Organic membrane photonic integrated circuits (OMPICs).

We propose the concept of organic membrane photonic integrated circuits (OMPICs), which incorporate various functions needed for optical signal processing into a flexible organic membrane. We describe the structure of several devices used within the proposed OMPICs (e.g., transmission lines, I/O couplers, phase shifters, photodetectors, modulators), and theoretically investigate their characteristics. We then present a method of fabricating the photonic devices monolithically in an organic membrane and demonstrate the operation of transmission lines and I/O couplers, the most basic elements of OMPICs.

On-chip membrane-based GaInAs/InP waveguide-type p-i-n photodiode fabricated on silicon substrate.

Toward the realization of ultralow-power-consumption on-chip optical interconnection, two types of membrane-based GaInAs/InP p-i-n photodiodes were fabricated on Si host substrates by using benzocyclobutene bonding. A responsivity of 0.95 A/W was estimated with a conventional waveguide-type photodiode with an ∼30-µm-long absorption region. The fitting curves based on the experimental data indicated that an absorption efficiency above 90% could be achieved with a length of 10 µm. In addition, increased absorption per length of a photonic crystal waveguide-type photodiode was obtained because of the enhanced lateral optical confinement or the slow-light effect, enabling a further reduction in the device length.

Analysis of plasmonic phase modulator with furan-thiophene chromatophore electro-optic polymer.

We analyzed two types of Mach-Zehnder plasmonic modulators on a silicon-on-insulator platform with a different furan-thiophene chromophore electro-optic polymer to compare to other reports. The metal-taper coupling structure and the metal-insulator-metal cross section in our design have been optimized based on the new material parameters. According to the simulation result, a modulator with a slot width of 50 nm and an on-off voltage of Vπ=20 V can be 21 µm long, leading to a total modulator loss of 15 dB, which is comparable to previously reported devices.

Optical transmission between III-V chips on Si using photonic wire bonding.

Photonic wire bonding (PWB) was used to achieve flexible chip-scale optical interconnection as a kind of 3D-freeform polymer waveguide based on the two-photon polymerization of SU-8. First, the fabrication conditions of PWB were determined for the two-photon absorption process, and the coupling structure between PWB and III-V optical components was numerically simulated in order to obtain high coupling efficiency. Then, using PWB, chip-to-chip optical transmission was realized between laser and detector chips located on a common Si substrate. We fabricated a 2.5-µm-wide PWB with 1:3 aspect ratio between two optical chips of 140-µm gap and achieved a connection loss of approximately 10 dB.