Fluorinated Styrene-Based Cladding Polymer Layers for EO or NLO Polymer Devices

摘要

Numerous electro-optic (EO) or nonlinear optical (NLO) polymers have been developed for practical applications in polymer optical devices over the last two decades because of their large EO coefficients (r_(33)) for low voltage operation, easy fabrication for lower cost, and comparatively low and steady dielectric constants for highspeed modulation. First of all, the large EO coefficients (r_(33)) are attractive for the realization of such optical devices. Electric poling is generally required for obtaining high r_(33) in the fields of EO polymers. The polymer films are heated to near their glass transition temperature (T_g), at which the polymer chain motion is free for dye molecules to align themselves to an applied DC electric field. In practical optical guided-wave devices, the EO polymer is sandwiched between two cladding layers. During poling, DC voltage is applied and is divided among the three layers according to their resistivity. Therefore, the resistivity of the cladding layers is similar to or lower than that of the core layer for maximizing the poling effect. Additionally, low optical losses of the cladding layer are needed for lessening propagation losses. In general, many researchers have intensively focused on an EO polymer system including a chromophore in the consideration of EO device operation. Even though the cladding layers play an important role for the realization of such EO devices as mentioned above, there have been few reports on development of cladding materials.