Published: Oct. 21, 2021

Low-loss, high-bandwidth, robust fiber-to-chip couplersBackground

Integrated photonics’ major challenge is the efficient coupling of standard optical fiber to on-chip photonics waveguides and devices. These coupling devices must connect vastly different sized modes, while preventing loss of light. The most common method of coupling is grating couplers, end coupling, and adiabatic tapers. Grating couplers are sensitive to alignment and can cause the chip to be bulky and large. Additionally, achieving fiber-to-chip insertion loss of a few percent with grating couplers is difficult, even in theory. End couplers also require precise alignment due to mode-matching at the interface. Adiabatic tapers are conducive to high-bandwidth and low loss operation. However, current adiabatic tapers are required to be suspended in air, which limits applications. 


Our adiabatically tapered fibers coupler is unsuspended and obtains low loss over a large optical bandwidth. Our design clads the tapered fiber with a high-index polymer. The cladding allows our invention to couple with waveguides on buried oxide and not be suspended. The cladding also prevents loss of light to buried oxide. Our coupler is less sensitive to alignment errors, simplifies optical alignment because the pitch angles do not need to be as accurately tuned, and requires very minimal space. 


  • Low loss – 1.3 dB – 0.25 dB, in a packaged device
  • High bandwidth – more than 200 nm (3 dB- bandwidth)
  • Scalable and robust

Future Applications

  • Photonics
  • Data centers
  • Quantum computing

Learn more

What's Next?

Available for licensing.


Nicole Forsberg: