There is a growing interest in integrated photonics systems that can operate over octave-spanning or multi-octave spectral windows, but such structures have operating requirements that bar them from achieving high performance while preserving all the desired features: low propagation losses, tight optical confinement, and accurate control over dimensional characteristics. To resolve these issues, this invention from UCF researchers has a highly scalable production method which allows all the desired features while being a simple and reliable fabrication process suitable for repetitive manufacturing of wafer-scale photonic systems.
This new production method creates an innovative integrated photonics platform for compact photonic devices that operate over a wide transmission band in the infrared (IR) range, spanning 1.2 – 8.5 microns. The resulting mechanically stable, air-clad optical waveguides have higher heat dissipation and improved high-index contrast that enhances optical confinement and boosts performance in harsh environments. This technological advance can be used in a number of applications including: supercontinuum-generation processes, optical spectrum analyzers, remote sensing, medical imaging, and nonlinear optics.
Based on silicon photonics technology, this unique manufacturing method utilizes silicon wafers and silicon-on-insulator wafers to produce T-shaped structures, or T-guides, and is the basis for the production of optical waveguides. At the intersection of the T-guide, the effective index experienced by propagating light is greater than that of the surrounding regions, resulting in confinement of the optical mode to the crossing section, and preventing leakage of the light into the silicon wafer. The use of this T-shaped structure to provide the waveguide core with index contrast is unique to this innovation, and it has the additional benefit of simultaneously defining the waveguide and providing a firm structural support for the top silicon layer. The waveguide core has demonstrated excellent thermal dissipation to the substrate, thereby increasing its tolerance to optical absorption losses and environmental temperature variations.
Another feature of this invention is the combined use of thermal oxidation and chemical-mechanical polishing (CMP) to reduce the sidewall roughness of the silicon post structure. CMP enables a completely vertical and flat-topped rectangular post, and the resulting waveguide retains high refractive index contrast and lacks the irregular curved features that would otherwise complicate the waveguide modeling and design. Additionally, active on-chip features such as modulation or phase-shifting can be achieved by the addition of doping profiles to the silicon, enabling the creation of P-N diodes.
- Boosts performance in harsh environments
- Simple, reliable, repetitive, highly scalable fabrication method
- Higher heat dissipation
- Improved high index contrast
- Remote sensing
- Integrated nonlinear optics in the mid-IR range
- Supercontinuum generation
- Optical spectrum analyzers