In May last year at a conference in Chengdu, southeastern China, electrical engineer Hugo Hernandez-Figueroa presented the results of a study by his research group from the University of Campinas (UNICAMP) into a device known as an optical isolator, fabricated in collaboration with the Tokyo Institute of Technology in Japan. At 150 square micrometers in size (1 micrometer = 1 thousandth of a millimeter), the item receives light from a source, typically a high-powered laser, and transmits it to the optical circuit without reflecting it, preventing light radiation being sent back from adversely affecting the function of the source.
In November there was another reason to celebrate: experiments by the same group to measure the neuronal activity of a mouse’s heart were successful, using a one-square-millimeter (mm²) photonic sensor fitted with nanoantenna, which capture variations in the electrical field produced by the neurons. As advances are made, this device, developed in collaboration with researchers from the nanoGune center in Spain, may prove useful in noninvasive medical diagnosis of neurodegenerative illnesses and preservation of organs for transplant.
The prototypes from UNICAMP and other research centers in Brazil demonstrate national efforts to accompany the development of a new generation of chips: photonic. Devices of this type generate, transmit, and capture information using photons—the particles associated to a light wave—controlling amplitude (vertical distance between the central axis and highest or lowest point of the wave), frequency (number of repetitions per unit of time), and phase (spatial or temporal movement of the wave). Telecommunications companies have eyes on the component for its efficiency in data transmission, compaction, and energy economy. Due to the high production costs, however, it may be some years before they are employed on a large scale.
As their use is expanded they may increase the performance and energy efficiency of 5G networks, supercomputers and datacenters (see Pesquisa FAPESP issue nº 337), enhance medical diagnosis, and increase safety in driverless cars, supplementing the functionalities of electronic chips, now close to size and processing speed limits. In other countries many research centers, companies, and governments have joined the race to be part of a global market estimated at US$9.4 billion (R$56.4 billion) by 2032 (see box).
Light processors or integrated photonic circuits are now a reality, albeit as yet produced to order by just a few manufacturers, primarily in China, Taiwan, Singapore, Belgium, the US, and Canada. “We have the capacity to fabricate and characterize photonic chips at universities and research centers in São Paulo, Rio de Janeiro, and Minas Gerais, but our production is still small-scale,” says Hernandez-Figueroa. “Generally speaking, it is researchers or students that have to deal with the equipment.” To obtain the support of specialized teams and assure the quality of future prototypes, he intends to commission the manufacture of the isolators and sensors with a company in Belgium at a cost of around R$200,000 for fifteen copies of the isolator, and the same amount of the sensor.
The advantage of the students themselves—generally doing PhD research—operating the prototype fabrication machinery is the possibility of qualifying specialists with a practical view and capable of resolving any issues through the production process, says UNICAMP physicist Gustavo Wiederhecker, coordinator of the FAPESP Quantum Technology Program (QuTIa). “The photonic chip is the cornerstone of quantum technologies, and the subarea with the most researchers, in São Paulo and across other states.”
To bolster the infrastructure, the UNICAMP Center for Semiconductor and Nanotechnology Components (CCSNano) is set to receive an electron beam lithography machine in October, capable of engraving the mold that etches pathways for the light to travel along the silicon plates. Acquired through the FAPESP Multiuser program at a cost of some US$2.8 million (R$17 million), the device will be used alongside another with the same functions, in operation since 2011.
“All prototyping devices need ongoing maintenance,” says Wiederhecker. “If there is only one, and it breaks, work could be suspended for months.” For this reason, the researchers sometimes have to go on what he calls a pilgrimage between universities in Mina Gerais, Rio, and São Paulo in search of machines they can use.
Photonic chips have two or more optical components added to the electronic ones, partially substituting their functions. “The chip is not exclusively photonic, and probably never will be because the laser, an indispensable component, needs electrical current to emit energy in the form of photons,” says electrical engineer Marcelo Segatto, of the Federal University of Espírito Santo (UFES). “One of the electrons’ functions is to heat up parts of the chip, change the refractive index, and alter the amount of light transmitted.”
In chips of this type, the photons move along a type of trail, and the electrons along another toward the transistors, made from indium phosphate or silicon, the primary material in computer and cell phone circuits. “The difference with modern-day chips is that the photonic does what the electronic chip does very well, and also what it can’t, due to the light properties,” he says. “An example? Two photons can pass through each other without interacting, like two ghosts; two electrons cannot.”
In response to a call for entries from the National Council of State Research Funding Agencies (CONFAP) and European Community, issued in 2022, Segatto built a prototype 1mm² photonic chip that simulates the function of a brain neuron. “A photonic chip functioning as a neuron expends a thousand times less energy than its electronic equivalent, as it has a simpler structure,” explains Segatto, a participant in one of the artificial intelligence Engineering Research Centers (CPE) supported by FAPESP.
Ufes Telecommunications LaboratoryChip from UFES, part of an optical neural network, with low energy useUfes Telecommunications Laboratory
Like a neuron
The UFES team designed the devices and chip functions on a computer program and sent the layout to a company from the UK, which then built it. The chip reproducing the function of a neuron was subsequently tested at the University of Trento, Italy, with the participation of the Brazilian team. An article published in December in the Journal of Lightwave Technology describes a mechanism to regulate the arrival of information at the other end of the chip. The light beam is divided into several sub-beams, each of which passes through between one and seven devices in a spiral pattern. The arrival of beams having to pass through more spirals is delayed more than those that pass through fewer. Each spiral delays the sub-beam by 25 picoseconds (10-12 seconds).
As the UFES chip prototype is made from silicon, Segatto had the idea that state-owned semiconductor manufacturer the National Center for Advanced Electronic Technology (CEITEC), in Porto Alegre, southern Brazil, would be able to continue its development, drawing on its experience with this type of material. To this end, in January 2023 the UFES group and other specialists from UNICAMP and the National Photonic Laboratory System (SISFÓTON) sent a letter to the Brazilian Ministry of Science, Technology and Innovation (MCTI) proposing the reinforcement of CEITEC, which has been facing difficulties.
Set up in 2002, the company suffered a significant blow in 2021 when the federal government decreed its permanent closure. The Federal Audit Court halted this move and the current government annulled the decree, but during this period 100 of the 170 staff left CEITEC. The restructuring plan, approved in December 2023, prioritizes the installation, starting this year, of equipment to produce power semiconductors, used for energy conversion at wind or solar farms.
“We will be able to use part of the infrastructure to develop prototypes in the photonics area, but this is not a priority,” says electrical engineer Eric Fabris, the company’s superintendent of Products, Research and Development. “For now, the chances of CEITEC moving into photonics on any significant scale are remote.”
When he started work with his photonic chip manufacturing team in 2018, telecommunications technologist Rafael Carvalho Figueiredo, of the Telecommunications Research and Development Center (CPqD), also in Campinas, already knew that it would be very difficult to get beyond the laboratory prototype stage. “The domestic market is largely focused on the integration of imported components, but projects like this one are important steps to drive local development and provide new opportunities for the industry,” he comments. The work was part of the project Teranet – Optical Systems at 1 Tb/s (terabyte per second) for the Internet of the Future, supported by the Brazilian Funding Authority for Studies and Projects (FINEP), with a grant from the Fund for Technological Telecommunications Development (FUNTTEL).
The chip was designed at CPqD, manufactured in Belgium, and finished at the Campinas center. With potential applications in telecommunications, the 25 mm² device has a transceiver—a transmitter and receiver combined—converting electrical signals into light signals or vice versa.
Léo Ramos Chaves / Revista Pesquisa FAPESPUNICAMP lithograph device for chip modeling: capable of writing in resolutions lower than 10 nanometersLéo Ramos Chaves / Revista Pesquisa FAPESP
Its transmission capacity is 1.2 Tb/s, much faster than the 800 gigabytes per second (Gbp/s) in more advanced commercial equivalents. In March, tests on the chip, used at one of the ends of a beam with 500 kilometers (km) of optical fibers, were concluded with satisfactory results. “We can improve with a partnership to advance development,” says Figueiredo.
His colleague Tiago Sutili, also an electrical engineer, says: “Even if the work does not go ahead, the knowledge is not lost.” Sutili says that the experiment has formed the basis for new research projects, such as the development of an electro-optic moderator, one of the transmitter’s main components, described in a September 2023 article in Scientific Reports in collaboration with researchers from São Paulo State University (UNESP). “We also drew upon what we learned to improve other microfabrication and electro-optic integration processes for photonic chips,” he adds.
Electrical engineer Arismar Cerqueira Sodré Junior, with his team from the National Telecommunications Institute (INATEL), a private higher-education facility in Santa Rita do Sapucaí, Minas Gerais State, discovered other pathways. During doctoral studies between 2019 and 2023 a researcher from his group, telecommunications engineer Eduardo Saia Lima, worked on the characterization and application of a photonic chip designed by researchers from two universities in Italy—with whom the Brazilians collaborated—and manufactured in the UK.
Turbocharged device
Lima used the chip to multiply light frequency from 2.6 gigahertz (GHz) to 26 GHz, as detailed in September 2022 in Scientific Reports. “We managed to generate a 5G signal using light with a device of relatively low cost and the same performance of a commercial radio frequency generator, which is a very expensive piece of equipment,” he says, adding that this gain could be very useful in 5G internet networks.
“The work has not stopped,” says Sodré Junior. Based on the results, he began working with a group from UNICAMP coordinated by electrical engineer Evandro Conforti to develop a semiconductor optical amplifier, for multiplication of frequency for high-speed internet. Designed by a company from the Netherlands, the chip will be made in Berlin, Germany, at an approximate cost of €20,000 (R$120,000). “The chip is 2 mm by 5 mm and should contain a high-speed photonics switch with several outlets for light,” says Conforti.
From this and other studies, the researchers gain experience in designing and testing photonic chips, in addition to building prototypes, even though national production in the short term is unfeasible, given the high investments required and international competition. “It’s not worth it to invest in a factory in Brazil,” says UNICAMP’s Wiederhecker. “What’s needed is a cleanroom [sterilized space] that enables researchers to complete their work uninterrupted, and technologists to develop new applications. That’s the successful model I have seen in other countries.”
Governments, corporations, and research institutes announce innovations and strive to break new ground in the area
FMN Lab / Wikimedia CommonsProduction of photonic chip that simulates the function of a neuron in the laboratory at the Bauman Moscow State Technical UniversityFMN Lab / Wikimedia Commons
Research centers in China and the US recently presented advances that could speed up the development of photonic chips. In May 2024, researchers from the Shanghai Institute of Microsystem and Information Technology, in collaboration with the Institute of Technology in Lausanne, Switzerland, announced an innovation capable of expanding and lowering the cost of producing photonic chips: the substitution of a high-cost semiconductor material used in their production—lithium niobate—with lithium tantalate, which also converts electricity into light at lower cost.
As reported last December in Nature Photonics, a group from the Massachusetts Institute of Technology (MIT) and Finnish corporation Nokia described a photonic chip built using commercial casting processes that may reduce production costs. With interconnected modules simulating a neural network, the device concluded the key calculations for a machine-learning classification task in less than half a nanosecond, at 92% accuracy, performance equivalent to that of the traditional electronic device.
Governments and companies are also getting busy. In October, the US Department of Trade announced that it would provide up to US$93 million (R$558 million) of funding for optical semiconductor manufacturer Infinera to effect a tenfold increase in the production of photonic chips in San Jose, California. US tech giants such as Intel, Cisco, Agilent, Ciena, Hewlett Packard, and IBM, and at least one from China—Huawei—are in the race to conclude the development of their products, integrating electronic and photonic components.
The same is happening in Europe. In May 2024, photonic computing company iPronics, a spin-off of Spain’s Valencia Polytechnic University, announced investments of €3.7 million (R$22 million) to up the output scale and provide end users with a multifunctional, programmable photonic chip, as presented three months ago in Nature Communications.
In September, Ephos announced the inauguration of a factory in Milan, Italy, to produce glass photonic chips for quantum computing, the fruit of US$8.5 million (R$51 million) in investments by companies in the US and the European Innovation Council (EIC). With a consortium of eleven countries, in November the European Union announced €380 million (R$2.3 billion) in investments to build a pilot photonic chip plant.
In September 2023, Rockley Photonics, of Oxford in the UK, communicated that it continued to “make rapid progress toward noninvasive detection of glucose using its own silicon photonic platform.” The aim is to monitor blood components using a wearable device fitted with sensors capable of monitoring the blood in a noninvasive manner, through real-time shortwave infrared spectroscopy. A similar device, used to measure blood pressure, obtained results considered satisfactory for the first phase of testing on humans.
The story above was published with the title “Building photonic chips” in issue in issue 348 of february/2025.
Projects
1. Photonics for the next-generation internet (nº 15/24517-8); Grant Mechanism Thematic Project; Agreement MCTI/MC; Principal Investigator Hugo Enrique Hernández Figueroa (UNICAMP); Investment R$1,916,985.63.
2. IARA – Artificial Intelligence Recreating Environments (nº 20/09835-1); Grant Mechanism Engineering Research Centers Program; Agreement MCTI/MC; Principal Investigator André Carlos Ponce de Leon Ferreira de Carvalho (USP); Investment R$4,303,073.88.
3. Strategic technologies for high-speed internet (nº 21/06569-1); Grant Mechanism Thematic Project (agreement with MCTIC); Principal Investigator Evandro Conforti (UNICAMP); Investment R$2,471,735.98 plus US$279,283.71.
Scientific articles
BANDYOPADHYAY, S. et al. Single-chip photonic deep neural network with forward-only training. Nature Photonics. Vol. 18, pp. 1335–43. Dec. 2, 2024.
LIMA, E. S. et al. Integrated optical frequency comb for 5G NR Xhauls. Scientific Reports. Vol. 12, 16421. Sept. 30, 2022.
MARCIANO, P. R. N. et al. Analysis of a photonic integrated circuit for passive optical network for 5G NR. Applied Optics. Vol. 62, no. 8, pp. 71–9. Mar. 10, 2023.
MARCIANO, P. R. N. et al. Chromatic distortion precompensation in OFDM-based optical systems through na integrated silicon photonic neural network. Journal of Lightwave Technology. Online. Dec. 5, 2024.
PAULA JR., R. A. de et al. Design of a silicon Mach–Zehnder modulator via deep learning and evolutionary algorithms. Scientific Reports. Vol. 13, 14662. Sept. 5, 2023.
PÉREZ-LÓPES, D. et al. General-purpose programmable photonic processor for advanced radiofrequency applications. Nature Communications. Vol. 15, 1563. Feb. 20, 2024.
