejected bands and attains isolation better than −21 dB in all reconfigurable modes. The proposed MIMO antenna shows good diversity behavior which has been proved through the study of various parameters, such as envelope correlation coefficient (ECC), CCL and diversity gain with values fulfilling the acceptable standard for practical usage. High diversity gain and ECC value below 0.0006 are obtained for all the modes. The suggested antenna structure is ideally suited for ultrawideband MIMO systems with on-demand suppression of WiMAX or WLAN signals.

TranCIM: Full-Digital Bitline-Transpose CIM-based Sparse Transformer Accelerator With Pipeline/Parallel Reconfigurable Modes

Transformer models achieve excellent results in the fields like natural language processing, computer vision, and bioinformatics. Their large numbers of matrix multiplications (MMs) lead to substantial data movement and computation. Although computing-in-memory (CIM) has proven to be an efficient architecture for MM computation, transformer’s attention mechanism raises new challenges in memory access and computation aspects: the dynamic MM in attention layers causes redundant off-chip memory access; Attention layers dominate transformer’s computation and require high precision. Thus, we design a bitline-transpose CIM-based transformer accelerator TranCIM with pipeline/parallel reconfigurable modes. The pipeline mode alleviates off-chip access for attention layers. The parallel mode is used by fully-connected (FC) layers for high parallelism. The full-digital CIM supports INT16 for attention layers and INT8 for FC layers, without analog CIM’s nonideal issues. Moreover, a sparse attention scheduler (SAS) is proposed to reduce attention computation. The fabricated TranCIM chip only consumes 15.59 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> J/Token for the bidirectional encoder representations from transformer (BERT)-base model, achieving 12.08 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> –36.82 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> lower energy than prior CIM-based accelerators.

An organic electrochemical transistor for multi-modal sensing, memory and processing

By integrating sensing, memory and processing functionalities, biological nervous systems are energy and area efficient. Emulating such capabilities in artificial systems is, however, challenging and is limited by the device heterogeneity of sensing and processing cores. Here we report an organic electrochemical transistor capable of sensing, memory and processing. The device has a vertical traverse architecture and a crystalline–amorphous channel that can be selectively doped by ions to enable two reconfigurable modes: a volatile receptor and a non-volatile synapse. As a volatile receptor, the device is capable of multi-modal sensing and is responsive to stimuli such as ions and light. As a non-volatile synapse, it is capable of 10-bit analogue states, low switching stochasticity and good state retention. We also show that the homogeneous integration of the devices could provide functions such as conditioned reflexes and could be used for real-time cardiac disease diagnoses via reservoir computing.

Reconfigurable ultra-broadband mode converter based on a two-mode fiber with pressure-loaded phase-shifted long-period alloyed waveguide grating.

We present a reconfigurable ultra-broadband mode converter, which consists of a two-mode fiber (TMF) and pressure-loaded phase-shifted long-period alloyed waveguide grating. We design and fabricate the long-period alloyed waveguide gratings (LPAWG) with SU-8, chromium, and titanium via the photo-lithography and electric beam evaporation technique. With the help of the pressure loaded or released from the LPAWG onto the TMF, the device can realize reconfigurable mode conversion between the LP01 mode and the LP11 mode in the TMF, which is weak sensitive to the state of polarization. The mode conversion efficiency larger than 10 dB can be achieved with operation wavelength range of about 105 nm, which ranges from 1501.9 nm to 1606.7 nm. The proposed device can be further used in the large bandwidth mode division multiplexing (MDM) transmission and optical fiber sensing system based on few-mode fibers.

Micro-electro-mechanically tunable optical phase matching and mode conversion.

Mode-division multiplexing (MDM) enables a large increase in the information-carrying capacity of an optical network. Recently, chip-scale MDM devices that can switch different mode orders to different output waveguides have been demonstrated. However, an important milestone showing dynamically tunable mode-order conversion in a single compact device has so far not been reported. In this work, we demonstrate via simulation and measurement a new, to the best of our knowledge, approach for reconfigurable mode conversion using optical micro-electro-mechanical systems (MEMS) to locally modify the effective index in an asymmetric coupler. Modeling shows that dynamic tuning to increase or decrease the mode order is possible. Measurements on fabricated devices are consistent with simulations of reconfigurable mode conversion based on tunable phase matching. Our experimental results demonstrate reconfigurable TE0-TE2 to TE0-TE1 conversion and validate this new tunable phase-matching approach for mode-division multiplexing.

Reconfigurable polarization and pattern microstrip antenna for IRNSS band applications

In this article, polarization and pattern reconfigurable antenna is designed for 2.492 GHz Indian Regional Navigational Satellite System (IRNSS) band. The proposed antenna consists of a square radiating element fed with quad coaxial probes for polarization reconfigurability. It is surrounded by switch loaded octagonal parasitic ring for pattern beamwidth reconfigurability. RF switch loaded Electronically feeding network is used to fed the proposed antenna. The right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) is realized by exciting feed ports in the antenna with 90° phase difference. At the same time switch loaded parasitic ring provides the pattern beamwidth reconfigurability for designed circularly polarized antenna. To verify the proposed design, a prototype is fabricated and tested experimentally. The measured axial ratio is well-below 3 dB in polarization mode. The measured 3 dB beam-width of the elevation gain patterns for the horizontal field component (Gϕ) varies between 107.40°∼113.51° and 74°∼77.55° in pattern reconfigurable modes. The maximum gain of 6.46 dBi is achieved in both polarization and pattern reconfigurable mode. The proposed antenna is intended for the IRNSS navigation receiver system and designed to minimize the effect of interference incident on the antenna by narrowing the pattern beamwidth near the horizon.

Inverse Design of Nonvolatile Reconfigurable Mode Generator and Optical Circulator Based on a Novel Concept of a Fully-Digitized Module

Based on the novel concept of a fully-digitized module, we employ a forward-designed-assisted inverse design method to design a nonvolatile reconfigurable mode generator and an optical circulator, assisted with a phase change material. The mode generator can selectively output different modes. The fundamental transverse electric (TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) or TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> modes can be selectively generated when the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> mode is launched in the input port. The mode generator with an effective footprint of 2.4 μm × 16 μm exhibits the simulated insertion losses of less than 1.0 dB and the simulated crosstalks of lower than –19.0 dB for both the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> modes from 1540 nm to 1560 nm. The optical circulator enables the light unidirectional propagation. Photons can be precisely routed from each input port to one adjacent output port in clockwise or counterclockwise directions. The simulated results indicate that the circulator with an effective footprint of 24 μm × 24 μm, can provide both the simulated insertion losses of less than 0.8 dB and the simulated crosstalks of lower than –16.3 dB from 1540 nm to 1560 nm in both clockwise and counterclockwise directions. The fabrication tolerances caused by the expansion or contraction of the etched pattern contour are also investigated. In principle, the proposed frameworks can be extended to an arbitrary number of ports for designing mode generators and optical circulators.

On-Chip Reconfigurable and Ultracompact Silicon Waveguide Mode Converters Based on Nonvolatile Optical Phase Change Materials.

Reconfigurable mode converters are essential components in efficient higher-order mode sources for on-chip multimode applications. We propose an on-chip reconfigurable silicon waveguide mode conversion scheme based on the nonvolatile and low-loss optical phase change material antimony triselenide (Sb2Se3). The key mode conversion region is formed by embedding a tapered Sb2Se3 layer into the silicon waveguide along the propagation direction and further cladding with graphene and aluminum oxide layers as the microheater. The proposed device can achieve the TE0-to-TE1 mode conversion and reconfigurable conversion (no mode conversion) depending on the phase state of embedded Sb2Se3 layer, whereas such function could not be realized according to previous reports. The proposed device length is only 2.3 μm with conversion efficiency (CE) = 97.5%, insertion loss (IL) = 0.2 dB, and mode crosstalk (CT) = -20.5 dB. Furthermore, the proposed device scheme can be extended to achieve other reconfigurable higher-order mode conversions. We believe the proposed reconfigurable mode conversion scheme and related devices could serve as the fundamental building blocks to provide higher-order mode sources for on-chip multimode photonics.

Aluminum Frenkel defects cause hysteresis in Al2O3/AlGaN capacitors

Al 2 O 3 /AlGaN metal-oxide-semiconductor capacitors show a hysteretic behavior in their capacitance vs voltage characteristics, often attributed to near-interface traps deriving from defects within the oxide layer. The origin as well as the structural/electronic properties of such defects are still strongly debated in the literature. Here, we use ab initio molecular dynamics and the climbing-image nudged elastic band method to show that aluminum Frenkel defects give rise to bistable trap states in disordered and stoichiometric Al2O3. Based on these results, we propose a calibrated polaron model representing a distribution of individually interacting energy levels with an internal reconfiguration mode and coupled to continuous bands of carriers to explain the hysteresis mechanism in Al2O3/AlGaN capacitors.

Reconfigurable Guided‐Mode Conversion Using Cladding Medium Switching Strategy in Subwavelength Grating Waveguide

AbstractIn a waveguide‐based coupled‐mode system, various mode conversions are achieved by designing mode evolution procedures. However, the differences of refractive indices among modes exceed the capability of conventional tuning mechanism, so most reported mode manipulation devices can only realize fixed mode conversions. This paper introduces the cladding medium switching strategy to the subwavelength grating waveguide‐based coupled‐mode system, and proposes a reconfigurable mode converter on silicon nitride platform. This work systematically analyzes the phase matching conditions on a coupled‐mode system. Results show that for both whole and partial upper‐cladding switchable, it is possible to achieve reconfigurable mode conversions. For whole cladding switchable case, this work demonstrates a double‐state mode converter, which converts the input mode to TE2 and TE1 modes under cladding refractive indices of 1 and 1.7. This work expands it to triple‐state mode conversion with window‐style cladding, which converts the input to TE2, TE1, and TE0 modes under cladding of 1, 1.54, and 1.7. The optical bandwidths are relatively large, and the conversion efficiencies exceed 56% for all cases. The mechanism provides a non‐volatile and energy‐efficient way for tunable mode conversions, which is promising for applications in optical networks, communications, and sensors, etc.

The Performance Effects of Internal Resource Redeployment versus External Resource Sourcing

The reconfiguration of strategically important resources through internal redeployment or sourcing from the external market is a vital aspect of corporate development. However, empirical studies that directly ascertain the relative performance of internal resource redeployment over acquiring/borrowing resources on the external market are lacking. We overcome the empirical challenges associated with comparing the effectiveness of both reconfiguration modes by examining the redeployment of human resources—professional soccer players in the English Football League Championship—following a significant injury to a key player. This approach further allows us to develop theory regarding the roles of important resource-level characteristics, including fungibility and similarity, and to circumvent endogeneity issues related to the resource reconfiguration-performance relationship. This study thereby extends existing theory and produces novel findings that illuminate the importance of resource-level characteristics as drivers of the relative performance advantages of different reconfiguration modes. We discuss implications for the literature on resource reconfiguration and strategic human capital.

Research on μPMU Configuration Optimization Considering Multiple Operation Modes of Distribution Network

A micro-phasor measurement unit (μPMU) configuration optimization approach is proposed in this article, considering the numerous operation modes of distribution network reconfiguration. The PSO algorithm with dynamic adaptability is used to optimize the setup of μPMU and improve the accuracy of state estimation for each distribution network operation mode. The configuration nodes of various operation modes are grouped and assessed by K-means according to the shortest distance, and the weights of the evaluation indexes are calculated by the AHP-CRITIC subjective and objective combination weighting method. The node with the highest comprehensive evaluation index is selected as the configuration node. The probability of multiple operation modes is then introduced. Finally, using the IEEE 118-bus distribution system as an example, the simulation demonstrates the proposed method’s effectiveness in improving distribution network state estimate.

A compact frequency reconfigurable patch antenna with asymmetric armed U and reversed L slots for handheld wireless devices

Abstract A frequency reconfigurable microstrip patch antenna with a combination of an asymmetric armed U-slot and a reversed L-slot etched on a rectangular base patch of 6 GHz resonant frequency designed on an FR4 substrate (ɛr = 4.4) is presented in this paper. Three RF PIN diodes are positioned at inimitable sites of these slots to achieve frequency reconfiguration. A DC bias circuitry, which includes DC blocking capacitors and RF blocking inductors, is integrated with the antenna structure for switching (ON/OFF) the PIN diodes. Six reconfigurable modes with resonant frequencies at 4.33, 4.63, 5.24, 5.87, 5.96, and 6.29 GHz is obtained with different ON-OFF combinations of these PIN diodes. These reconfigurable resonant frequencies cover two continuous bands from 4.21 to 5.43 GHz and 5.69 to 6.6 GHz and is considered to be useful for the applications like aeronautical radio navigation (4.3 GHz), sub-6-GHz 5G (4.4–5 GHz), WLAN (5.2 and 5.8 GHz) and Wi-Fi 6E (5.925–6.425 GHz). Measured gain of the antenna for all the modes varies between 5.86 dBi and 8.72 dBi.