Novel Devices and Fabrication Techniques for Integrated Photonics
Abstract
Integrated photonics is an emerging field that aims to miniaturize optical devices and systems, as well as to take advantage of low-cost manufacturing through well-established complementary metal-oxide-semiconductor (CMOS) fabrication technology. It is a promising solution to ultra-broad bandwidth interconnects required in future electronic systems, and can also provide various sensing and transmission functionalities. Photonic devices such as resonant cavities and waveguides are investigated over the years to effectively confine or guide light in micron- and nano-meter scale. However, there is still an absence of fundamental building blocks for optical signal processing and there are still significant challenges in realizing photonic devices on metal and flexible substrate. This dissertation contains two parts of work. The first part is the demonstration of an all-silicon optical diode and optical transistor. By utilizing the thermal-optic effect in silicon microring resonators, the optical diode can realize nonreciprocal transmission up to 40 dB, the highest ever reported on-chip, without any external assistance such as magnetic fields, radio-frequency modulation, or optical pumping. The optical diode can work with a broad input power range and has the ability to block backward input much stronger than the forward input, functionally similar to electrical diodes. Furthermore, an optical transistor is constructed using the same architecture of the diode. A small optical signal is able to control a large signal, achieving an output ON/OFF ratio over 18 dB with an input ON/OFF ratio of merely 2 dB. We also show that it is cascadable and can accomplish basic logic operations such as NAND or NOR in a single device. The second part of the work is focused on novel fabrication techniques. We first explore a direct fabrication method of integrating Si photonic devices on a flexible plastic film. An optical strain sensor is shown as an application using the resonance shifts of the microring resonators during bending of the substrate. Next, we demonstrate a technique called resistless nanoimprinting in metal (RNIM) for plasmonic applications, which can direct pattern high-fidelity 3D metal nanostructures using silicon mold without the need of resists, using pressures of < 4 MPa and temperatures between 25 - 150°C. Using this scheme, large-scale vivid images through extraordinary optical transmission and strong surface enhanced Raman scattering substrates are realized.
Degree
Ph.D.
Advisors
Qi, Purdue University.
Subject Area
Electrical engineering|Nanotechnology|Optics
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