Study Of Silicon-based Micro/Nano Optoelectronics

Optoelectronics are one of the most important elements for fiber communication development, since they are the basic components and the core technology to construct the communication systems. With the rapid development of fiber communication technology, the communication systems require more and more smart devices with high integration density, low cost and high reliability. Silicon based optoelectronics are fabricated by using low-cost silicon material and mature CMOS fabrication technology with a good optoelectronic hybrid-integration ability, which are dominating in the optoelectronics industry and taking the place of the traditional optoelectronics fabricated on III-V materials. Moreover, the silicon optoelectronics are also important to design various micro-optic devices with multi-function by integrating with other components. And they also have become a thriving field known as optical micro-electro-mechanical system (MEMS) and nano-electro-mechanical system (NEMS), which provide wide applications in optical detection, military reconnaissance and space exploration. The researches on silicon optoelectronics are highly necessary to improve our country’s competence in the field of optoelectronics technology. Therefore, this dissertation focuses on the silicon optoelectronics development and their applications by discussing and developing two kinds of typical silicon optoelectronics devices.There are five chapters in this dissertation, and the main contents are as following.In the first part, the development situation and achievements on silicon optoelectronics have been reviewed, in which the development tendency, the most common techniques and research methods have been summarized. This part is concluded by looking ahead the challenges as well as the crucial devices based on these technologies.In the second part, a novel MEMS tunable laser have been designed, fabricated, packaged and tested. It is configured as the Littrow typed external cavity tunable laser with high output power and large tuning range. In its external cavity, a normal optical fiber acts as a rod-lens for light convergence in the vertical plane, while a deep-etched silicon parabolic mirror confines the light in the horizontal plane. Compare with previous designs, the proposed MEMS tunable laser is a real single-chip device without any external lenses. After solving the fabrication problems, such as release process, passive alignment, flip-chip gain chip bonding and roughness induced by deep-reactive-ion-etching (DRIE), we have successfully developed a process flow for MEMS tunable laser fabrication and packaging. The full-print chip size is only3mm×3.2mm, and its tuning range is tested up to48.3nm when the side-mode suppression ratio (SMSR) is higher than20dB.In the third part, a silicon based miniature optical power detector is designed by using NEMS technology, in which optical gradient force is used to actuate a nano-scaled cantilever beam. The optical power is detected by an integrated a high sensitive electron-tunneling displacement transducer, in which optical gradient force is employed as the bridge between optical energy and mechanical energy transition. The working wavelength covers C&L-band which is a traditional detection region of III-V materials based devices by using photon absorption phenomenon. Moreover, the proposed optical power detector has advantages of small size (0.024mm2), large detection power range (0-20mW) and low thermal noise.In the fourth part, a NEMS all-optical logic gate is developed. The NEMS all-optical logic gate is constructed by a pair of partially released micro-ring resonator in which the output optical signals are controlled by opto-mechanical effect. The suspended parts of the micro-ring resonators are driven by the optical gradient force between the suspended micro-ring resonator and the SiO2substrate. The device is fabricated by using NEMS technology and packaged by using laser welding technology. Compare with the traditional all-optical logic gates which are based on the semiconductor optical amplifier (SOA) or high nonlinear fibers, the proposed NEMS all-optical logic gate has the advantages of low power consumption (-0.5mW), high compact size (40μm×45μm), low cost and easy batch fabrication, which provides a potential application in silicon-photonic integration for digital signal processing.