Polyimides Derived from 2,2'-Bis(trifluoromethyl)-4,4'-diaminobiphenyl. 4. Optical Properties of Fluorinated Polyimides for Optoelectronic Components

Abstract

Optical loss and refractive indices of fluorinated polyimides and copolyimides are studied for application to optoelectronic components. These polyimides and copolyimides are prepared from 2,2-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), pyromellitic dianhydride (PMDA), and 2,2'bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). The polyimide 6FDA/TFDB prepared from 6FDA and TFDB cured at 350 °C has an optical loss of 0.7 dB/cm at 0.63 nm, and this is the lowest of all polyimides cured at high temperature. Direct measurement of the optical loss of a polyimide at 1.3 pm was achieved for the first time by using a 6FDA/TFDB block with unequal length, width, and thickness. The optical loss was also low, 0.3 dB/cm. 6FDA/TFDB, PMDA/TFDB, and their copolyimides cured on a silicon substrate at 350 0 C have two different refractive indices, an in-plane refractive index («te) and an out-of-plane refractive index («tm). The wte of the copolyimide at 1.3 pm can be controlled between 1.523 (6FDA/TFDB) and 1.614 (PMDA/TFDB) by changing the 6FDA/TFDB content. It decreases monotonically with increasing 6FDA/ TFDB content. The Rtmi on the other hand, can be controlled between 1.514 (6FDA/TFDB) and 1.521 (copolyimides with 60 mol % 6FDA/TFDB), but it has a maximum value at a 6FDA/TFDB content of 60 mol %. These polyimides and copolyimides prepared on a silicon substrate have birefringences between 0.008 (6FDA/TFDB) and 0.123 (PMDA/TFDB). Low optical loss and precise refractive index control are very important characteristics for optoelectronic components, especially at the telecommunication wavelength of 1.3 pm.

Structure-property relationship of fluorinated co-poly(arylene ether sulfide)s and co-poly(arylene ether sulfone)s for low-loss and low-birefringence waveguide devices

“…The densities are reasonable if we consider that the polymers are fluorinated and contain a sulfone or sulfide group. In the table, the calculated density of common polymers such as polymethylmethacrylate, polystyrene, polyamides, polycarbonate, perfluorocyclobutane (PFCB), Cytop, and polyimide (6FDA-TFDB) are included and compared with the experimentally obtained density [7], [23], [24]. The calculate densities match very well with the experimental data.…”

“…By changing the co-polymer composition, the birefringence was reduced significantly down to 0.0009 at a wavelength 2) with Lorentz-Lorenz equation for general polymers, co-poly(arylene ether sulfide)s, and co-poly(arylene ether sulfone)s. From the slope (1=), the density of polymers can be calculated. of 1.55 m. This is much lower than those of fluorinated polyimides [7]. For anisotropic media, which have the difference between the refractive indexes in the two principal directions, the birefringence must be related to the polarizability difference between the polymer chain axes ( , ) and perpendicular to the chain axes and molecular orientations in bulk material.…”

Integrated Photonic Devices Incorporating Low-Loss Fluorinated Polymer Materials

“…By replacing the C-H bond with the C-F bond, one can reduce the optical loss and increase the thermal stability due to the heavy mass of fluorine and the higher bond strength of C-F bond. There have been various approaches to synthesizing low-loss optical polymers based on acrylates [15], polyimides [16], polyarylene ethers [17,18], and perfluorocyclobutane [19]. Among them, fluorinated UV-curable acrylates have been most actively investigated because of their convenient low temperature processing with UV curing.…”

Synthesis, Characterization, and Optical Properties of Uniaxially Drawn and Gold Nanoparticle Dispersed Fluorinated Polyimide Films.

“…The fluorinated polyimides developed by the authors show almost no color and their transmittance and refractive indices are stable even after curing at 380°C. [4] One of the polyimides is desirable for the purpose of this study as a matrix polyimide. Furthermore, distinct anisotropy in optical transmittance in the visible and near-infrared region were observed for uniaxially drawn and silver-dispersed polyimide films.…”

“…The preparation of poly(amic acid) (PAA), the precursor of the polyimide, and the thermal, mechanical, and optical properties of the polyimide has been described elsewhere. [4,8] Hydrogen tetrachloroaurate(III)trihydrate (HAuC14.3H2O) was obtained from Aldrich Chemical Co. and was used as received.…”