Silicon Bridge Research Articles

Molecularization of Metasurfaces for Multifunctional Ultrafast All‐Optical Terahertz Waves

Hybrid metasurfaces incorporated by active materials hold great promise for state‐of‐the‐art terahertz functional devices. However, it is still a major challenge to achieve ultrafast, dynamic, and multifunctional effective control of THz waves via hybrid metasurfaces. Herein, a modulator consisting of split rings and cut‐wires is first demonstrated, with an amplitude of −35.6 dB at 0.524 THz. By embedding semiconductor silicon into specified locations to form a hybrid metasurface, the ultrastrong connectivity of the silicon bridges leads to rapid optical molecularization. Under photoexcitation, the frequency tuning range is 26.7%, the phase shifting reaches 357.5°, and the maximal modulation depth is 94.54%. Taking advantage of the rapid relaxation of photocarriers in the silicon bridges, the ultrafast frequency switching is within 1400 ps. More interestingly, by changing the positions of the silicon bridges, the frequency tuning range is further promoted to 60%, the phase shifting is 353.5°, the modulation depth of 100% is achieved, and the full recovery time is 1600 ps. Furthermore, the underlying mechanism of the ultrafast tuning process is elucidated. This work demonstrates the feasibility of all‐optical‐controlled hybrid metasurface to achieve multifunctional dynamic modulation of THz waves, which has tremendous potential for applications in optical switching, signal processing, and frequency conversion.

High-response humidity sensor based on silicon microbridge with edge-constrained sandwich sensing structure

Silicon microbridge structures have attracted the attention of researchers in humidity sensing area owing to their small size and ease of integration with the integrated circuit (IC). However, the preparation of silicon microbridge humidity sensors with high response are still a challenge. This paper proposed a silicon microbridge humidity sensor based on an edge-constrained sandwich sensing structure, in which a graphene oxide core layer with small area was covered on the surface of the silicon bridge by a larger area of Nafion film. Due to the constraint of the peripheral edge, the swelling deformations of this sandwich structure in the vertical direction were effectively magnified during humidity detection. Hence, the proposed humidity sensor exhibited a higher humidity sensitivity (109.97 µV/%RH) compared to the silicon microbridge sensors with general sandwich sensing structure or monolayer sensing film. Meanwhile, the novel sensor also demonstrated a small humidity hysteresis and good linearity in humidity range of 11.3–97.3%.

Multifunctional metasurface for ultrafast all-optical efficient modulation of terahertz wave

Metasurfaces have been widely used to terahertz (THz) modulators due to their unique electromagnetic (EM) modulation properties. However, to realize ultrafast and efficient control of the active metasurfaces remains a critical challenge. Herein, we first demonstrate a multifunctional metasurface modulator based on metal square rings, which have central rotational symmetry with local asymmetry. The former captures more EM energy to achieve strong enhancement of the local EM responses, and the latter generates high quality factor (Q-factor) Fano resonance. By scaling the unit structure, the resonant frequency shifts in an ultra-wideband range of ∼0.29-10 THz, which shows a linear relation between the Q-factor and the scaling factor, and an exponential variation between the full width at half maximum (FWHM) and the scaling factor. The results provide an effective approach to predict the frequency selection characteristics of the modulators in the THz regime. More importantly, by embedding the silicon into the specific position of the metasurface, external optical control results in the unit structure is constructed from meta-atom to molecularization model, the shifting of resonant frequency and the multi-level modulation of amplitude are realized, and the maximum modulation depth (MD) reaches ∼100 %. By systematically studying the dynamics of frequency and amplitude regulation, benefiting from the ultra-short relaxation time of the photo-carriers in silicon bridge, an ultrafast full recovery time of 2000 ps is achieved. Combined with the local field characteristics, the scaled unit structure achieves efficient modulation of the resonant frequency and amplitude under optical pumping, which provides a promising approach for the development of active metasurface modulator suitable for the whole THz band. This work demonstrates the viability of optical control molecularization of specific meta-atoms is applicable to the entire THz band, which has great potential use for future state-of-the-art THz modulators.

A Novel 2D/3D X-ray Microscopy Alignment and Inspection Solution for Thermocompression Bonding (TCB) in a Highly Integrated Flip Chip Fan-Out Wafer Level Package (FO-WLP)

As packaging drives to extend the capabilities of Moore’s Law via heterogenous integration, numerous bonding technologies have emerged as potential pathways, allowing for integration of both a variety of devices in the lateral space as well as vertical integration of chips via stacking. As vertical integration on interposer becomes more complex due to shrinking CDs and increasing die layers, alignment and shape control in the bonding process becomes critical. Thermocompression bonding (TCB) is particularly well-suited for larger die, where localized reflow allows a better control of chip gap height and tilt throughout the bonding process. TCB systems require both high accuracy and repeatability in all dimensions to provide a reliable system in package. While a 2D system can provide a plan view assessment of a single bond layer between two chips, it falls short in characterizing the critical z-dimension in a highly integrated chip stacking scenario. Therefore a robust solution is needed for both system alignment validation in the x,y plane as well as a capability to explore gap height and bump quality/buried issues in high aspect ratio TSV. This paper will explore an x-ray application of a stacked 15-layer die-to-interposer structure to qualitatively validate overall health of the TSV (bond, pad, fill) via a nondestructive volumetric method as well as quantitatively evaluate stacked die for via/ball/pad alignment to determine overall alignment shift during the bonding process. In the test vehicle for a flip chip FO-WLP process flow first presented by IMEC, a silicon (Si) bridge is utilized to connect the logic and through-package via dies with a bump pitch of 20µm for the logic die interconnect. This is done by carefully aligning the logic dies on the carrier and then placing the through-package dies aligned to the carrier and logic dies. In the final step, a high accuracy placement and stacking TCB tool attaches the Si bridge. To perform an accurate assessment for bump alignment and bond quality, an initial high-resolution 3D x-ray scan is performed on a 1.5mm3 region of interest with over 2,000 individual projections at a 1.4µm voxel resolution with a 4x objective, taking approximately two hours. The dataset is put through a deep-learning algorithm which generates an AI model. This model is then applied to a faster scan of 15 minutes with a 1.4µm voxel resolution for the same field of view (FOV) on a nearby array and the data is collected and processed. To verify alignment of the entire sample, data is collected on the tightest pitch (in this case 20µm) oriented in both the vertical (x) and horizontal (y) plane in the through-silicon via (TSV) region. The z-plane is analyzed and processed by computer vision algorithms, and individual interconnects are then quantified and sorted for solder height (z), width (x,y) and TSV misalignment (deviation from expected center, x1y1 → x2y2). To validate the model, a high-resolution uncorrected 20h scan and a 15min scan based on deep learning are collected for the same region of interest (ROI). The data is comparable. Furthermore, the global misalignment data between both datasets demonstrates similar misalignment propagating through the 15-layer stack.

Copolymerization of ethylene and isoprene via silicon bridge metallocene [rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2] catalyst: A new way to control the composition and microstructure of copolymers

The copolymerization of ethylene (E) with isoprene (Ip) was performed catalyzed by a symmetrical catalyst exhibiting a silicon bridge [rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 with the combination of borate/TIBA activator. The effect of cocatalyst, Ip concentration, and polymerization temperature on the activity, molecular weight (Mw), distribution (MWD), comonomer composition, chain structure (regio- and stereoselectivity), and resulting side reactions were logically addressed. Gel-permeation chromatography (GPC) was used to characterize the Mw and polydispersity, while nuclear magnetic resonance (NMR) was employed for the chain structure of the polymers. The catalytic activity was significantly lower by increasing the Ip concentration in the feed, and the isoprene content in resulting polymers was lower under the reaction condition, leading to higher activity. Insertion of isoprene units in polymer structure demonstrates the higher regioselectivity for the 3,4 connections than the 1,4 connections and is expected to be a high-resistance polymer against acids. The MWD presented monomodal even with a higher concentration (1.44 mol/L) and did not appear as low Mw peaks of Ip. The Mw was higher with a broader MWD when purely TIBA was used as a cocatalyst, and it significantly reduced and presented a narrowed MWD with TEA in the cocatalyst. The higher efficiency of the catalyst for the higher insertion of Ip (C=C double bond) effectively modifies the polymer backbone. It is expected to be a promising candidate for easily degradable and favorable solutions for solving environmental problems caused by PE. wastes.

Scaling Interconnect Densities Meeting the Growing Demand for Chiplet Integration

With the increasing demand for heterogenous chiplet integration, the demand for high density chip to chip interconnects grows equivalently. In 2022 there were two significant announcements on breakthroughs in chip integration. At the highest end is AMD’s v-cache, which utilizes hybrid bonding to make connections between cache and processor. Also introduced to industry, was Apple’s M1-Ultra processor which achieves advanced flip-chip pitch at 25µm x 35µm. Through teardowns it is apparent that the M1-Ultra is made up of two chips first embedded processors, a flip-chip bridge, and molded fanout technology. These silicon-based solutions are complex and costly, but they demonstrate the industry’s strong demand for high density interconnects. This paper outlines an alternate approach to achieving high density die-to-die interconnects through purely organic wafer or panel level packaging (PLP) that can meet or exceed the density provided by a silicon bridge. Deca Technologies’ Gen 2 M-Series™ fan-out with Adaptive Pattering® provides 20µm pitch capability with 2µm line and space widths. This interconnect density can match or exceed that offered by a silicon bridge, while significantly reducing the cost and yield risk. A specific 10 die test vehicle build will be presented that demonstrates this capability. This 20µm pitch is only the starting point as the technology will continue to scale. Through the new, MDX™ technology, capture pads are eliminated from all metal layers allowing unprecedented routing density increases on organic fan-out structures in combination with finer device interface pitch. While the details of this technology are still proprietary, a high-level overview will be provided.

Tuning the Emission of a Nonconventional Aggregation-Induced Emission Polymer via Silicon-Bridged Twisted Intramolecular Charge Transfer for Targeted Delivery and Visualized Drug Release.

The design of tunable luminescent biomaterials with large Stokes shifts is usually pursued by a twisted intramolecular charge transfer (TICT) effect with switchable emission colors in response to various external stimuli. However, such a strategy is usually realized in conjugated molecules containing benzene or its derivatives and consequently suffers from poor biocompatibility. In this work, a hyperbranched polysiloxane (HBPSi)-based non-conjugated fluorescent polymer with TICT and aggregation-induced emission (AIE) features is developed, and its luminescent properties, fluorescence mechanism, and potential applications are investigated. Initially, the non-conjugated HBPSi exhibits remarkable AIE characteristics due to the formation of through-space conjugation. With the introduction of the sulfur atom, a non-conjugated D-A type AIE material, HBPSi-Cys, that exhibits a dual-state emission with a large Stokes shift of 213 nm, is obtained. The correlation of the lower-energy emission band with solvent polarity suggests the existence of the TICT state. TICT and AIE characteristics direct different properties of HBPSi-Cys, with TICT regulating solvatochromic emission wavelengths and AIE manipulating the emission intensity with a compensation effect. Density functional theory calculations reveal that the non-conjugated D-A structure in HBPSi-Cys was formed across the silicon bridge, with auxochromic sulfhydryl groups and adjacent amide groups as acceptor units and amine and hydroxyl groups as donor units. Additionally, the AIE-active HBPSi could be utilized as a fluorescent probe for the analysis of metal ions. After grafting the AS1411 aptamer to HBPSi-Cys as the recognition motif, HBPSi-Apt possesses excellent targeted bioimaging, drug loading, pH/GSH dual-responsive drug release, and visualized drug delivery performance. This work provides a new way to design functional AIE polymers with tunable optical properties, and the synthesized HBPSi-Cys shows great potential as a smart fluorescent biomaterial.

Synchronization in Pairs of Opto-Thermally Driven Mechanically Coupled Micro-Oscillators

We study the phenomenon of synchronization in pairs of doubly clamped, mechanically coupled silicon micro-oscillators. A continuous-wave laser beam is used to drive the micro-beams into limit cycle oscillations and to detect the oscillations using interferometry. Devices of different dimensions are used to introduce frequency detuning, and short silicon bridges connecting the micro-beams are used as mechanical coupling between the oscillators. The region of synchronization is plotted for the MEMS system in the detuning vs. coupling parameter space and compared with the numerical analysis of a corresponding, lumped-parameter model. Three states of oscillations are observed i.e. the drift state, quasi-periodic state, and the synchronized state. The numerical model also distinguishes between in-phase and out-of-phase synchronization where out-of-phase synchronization is observed at low coupling strengths and low frequency detuning. [2022-0140]

First Configurational Study of the CryoAC Detector Silicon Chip of the Athena X-Ray Observatory

The 50 mK cryogenic focal plane anticoincidence detector of the Athena X-ray observatory (CryoAC) is a silicon-suspended absorber sensed by a network of 400 Ir/Au transition edge sensors (TES) and connected through silicon bridges to a surrounding silicon frame plated with gold. The device is shaped by deep reactive ion etching from a single silicon wafer of 500 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m. In operating test of prototypes of the demonstration model of the CryoAC, we have highlighted the importance of the phonon hot spot in the signal generation. A fast response to the cosmic particle of a large area of about 4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a thin 0.5 mm silicon absorber covered by a TES array can be assured by matching the array configuration to the size and properties of the hot spot. In this article, we present the preparatory study of a proposal for measuring the phonon hot spot that is predicted by the particle-absorber interaction model.

Diazulenylmethyl Cations with a Silicon Bridge: A π-Extended Cationic Motif to Form J-Aggregates with Near-Infrared Absorption and Emission.

We disclose a series of silicon-bridged diazulenylmethyl cations as stable and one-dimensionally π-extended carbocations. Connecting nonbenzenoid azulenes to a carbocation center at an appropriate position while reinforcing a planar arrangement effectively delocalizes a positive charge over the π-conjugated skeleton. This structural constraint endows the carbocations with not only high chemical stability with the pKR+ value of around 9.5, despite the absence of any electron-donating substituents, but also an intense absorption in the red region due to the effective enhancement of the transition dipole moment. X-ray crystallographic analysis revealed an offset π-stacked arrangement with the outer seven-membered ring overlapping in a face-to-face manner, in which both the steric bulk of the vertically oriented substituents on the silicon atom and the location of the counter anion should play a crucial role. Reflecting this molecular arrangement, the π-extended cations exhibited a red-shifted absorption in the near-infrared (NIR) region in both the solid state and aggregated state in solution, indicative of the formation of J-aggregates. More pronounced redshifts in the absorption band upon the formation of the aggregates were observed by proper choice of the substituents on the silicon bridge and the counter anions, and the aggregates exhibited sharp fluorescence bands with the maximum emission wavelength exceeding 800 nm. These results demonstrate the impact of the nonbenzenoid aromatic stabilization of a carbocation and the efficacy of the present design strategy for the construction of a promising π-extended cationic motif that can form NIR-absorbing and emissive J-aggregates.

Nanometer-scale photon confinement in topology-optimized dielectric cavities

Nanotechnology enables in principle a precise mapping from design to device but relied so far on human intuition and simple optimizations. In nanophotonics, a central question is how to make devices in which the light-matter interaction strength is limited only by materials and nanofabrication. Here, we integrate measured fabrication constraints into topology optimization, aiming for the strongest possible light-matter interaction in a compact silicon membrane, demonstrating an unprecedented photonic nanocavity with a mode volume of V ~ 3 × 10−4 λ3, quality factor Q ~ 1100, and footprint 4 λ2 for telecom photons with a λ ~ 1550 nm wavelength. We fabricate the cavity, which confines photons inside 8 nm silicon bridges with ultra-high aspect ratios of 30 and use near-field optical measurements to perform the first experimental demonstration of photon confinement to a single hotspot well below the diffraction limit in dielectrics. Our framework intertwines topology optimization with fabrication and thereby initiates a new paradigm of high-performance additive and subtractive manufacturing.

Calibration-free, high-precision, and robust terahertz ultrafast metasurfaces for monitoring gastric cancers

Optical sensors, with great potential to convert invisible bioanalytical response into readable information, have been envisioned as a powerful platform for biological analysis and early diagnosis of diseases. However, the current extraction of sensing data is basically processed via a series of complicated and time-consuming calibrations between samples and reference, which inevitably introduce extra measurement errors and potentially annihilate small intrinsic responses. Here, we have proposed and experimentally demonstrated a calibration-free sensor for achieving high-precision biosensing detection, based on an optically controlled terahertz (THz) ultrafast metasurface. Photoexcitation of the silicon bridge enables the resonant frequency shifting from 1.385 to 0.825 THz and reaches the maximal phase variation up to 50° at 1.11 THz. The typical environmental measurement errors are completely eliminated in theory by normalizing the Fourier-transformed transmission spectra between ultrashort time delays of 37 ps, resulting in an extremely robust sensing device for monitoring the cancerous process of gastric cells. We believe that our calibration-free sensors with high precision and robust advantages can extend their implementation to study ultrafast biological dynamics and may inspire considerable innovations in the field of medical devices with nondestructive detection.

(Invited) Tutorial on Semiconductor Advanced Packaging

In this lecture semiconductor advanced packaging is defined. The kinds of advanced packaging are ranked based on their interconnect density and electrical performance and are grouped into 2D, 2.1D, 2.3D, 2.5D, and 3D IC integration, which will be presented and discussed. Key enabling technologies such as flip chip and fan-out will be briefly mentioned. The trends and challenges (opportunities) of advanced packaging will be discussed. Also, in this lecture, chiplet design and heterogeneous integration packaging are defined. The chiplet design and heterogeneous integration packaging such as those given by Xilinx, AMD, Intel, TSMC, and Samsung will be presented and discussed. The lateral communication between chiplets such as the silicon bridges embedded in organic build-up package substrate (Intel’s EMIB and IBM’s DBHi) and fan-out epoxy molding compound (Applied Materials’ chip-first face-up, Unimicron’s chip-first face-down, TSMC’s LSI, SPIL’s FO-EB, ASE’s sFOCoS, IME’s EFI, and Amkor’s S-Connect Fan-Out Interposer) as well as flexible bridges will be presented. Key enabling technologies such as thermocompression bonding and hybrid bonding will be briefly mentioned. The trends and challenges (opportunities) of chiplet design and heterogeneous integration packaging will be discussed.

Know Time to Die – Integrity Checking for Zero Trust Chiplet-based Systems Using Between-Die Delay PUFs

Industry trends are moving toward increasing use of chiplets as a replacement for monolithic fabrication in many modern chips. Each chiplet is a separately-produced silicon die, and a system-on-chip (SoC) is created by packaging the chiplets together on a silicon interposer or bridge. Chiplets enable IP reuse, heterogeneousintegration, and better ability to leverage cost-appropriate process nodes. Yet, creating systems from separately produced components also brings security risks to consider, such as the possibility of die swapping, or susceptibility to interposer probing or tampering. In a zero-trust security posture, a chiplet should not blindly assume it is operating in a friendly environment.In this paper we propose a delay-based PUF for chiplets to verify system integrity. Our technique allows a single chiplet to initiate a protocol with its neighbors to measure unique variations in the propagation delays of incoming signals as part of an integrity check. We prototype our design on Xilinx Ultrascale+ FPGAs, which are constructed as multi-die systems on a silicon interposer, and which also emulate the general features of other industrial chiplet interfaces. We perform experiments on, and compare data from, dozens of Ultrascale+ FPGAs by making use of Amazon’s Elastic Compute Cloud (EC2) F1 instances as a testing platform. The PUF cells are shown to reject clock and temperature variation as common mode, and each cell produces approximately 5 ps of unique delay variation. For a design with 144 PUF cells, we measure the mean within-class and between-class distances to be 68.3 ps and 847.7 ps, respectively. The smallest between-class distance of 686.0 ps exceeds the largest within-class distance of 124.0 ps by more than 5x under nominal conditions, and the PUF is shown to be resilient to environmental changes. Our findings indicate the PUF can be used for authentication, and is potentially sensitive enough to detect picosecond-scale timing changes due to tampering.

Recent Advances and Trends in Advanced Packaging

In this study, advanced packaging is defined. The kinds of advanced packaging are ranked based on their interconnect density and electrical performance, and are grouped into 2-D, 2.1-D, 2.3-D, 2.5-D, and 3-D IC integration, which will be presented and discussed. Chiplet design and heterogeneous integration packaging provide alternatives to the system on chips (especially for advanced nodes) will be discussed. Different substrates, such as size, pin-count, and metal linewidth and spacing for advanced packaging, are examined. The lateral communication between chiplets, such as the silicon bridges embedded in organic build-up package substrate and fan-out epoxy molding compound, as well as flexible bridges, will be presented. Fan-in packaging, such as the six-side molded wafer-level chip-scale package (WLCSP) and its comparison with the ordinary WLCSP, are presented. Fan-out packaging, such as the chip-first with die face-up, chip-first with die face-down, and chip-last and their difference, will be provided. Low-loss dielectric materials for high-speed and high-frequency applications in advanced packaging will be presented. Flip-chip assembly by mass reflow, thermocompression bonding, and bumpless hybrid bonding will be briefly mentioned first.

Analogue of electromagnetically induced transparency in square slotted silicon metasurfaces supporting bound states in the continuum.

In this work, a silicon metasurface designed to support electromagnetically induced transparency (EIT) based on quasi-bound states in the continuum (qBIC) is proposed and theoretically demonstrated in the near-infrared spectrum. The metasurface consists of a periodic array of square slot rings etched in a silicon layer. The interruption of the slot rings by a silicon bridge breaks the symmetry of the structure producing qBIC stemming from symmetry-protected states, as rigorously demonstrated by a group theory analysis. One of the qBIC is found to behave as a resonance-trapped mode in the perturbed metasurface, which obtains very high quality factor values at certain dimensions of the silicon bridge. Thanks to the interaction of the sharp qBIC resonances with a broadband bright background mode, sharp high-transmittance peaks are observed within a low-transmittance spectral window, thus producing a photonic analogue of EIT. Moreover, the resonator possesses a simple bulk geometry with channels that facilitate the use in biosensing. The sensitivity of the resonant qBIC on the refractive index of the surrounding material is calculated in the context of refractometric sensing. The sharp EIT-effect of the proposed metasurface, along with the associated strong energy confinement may find direct use in emerging applications based on strong light-matter interactions, such as non-linear devices, lasing, biological sensors, optical trapping, and optical communications.

(Invited) Heterogeneous Packaging Integration for AI Workloads

Semiconductor scaling to smaller dimensions has led to tremendous improvement in electronic systems performance. Computer systems that used to occupy several rooms are now available in the palm of your hand. However, as semiconductor scaling saturates, other paradigms are necessary for improving the systems performance. One such paradigm of performance improvement is advanced packaging of heterogeneous chips from different semiconductor nodes, different construction and different sources - often called heterogeneous integration (HI). HI is necessary because system performance is required to grow 1000x over the next 7-10 years, especially for Artificial Intelligence (AI) applications. A subset of AI, called machine learning, relies of artificial neural networks that simulate a human brain. In this talk, we compare and contrast the different HI packaging options which include conventional 2D single-chip and multi-chip packages with high-density laminates, package-on-package (PoP) configurations, 2.5D silicon interposers, silicon bridge packages, and fully 3D stacked packages. Many of these configurations are being developed in the IBM AI Hardware Research Center (AIRC). We also describe the tooling and EDA infrastructure required for the successful development of these packaging solutions.

Piezoelectric MEMS Linear Motor for Nanopositioning Applications

This paper reports the design, fabrication, and performance of piezoelectric bidirectional conveyors based on microelectromechanical systems (MEMS) and featuring 3D-printed legs in bridge resonators. The structures consisted of aluminum-nitride (AlN) piezoelectric film on top of millimeter-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimized for travelling or standing wave generation, while the addition of 3D-printed legs allowed for a controlled contact and amplified displacement, a further step into the manufacturing of efficient linear motors. Such hybrid devices have recently demonstrated the conveyance of sliders of several times the motor weight, with speeds of 1.7 mm/s by travelling waves generated at 6 V and 19.3 kHz. In this paper both travelling and standing wave motors are compared. By the optimization of various aspects of the device such as the vibrational modes, leg collocation and excitation signals, speeds as high as 35 mm/s, and payloads above 10 times the motor weight were demonstrated. The devices exhibited a promising positional resolution while actuated with only a few sinusoidal cycles in an open-loop configuration. Discrete steps as low as 70 nm were measured in the conveyance of 2-mg sliders.

Design and Modeling of MOEM based strain sensor using ANSYS

Conventionally to constitute a waveguide for the propagation of light across the photonic crystal (PhC), imperfections or dislocations i.e. a line defect is used. A filter based on Photonic Crystal can be created with the introduction of line defect with micro-cavities, so as to form the bandgap structure that possesses resonant property. A filter like this PhC waveguide (PhCWG) exhibits the highest resonant value in the wavelength output and amplification in the light spectrum. For this PhCWG filter, a suspended silicon bridge structure is proposed with micro-cavity in middle. The defect length of the micro-cavity is defined as the distance that is spread between middle two holes, and along with the shape of air holes is modified by the output resonant wavelength. Under particular strain loading, shift in the resonant wavelength is observed for PhCWG. The induced force modifies not only the air holes shape, but also the spacing among them. For each and every strain applied, such an effect leads to shift in wavelength. For inducing strain we used ANSYS 16.0 software and to check wavelength shift we used MEEP software.

Bidirectional Linear Motion by Travelling Waves on Legged Piezoelectric Microfabricated Plates.

This paper reports the design, fabrication and performance of MEMS-based piezoelectric bidirectional conveyors featuring 3D printed legs, driven by linear travelling waves (TW). The structures consisted of an aluminium–nitride (AlN) piezoelectric film on top of millimetre-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimised for TW generation in three frequency ranges: 19, 112 and 420 kHz, by the proper combination of two contiguous flexural modes. After fabrication, the generated TW were characterized by means of Laser–Doppler vibrometry to obtain the relevant tables of merit, such as the standing wave ratio and the average amplitude. The experimental results agreed with the simulation, showing the generation of a TW with an amplitude as high as 6 nm/V and a standing wave ratio as low as 1.46 for a device working at 19.3 kHz. The applicability of the fabricated linear actuator device as a conveyor was investigated. Its kinetic performance was studied with sliders of different mass, being able to carry a 35 mg silicon slider, 18 times its weight, with 6 V of continuous sinusoidal excitation and a speed of 0.65 mm/s. A lighter slider, weighting only 3 mg, reached a mean speed of 1.7 mm/s at 6 V. In addition, by applying a burst sinusoidal excitation comprising 10 cycles, the TW generated in the bridge surface was able to move a 23 mg slider in discrete steps of 70 nm, in both directions, which is a promising result for a TW piezoelectric actuator of this size.