Optical modulators fabricated on silicon to work at low temperatures

Silicon-based photonic integrated circuits (PICs) are of high interest for their many applications in communications, sensing, quantum computing and metrology. The reduced size and cost of silicon-based PICs may satisfy the need of portable sensors used in applications under extreme conditions such as in outer space. However, active optical components, such as electro-optical modulators, suffer from several detrimental effects at low temperatures, which limit their potential.

In order to expand the range of applications to extreme environments, Pintus et al. designed and fabricated optical modulators that can operate from room temperature down to 77 K. This temperature range covers that on the surface of some celestial bodies of the solar system, like Mars (130 K - 293 K), Europa (93 K - 133 K), and Titan (90 K - 153 K).

The team made the devices by integrating InP modulators on patterned silicon waveguides. They tested both bulk modulators and quantum well modulators and found that bulk modulators can operate over a wider range of temperatures. Although the researchers only tested the modulators down to 77 K, they believe that their modulators should work at even lower temperatures.

“To date, only a few integrated opto-electronic components have been demonstrated to work efficiently at such a low temperature,” said author Paolo Pintus. “Demonstrating that PICs can operate at lower temperature can be also beneficial for next-generation quantum computing systems which can exploit optical link to connect different units”

Pintus hopes their research can inspire engineers to consider new applications for PICs beyond data center and the telecommunication fields.

Source: “Characterization of heterogeneous InP-on-Si optical modulators operating between 77 K and room temperature,” by Paolo Pintus, Zeyu Zhang, Sergio Pinna, Minh A. Tran, Aditya Jain, MJ Kennedy, Leonardo Ranzani, Mohammad Soltani, and John E. Bowers, APL Photonics (2019). The article can be accessed at https://doi.org/10.1063/1.5120046 .