The laser technology improves the agricultural machinery

The team of EPFL’s Photonic Systems Laboratory (PHOSL) has developed a chip-scale laser source that improves the performance of semiconductor lasers while enabling the generation of short wavelengths.

This pioneering work, led by Professor Camille Brès and postdoctoral researcher Marco Clementi from EPFL’s School of Engineering represents an important advance in the field of photonics, with implications for communications, metrology, and other high precision applications.

The study, published in the journal Knowledge: Science & Applications, shows how PHOSL researchers, in collaboration with the Laboratory of Photonics and Quantum Measurements, have successfully integrated semiconductor lasers with silicon nitride photonic circuits containing microresonators. This combination results in a powerful device that delivers high-precision light in the near-infrared and visible ranges, filling a long-standing technological gap. challenging the industry.

“Semiconductor lasers are ubiquitous in modern technology, found in everything from smartphones to fiber optic networks. However, their potential is limited due to lack of compatibility and lack of able to efficiently produce visible light,” said Professor Brès. “Our work not only improves the connectivity of these lasers but also changes their activity in the visible spectrum, opening new avenues for their use.”

Coherence, in this case, refers to the uniformity of the light waves emitted by the laser. High coherence means that the light waves are synchronized, resulting in a beam with a precise color or frequency. This property is very important for applications where the accuracy and stability of the laser are very important, such as time tracking and precision sensing.

Increase accuracy and improve performance

The team’s approach involves combining commercially available semiconductor lasers with a silicon nitride layer. This small chip is built with commercially available CMOS technology. Thanks to the special low-loss material, little or no light is absorbed or escaped.

The light from the semiconductor laser flows through optical guides in very small cavities, where the beam is captured. These holes, called micro-ring resonators, are sensitively designed to emit specific frequencies, amplifying desired wavelengths while attenuating others. , resulting in improved coherence in the light output.

Another impressive feat is that the hybrid system can double the amount of light coming from a commercial semiconductor laser—allowing it to switch from the near-infrared spectrum to the bundle of visible light.

The relationship between time and wavelength is proportional, meaning that if the time is doubled, the wavelength is reduced by half. While the near-infrared spectrum is used for communication, higher frequencies are needed to build smaller, more efficient devices that require shorter wavelengths, such as clocks. atomic and medical devices.

These short waves are produced when captured light enters the cavity in a process called all-optical poling, which induces the so-called second-order nonlinearity in silicon nitride. The non-linearity in this case means that there is a big change, a jump in size, in the behavior of the light that is not directly proportional to its increase from the interaction with things.

Silicon nitride doesn’t usually have this second-order linear effect, and the team did an amazing engineering job to make it happen: The system uses light energy when it’s absorbed into the cavity produces an electric wave that drives the nonlinearities inside. materials.

It is a technology reserved for future use

“We are not only improving the current technology but also pushing the boundaries of what is possible with semiconductor lasers,” said Marco Clementi, who played an important role in the project. “By bridging the gap between telecom and long-wave vision, we are opening the door to new applications in fields such as biomedical imaging and real-time.

One promising application of this technology is in metrology, particularly in the development of sustainable atomic clocks. The history of navigational progress depends on the transmission of accurate time—from determining longitude at sea in the 16th Century to ensuring the accuracy of navigational missions in the space and achieving better geo-localization today.

“This important advance lays the groundwork for future technologies, some of which are unimaginable,” Clementi said.

The team’s deep understanding of photonics and materials science will lead to smaller and lighter devices and lower energy consumption and production costs of lasers. Their ability to take a basic scientific idea and translate it into a practical application using industry-specific manufacturing emphasizes the ability to solve problems. complex technological challenges that can lead to unexpected advances.