PhD Defense: "GaAs/AlGaAs based Intensity and Phase Modulators @ 1.55 μm directly grown on Silicon Substrates"

Prashanth Bhasker

May 30th (Thursday), 2:00pm
Engineering Science Building (ESB), Room 2001

By combining the mature processing technology and low cost of silicon wafer, silicon photonics have seen extensive advancement and have demonstrated low loss passive photonic devices and Mach-Zehnder Modulators (MZM) @ 1.3 μm and 1.55 μm. Physical effects used in silicon modulators for refractive index change are limited to free-carrier plasma dispersion effect as opposed to Pockel’s effect and Quantum confined stark effect used in III-V based modulators which would enable one to design even more efficient devices. In the past years, heterogeneous approach enabled to integrate III-V based active photonic devices on to Silicon using bonding. However, the size and the cost of III-V substrate limits scaling this approach over bigger silicon wafers. In recent years, there has been significant development of GaAs material growth directly on Silicon substrates. High performance GaAs material system-based quantum dot lasers @ 1.3 μm have been demonstrated with this technique. This approach can overcome the size limitation on III-V based substrates.
GaAs and its lattice matched layers exhibit Pockel’s effect and could be used to design modulators on silicon substrate. In this work, we demonstrate low propagation loss GaAs/AlGaAs based MZM’s directly grown on mis-cut silicon substrates. Challenges in designing high speed MZM’s on silicon substrate is analyzed and a modified transmission line design with improvement in terms of electrical loss as opposed to the widely used coplanar electrodes is demonstrated. These electrodes are then integrated with GaAs MZM as a traveling wave design. High optical power handling capability of these modulators are also demonstrated.

About Prashanth Bhasker:

Prashanth Bhasker is a PhD candidate working in Nadir Dagli’s lab. He received his B.E degree from Madras Institute of Technology, India in 2012 and M.S. degree from University of California, Santa Barbara in 2014. His work concentrates on developing high speed III-V optical modulators.

Hosted by: Nadir Dagli