Thermo-Absorption Optical Modulators Based on Germanium-on-Insulator (GOI) Structure
Date Issued
2008
Date
2008
Author(s)
Huang, Ying-An
Abstract
The optical communication has advantages in high capacity, low transmission loss, and low interference, therefore it is one of the best communication methods and can significantly enhance the communication speed. The optic modulator is indispensable part in modern high-speed optical communication system. This thesis study is focused on the design, fabrication, and measurement of novel thermo-absorption optical modulators, which utilize lateral self-resistive-heating method to change the device temperature and modulate the light intensity passing through the device. The heating mode utilizes the difference of resistivity between semiconductor materials and metals, thus most of the voltage drop is applied on the semiconductor region to increase the temperature due to its higher resistance. The modulator devices are based on the germanium-on-insulator (GOI) structure. We also establish a process of GOI bonding technology at low temperature that can effectively control the germanium thickness and the surface uniformity. Comparing with other semiconductor materials, germanium has a steep optical absorption curve and therefore the curve can move fast with varying temperature; the use of germanium as the device material is also beneficial to the integration of silicon process technology and electro-optical system. Besides, a bottom metal reflector structure is used to induce cavity effect and to enhance effective light path as well as modulation effect. When the GOI thermo-absorption optical modulator is biased at 0.8V or 1.2V, the increasing temperature causes absorption curve shift. The modulation contrast reaches 8.71dB under the 1563nm wavelength. Therefore this study demonstrated that the thermo-absorption optical modulator is an effective device with low-operation-voltage and high contrast ratio and suitable for optical communication and interconnects.
Subjects
Thermo-optic
modulator
Germanium
Electro-thermo structure
GOI
Type
thesis
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