"Do you believe in light?" If a chip enthusiast asks you this question, it's not that he's suddenly an Ultraman fan. It's that he's starting to notice that "light" is starting to stir up the chip world.
The 2023 Nobel Prize in Physics was awarded to "asymmetric light pulse technology", and "how to use light to calculate" has also become an important topic in the industry and academia. Can light, which is naturally fast, complete the upgrading of the "infrastructure" of the intelligent world in the era of artificial intelligence at an incredible speed?
Photons take over from electrons
Compared with the more traditional electronic chips, photonic chips are a new type of chips that use the properties of photons to calculate.
In essence, chips rely on the physical properties of semiconductor materials to manipulate microscopic particles that carry information, but different types of chips use different particle carriers. "Photonic chips use photons to generate, process, transmit and display information," said Lei Mi, founding partner of China Innovation Star.
Compared with electrons, the advantages of photons are obvious: they have a very fast response time for information transmission, 3-4 orders of magnitude higher information capacity than electrons, strong storage, computing and even parallel interconnection capabilities, and ultra-low energy consumption... It is self-evident what potential these advantages mean for the information industry.
Now, with the advent of the age of artificial intelligence, the demand for computing power is rising. However, the development of electronic chips has reached the limit of physical and economic costs, and the "failure of Moore's Law" is constantly heard.
Electronic chips are based on silicon, with silicon atoms having a diameter of about 0.22 nanometers. When the process is reduced to below 7 nanometers, electronic chips are highly susceptible to electrical surges and electron breakdown issues, making it difficult to perfectly control electrons. In the wave of large models that emerged in 2023, the shortcomings of traditional electronic chips have become evident.
Photonics chips herald a new dawn. They not only promise to address the insurmountable challenges of power consumption and memory access in electronic chips but also give rise to numerous innovative application scenarios. In line with this, optical paths replace electrical circuits, and laser sources take the place of power supplies... By eliminating the need for photoelectric conversion, it is possible to bypass existing physical limits and break through the computational bottleneck of chips. Currently, the competition in this field has already begun among top research institutions both domestically and internationally.
In April this year, a research team from Tsinghua University pioneered a distributed breadth intelligent optical computing architecture in the world. They designed a photonic chip -- "Taiji" for advanced AI tasks, which has an energy efficiency 2 to 3 orders of magnitude higher than that of existing intelligent chips, and can provide computing power support for tasks such as intelligent analysis of large scenes and training and reasoning of large models.
In May, a research team at the Shanghai Institute of Microsystem and Information Technology of the Chinese Academy of Sciences developed a lithium tantalate hetero-integrated wafer, which was also used for the first time to make high-performance and mass-produced photonic chips.
Is the photon chip really not far away?
How to tame light?
In addition to looking forward to the future, let's think more about how photonics chips work?
An electronic chip is made up of an electronic transistor and a conductive copper wire. A photonic chip is made up of a photonic transistor and a waveguide that conducts light. The waveguide is the medium for light propagation, such as the familiar optical fiber.
According to their functions, photonic chips can be divided into two categories: laser chips and detector chips. Laser chips need to use the electric energy of injected current by semiconductor materials to realize the conversion of electricity and light. Detector chips identify optical signals through photoelectric effect and convert them into electrical signals.
How to control light output? Ideally, it would be a fully optical transistor driven and controlled by light. However, the technology is not yet mature; pure photonic chips are still in the conceptual stage, and the basic components of photonic chips are still electro-optic hybrid devices that use light for driving and electricity for control. Based on optoelectronic modulation, Tsinghua University launched the Taiji II chip in August this year, achieving online training of optical neural networks without the need for a GPU.
Through the integration of electro-optical hybrid devices, the entire process of modulation, transmission, and demodulation between optical signals and electrical signals is integrated on a single substrate. This forms the foundation for high-speed data processing in chips. Thanks to the wavelength size advantage of light waves, photonic chips can be fabricated using mature processes with wavelengths as small as a hundred nanometers, enabling complete domestic production of these chips.
Where are the photons chips going to be used?
As I said, photonic chips have the potential to break through the computing power bottleneck of electronic chips. In addition, what other areas can they be used?
It is well known that the speed of light is the fastest known in the universe. Leveraging the high-speed transmission characteristics of light, the first thing that comes to mind with photonic chips is ultra-high-speed data transfer. "Fiber optic network + photonic chip" signifies a new era of high-speed communication. Moreover, the interference resistance of photonic chips also makes it possible for photonic radar to become a reality.
The application of photonic chips in other fields is also promising. For instance, in biomedicine, photonic chips can be used for optical imaging and spectroscopic analysis, enabling rapid detection and analysis of cells, tissues, and drugs. In environmental monitoring, photonic chips can be applied to gas sensors and pollution monitoring, making real-time monitoring and assessment of environmental quality more efficient.
Optical computing chips are starting to move out of the lab, and scientists are hoping that after a series of engineering efforts, commercial photonic chips can be produced in a stable way as soon as possible. That means the cost of photonic chips can be widely accepted by the industry.
