At Columbia University, our Silicon Photonics research group focuses on the design, numerical simulation, fabrication, and performance analysis of integrated optics based on Silicon-On-Insulator (SOI) platform. Silicon photonics is an important research field for both academia and industry for the following reasons:
- Strong light confinement in silicon core enables designs for nano-scale optical devices and ultra-compact optoelectronic systems.
- Si photonics fabrication process is fully compatible with CMOS processing technology, allowing economical and mass production of monolithically integrated optoelectronic system-on-a-chip.
- Silicon has low absorption in common wavelength range for optical communication, i.e. 1.3 mm to 1.6 mm. With metal interconnects reaching their performance limits, silicon waveguides can serve as an exceptional medium for guiding optical data streams among active components.
- Silicon can be doped, bonded or alloyed with other materials to have novel properties. One can “engineer” these modified properties to create active optical components such as modulators, isolators, and lasers.
The goal of our group is to demonstrate active and passive optical functionalities of silicon-based platform, such as the generation, control, guidance, and detection of light. We have been pursuing active research in deeply-scaled waveguide devices, with cross-sectional area less than 0.1 mm2. We collaborate closely with Dr. Vlasov and Dr. McNab at IBM T. J. Watson Research Center on nano-scale waveguide fabrication. The ultra-small area provides us several advantages:
- Small cross-sectional area enhances the nonlinear response of the medium thereby permitting the use of low power, cw laser sources.
- Deeply scaled devices have an inherently reduced photogenerated carrier lifetime, and thus free-carrier absorption effect is greatly reduced.
- Reduced cross sectional area allows for the possibility of dispersion engineering.
Photos of deeply-scaled waveguides fabricated at IBM T.J. Watson Research Center
A. Waveguides with varying lengths
B. Polymer taper spot-size converter
C. Polymer with inverted silicon taper tip