Trimmable Athermal Si Resonators

Technology   

This invention is about a Silicon based trimmable athermal ring resonator with energy efficiency driving Moore’s law. The prototype design rule requires encapsulation of a-Si core with a thin layer of As2S3 before the polymer top cladding deposition. Trimmable athermal waveguides leverage the photosensitivity of As2S3 and negative TO coefficient of polymers to address the fabrication and temperature sensitivities of Si based resonators. Constraints of TO resonance shift lower than 1.3 pm/K and trimming window of 5 GHz imposed by a 20 GHz channel spacing can been successfully satisfied by resonators fabricated with these waveguides.  

Problem Addressed

Silicon based ring resonators form an integral part of the WDM architecture of an electronic-photonic integrated chip. However, fabrication variations and temperature fluctuations alter the response of the optical filters. Active tuning involving heaters and thermo-electric coolers of these resonators have been proposed to keep the response within desirable limits, but these solutions prove power inefficient and the number of I/O lines limits the integration density, and thermal tuning energy constitutes a significant portion of the energy cost.Also, there is a shift in filter response of an athermal ring, which consists of a negative thermo-optic (TO) polymer cladding, which needs to be tuned back to its desired value due to fabrication variations.  

Advantages   

• Minimum TO peak shift and high trimming resolution
• Closer channel spacing and higher channel count
• Bandwidth multiplication due to wavelength division multiplexing (WDM) (incentive for electronic-photonic integration)  

Publications

"Post-Fabrication Trimming of Athermal Silicon Waveguides." Optics Letters 38, no. 24 (December 15, 2013): 45-47.

"High Capacity, Photo-Trimmable Athermal Silicon Waveguides." In Proceedings of the IEEE 9th International Conference on Group IV Photonics (GFP), 45-47. August 29-31, 2012.