Tag Archives: letter-pulse-tech

In a paper published in NANO, researchers from the School of Microelectronics in Tianjin University have discovered a two-step sputtering and subsequent annealing treatment method to prepare vertically aligned WO3-CuO core-shell nanorod arrays which can detect toxic NH3 gas.

A schematic illustration of the gas sensor device based on the hybrid nanorod arrays. The real time resistance versus time of the vertically aligned WO3-CuO core-shell nanorod arrays-based gas sensor to varied concentrations of NH3 decreasing from 500 ppm to 50 ppm at 150 ?. The resistance of the WO3-CuO hybrid increases upon exposure to NH3, consistent with p-type semiconductor behavior. The response of the hybrid sample increasing with increasing NH3 concentration at 150. The response and recovery times range from 10 to 15 s for all NH3 concentrations. Credit: Author

Over the years, WO3 has received considerable attention among the numerous transition metal oxides as a wide band-gap n-type semiconductor in various gas detection, such as NOx, H2S, H2, and NH3. CuO has the unique property of being intrinsically p-type. In the last decade, p-n heterojunction sensors composed of an n-type metal oxide and CuO were reported to have a good sensitivity to reducing gases owing to the interface between n-metal oxide and CuO. Much effort has been focused on the WO3-based nanocomposites, since the synergetic enhancement and heterojunction effects attributes to the enhanced gas sensing properties. However, gas sensors based on 1D WO3-CuO composite structures are limited. Additionally, the template or catalyst was usually necessary to synthesize WO3-based nanorod arrays, including using chemical vapor deposition, electrochemical anodization and hydrothermal approaches.

Among toxic gases causing adverse impact on living organisms, NH3 is one of the most hazardous substances. It is necessary to build up ultrasensitive NH3 gas sensors with short response and recovery time. Metal oxides have been widely used in gas sensor applications. In order to obtain great sensing performances of metal oxide sensors, 1D metal oxide nanostructures and 1D heterojunction composite nanostructures have been investigated due to their large surface area, size-dependent properties, and the nano-heterojunction effects. Vertically aligned ordered 1D arrays effectively avoid the dense stacking of rod monomers, especially, resulting in novel physicochemical characteristics, such as higher gas response and shorter gas recovery.

Here, vertically aligned WO3-CuO core-shell nanorod arrays are synthesized using a non-catalytic two-step annealing process of sputtered metal film on silicon wafer. The growth mechanism of the vertically aligned nanorod arrays are discussed. The NH3 sensing behaviors of the WO3-CuO core-shell arrays at different temperatures are reported. A possible NH3sensing mechanism for the hybrid is proposed.

pSemiTM Corporation (formerly Peregrine Semiconductor), a Murata company focused on semiconductor integration, announces volume production of the PE43508 digital step attenuator (DSA). This mmWave product is the world’s first single-chip silicon-on-insulator (SOI) DSA to support the entire 9 kHz to 55 GHz frequency range. Ideal for 5G test and measurement applications, the PE43508 exemplifies pSemi’s high-performance capabilities at mmWave frequencies. The 55 GHz DSA maintains a monotonic response across the entire frequency range and features low insertion loss, low attenuation error and good return loss.

“At the IMS 2018 exhibition in June, we introduced the newest product in the pSemi high-frequency portfolio—a mmWave digital step attenuator,” says Jim Cable, CEO at pSemi. “As we announce volume production, I am excited to share that we are extending the operating frequency range of the PE43508 to 55 GHz. After additional testing, we concluded the original 50 GHz DSA name was selling this impressive product short. The PE43508 delivers exceptional performance beyond 50 GHz, further supporting pSemi’s claim that RF SOI can deliver a high-performing and reliable solution at high frequencies. It also demonstrates pSemi’s superior engineering talents and process capabilities in mmWave design.”

The 55 GHz DSA joins pSemi’s high-frequency portfolio which includes a 40 GHz switch (PE42524) and two 60 GHz switches (PE42525 and PE426525) based on the same UltraCMOS® technology platform. These monolithic ICs are ideal for applications, such as test and measurement and 5G wireless infrastructure, and can be used in more traditional high-frequency applications, such as very small aperture satellite terminals.

Features, Packaging, Pricing and Availability
The PE43508 is a 6-bit, 50-ohm DSA that offers wideband support from 9 kHz to 55 GHz. The PE43508 covers a 31.5 dB attenuation range in 0.5 dB and 1 dB steps, and it is capable of maintaining 0.5 dB and 1 dB monotonicity through 55 GHz. The PE43508 also delivers glitch-safe attenuation state transitions, meaning no increased power spike during a state transition.

The PE43508 has an extended temperature range from −40°C to +105°C, an HBM ESD rating of 1 kV and an easy-to-use digital control interface supporting both serial addressable and parallel programming. The DSA supports 1.8 V control signals and has an optional VSS_EXT bypass mode.

Offered as a flip-chip die, volume-production parts, evaluation kits and samples are available now. For 1K-quantity orders, each PE43508 is $50 USD.

In the quest for abundant, renewable alternatives to fossil fuels, scientists have sought to harvest the sun’s energy through “water splitting,” an artificial photosynthesis technique that uses sunlight to generate hydrogen fuel from water. But water-splitting devices have yet to live up to their potential because there still isn’t a design for materials with the right mix of optical, electronic, and chemical properties needed for them to work efficiently.

The HPEV cell’s extra back outlet allows the current to be split into two, so that one part of the current contributes to solar fuels generation, and the rest can be extracted as electrical power. Credit: Credit: Berkeley Lab, JCAP

Now researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub, have come up with a new recipe for renewable fuels that could bypass the limitations in current materials: an artificial photosynthesis device called a “hybrid photoelectrochemical and voltaic (HPEV) cell” that turns sunlight and water into not just one, but two types of energy – hydrogen fuel and electricity. The paper describing this work was published on Oct. 29 in Nature Materials.

Finding a way out for electrons

Most water-splitting devices are made of a stack of light-absorbing materials. Depending on its makeup, each layer absorbs different parts or “wavelengths” of the solar spectrum, ranging from less-energetic wavelengths of infrared light to more-energetic wavelengths of visible or ultraviolet light.

When each layer absorbs light it builds an electrical voltage. These individual voltages combine into one voltage large enough to split water into oxygen and hydrogen fuel. But according to Gideon Segev, a postdoctoral researcher at JCAP in Berkeley Lab’s Chemical Sciences Division and the study’s lead author, the problem with this configuration is that even though silicon solar cells can generate electricity very close to their limit, their high-performance potential is compromised when they are part of a water-splitting device.

The current passing through the device is limited by other materials in the stack that don’t perform as well as silicon, and as a result, the system produces much less current than it could – and the less current it generates, the less solar fuel it can produce.

“It’s like always running a car in first gear,” said Segev. “This is energy that you could harvest, but because silicon isn’t acting at its maximum power point, most of the excited electrons in the silicon have nowhere to go, so they lose their energy before they are utilized to do useful work.”

Getting out of first gear

So Segev and his co-authors – Jeffrey W. Beeman, a JCAP researcher in Berkeley Lab’s Chemical Sciences Division, and former Berkeley Lab and JCAP researchers Jeffery Greenblatt, who now heads the Bay Area-based technology consultancy Emerging Futures LLC, and Ian Sharp, now a professor of experimental semiconductor physics at the Technical University of Munich in Germany – proposed a surprisingly simple solution to a complex problem.

“We thought, ‘What if we just let the electrons out?'” said Segev.

In water-splitting devices, the front surface is usually dedicated to solar fuels production, and the back surface serves as an electrical outlet. To work around the conventional system’s limitations, they added an additional electrical contact to the silicon component’s back surface, resulting in an HPEV device with two contacts in the back instead of just one. The extra back outlet would allow the current to be split into two, so that one part of the current contributes to solar fuels generation, and the rest can be extracted as electrical power.

When what you see is what you get

After running a simulation to predict whether the HPEC would function as designed, they made a prototype to test their theory. “And to our surprise, it worked!” Segev said. “In science, you’re never really sure if everything’s going to work even if your computer simulations say they will. But that’s also what makes it fun. It was great to see our experiments validate our simulations’ predictions.”

According to their calculations, a conventional solar hydrogen generator based on a combination of silicon and bismuth vanadate, a material that is widely studied for solar water splitting, would generate hydrogen at a solar to hydrogen efficiency of 6.8 percent. In other words, out of all of the incident solar energy striking the surface of a cell, 6.8 percent will be stored in the form of hydrogen fuel, and all the rest is lost.

In contrast, the HPEV cells harvest leftover electrons that do not contribute to fuel generation. These residual electrons are instead used to generate electrical power, resulting in a dramatic increase in the overall solar energy conversion efficiency, said Segev. For example, according to the same calculations, the same 6.8 percent of the solar energy can be stored as hydrogen fuel in an HPEV cell made of bismuth vanadate and silicon, and another 13.4 percent of the solar energy can be converted to electricity. This enables a combined efficiency of 20.2 percent, three times better than conventional solar hydrogen cells.

The researchers plan to continue their collaboration so they can look into using the HPEV concept for other applications such as reducing carbon dioxide emissions. “This was truly a group effort where people with a lot of experience were able to contribute,” added Segev. “After a year and a half of working together on a pretty tedious process, it was great to see our experiments finally come together.”

Finding ways to improve the drug development process – which is currently costly, time-consuming and has an astronomically high failure rate – could have far-reaching benefits for health care and the economy. Researchers from the Georgia Institute of Technology have designed a cellular interfacing array using low-cost electronics that measures multiple cellular properties and responses in real time. This could enable many more potential drugs to be comprehensively tested for efficacy and toxic effects much faster. That’s why Hua Wang, associate professor in the School of Electrical and Computer Engineering at Georgia Tech, describes it as “helping us find the golden needle in the haystack.”

Built on standard complementary metal oxide semiconductor (CMOS) technologies, the cellular sensing array chip uses a standard 35 mm cell culture dish with the bottom removed to host the cells and expose them to the sensing surface.

Pharmaceutical companies use cell-based assays, a combination of living cells and sensor electronics, to measure physiological changes in the cells. That data is used for high-throughput screening (HTS) during drug discovery. In this early phase of drug development, the goal is to identify target pathways and promising chemical compounds that could be developed further – and to eliminate those that are ineffective or toxic – by measuring the physiological responses of the cells to each compound.

Phenotypic testing of thousands of candidate compounds, with the majority “failing early,” allows only the most promising ones to be further developed into drugs and maybe eventually to undergo clinical trials, where drug failure is much more costly. But most existing cell-based assays use electronic sensors that can only measure one physiological property at a time and cannot obtain holistic cellular responses.

That’s where the new cellular sensing platform comes in. “The innovation of our technology is that we are able to leverage the advance of nano-electronic technologies to create cellular interfacing platforms with massively parallel pixels,” said Wang. “And within each pixel we can detect multiple physiological parameters from the same group of cells at the same time.” The experimental quad-modality chip features extracellular or intracellular potential recording, optical detection, cellular impedance measurement, and biphasic current stimulation.

Wang said the new technology offers four advantages over existing platforms:

Multimodal sensing: The chip’s ability to record multiple parameters on the same cellular sample gives researchers the ability to comprehensively monitor complex cellular responses, uncover the correlations among those parameters and investigate how they may respond together when exposed to drugs. “Living cells are small but highly complex systems. Drug administration often results in multiple physiological changes, but this cannot be detected using conventional single-modal sensing,” said Wang.

Large field of view: The platform allows researchers to examine the behavior of cells in a large aggregate to see how they respond collectively at the tissue level.

Small spatial resolution: Not only can researchers look at cells at the tissue level, they could also examine them at single-cell or even sub-cellular resolution.

Low-cost platform: The new array platform is built on standard complementary metal oxide semiconductor (CMOS) technologies, which is also used to build computer chips, and can be easily scaled up for mass production.

Wang’s team worked closely with Hee Cheol Cho, associate professor and the Urowsky-Sahr Scholar in Pediatric Bioengineering, whose Heart Regeneration lab is part of the Wallace Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. They used neonatal rat ventricular myocytes and cardiac fibroblasts to illustrate the multi-parametric cell profiling ability of the array for drug screening. The recent results were published in the Royal Society of Chemistry’s journal Lab on a Chip on August 31, 2018.

Monitoring cellular responses in multi-physical domains and holistic multi-parametric cellular profiling should also prove beneficial in screening out chemical compounds that could have harmful effects on certain organs, said Jong Seok Park, a post-doctoral fellow in Wang’s lab and a leading author of the study. Many drugs have been withdrawn from the market after discoveries that they had toxic effects on the heart or liver, for example. This platform should enable researchers to comprehensively test for organ toxicity and other side effects at the initial phases of drug discovery.

The experimental chip may be useful for other applications, including personalized medicine – for example, testing cancer cells from a particular patient. “Patient to patient variation is huge, even with the same type of drug,” said Wang. The cellular interface array could be used to see which combination of existing drugs would give the best response and to find the optimum dose that is most effective with minimum toxicity to healthy cells.

The chip is capable of actuation as well as sensing. In the future, Wang said that cellular data from the chip could be uploaded and processed, and based on that, commands for new actuation or data acquisition could be sent to the chip automatically and wirelessly. He envisions rooms and rooms containing culture chambers with millions of such chips in fully automated facilities, “just automatically doing new drug selection for us,” he said.

Beyond these applications, Wang noted the scientific value of the research itself. Integrated circuits and nanoelectronics are some of the most sophisticated technology platforms created by humans. Living cells, on the other hand, are complex products produced through billions of years of natural selection and evolution.

“The central theme of our research is how we can leverage the best platform created by nature with the best platform created by humans,” he said. “Can we let them work together to create hybrid systems that achieve capabilities beyond biology only or electronics only systems? The fundamental scientific question we are addressing is how we can let inorganic electronics better interface with organic living cells.”

Rice University scientists are counting on films of carbon nanotubes to make high-powered, fast-charging lithium metal batteries a logical replacement for common lithium-ion batteries.

Rice University graduate student Gladys López-Silva holds a lithium metal anode with a film of carbon nanotubes. Once the film is attached, it becomes infiltrated by lithium ions and turns red. Credit: Jeff Fitlow/Rice University

The Rice lab of chemist James Tour showed thin nanotube films effectively stop dendrites that grow naturally from unprotected lithium metal anodes in batteries. Over time, these tentacle-like dendrites can pierce the battery’s electrolyte core and reach the cathode, causing the battery to fail.

That problem has both dampened the use of lithium metal in commercial applications and encouraged researchers worldwide to solve it.

Lithium metal charges much faster and holds about 10 times more energy by volume than the lithium-ion electrodes found in just about every electronic device, including cellphones and electric cars.

“One of the ways to slow dendrites in lithium-ion batteries is to limit how fast they charge,” Tour said. “People don’t like that. They want to be able to charge their batteries quickly.”

The Rice team’s answer, detailed in Advanced Materials, is simple, inexpensive and highly effective at stopping dendrite growth, Tour said.

“What we’ve done turns out to be really easy,” he said. “You just coat a lithium metal foil with a multiwalled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.”

“Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions,” said Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva. “The ions distribute themselves throughout the nanotube film.”

When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.

The tangled-nanotube film effectively quenched dendrites over 580 charge/discharge cycles of a test battery with a sulfurized-carbon cathode the lab developed in previous experiments. The researchers reported the full lithium metal cells retained 99.8 percent of their coulombic efficiency, the measure of how well electrons move within an electrochemical system.

Solar cells are a cost-effective, alternate source of energy. A subtype of these, organic solar cells make use of organic polymers inside the cell. Using these polymers makes the cells light-weight and increases their flexibility. Organic solar cells are produced by two different chemical methods: dry processing and wet processing, with the latter being a faster method. There are several parameters used to assess the efficiency of solar cells with absorption of light and transportation of charge being widely used.

A prevailing problem with the structure of organic cells is that molecules in the active organic layer responsible for light absorption and charge transport tend to face both towards the edges of cells, as well as towards the light absorbing substrate. Maximizing the number of molecules facing the substrate, however, is the key to maximising absorption and conductivity of the cell. Scientists have modified the dry processing method to achieve such an orientation, but it has not been possible with the wet method. The research team led by Tetsuya Taima at Kanazawa University, is the first to successfully do so.

The premise of their method is the introduction of a copper iodide (CuI) layer between the active molecules and the substrate. In their study, the researchers used a film of active molecules called DRCN5T and coated them onto either CuI/PEDOT: PSS (30 nm)/indium tin oxide (ITO) mixed substrates, or substrates without the CuI layer. The ratio of substrate facing to edge facing DRCN5T molecules was then compared between both. Subsequent high-resolution imaging revealed that the CuI containing cells had active molecules with a ten times higher substrate facing orientation, along with enhanced light absorption. The researchers attributed this altered orientation of the molecules to strong chemical interactions between the DRCN5T and CuI atoms. To further confirm this, DRCN5T molecules with bulky side chains that do not interact with CuI were used, and a higher substrate facing ratio was not seen.

This is the first study that effectively demonstrates a method of producing such efficient organic solar cells using the wet processing method. Besides saving time, the wet method also results in larger film areas. “This technique is expected to greatly contribute to the development of organic thin film solar cells fabricated by wet processing in the future”, conclude the authors. Their approach paves the way for producing high-performance solar cells faster.

Gyroscopes are devices that help vehicles, drones, and wearable and handheld electronic devices know their orientation in three-dimensional space. They are commonplace in just about every bit of technology we rely on every day. Originally, gyroscopes were sets of nested wheels, each spinning on a different axis. But open up a cell phone today, and you will find a microelectromechanical sensor (MEMS), the modern-day equivalent, which measures changes in the forces acting on two identical masses that are oscillating and moving in opposite directions. These MEMS gyroscopes are limited in their sensitivity, so optical gyroscopes have been developed to perform the same function but with no moving parts and a greater degree of accuracy using a phenomenon called the Sagnac effect.

This is the optical gyroscope developed in Ali Hajimiri’s lab, resting on grains of rice. Credit: Ali Hajimiri/Caltech

What is the Sagnac Effect?

The Sagnac effect, named after French physicist Georges Sagnac, is an optical phenomenon rooted in Einstein’s theory of general relativity. To create it, a beam of light is split into two, and the twin beams travel in opposite directions along a circular pathway, then meet at the same light detector. Light travels at a constant speed, so rotating the device–and with it the pathway that the light travels–causes one of the two beams to arrive at the detector before the other. With a loop on each axis of orientation, this phase shift, known as the Sagnac effect, can be used to calculate orientation.

The Problem

The smallest high-performance optical gyroscopes available today are bigger than a golf ball and are not suitable for many portable applications. As optical gyroscopes are built smaller and smaller, so too is the signal that captures the Sagnac effect, which makes it more and more difficult for the gyroscope to detect movement. Up to now, this has prevented the miniaturization of optical gyroscopes.

The Invention

Caltech engineers led by Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering in the Division of Engineering and Applied Science, developed a new optical gyroscope that is 500 times smaller than the current state-of-the-art device, yet they can detect phase shifts that are 30 times smaller than those systems. The new device is described in a paper published in the November issue of Nature Photonics.

How it works

The new gyroscope from Hajimiri’s lab achieves this improved performance by using a new technique called “reciprocal sensitivity enhancement.” In this case, “reciprocal” means that it affects both beams of the light inside the gyroscope in the same way. Since the Sagnac effect relies on detecting a difference between the two beams as they travel in opposite directions, it is considered nonreciprocal. Inside the gyroscope, light travels through miniaturized optical waveguides (small conduits that carry light, that perform the same function as wires do for electricity). Imperfections in the optical path that might affect the beams (for example, thermal fluctuations or light scattering) and any outside interference will affect both beams similarly.

Hajimiri’s team found a way to weed out this reciprocal noise while leaving signals from the Sagnac effect intact. Reciprocal sensitivity enhancement thus improves the signal-to-noise ratio in the system and enables the integration of the optical gyro onto a chip smaller than a grain of rice.

Cadence Design Systems, Inc. (NASDAQ: CDNS) today announced that its custom and analog/mixed-signal (AMS) IC design tools have achieved certification for Samsung Foundry’s 7nm Low Power Plus (7LPP) process technology. This certification ensures Cadence and Samsung Foundry mutual customers of a highly automated circuit design, layout, signoff and verification flow with full extreme ultraviolet lithography (EUV) support. This certification complements the earlier announced certification of the Cadence® full-flow digital and signoff tools on Samsung 7LPP process technology.

The Cadence custom and AMS flow includes the Virtuoso® Analog Design Environment (ADE), Virtuoso Schematic Editor, Virtuoso Layout Suite with its Advanced-Node Platform, Virtuoso Space-Based Router, Spectre® Circuit Simulator, Voltus™-Fi Custom Power Integrity Solution, Quantus™ Extraction Solution, Physical Verification System, Litho Physical Analyzer, Cadence CMP Predictor and LDE Electrical Analyzer. These tools can be used throughout the complete custom AMS flow, including:

  • Custom layout design: An advanced, electro-migration and parasitic-aware environment that includes device and module generation, automated placement and routing, layout editing, and dynamic DRC checking with Virtuoso Integrated PVS DRC, interactive PVS metal fill, in-design DFM flows for LDE, process hotspot repair (PHR), pattern analysis and optimization, and chemical mechanical polishing (CMP) check, as well as support for correct-by-design multiple patterning flow.
  • Post-layout parasitic simulation and IR drop (IREM) analysis and integrated signoff: Including parasitic extraction, design rule checks, layout versus schematic checks, dummy metal fill and programmable electrical rule checks (PERC).
  • AMS design: Digital standard cell placement, pin optimization and automated space-based routing.

“In close collaboration with Samsung, we have delivered a certified, integrated flow for custom and AMS design at 7LPP technology based on our industry-leading Virtuoso and Spectre platforms,” said Wilbur Luo, Cadence vice president, product management, analog/custom marketing. “Samsung customers can now take advantage of the most advanced features for circuit design, performance and reliability verification, and automated layout, block and chip integration for custom and digitally controlled analog designs.”

“By working closely with Cadence, we can provide our customers the most advanced FinFET performance for their custom and AMS chip designs,” said Ryan Lee, vice president of Foundry Marketing at Samsung Electronics. “Cadence helps us offer our customers the best power, performance and area for their leading-edge designs.”

ClassOne Technology, a supplier of new wet process tools to the 200mm and below semiconductor manufacturing industry, today announced the sale of its flagship Solstice® S8 wet process tool to the Ferdinand-Braun-Institute (FBH) in Berlin, Germany. As a leading research institute in the fabrication of III-V compound semiconductors, FBH specializes in prototyping leading-edge microwave and optoelectronic devices for a diverse range of industries, including communications, energy, health, and mobility.

“Solstice is a perfect fit for the III-V compound semiconductor processes that FBH specializes in,” explains Olaf Krüger, Head of FBH’s Process Technology Department. “The exceptional flexibility of the Solstice platform will allow FBH to efficiently automate a number of distinct processes on a single tool. We expect to retain the fine-grained control needed in our research environment with the added production benefits of complete cassette-to-cassette automation.“

FBH is the latest example of a growing trend in the compound semiconductor industry—the need for integrated plating-related processes as part of a comprehensive plating solution. ClassOne’s eight-chamber Solstice S8 will provide FBH with sophisticated electroplating and wet processing capabilities for a range of processes. In particular, gold plating will be performed by a pair of ClassOne’s class-leading GoldPro™ chambers, and a new high-pressure spray solvent chamber will process highly-efficient Metal Lift-off. ClassOne has dubbed the wide range of plating-related wet processing capabilities on the Solstice platform as Plating-PlusTM.

“The configuration flexibility of Plating-PlusTM and the exceptional quality of our plating chambers are why ClassOne has become the supplier of choice for the compound semiconductor industry,” says Roland Seitz, Director of ClassOne’s European Operations. “Solstice is perfectly suited to the complex processing requirements of compound semiconductors. By placing several related processes on a single tool, FBH will enjoy processing efficiencies and device quality that simply cannot be achieved by any other supplier.”

Spectrometers — devices that distinguish different wavelengths of light and are used to determine the chemical composition of everything from laboratory materials to distant stars — are large devices with six-figure price tags, and tend to be found in large university and industry labs or observatories.

A collection of mini-spectrometer chips are arrayed on a tray after being made through conventional chip-making processes. Credit: Felice Frankel

A new advance by researchers at MIT could make it possible to produce tiny spectrometers that are just as accurate and powerful but could be mass produced using standard chip-making processes. This approach could open up new uses for spectrometry that previously would have been physically and financially impossible.

The invention is described today in the journal Nature Communications, in a paper by MIT associate professor of materials science and engineering Juejun Hu, doctoral student Derek Kita, research assistant Brando Miranda, and five others.

The researchers say this new approach to making spectrometers on a chip could provide major advantages in performance, size, weight, and power consumption, compared to current instruments.

Other groups have tried to make chip-based spectrometers, but there is a built-in challenge: A device’s ability to spread out light based on its wavelength, using any conventional optical system, is highly dependent on the device’s size. “If you make it smaller, the performance degrades,” Hu says.

Another type of spectrometer uses a mathematical approach called a Fourier transform. But these devices are still limited by the same size constraint — long optical paths are essential to attaining high performance. Since high-performance devices require long, tunable optical path lengths, miniaturized spectrometers have traditionally been inferior compared to their benchtop counterparts.

Instead, “we used a different technique,” says Kita. Their system is based on optical switches, which can instantly flip a beam of light between the different optical pathways, which can be of different lengths. These all-electronic optical switches eliminate the need for movable mirrors, which are required in the current versions, and can easily be fabricated using standard chip-making technology.

By eliminating the moving parts, Kita says, “there’s a huge benefit in terms of robustness. You could drop it off the table without causing any damage.”

By using path lengths in power-of-two increments, these lengths can be combined in different ways to replicate an exponential number of discrete lengths, thus leading to a potential spectral resolution that increases exponentially with the number of on-chip optical switches. It’s the same principle that allows a balance scale to accurately measure a broad range of weights by combining just a small number of standard weights.

As a proof of concept, the researchers contracted an industry-standard semiconductor manufacturing service to build a device with six sequential switches, producing 64 spectral channels, with built-in processing capability to control the device and process its output. By expanding to 10 switches, the resolution would jump to 1,024 channels. They designed the device as a plug-and-play unit that could be easily integrated with existing optical networks.

The team also used new machine-learning techniques to reconstruct detailed spectra from a limited number of channels. The method they developed works well to detect both broad and narrow spectral peaks, Kita says. They were able to demonstrate that its performance did indeed match the calculations, and thus opens up a wide range of potential further development for various applications.

The researchers say such spectrometers could find applications in sensing devices, materials analysis systems, optical coherent tomography in medical imaging, and monitoring the performance of optical networks, upon which most of today’s digital networks rely. Already, the team has been contacted by some companies interested in possible uses for such microchip spectrometers, with their promise of huge advantages in size, weight, and power consumption, Kita says. There is also interest in applications for real-time monitoring of industrial processes, Hu adds, as well as for environmental sensing for industries such as oil and gas.