Chinese researchers have developed a new technique to manipulate the speed of light on a microchip, making it over 10,000 times slower than in a vacuum. This could enhance the performance and applications of these microchips, which are known as photonic chips, in light sensing, communications and computing.
Photonic chips use photons, or light particles, instead of electrons to process information. They have several advantages over conventional electronic chips, such as:
- Higher speed: Photons can travel faster than electrons, allowing faster data transmission and computation.
- Lower power consumption: Photons generate less heat than electrons, reducing the energy and cooling costs of the devices.
- Higher bandwidth: Photons can carry more information than electrons, enabling more complex and diverse functions.
Photonic chips are widely used in optical communication, such as fiber-optic networks, and optical sensing, such as lidar and medical imaging. They also have potential applications in quantum computing, artificial intelligence and neuromorphic computing.
How did the Chinese researchers slow down light?
The speed of light in a vacuum is a constant and cannot be exceeded, but it can be slowed down in other media, such as air, water or glass. The degree to which light slows down in a medium is called the refractive index. The higher the refractive index, the slower the light travels.
The Chinese researchers, from the Shenzhen Institute of Advanced Technology, under the Chinese Academy of Sciences, designed a photonic chip with a high refractive index, which reduced the speed of light by more than 10,000 times. They published their findings in the peer-reviewed journal Nano Letters on January 5.
The key to their technique was to create a periodic structure on the surface of the chip, which consisted of tiny pillars of silicon. These pillars acted as artificial atoms that resonated with the incoming light, altering its amplitude and phase. This created a phenomenon called slow light, which is light that travels at a fraction of its original speed.
The researchers said that slowing down light increased the energy density of the light, which meant that the light interacted more effectively with the chip. This enhanced the performance of the photonic device, such as its sensitivity, modulation and switching.
What are the challenges and implications of this technique?
The main challenge of slowing down light on a chip is to minimize the loss of light due to absorption and scattering by the material. The researchers said that they achieved a low loss of light, which was only about 20 per cent of the loss seen in previous attempts. They did this by choosing materials with low or no absorption loss at the wavelengths of interest, such as silicon, silicon nitride or titanium dioxide.
The researchers also improved the structural design of the chip, such as the shape, size and arrangement of the pillars, to optimize the slow light effect. They said that their technique was compatible with the current fabrication technology of photonic chips, and could be easily integrated with other components.
The researchers said that their technique could have significant implications for the field of photonics, as it could enable new functionalities and applications for photonic chips. For example, they said that their technique could improve the performance of optical modulators, which are devices that control the amplitude, phase or frequency of light. Optical modulators are essential for optical communication, as they encode information onto light signals.
The researchers also said that their technique could enhance the performance of optical switches, which are devices that direct the flow of light. Optical switches are important for optical networks, as they route light signals to different destinations. They said that their technique could enable faster and more efficient optical switching, which could improve the capacity and reliability of optical networks.
The researchers said that their technique could also improve the performance of optical sensors, which are devices that detect changes in light. Optical sensors are widely used in various fields, such as environmental monitoring, biomedical diagnosis and security. They said that their technique could increase the sensitivity and resolution of optical sensors, which could enable more accurate and precise measurements.
How does this technique compare with other methods?
The current mainstream method to manipulate the speed of light on a chip relies on metasurfaces, which are artificial materials made up of nanostructures. Metasurfaces can also create slow light effects, but they have some limitations, such as:
- Higher loss of light: Metasurfaces can cause more absorption and scattering of light, which reduces the quality and efficiency of the photonic device.
- Lower compatibility: Metasurfaces require special fabrication techniques, which are not compatible with the existing technology of photonic chips. This makes it difficult to integrate metasurfaces with other components on a chip.
- Lower scalability: Metasurfaces have a limited range of wavelengths that they can operate at, which restricts the functionality and diversity of the photonic device.
The researchers said that their technique overcame these limitations, and offered a more effective and versatile way to manipulate the speed of light on a chip. They said that their technique could pave the way for the development of next-generation photonic chips, which could revolutionize the fields of light sensing, communications and computing.
