Frustrated Total Internal Reflection Based Optical Waveguide Devices And Integrated Nano Light Sources For On-chip Optical Interconnects

Optical interconnect is an important measure to break through the performance“bottle neck”of the traditional microelectronics IC chips due to the advantages in low latency,broad bandwidth,high integration density,low power consumption capered to the traditional electrical interconnects.Therefore,there is an important development needed for photonic components in high speed,small footprint,and low power consumption.Optical switches and as-formed matrix are critical devices in light transmission path switching link.However,conventional Mach-Zehnder interferometer（MZI）based switches are still limited for high density integration due to either a large footprint or longer one-dimensional scale of the device.Meanwhile there is great demand for the processing technic of optoelectronic devices with the sub-micron and nanometer level features,and thus successful fabrication of～100 nm hole,line,trench,or pillar is a key factor for device fabrication.On the other hand,although optical devices have broad bandwidth and fast information processing speed,their physical size is limited by the diffraction limit,which leads to certain obstacles to high-density optical integration and make it difficult to achieve high density integration.The surface plasmon technology connects the traditional photonic technology and electronic technology.Without the limitation of diffraction limit,the physical size of the component is usually below submicron,and the response speed can be comparable with the photonic devices,which may reach THz in theory.In recent years,the research on surface plasmons has become a hot topic for the next generation of nano devices.The research of surface plasmons based nano light source is one of the important branches in the plasmonic circuits.With the ability to generate high intensity electromagnetic radiation at the nanoscale in femtosecond timescales,the recent emergence of plasmon lasers now stimulates the exploration of nanometer-scale science and application towards the rich physics of deep sub-wavelength optics and the development of high-performance devices.This dissertation focused on the system on chip.The high density integrated InP trench-based MZI optical switch and switch matrix,the ultracompact trench-based MZI thermo-optic switch on silicon,the ultracompact refractive index sensor based on integrated optical waveguide trench coupler and the integrated metal-clad nanocavity plasmon nano light sources were studied.The main research works are as follows:1.The processing technique for sub-micron opening and high aspect ratio up to16:1 trench was studied.A range of 100～300 nm wide opening trench was successfully fabricated by HBr gas system.A novel trench coupler was formed based on a principle of frustrated total internal reflection（TIR）.The coupler size is comparable to the comparable to the waveguide intersection area,i.e.,～22μm~2,which is far less than footprint of conventional Y branch,directional coupler,and multimode interference couplers.2.Utilizing these compact trench couplers,a rearrangeable nonblocking 4×4photonic switch fabric based on 2×2 MZI electro-optic switch elements which size is about 40μm×40μm was proposed on an InP/InGaAsP platform.Each switch element consists of two trench couplers and TIR mirrors,forming the flexible rectangular layout of the switches.The processed switch matrix exhibits an ultra-compact chip size of～340μm×120μm,representing at least one order of magnitude footprint reduction compared to the state of the art switches.This achievement provides a new idea and anew method for two-dimensional dense planar integration of InP-based passive/active photonic integrated circuits.At the same time,an ultra-compact silicon-based 2×2 MZI thermal-optical switch with the same structure of InP-based 2×2 MZI switch was also proposed.3.An ultra-compact refractive index（RI）sensor based on an integrated optical waveguide trench coupler fabricated on a chip was presented.The coupler consists of an input waveguide,a reflective waveguide,and a transmission waveguide as well as a subwavelength-wide trench that is located at the intersection of the three waveguides.Light guided in the input waveguide undergoes frustrated total internal reflection on the sidewall of the trench,resulting in the evanescent coupling of light into the transmission waveguide and thus attenuation of light in the reflective waveguide.Because the evanescent field coupling efficiency is dependent on RI of the medium filling in the trench,both the transmitted and reflected light intensities are very sensitive to changes in RI of the liquid in the trench.This means that the integrated optical trench coupler mentioned above can be used as a micro-nano sensor for real-time detection of liquid RI or solution concentration.Performance of this novel optical sensor was theoretically analyzed based on the FDTD method with use of the aluminum nitride ridge waveguide as the simulation model.After optimization of the sensor’s geometry,its refractive index sensitivity can reach 207.05%/RIU.4.The integrated metal-clad nanocavity plasmon nano light sources and sources arrays were studied.A square metal-dielectric nanocavity with～500 nm width and～300nm height based on InP/InGaAsP multiple quantum wells was proposed.The desired emission wavelength of c-band was obtained by the FDTD method.The Q-factor of the nanocavity is up to 300.A plasmon laser array consisting of N×N metal-dielectric-semiconductor-dielectric-metal nanocavities with spacing of 100～300 nm was demonstrated.The fabrication of the nanolaser array depends on the process of the～100 nm trenches.This achievement provides a feasible way to scale nanolasers on chip,extending it to the important theory development and significant practical applications.