In this paper, we demonstrate recent progress in graphene-based photonic waveguide devices such as polymer
waveguide polarizer, thermo-optic mode extinction modulator and plasmonic photodetector for graphene-based
photonic integrated circuits.
Polymer-based flexible Cu stripe optical waveguides have been developed to configure a board-level optical
interconnection. By embedding Cu stripe in a dual slab waveguide with high refractive-index contrast, the field of the
guided mode is confined more in the two dielectric core layers. Thus, significant reduction of the propagation and
vertical bending loss are expected. The fabricated Cu plasmonic waveguide is flexible enough to be bent down to a
radius of 0.5 mm. The measured optical properties are satisfactory for very short distance board-level optical
interconnection. Based on the experimental results, we concluded that hybrid Cu plasmonic waveguides have a great
potential to be developed as a means of optical signal guiding medium in the optical interconnections.
Replication technologies have been recommended as an alternative means of high volume manufacturing of the polymer
optical components with low-cost. We demonstrated replication technology as a means of implementing polymer-based
MOEMS. To achieve this, a polymer optical bench with embedded electric circuits was designed to integrate the
functional planar-lightwave-circuit (PLC)-type optical waveguide devices; the designed packaging structures were
realized using a novel fabrication process that incorporated the UV imprint technique. In addition, the detail fabrication
steps of the UV imprint process were investigated. The optical bench has v-grooves for the fiber ribbon and the
alignment pits for opoelectronic interconnection. The plastic mold for imprinting the designed optical bench was made of
UV-transparent perfluorinated polymer material. The designed optical bench was configured on the electric-circuitpatterned
silicon substrate. Flip-chip bonded polymer optical waveguide device showed not only a good electric contact
but also a coupling loss of 0.9 dB at a wavelength of 1.5 ?m. It was concluded that replication technology has versatile
application capabilities in manufacturing next generation optical interconnect systems.
A fully optical PCB with transmitter/receiver system boards and optical bakcplane was prepared, which is board-to-board interconnection by an optical slot. We report a 10 Gb/s PRBS NRZ data transmission between transmitter system board and optical backplane embedded multimode polymeric waveguide arrays. The basic concept of the optical PCB is as follows; 1) Metal optical bench is integrated with optoelectronic devices, driver and receiver circuits, polymeric waveguide and access line PCB module. 2) Multimode polymeric waveguide inside an optical backplane, which is embedded into PCB, 3) Optical slot and plug for high-density (channel pitch : 500 um) board-to-board interconnection. The polymeric waveguide technology can be used for transmission of data between transmitter/receiver processing boards and backplane boards. The main components are low-loss tapered polymeric waveguides and a novel optical plug and slot for board-to-board interconnections, respectively. The transmitter/receiver processing boards are designed as plug types, and can be easily plugged-in and -out at an optical backplane board. The optical backplane boards are prepared by employing the lamination processes for conventional electrical PCBs. A practical optical backplane system was implemented with two processing boards and an optical backplane. As connection components between the transmitter/receiver processing boards and backplane board, optical slots made of a 90°-bending structure-embedded optical plug was used. A 10 Gb/s data link was successfully demonstrated. The bit error rate (BER) was determined and
is 5.6×10<sup>-9</sup>(@10Gb/s) and the BER of 8 Gb/s is < 10<sup>-12</sup>.
Polymer waveguides have attracted a great deal of attention for their potential applications as optical components in optical communications, optical interconnections and optical sensors because they are easy to manufacture at a low temperature, and they have a low processing cost. Hot embossing is powerful and effective tools to produce a large volume of waveguides and structure high-precision micro/nano patterns of thin polymer films using a stamp for optical applications. In this work, fabrication techniques of hot embossed polymeric optical waveguides for parallel optical interconnection module, multi-channel variable optical attenuator and optical printed circuit boards are demonstrated. The single- and multi-mode waveguides are produced by core filling and UV curing processes. New approaches to fabricating single-mode polymeric waveguides with the high thermal stability in thermosetting polymers and two-dimensional multi-mode polymeric waveguides for high-density parallel optical interconnections as well as a simultaneous fabrication of single-mode polymeric waveguides with micro pedestals for passive fiber alignment are also reported.
A novel optical PCB with transmitter/receiver system boards and optical bakcplane was prepared, which is board-to-board interconnection by optical plug and slot. We report an 8Gb/s PRBS NRZ data transmission between transmitter system board and optical backplane embedded multimode polymeric waveguide arrays. The basic concept of ETRI's optical PCB is as follows; 1) Metal optical bench is integrated with optoelectronic devices, driver and receiver circuits, polymeric waveguide and access line PCB module. 2) Multimode polymeric waveguide inside an optical backplane, which is embedded into PCB. 3) Optical slot and plug for high-density(channel pitch : 500um) board-to-board interconnection. The polymeric waveguide technology can be used for transmission of data on transmitter/ receiver system boards and for backplane interconnections. The main components are low-loss tapered polymeric waveguides and a novel optical plug and slot for board-to-board interconnections, respectively. The optical PCB is characteristic of low coupling loss, easy insertion/extraction of the boards and, especially, reliable optical coupling unaffected from external environment after board insertion.
A practical optical printed circuit board (PCB) was demonstrated, using a waveguide-embedded optical backplane and processing boards. The polymeric waveguide was produced by means of a hot embossing technique then embedded following a conventional lamination processes. The core size of waveguide was 100 x 60 μm<sup>2</sup> (input section), 60 x 60 μm<sup>2</sup> (output section), and the propagation loss of tapered polymeric waveguide was approximately 0.1 dB/cm at 850 nm. We prepared a optical backplane with polymeric waveguide by using conventional multilayer board lamination processes. The transmission power and dimension of the optical backplane was same as those of waveguide before lamination. A metal optical bench was used as a packaging die for the optical devices and the integrated circuit chips in both the transmitter and the receiver processing boards. We used a 1×4 850 nm VCSEL array with 2 dBm of output power for the transmitter and a PIN photodiode array for the receiver. We successfully demonstrated 8 Gb/s of data transmission between the transmitter processing board and the optical backplane board.
The optical interconnection between fibers and optical waveguides has been the most important factor for low-cost packaging of multi-channel PLC-type optical devices. Recently, polymer based PLC-type optical devices have been considered as an alternative fabrication method and are particularly attractive because of their satisfactory light guiding characteristics and easy fabrication process. In this study, a novel micro-mechanical passive alignment method for multi-channel polymer PLC devices has been designed and fabricated using a hot embossing technique. The main design issue is simultaneous fabrication of micro channels for single-mode waveguides and micro-pedestals for passive alignment on a polymer PLC surface in one step by hot embossing. Since the hot embossing process uses wet-etched silicon mould for pedestals, and alignment pits on silicon optical bench (SiOB) are also wet-etched in KOH solution, optical alignment was achieved through the simple insertion of micro pedestals into the alignment pits on SiOB. The hot embossed waveguide and passive alignment pedestals have been shown an accuracy of ± 0.5 μm. The propagation loss of fabricated single-mode polymer PLC was 0.83 dB/cm at a wavelength of 1550 nm, and passively aligned polymer PLC device with an accurate SiOB showed an average 0.67 dB coupling loss.