Photonic Crystal Nanobeam Cavities And Their Applications

Size reduction is a key issue in the development of contemporary integrated photonics.Optical microcavity is a optical resonator with the size of a few micrometers to a few hundred micronmeters, aiming to the requirements of miniaturization and integration of the optical devices.The periodic waveguide enjoy a simple structure and compact size, which can be easily integrated with the traditional waveguides and the fabrication processes are CMOS compatible.By introducing a defect into the periodic waveguide, a microcavity can be formed. Compared with the cavities based on photonic crystal slab, the periodic waveguide cavity enjoy the comparable quality factor but with much small volume, more simple design and easy fabrication processes.This thesis mainly study the periodic waveguide cavities and their applications. The main research work can be summarized as:1. We proposed and analyzed a Bragg reflector based on a periodic hybrid plasmonic waveguide. Owning to the low loss of our hybrid plasmonic waveguide,the insertion loss of our reflector is only0.34dB with the total device length6.46μm.By introducing a defect into the periodic waveguide,we constructed a cavity based on hybrid surface plasmonic waveguides.The simulated results show that such hybrid plasmonic microcavity can have high Q-factor up to1526, which is one order larger than the traditional plasmonic cavity based on metal-insualtor-metal structure.2. We investigated and analyzed a hybrid surface plasmonic periodic waveguide based cavity.By introducing the defect into the periodic hybrid plasmonic waveguide, we obtain an optical cavity with the Q/V up to31130(λ/n)-3. Based on this structure, we use quantum dots (QDs)-polymer as the active medium for the low-index slot layer and a nanolaser is formed. The numerical result shows that such hybrid nanolaser has a gain threshold as low as gth=374cm-1.3. By combining the concept of the one-dimensional (1D) PhC nanobeam cavities and the "slot waveguide", we present the design, fabrication, and the characterization of high-Q slotted1D photonic crystal (PhC) cavities with parabolic-width stack. By quadratically modulating the width of the slot waveguide, the coupling loss to radiation mode can be reduced and the transmission is enhanced due to the natural coupling between the cavity and the feeding waveguides. We fabricate and characterize our device on the Silicon-on-Insulator (SOI) platform. A cavity with small footprint (16.8×2.5μm2) and high Q-factor near104has been achieved. The refractive index sensing measurement for NaCl solutions with different concentrations gives a sensitivity around410nm/RIU which shows good agreement to the simulations (-413nm/RIU). 4. Pillar type one dimensional photonic crystal cavity is proposed to improve the sensitivity of the sensors. The1-D pillar-type PhC cavity is worked for the TM polarization. The numerical results using FDTD simulation show that the achieved Q-factor, mode volume, sensitivity are as good as or even better than the reported results using2D PhC cavity which has a much larger size. The quality factor Q of our cavity is6.3×105,the mode volume V is2.1(λ/nsi)3,and the sensitivity is435nm/RIU. The silicon layer is the thinnest one ever reported which makes the fabrication easily (especilly for the etching process)..