DMSE Doctoral Thesis Defense - Danhao Ma
Thursday, June 04, 2020 at 1:30pm to 2:30pmVirtual Event
DMSE Doctoral Thesis Defense
Ge and GeSi Electroabsorption Modulator Arrays via Strain and Composition Engineering
Thursday, June 4, 2020
1:30 – 2:30 PM EDT
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Electronic and photonic integrated circuits serve as a promising platform for telecommunications and sensing applications. Waveguide-integrated photonic modulators are key devices when encoding optical signals for electronic–photonic integration on silicon. Electroabsorption modulators provide fast modulation, small device footprint, and low power consumption. Integrating more modulators for multiple operating wavelengths allows a broader optical band coverage and higher optoelectronic data processing capacity, which is desirable with lower cost, simpler layout, and easier electronic and photonic circuits integration. A modulator’s operation wavelength adjustment and its system integration for broadband modulation are two major challenges of fabricating on-chip modulator arrays for telecommunication.
In this thesis work, a one-for-all strained GeSi modulator array design is proposed and demonstrated to cover a broad telecommunication band with multiple modulators designed and fabricated simultaneously in the same process flow. A stressor layer applies a homogeneous strain to a waveguide modulator, which tunes the material bandgap, and adjusts the modulator operation wavelength. The strain and composition engineered GeSi modulators have demonstrated an improved extinction ratio/insertion loss value from 1 to 1.7, which is the highest value among Si Mach-Zehnder, and GeSi electroabsorption modulators. Strained Ge0.99Si0.01 modulator arrays have demonstrated a broad optical bandwidth of ~100nm in C- and L-bands in telecommunication. An ultralow insertion loss of 2dB and high modulation speed above 100 GHz is achievable with minor improvements in the design. An increase in Si composition to 4% allows a strained Ge0.96Si0.04 modulator array to cover the optical wavelength from 1300nm to 1450nm. Strained GeSi modulator and photodetector arrays can be fabricated in the same process flow with the same stressor layers to achieve an integration of transmitters and receivers on a single chip with a simplified design layout and fabrication procedure. That presents a promising platform for integrated photonic transceivers with an ultrawide optical coverage in the entire telecommunication bands.
Jurgen Michel, Senior Research Scientist, Materials Research Laboratory, Massachusetts Institute of Technology
Lionel C. Kimerling, Thomas Lord Professor, Materials Science and Engineering, Massachusetts Institute of Technology
Anuradha M. Agarwal, Principal Research Scientist, Materials Research Laboratory, Massachusetts Institute of Technology
Juejun Hu, Associate Professor, Materials Science and Engineering, Massachusetts Institute of Technology
Caroline Ross, Professor, Materials Science and Engineering, Massachusetts Institute of Technology