On-Chip Optics Find Their Groove
July 27, 2017 | A*STAREstimated reading time: 2 minutes
High-speed optical circuits and sensors generally require strict control over light polarization to minimize loss and cross-talk in photonic devices such as waveguides. An A*STAR team now predicts that noise resulting from imperfect polarizations can be eliminated using microstructures known as ‘slot’ waveguides.
Discovered just over a decade ago, slot waveguides trap electromagnetic fields into a narrow region between two microfabricated strips of materials, such as silicon. Differences in the refractive indices between the slots and rails help focus the light into the slot with optical intensity and power not seen in typical waveguides. These properties impart improved sensitivity to sensors and generate useful amplification effects.
One difficulty with photonic waveguides, however, is splitting incoming radiation into electric and magnetic polarization components within nanometer-scale spaces. “Inevitably, there will be contamination from the light source or defects along the waveguides,” says Jun Rong Ong from A*STAR’s Institute of High Performance Computing. “Unwanted polarization acts as noise, and this deteriorates device performance.”
Ong, along with colleagues Valerian Chen and Ching Eng Png, hypothesized that a special state known as ‘zero birefringence’ might negate the need for specialized splitter devices currently used in photonic waveguides. Birefringence describes how light with a mix of polarizations can refract into two directions when passing through crystals with specific shapes. The team undertook a systematic theoretical analysis to determine if changes to the waveguide’s height, angle, and slot size could remove birefringence from the waveguide, leaving just a single ray.
“By having zero birefringence, we can process the inevitable mix of both polarizations simultaneously,” explains Ong. “This means the device footprint could be effectively halved.”
The trio’s simulations showed that many structural parameters could produce zero birefringence in the waveguide, but some were more effective than others. Surprisingly, they discovered the two rails need not be symmetric — having unequal widths enabled one side to confine greater amount of light, and give better control over the waveguide’s refractive index. Conversely, when the team tested waveguides with bent orientations to go around corners, symmetrical rails proved most effective.
Currently, the tolerances needed to produce the researchers’ zero birefringence waveguides could only be realized through electron beam lithography, a relatively slow process. However, they are confident that practical demonstrations of this technology are within reach.
“It would be useful to explore if short devices, less than a few hundred micrometers, can be polarization-independent on a wafer scale,” says Ong. “This could lead to applications with real impact.”
Suggested Items
TRI to Unveil New High-Throughput AOI and AXI at productronica 2023
09/15/2023 | TRITest Research, Inc. (TRI), the leading test and inspection systems provider for the electronics manufacturing industry, will join productronica 2023, which will be held at Messe München Center from November 14 – 17, 2023.
UK Space Agency Launches Consultation on Variable Liability Limits for Orbital Operations
09/15/2023 | UK Space AgencyThe proposals from the UK Space Agency follow a review into the UK’s approach to setting the amount of an operator’s liability in licences for orbital operations, a key commitment of the government’s National Space Strategy.
MediaTek Successfully Develops First Chip Using TSMC's 3nm Process, Set for Volume Production in 2024
09/14/2023 | MediaTekMediaTek and TSMC announced that MediaTek has successfully developed its first chip using TSMC's leading-edge 3nm technology, taping out MediaTek’s flagship Dimensity system-on-chip (SoC) with volume production expected next year.
MKS’ Atotech to Participate in IPCA Expo 2023
09/14/2023 | MKS’ AtotechMKS’ Atotech, a leading surface finishing brand of MKS Instruments, will participate in the upcoming IPCA Expo at Bangalore International Exhibition Centre (BIEC) and showcase its latest PCB manufacturing solutions from September 13 – 15.
Comtech Unveils New BRIDGE Solutions to Increase Access to Global Hybrid Connectivity
09/12/2023 | Business WireComtech launched its new blended, resilient, integrated, digital, global, end-to-end (BRIDGE) connectivity solutions. Comtech’s BRIDGE solutions provide portable, adaptable, full-service communications networks that can be established in a matter of hours and help “bridge the gap” for traditional satellite and terrestrial infrastructures.