This thesis presents novel results in the field of plasmonics and optoelectronics application. Plasmonics is the rapidly expanding branch of photonics. It opens up capabilities of electronic and photonic device implementation within the same integrated circuits as well as enhances the limit of detection for chemical and biological-based sensors. The first finding lies in solving the dilemma in search of ultimate plasmonics materials for plasmonics application. It is well known that Cu and Ag are metals that have incredible electric and optic properties. However, they are easily oxidized in contact with air. Both experimental and theoretical findings demonstrate that application of a mono or bilayer graphene protects Cu and Ag from oxidation and degradation of its plasmonic properties. The performance of each metal is evaluated based on the quality factor Q and the minima in amplitude of reflection intensity Rmin of the Surface plasmon-polariton (SPP) curve. The second novelty of this thesis comprises the fabrication of low loss, high efficient broadband, as well as narrowband, graphene-based electro-absorption modulators. The studied graphene-based modulators made use of Fabry-Perot resonator geometries. It has been shown that high-k dielectric hafnium dioxide (HfO2) provides solid state âsupercapacitorâ effects and allows to observe light modulation from the near-infrared to shorter wavelengths close to the visible spectrum with remarkably low gate voltages (~4 V). The electro-absorption modulators based on Fabry-Perot resonator geometry reached the modulation depth in transmission mode of 28% at a wavelength of 1.1 Âµm.