Silicon-organic (SOH) and plasmonic-organic (POH) hybrid integration: Extending the capabilities of silicon photonics and plasmonics

Summary form only given. Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration by enabling fabless fabrication and joint processing of photonic and electronic circuitry. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, thereby reducing the device footprint by more than an order of magnitude. Silicon and metals, however, fall short of certain optical properties that are indispensable for high-performance photonic devices. In particular, neither material exhibits an appreciable second-order optical nonlinearity, thereby making efficient electro-optic modulators challenging. These deficiencies can be overcome by the concepts of silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) integration, which combine silicon-on-insulator (SOI) waveguides and plasmonic nanostructures with organic electro-optic materials. In this paper, we give an overview of our recent progress in the field of SOH [1][8] and POH [9] photonics. Our work covers basic material aspects and device concepts of highly efficient phase modulators [1], [2] and phase shifters [3]. We demonstrate Mach-Zehnder and Inphase-Quadrature(IQ-)modulators [4], [5] having energy consumptions down to a few fJ/bit [2], as well as high-speed transmission experiments using advanced modulation formats such as 16QAM at symbol rates (bit rates) of up to 40 GBd (160 Gbit/s) [6]. We further show that the extraordinarily low operating voltage of SOH modulators allows to drive them directly from standard output ports of field-programmable gate arrays (FPGA), without the need for external amplifiers and analog-to-digital converters. Such schemes can be used even if high-order modulation formats such as 16QAM are to be generated [7]. Moreover, we use SOH devices for generating broadband frequency combs, which are well suited as optical multi-wavelength sources for terabit/s transmission [8]. POH integration finally enables ultra-short phase modulators of less than 30 μm length, operating at data rates of 40 Gbit/s [9]. The POH modulators feature a flat frequency response up to at least 65 GHz, and potentially open the route for modulation at THz frequencies.