Investigation On Silicon-based Polymer Optical Switches

During the12th Five-Year Plan, convergence of three networks has beenpromoted as the high level project by the government of China and it will take greatchance to all telecommunication fields. Triple-play is based on the broadband network.Fiber to the home (FTTH), the major project of12th Five-Year Plan, will get CHY160billion Yuan foundation. This is a chance for Network vendors. All the relatedequipment, such as opto-electrical device, transmitter, receiver, transition medium,EPON will get a huge order. The progress of Triple-play must put the opticalcommunication field.In optical communication field, optical switches have important applications inOptical Cross-connect (OXC), optical receiver, signal regeneration and etc. Currently,the commercial optical switches are mainly based on inorganic material. Someinternational companies have start to sale optical switch products based on polymermaterials. In china, studying in polymer optical switch was started in recent years.There are no related products.In this thesis, a non-lineat optical guest-host material is synthesized forelectro-optical switch which P(MMA-GMA) as host, DR1(Dispersed red1) as guest.This material has some advantages such as simple synthesis method, good filmqualities, high cost performance and etc. The optical constant of the material isinvestigated, the refractive index is1.5037(@1550nm). The AFM analysis resultshows that film, spin coated on Si water, have0.441nm surface roughness (18×18μm2). Compared to the integrated optical switch, of which waveguide width is microndimension, this is a good performance and absolutely can apply in waveguide devices.Thermal properties of this material are studied. TGA result shows that5%weight lose point of this material is to be300degree. DSC analysis shows that Tg of the materialis102℃, which is one of the key issues in the process.The corona poling method is carried out to pole the polymer film and reflectionmethod to measure the electro-optical coefficient of film. Experimental results showthat electro-optical coefficient of film is10pm/V at1310nm.A Top-Down design flow is proposed for the optical switch. In this method, asuitable waveguide width based on the core material index is chosen, film thicknessand the capability width of photolithography. Then the cladding material index rangeis chosen to ensure the single mode condition. A program to compute the mask layoutparameters is designed. This program can compute the positions of waveguide,electrode, markers and additional information.The CPW traveling waveguide is adopted in guest-host type optical switch. Apair of microwave probe is used to load driving signal to the electrode. Test resultshows that switching time is nanosecond on a10kHz square wave. The insertionloss of device is14dB.An optical switch based on the DR1-co-PMMA material is fabricated.Meanwhile, the switch with thermo-optical bias is proposed which can solve theworking point shift. This design utilizes the large thermo-optical coefficient ofpolymer by heating an arm to adjust device working point to keep stable output. Thetest result shows that switching time is ns level under a50kHz square wave signaldriving.Polymers have a large absorption loss in infrared communication region due toC-H bond vibrational absorption. In order to reduce this loss, fluorine atoms couldsubstitute hydrogen in C-H bond. Because the wavelength of the vibrational modesobtained from carbon-fluorine is longer than that of C-H bond. Fluorinatedhyperbranched polyimides (FHBPIs) were synthesized for application on integratedoptical devices. The absorbance spectrum shows that there is little absorption attelecommunication wavelength of1310and1550nm due to their high fluorinecontents. And the glass transition temperature and thermal decomposition temperature were189℃and596℃, respectively. According to the atomic force microscopy,the surface roughness of the FHBPI films is0.54nm. Based on these characteristics,the FHBPIs are very suitable for fabricating the optical waveguide device. Under thisconsideration, a Mach–Zehnder interferometer thermo-optic switch with single modewaveguide is designed and fabricated. Test result shows the rise time is267.9μs andfall time is254.1μs. This result indicated that the FHBPIs are good candidates for theoptical switches.