Study On Direct UV-written Fluorinated Polycarbonate Waveguide Materials For Optical Switch

Optical communication system is composed of the laser source,optical modulator,optical amplifier,optical switch and photodetector.With the development of microelectronics,optoelectronics and microfabrication technology,Photonic Integrated Circuit(PIC)is the trend in the development of planar optical waveguide in future optical communication system.Due to many advantages of polymer materials,such as,a wide variety,chemical structure flexibility,performance adjustable,low cost and ease of processing as compared to inorganic materials,extensively research had been conducted.At present,it is a challenge to design and synthesize optical waveguide materials with low optical loss,adjustable refractive index,high thermal stability and ease to process to fit the requirements of optical waveguide device.Optical switch is one of the key elements in the optical communication system,and has been widespread used in the optical cross-connect(OXC),optical add-drop multiplexer(OADM),optical network monitoring and chip optical interconnect.Besides,polymer materials also have a high thermal coefficient,lower heat transfer rate,which makes it suitable for both thermo-optical switch and electro-optical switch.In this dissertation,we attempt to optimizeoptical waveguide materials for device requirement,especially aiming to reduce the optical loss,improve the refractive index and workability.Recent progress of organic optical waveguide materials is reviewed in Chapter 1.Based on a brief introduction to polymer planar optical waveguide,the design and synthesis of optical waveguide materials,comparing the merits and defects of different optical waveguide materials,we put forward the design ideas of this thesis and outline the main contents as follows.In Chapter 2,we present the synthesis of a series of epoxy-terminated fluorinated polycarbonate(AF-Z-PC EP 1-3 and FBPA-PC-EP 1-3).Herein,epoxy groups as crosslinking sites and bisphenol Z(BPZ)and(3-Trifluoromethyl)phenyl hydroquinone(3F-PQ)to adjust the refractive indices were introduced into the polycarbonate backbone.A series of photoresists(NFPR 1-3 and FPC-PR 1-3)were prepared by mixing AF-Z-PC EP 1-3 and FBPA-PC-EP 1-3 with the solvent and photo-initiator.The optical films with low surface roughness,high thermal stability and optical transparence were achieved by spin coating,pre-baking,UV exposure and post-baking.As for NFPR 1-3,the refractive index can be adjusted between 1.500 and 1.532(1550 nm).Channel optical waveguide and MZI thermo-optic waveguide switch arrays were fabricated based on the direct UV-written technique using the NFPR 1.The propagation loss of the channel waveguide was only 0.19 d B cm-1 at 1550 nm.The rise and fall times of the device applied 200 Hz square-wave voltage were 1.546 ms and 1.226 ms,respectively.The applied electric power was about 15.5 m W as the switching power,the insertion loss is 9.0 d B,and the extinction ratio was measured to be about 13.0 d B.As for FPC-PR 1-3,the refractive index(1.51-1.58 at 1550 nm)was higher than those of the commercially important optical plastics such as poly(methyl methacrylate),polycarbonate and polystyrene.This was mainly arising from the existence of biphenyl,whose atomic refraction is 1.733,much higher than F atoms(0.95).The propagation loss of the channel waveguide was only 0.17 d B cm-1 at 1550 nm.The rise and fall times of the device applied 500 Hz square-wave voltage were 837 ?s and 381.8 ?s,respectively.The applied electric power was about 35 m W as the switching power,and the extinction ratio was measured to be about 14.0 d B.In Chapter 3,fluorinated polycarbonates containing dodecyl groups(AF-Ali-PC EPs),biphenyl(AF-Ar-PC EPs)and cross-linkable epoxy groups were synthesized to research the effect of the flexibility of the monomers on the properties of thermo-optic waveguide devices.Transparent polymer films were prepared by photo curing of a solution(FPRs) containing AF-Ali-PC EPs or AF-Ar-PC EPs,photo initiator and cyclopentanone.The optical films have high thermal stability and tunable refractive index.As for Ali-PRs,the refractive index can be adjusted between 1.51 and 1.495(1550 nm).As for Ar-PRs,owning to the presence of biphenyl structure in the polycarbonate chains,the typical droplet-like morphology with the average size of 1 ?m was formed during the process of preparation of the polymer films and UV exposure,the refractive index can be adjusted between 1.60 and 1.54(1550 nm).The straight optical waveguide and MZI thermo-optic waveguide switch arrays were fabricated by using the Ali-PR 1 and Ar-PR 1.The propagation loss of the channel waveguide measured by the cutback measured was 0.21 d B cm-1 and 0.19 d B cm-1 at the monitoring light of 1550 nm,respectively.The rise and fall times of the thermo-optic switch applied 200 Hz square-wave voltage were 1.822 ms and 1.364 ms respectively for Ali-PR 1;2.994 ms and 2.301 ms for Ar-PR 1 at the 110 Hz square-wave voltage.The insertion loss and extinction ratio were 9.2 d B and 12.0 d B for the aliphatic segment contained photoresists;8.9 d B and 12.3 d B for the aromatic segment contained photoresists.The applied electric power was 15.0 m W and 20.0 m W,which were the switching power,too.By contrast with our previous work,fluor-polycarbonates containing 3F-PQ were more suitable for the optical waveguide devices.In Chapter 4,we present the synthesis of a series of fluorinated polycarbonates having end groups as double bonds(AF-Z-PC MA 1-3 and AF-Ali-PC MA 1-3)and fluorinated polycarbonates containing multi-double bonds(AF-3OH-PC MA 1-3)using as an electro-optical polymer material.At the same time,a simple chromophore(N-TCF)was synthesized.A series of photoresists(Z-N-TCF PR 1-3,Ali-N-TCF PR 1-3 and 3OH-N-TCF PR 1-3)were prepared by mixing AF-Z-PC MA 1-3,AF-Ali-PC MA 1-3 and AF-3OH-PC MA 1-3 with the solvent and photo-initiator.The second-order nonlinear optical film were achieved by spin coating,pre-baking,polarization and UV exposure.The temporal stability showed record-high in electro-optical polymer materials,which retain >90% of original r33 after 85 ?C for 200 h.Compared with AF-Z-PC MA 1-3 and AF-Ali-PC MA 1-3,the key advantage of AF-3OH-PC MA 1-3 is that the content double bonds in the polymer backbone can be controlled,which can control the degree of crosslinking.In summary,AF-Z-PC MA 1-3,AF-Ali-PC MA 1-3 and AF-3OH-PC MA 1-3 can be used as electro-optical polymer materials.