Electro-optic (EO) polymer modulators have demonstrated high speed external modulation of optical signals. Additionally, EO polymers have closely matched refractive indices at optical and microwave wavelengths, which enables high bandwidth operation. An EO polymer includes a polymer matrix and an organic "push-pull" chromophore that can be modified to give poled polymers with high EO activity. This high EO activity and optical-microwave velocity match offer the promise of accomplishing broadband, high speed optical modulation with low drive voltage. Such optical signal modulation is critical for applications in phased array radar and RF photonics. Practical issues such as electrode design, optical fiber coupling, and hermetic packaging are critical in final device performance. Herein, we report on high-speed electrode parameters as well as electro-optic performance versus frequency of packaged modulators fabricated with novel, highly photostable chromophores.
Low Vπ modulators are desirable in RF photonic and phased array radar applications. In general, there is still a need for optical modulators that have lower drive voltage, lower loss, and large bandwidth to decrease complexity, expense, and size in other parts of the packaged transmission system. This is particularly important for space based applications where reducing launch weight is crucial. Polymer modulators potentially enable space-based RF photonics because low Vπ can be achieved by modifying the organic constituents of the material. Additionally, polymers tend to have relatively low loss tangent and good RF-optical velocity match, which enables broadband devices. One fundamental issue for polymer modulator usability in space is the resistance of the materials to radiation. Previous reports have shown a small but measurable change in modulator properties on irradiation with gamma-rays and protons. Herein we report on the fabrication of polymer modulators, the results of irradiation, and potential lifetimes in earth orbits.
Electro-optic (EO) polymer modulators have demonstrated high speed external modulation of optical signals. Additionally, EO polymers have closely matched refractive indices at optical and microwave wavelengths, which enables high bandwidth operation. An EO polymer includes a polymer matrix and an organic "push-pull" chromophore that can be modified to give poled polymers with high EO activity. This high EO activity and optical-microwave velocity match offer the promise of accomplishing broadband, high speed optical modulation with low drive voltage. Such optical signal modulation is critical for applications in phased array radar and RF photonics. However, practical fabrication of optical modulators that realize the potential of EO polymers requires clad materials with optimized properties such as conductivity, dielectric constant, optical loss, and refractive index. In addition, other practical issues such as electrode design, optical fiber coupling, and hermetic packaging are critical in final device performance. We report on high-speed electrode parameters as well as electro-optic performance versus frequency of modulators fabricated on 6" silicon wafers. The r33 values measured on single layer thin films are compared with those resulting from Vπ measurements on devices. We compare the effect of EO polymer morphology on device fabrication and optical loss for different EO polymers.
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