This work demonstrates waveguide devices based on a novel photocrosslinkable fluorinated poly(arylene ether ketone). A new molecular design has enabled waveguide fabrication to be achieved for the first time using this kind of polymer, through direct UV patterning and a wet-etch process, which is faster and more convenient and economical than the process based on standard reactive-ion etching that has been applied to previously reported poly(arylene ether ketone) materials. High-quality waveguides with smooth, well-defined sidewalls have been produced, and optical splitter devices based on directional coupling are demonstrated. Optical characterization of these devices suggests that the waveguide quality is comparable to that of waveguides fabricated using a dry-etch process, and the experimental data obtained from the fabricated optical splitters are in excellent agreement with theoretical predictions.
Fluorinated poly(arylene ether)s are attractive for the fabrication of optical waveguide devices for photonic applications
due to their low optical attenuation and high thermal stability. A variety of waveguide devices have been fabricated in
these polymers through thermal crosslinking followed by a reactive ion etch process. This work reports on the use of a
novel fluorinated poly(arylene ether ketone) incorporating tetrafluorostyrol groups for photo-crosslinking. This new
molecular design allows sufficient photosensitivity to fabricate waveguides through a UV direct patterning and wet-etch
method, offering a fast, convenient and economic approach to making polymer photonic devices. Data concerning the
polymer molecular structure and choice of suitable photo-initiators for the fabrication of the devices are presented in this
paper. Based upon the optical and thermal properties of the resultant materials it appears that similar degrees of polymer
crosslinking can be achieved using the photo-curing process as those using a thermal crosslinking process. High quality
waveguide devices with smooth, well-defined sidewalls are demonstrated. Optical characterization of these devices
suggests that the waveguide quality is comparable to that of waveguides fabricated using a dry etch process.
New fluorinated poly(arylene ether sulfone)s (FPAES) and poly (arylene ether ketone)s (FPAEK) with two types of NLO chromophores as pendant groups were obtained by a polycondensation reaction carried out using very mild reaction conditions. The glass transition temperature (Tg) of these copolymers is between 168 and 190°C. The SHG intensity was measured during thermal corona poling : the dipole orientation starts at 100°C, and reaches a maximum at 160°C, which is lower than Tg. During cooling of the film under the applied electric field, we observed an unusual drop of the SHG intensity starting at 120°C and reaching 70 % of the maximum value. The physical origin of this drop has been investigated and is possibly attributable to a secondary phase transition of the copolymers. Despite this decrease, d33 coefficients measured after poling vary between 2 and 15 pm/V at 1907 nm fundamental wavelength, depending on the first hyperpolarisability of the NLO chromophore. The dipole orientation of all these copolymers is very stable provided the temperature of the films is kept below the temperature threshold of 120 °C, which is below the Tg of the polymers.
Photonic devices based on novel bromo-fluorinated poly(arylene ether ketone)s have been prepared. In these materials, the intrinsic optical losses at 1550 nm, due to the absorption of hydrocarbon bond overtone vibration, have been minimized by replacing H in the C-H bonds with Br or F, thereby shifting the overtone absorption to a longer wavelength. Typical optical slab losses of these materials are ~ 0.5 dB/cm at 1550 nm. In addition these materials have high thermal stability (5 wt% loss at temperature greater than 450°C), and are easily processed at temperatures lower than those previously reported for other poly(arylene ether)s (< 200°C). High quality waveguides have been fabricated using standard photolithographic processes. A thin film of silicon dioxide deposited by rf sputtering or e-beam evaporation on the polymer surface was used as a mask for reactive ion etching. Data on the design, fabrication and characterization of wide-band wavelength division multiplexers are reported. The devices exhibit on-chip losses of 7 dB including the fiber to chip coupling loss, output uniformity of ± 0.5dB and central wavelength thermal sensitivity lower than 0.06 nm/<sup>o</sup>C. Optimization of devices through material properties and fabrication process parameters is discussed.
Polymeric materials have been widely used for the fabrication of photonic devices, in particular for applications in short haul optical networks employing coarse wavelength division multiplexing (CWDM). However, the molecular design and processing of polymeric materials to have all the properties required for the fabrication of high performance photonic devices continue to present challenges. This paper presents data on the design, fabrication and characterization of waveguide devices using novel fluorinated poly(arylene ether ketone) materials. These materials exhibit low optical loss (slab loss ~ 0.5 dB/cm at 1550 nm), high thermal stability (1 wt% loss at temperatures up to 430 °C), and are easily processed at temperatures lower than those previously reported for poly(arylene ether)s (< 200 °C). High quality waveguides have been fabricated using standard photolithographic processes. Issues affecting polymer layer and device birefringence and optical loss have been investigated, including molecular structure, processing conditions and substrate selection. Coupling devices sensitive to waveguide dimensions have been designed and fabricated, and their output compared to numerical simulations. Characterization of these devices allows further optimization of the materials and the waveguide process and assists with the design of more complex polymer photonic components.
With the development of telecommunications and high-speed computations, polymeric materials for optical applications are attracting much attention in highly integrated optical waveguides and circuits. In comparison with current inorganic waveguiding materials (e.g., silica and other III-V semiconductor materials), organic polymers offer several advantages including cheap fabrication, tunable properties, good processability and the ability for integration into large scale semiconductor circuits.
In this presentation, we describe the design and synthesis of novel crosslinkable optical polymers for use in optical waveguides based upon a bisphenol monomer containing crosslinkable tetrafluorostyrol units. The introduction of this crosslinkable bisphenol into perfluorinated poly(arylene ethers) allows the synthesis of crosslinkable fluorinated polymers with adjustable refractive index and controllable high crosslinking densities. These polymers have been shown to exhibited low optical loss at 1550 nm, low birefringence, high glass transition temperatures, good mechanical properties, and excellent processability. In the presence of a suitable initiator, these polymers can undergo rapid crosslinking either thermally or optically allowing for multilayer device fabrication.