Using phase change materials (PCMs), U.S. researchers have developed photonic integrated circuits (PICs) with rapid prototyping and reprogramming capabilities.
The direct-write and rewritable photonic chip technology developed by the University of Washington in Seattle uses a low-loss phase change material (PCM) thin film that can be laser written directly to a complete end-to-end PIC in a single step, and any part of the circuit can be erased and rewritten, allowing for rapid design modifications.
The team has applied the technology to optical interconnect structures for reconfigurable networks, photonic crossover arrays for optical computing, and tunable optical filters for optical signal processing. Combining the programmability of direct laser writing technology with PCM opens up opportunities for programmable photonic networks, computing, and signal processing. It also provides rapid prototyping and testing in a convenient and cost-effective manner, and eliminates the need for nanofabrication facilities.
The photonic chip was created by using a significant refractive index contrast between two non-volatile phases (amorphous and crystalline) in PCM, which can be used using a laser writing system from a commercial Heidelberg DWL 66+ laser writing system (operating at 405nm and 27.).5MW).
The photonic circuit is written on a standard silicon oxide substrate coated with a 200 nm thick SiO2 layer covering a 30 nm Sb2SE3 layer on a 330 nm Si3N3 film. The SiO2 overlay protects and prevents the SB2SE3 layer from oxidizing.
A waveguide is created in the SB2SE3 film by using the crystalline phase (CSB2SE3) as the high refractive index core and the amorphous phase (ASB2SE3) as the cladding. This binary phase configuration is able to limit the basic transverse electrical (Te0) optical mode to the CSB2SE3 waveguide with the assistance of the Si3N4 underlay.
A series of rectangular ASB2SE3 structures created by the laser range in width from 1 m to 200 nm, with the smallest achievable feature size of 300 nm, which is significantly smaller than other systems.
The team used the technology to build waveguides, gratings, ring resonators, couplers, crosspoints, and interferometers to build photonic chips.
What is a Photonic Chip?
A photonic chip, or photonic integrated circuit (PIC), is a special type of chip.
Unlike traditional electron-dominated chips, photonic chips are devices that use photons (particles of light) for information processing and transmission. In such devices, data is encoded onto photons and then transmitted via optical fibers, enabling ultra-high-speed data transmission.
Photonic chips have a number of significant advantages. First of all, because the speed of light is fast and the frequency of light is much higher than that of electrons, the data transmission speed and processing power of photonic chips far exceed those of electronic chips.
Secondly, the signal transmission loss of photonic chips is small, so long-distance, high-capacity data transmission can be realized. In addition, photonic chips have low energy consumption because the transmission of optical signals does not generate heat.
Finally, photonic chips have good anti-electromagnetic interference performance and strong adaptability to the environment. The realization of photonic chips is not out of reach. In fact, there are already many scientific research institutions and companies developing this new chip, and some products have been used in optical fiber communication, biomedicine, environmental monitoring and other fields.
However, photonic chips also face some technical challenges, such as manufacturing accuracy, optical and electrical conversion efficiency, modulation and detection of optical signals, etc. These problems need to be further overcome by researchers, but overall, the prospects for photonic chips are optimistic.
In addition to photonic chips, researchers are also exploring many other new types of chips, such as quantum chips, nanochips, biochips, etc.
The core components of optical modules
Among the optical module manufacturers, half of the world is in China, but the core of the optical module is the optical chip, which accounts for most of the cost of the optical module, and the domestic optical chip companies are mainly concentrated in 2In the production and manufacturing of 5G series products, 10G and 25G medium and high-speed optical chips have gradually achieved mass production, while the production of high-end optical chips of 50G and above is still mainly concentrated in American and Japanese enterprises, and the domestic demand for high-end optical chips is extremely dependent on imports. Like China, which makes optical modules, but most of the high-end optical chips rely on imports, and only self-developed silicon photonic chips are used in some optical module products and application fields.
The optical module industry chain is also very long, covering chips (electro-optical), devices (passive active), and module finished products, among which chip technology barriers are high, which can account for most of the proportion, and high-end products are monopolized by foreign countries, such as according to ICC data, February 2021The localization rate of optical chips at 5G and below rates exceeds 90%; The localization rate of 10G optical chips is about 60%, and some 10G optical chips with high performance requirements and great difficulty still need to be imported; In 2021, the localization rate of 25G optical chips will be about 20%, but the localization rate of optical chips above 25G will only be 5%, and most of them are overseas optical chip manufacturers.
There are two major growth factors for optical modules
From the perspective of the capital market, there have been two climaxes in the optical module industry in recent years
The first is the peak of the construction of 5G networks in China.
Around 2019-2020, with the issuance of 5G licenses in China, the three major operators vigorously prepared to build 5G networks. Since its expenditure is mainly focused on wireless networks and bearer networks, the demand for fronthaul and midhaul optical modules is very high. Due to the large-scale rendering of 5G networks at that time, the capital market was also very optimistic about the development of 5G, stimulating a wave of annual optical module concepts**.
However, since the second half of 2020, the concept of optical modules has also declined due to the slowdown in 5G network construction and the obstruction of commercial promotion, resulting in a downturn in the past two and a half years. However, optical modules only account for a part of the application of telecommunications, and the larger application is in the field of data communication.
The second is the new era of AI detonated by ChatGPT.
At the end of last year, OpenAI unveiled a new conversational AI model, ChatGPT. Due to its high level of creativity, it quickly went out of the circle and intensified.
At the beginning of the year, various news gradually came to China. Especially after Microsoft launched a new version of the Bing search engine and announced that it would launch "Wenxin Yiyan", related topics broke out on major traffic platforms.
Major manufacturers around the world are engaged in an "arms race" with large AI models. But behind the large-scale model competition, it is actually a competition of computing power.
Take the OpenAI team as an example, they used 10,000 NVIDIA A100 graphics cards to train the GPT3 model. Training GPT4 and higher-level models requires more computing power, and OpenAI is said to have more than 30,000 A100 graphics cards. The industry believes that 10,000 graphics cards are almost the threshold of a large model, and almost all major domestic manufacturers have deployed 20,000 or 30,000 graphics cards.
For example, a SuperPod architecture (NVIDIA's AI infrastructure solution) requires 140 AI servers; 1120 A100GPUs; 186 switches with 5760-8000 transceivers.
Therefore, in a word, the demand for computing power is exponentially exploding, bringing huge new increments to optical modules.