Graphene, a one-atomic carbon sheet with a honeycomb structure, has attracted significant attention due to its unique physical properties. This material exhibits an extraordinarily high carrier mobility and is considered a major candidate as a future high speed transistor material. One of the many interesting properties of Dirac electrons in graphene are the drastic changes of the conductivity of graphene-based structures with the confinement of electrons. Structures that realize this behavior are carbon nanotubes and Graphene NanoRibbons (GNRs) that impose periodic and zero boundary conditions, respectively, on the transverse electron wave-vector. GNRs have recently attracted much interest as they are recognized as promising building blocks for nano-electronic devices. Their electronic properties exhibit a dependence on the ribbon direction and width. The electronic band-structure of GNRs depends on the nature of their edges, which can be zigzag or armchair. Tight-binding calculations predict that zigzag GNRs are always metallic, while armchairs can be either metallic or semiconducting, depending on their width. The direct band-gap and the tuneability of the band-gap with the GNRs width render these structures as suitable candidates for opto-electronic devices, especially for infrared applications, due to the relatively narrow band gap. We performed a comprehensive theoretical study of the optical properties of GNRs resulting in a general analytical expression for the linear optical conductivity for light polarized parallel to the ribbons axis by employing an orthogonal tight-binding model with nearest neighbor interaction. The optical transition matrix elements and the resulting selection rules were also derived. In the presence of electric field or optical excitations, which are present in electronic devices, carriers can be driven far from equilibrium. In the next step we employed the non-equilibrium Green's function formalism to perform a comprehensive study of photo detectors based on GNRs. The device response was studied for a wide range of photon energies. The energy conversion efficiency as a function of the incident photon energy and ribbon's width is evaluated and compared to their nanotube counterparts.