Theoretical Analysis And Experiment On 2×2 MMI-MZI Optical Switch Based On InP

Photonic integrated circuits (PICs) have already become extremely attractive research topic in the area of optical communications because of smaller dimension, lower power, lower cost, better performance and higher reliability compared to the modules based on discrete devices. Optical switching is a cornerstone of wavelength-division-multiplexed networks based on optical add-drop multiplexers (OADM), cross-connects, and other advanced optical system architectures, whose PICs become the significant research subjects. And multimode (MMI) devices, which are based on the self imaging effect, have many merits, such as compact size, low insertion loss, ease of production and good fabrication tolerances. The MMI devices are of great prospect in integrated opticsIn this thesis, which is the foundational part of research on monolithically integrated ROADM (Reconfigurable Optical Add-Drop multiplexer), a 2x2 optical switch, as its key component, has been designed and fabricated, which is based on InP and consists of dual multimode interference (MMI) couplers that are connected in the Mach-Zehnder-interferometer (MZI) configuration. The following contents listed the main work of this thesis:1. The development of integrated optical switches is intrduced, and Photonic Integration using ATG technology with vertical-taper coupler is studied, we aim to integrated a detector on our switch using vertical-taper coupler, who was produced by a dynamic etch mask technique firstly put forward by a team lead by XiaoMin Ren.2. Make analysis and discussion towards bend-filling effects, band-gap shrinkage, and free-carrier absorption induced by current injected carriers. Finished the calculation and emulation related to injected carriers about InP/InGaAsP material. Summarized a method to get the injected current which made semiconductor produced aπphase excursion to realize optical switch function.3. Considering much factors, such as single mode operation, low polarization sensitivity, and good coupling efficiency and loose alignment tolerance between the waveguide and the fiber, the InP/InGaAsP 2×2 optical switch based on MMI-MZI was analyzed and designed in detail, which has a simple structure and is much easier to be integrated with other components. The fabrication tolerance was also discussed.4. The processing steps for fabricating InP/InGaAsP optical switch was found, and the measurement platform was setup. The modification and improvement of mask design, post-process and measuring equipment was put forward. The light signal can be switched from cross port to bar port with a control voltage of 6.4V by carrier modulation on the principle of injection free carriers, bend-filling effects. The measured crosstalk is -20.49dB and -19.19dB at the on and off state, respectively.