Cutting-edge Technology for Building Ultralow-Loss Incorporated Photonic Circuits

Encoding data into light and transferring it using fiber optics is at the core of optical communications. With an exceptionally minimal loss of 0.2 dB/km, fiber optics made from silica have laid the foundations of today’s international telecommunication networks and our data society.

Such ultralow optical loss is just as crucial for incorporated photonics, which allows the synthesis, handling, and identification of optical signals using on-chip waveguides. Today, a range of cutting-edge technologies are based upon incorporated photonics, including semiconductor lasers, modulators, and photodetectors, and are employed extensively in data centers, communications, sensing, and computing.

Integrated photonic chips are generally made from silicon that is plentiful and has excellent optical qualities. However, silicon can not do everything we require in integrated photonics, so new material systems have arisen. Among these is silicon nitride (Si3N4), whose incredibly low optical loss (several times lower than silicon) has made it the ideal material for applications in which reduced loss is crucial, such as photonic delay lines, narrow-linewidth lasers, and nonlinear photonics.

Researchers in the team of Professor Tobias J. Kippenberg at EPFL’s School of Basic Sciences have designed a new technology for constructing silicon nitride integrated photonic circuits with all-time low optical losses and small footprints. The work was released in Nature Communications.

As a result of merging nanofabrication and material science, the technology is based upon the photonic Damascene process created at EPFL. Utilizing this process, the group made integrated circuits of optical losses of just 1 dB/m, a record value for any nonlinear incorporated photonic material. Such low loss considerably lowers the power restrictions for constructing chip-scale optical frequency combs (micro combs), used in applications like coherent optical transceivers, low-noise microwave synthesizers, LiDAR, neuromorphic computing, and even optical atomic clocks. The group made use of the new technology to create meter-long waveguides on 5×5 mm2 chips and high-quality-factor microresonators. They additionally report high fabrication yield, which is crucial for scaling up to industrial production.

The manufacture at EPFL’s Center of MicroNanoTechnology (CMi) was led by Dr. Junqiu Liu how stated that the chips devices have currently been employed for parametric optical amplifiers, narrow-linewidth lasers, and chip-scale frequency combs. Dr. Junqiu Liu adds that he and his team additionally anticipate seeing their technology being applied in emerging applications such as coherent LiDAR, photonic neural networks, and quantum computing.

Originally published by: scitechdaily.com

Reference: “High-yield, wafer-scale fabrication of ultralow-loss, dispersion-engineered silicon nitride photonic circuits” by Junqiu Liu, Guanhao Huang, Rui Ning Wang, Jijun He, Arslan S. Raja, Tianyi Liu, Nils J. Engelsen and Tobias J. Kippenberg, 16 April 2021, Nature Communications.