A Combination of Microwave Engineering and Optoelectronics to Improve Signal Processing
Researchers at the École Polytechnique Fédérale de Lausanne (EPFL), an institute in Switzerland, created a process that uses deep ultraviolet stepper lithography that outperforms current nanofabrication techniques.
Improving Chip-Scale Frequencies
There are many challenges in the semiconductor industry that researchers around the world are aiming to solve through experimental trials. One of those challenges is not being able to adequately process microwave signals in wireless networks, telecommunications, and radars.
These applications require carriers in High Frequency (HF) bands to have strong instantaneous bandwidths. Bandwidth is a demanding factor found in 5G implementation and the Internet of Things (IoT). Researchers at the EPFL was determined to bring microwave engineering and optoelectronics together to solve this problem.
Method of Optical Frequency Combs
A team of researchers at EPFL had their objective set on gaining the ability to control light using silicon photonics at chip-scale frequency. The researchers developed a process involving integrated soliton microcombs which enhanced lasers with repetition rates as low as 10GHz. There was enough light to propagate approximately 1 meter in a waveguide with a diameter 100 times smaller than a strand of human hair.
During photodetection, the researchers created a Silicon nitride photonic Damascne process, which was carried out using deep ultraviolet stepper lithography. This process benefits existing manufacturing plants by providing a new nanofabrication technique to reduce electrical power loss. The generated silicon nitride waveguides offered the lowest loss in photonic integrated circuits.
Single solitons with microwave K-band and X-band repetition rates. Image credited to EPFL
Benefits to 5G and Radar Applications
How does this help applications such as 5G and Radar? By combining microwave engineering and optoelectronics, these researchers generated coherent soliton pulses that have repetition rates in both the microwave K-band (used in 5G) and X-band (used in Radar).
The ultraviolet optical pulses emitted with a stable repetition rate are similar to that of frequency spacing of comb lines. Since instantaneous bandwidth is needed for achievable real-time and high-resolution target detection, the sounds of a photonics-based system could be a promising solution.
Even though this is considered a new fabrication technique, frequency combs can be achieved with current CMOS compatible photonic integrated circuits. Microcombs and their respective microwave signals will be key factors in establishing fully integrated low noise microwave oscillators that would be used in radars and information networks.
Principle of photonic microwave generation using integrated soliton microcombs and characteristics of the Si3N4 microresonators. Image credited to EPFL
Impact of Microwave Photonics on Telecommunications
At this day in age, digital traffic jams are a huge issue for telecommunication providers. There is a never-ending demand for a better wireless network for mobile devices and IoT. By increasing research such as the one from EPFL, microwave photonic can be utilized to alleviate telecom bandwidth issues.
Photonic signal processing offers the prospect of realizing extremely high multi-gigahertz sampling frequencies while overcoming inherent electronic limitations. By utilizing photonic-based processors, there will be new capabilities for high time-bandwidth operation and high-resolution performance.
In-fiber signal processors are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning. Introducing photonic signal processing will be a great step forward for telecom developers.
The Future of Radars, Telecom, and Wireless Networks
The team of researchers from EPFL has been collaborating with several semiconductor manufacturers on introducing microcomb modules to combine with chip-scale semiconductor lasers. This will impact how developers approach processing microwave signals in wireless networks, telecommunications, and radars.
Not only were they able to bridge the gap between integrated photonic-nonlinear optics and microwave photonics but they brought a wave of change in the future architecture of radars and information networks!