Seung Koo Park

Chip-to-chip optical interconnect using gold long-range surface plasmon polariton waveguides.

We demonstrate a novel on-board chip-to-chip optical interconnect using long-range surface plasmon polariton (LR-SPP) waveguides that feature 2.5-cm-long gold strips embedded in a low loss polymer cladding. A TM-mode vertical-cavity surface-emitting laser (VCSEL) operating at a wavelength of 1.3 microm was butt-coupled into the waveguides in order to excite a fundamental LR-SPP mode and then the transmitted light was received with a photo-diode (PD). The waveguide width is varied in the range of 1.5-5.0 microm in order to optimize the insertion loss where the 3-microm-wide waveguide provides a minimum insertion loss of -17 dB, consisting of 6 dB/cm propagation loss and 2 dB coupling loss. An interconnect system based on the optimized waveguide with a 4-channel array is assembled with the arrayed optoelectronic chips. It shows the feasibility of 10 Gbps (2.5 Gbps x 4 channels) signal transmission indicating that the LR-SPP waveguide is a potential transmission line for optical interconnection.

40Gbit∕s light signal transmission in long-range surface plasmon waveguides

We demonstrate a high bit-rate optical signal transmission by using long-range surface plasmon polariton (LRSPP) waves in a guided geometry. With a 40Gbit∕s optical communication signal, eye patterns and bit-error-rates were measured to access the quality of the transmission properties of the LRSPP mode. A thin gold strip line embedded in a low loss optical polymer supports a LRSPP mode, which propagates with a 2dB∕cm loss, and couples to standard single mode fibers at 1.55μm with a 2dB coupling loss. A 40Gbit∕s optical signal was transmitted via a 4cm long LRSPP waveguide without any distortion of the eye patterns. The experiment also showed error-free transmissions. These results indicate that the LRSPP waveguide is a potential transmission line for optical interconnections overcoming the inherent problems in electric interconnections.

Hybrid plasmonic waveguide for low-loss lightwave guiding.

A hybrid plasmonic waveguide structure is proposed and fabricated for low-loss lightwave guiding along a metal stripe core. By embedding Au stripe in dual slab waveguides with high refractive-index contrast, the field of the guided mode is confined more in the two dielectric core layers. Thus, the propagation loss is significantly reduced. The guided mode is like a combination of a fundamental long-range surface plasmon polariton strip mode and a dual symmetric dielectric slab mode. We fabricate 5 nm-thick Au stripe optical waveguides and measure the optical properties at a wavelength of 1.31 microm. The propagation loss is less than 1.0 dB/cm with the metal stripe width of 1-5 microm.

Polymer‐Waveguide‐Based Flexible Tactile Sensor Array for Dynamic Response

A polymer-waveguide-based transparent and flexible force sensor array is proposed, which satisfies the principal requirements for a tactile sensor working on curvilinear surfaces, such as thinfilm architecture (thickness < 150 μm), localized force sensing (ca. 0-3 N), multiple-point re cognition (27 points), bending robustness (10.8% degradation at R = 1.5 mm), and fast response (bandwidth > 16 Hz).

Low-Loss Polymer-Based Long-Range Surface Plasmon-Polariton Waveguide

To improve the propagation loss of polymer-based long-range surface-plasmon-polariton (LR-SPP) waveguide devices at the telecom wavelength range, low-loss LR-SPP waveguides were fabricated in an ultraviolet-curable acrylate polymer with a low refractive index and absorption loss. A propagation loss of 1.72 dB/cm at a wavelength of 1.55 mum was achieved with a 14-nm-thick and 3-mum-wide metal stripe.

Polymer-Based Long-Range Surface Plasmon Polariton Waveguides for 10-Gbps Optical Signal Transmission Applications

We present characteristics of very thin Au strip waveguides based on long-range surface plasmon polaritons (LR-SPPs) along thin Au strips embedded in polymers. We also report a 10 Gbps optical signal transmission via LR-SPPs with the pig-tailed Au strip waveguide at a telecommunication wavelength of 1.55 mum. We limited the thickness, width, and length up to ~20 nm, ~ 10 mum, and ~5 cm, respectively, for practical applications. At 1.55 mum, loss properties of the Au strip waveguides were theoretically and experimentally evaluated with thickness, width and cladding material. The lowest propagation loss of ~1.4 dB/cm was experimentally obtained with the 14-nm-thick and 2-mum-wide Au strip. With a single-mode fiber, the lowest coupling loss of less than 0.1 dB/facet was achieved with the 14-nm-thick and 7.5-mum-wide Au strip. The lowest insertion loss was obtained 7.7 dB with the 14-nm-thick, 5-mum-wide, and 1.5-cm-long Au strip. The propagation loss was improved approximately 30% for the 17-nm-thick Au strip with lowering the refractive index of the cladding polymer by 0.01. In the 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10-12 bit error rate. These all results indicate that the LR-SPP waveguide is a potential transmission line for optical interconnects to overcome inherent problems in electric interconnects.

Polymeric 16/spl times/16 arrayed-waveguide grating router using fluorinated polyethers operating around 1550 nm

A 16/spl times/16 arrayed waveguide grating (AWG) router with a channel spacing of 0.8 nm (100 GHz) operating around the 1550-nm wavelength has been fabricated using newly synthesized fluorinated polyethers. It has a good processibility and a high thermal stability up to 510/spl deg/C. The propagation loss of the buried-channel waveguide is about 0.4 dB/cm at the 1550-nm wavelength. The on-chip insertion loss ranges from 5.5 to 11 dB and the crosstalk is less than -27 dB. The AWG router shows good cyclic rotation property of the wavelength channels with an error smaller than 0.03 nm.

Sub-dB/cm propagation loss in silver stripe waveguides

We demonstrate sub-dB/cm propagation losses in polymer-based silver stripe waveguides at the wavelength of 1.31 microm. The silver stripe waveguides were fabricated in a low-loss fluorinated polymer clad. To form uniform metal stripe patterns, which are essential for reducing propagation loss, we developed a lift-off process using double layers of photoresist and SiNx. A propagation loss of less than 1.0 dB/cm was obtained with the 11- nm-thick silver stripes in the width range of 1.5 - 4.5 microm. A coupling loss of approximately 1.0 dB with a polarization maintaining single mode fiber was achieved for a width of 4.5 microm. For a width of 2.0 microm, we recorded a minimum propagation loss of 0.4 dB/cm, which is comparable with that of dielectric multi-mode waveguides.

Second-harmonic generation in periodically poled nonlinear polymer waveguides

We demonstrate quasi-phase-matched (QPM) second-harmonic generation (SHG) at the optical communication wavelengths with side-chain polymer waveguides. A ridge waveguide structure is designed to support fundamental mode guiding at both the pump and the second harmonics, leading to a high field overlap integral of the guided modes. The nonlinearity contrast in the +/0 type QPM waveguide is maximized under a QPM poling electrode width of nearly half the coherence length. Using these configurations, we record a normalized SHG efficiency of 2.2% W(-1) cm(-2) in the polymer waveguide.

Structural and optical characterizations of multi-layered and multi-stacked PbSe quantum dots

A multi-layered nanocomposite thin film was fabricated to increase the density of PbSe quantum dots. It consisted of low-loss polymer layers and multi-stacked PbSe quantum dot layers in series. The solutions of a UV-curable low-loss polymer and PbSe quantum dots were spin-coated layer-by-layer. An arrayed and multi-stacked PbSe quantum dot layer was self-assembled by spin-coating and solvent evaporation. The multi-stacked layers of PbSe quantum dots have a face-centred cubic structure with an average {111} plane distance of ~6.1?nm, determined by small-angle x-ray scattering. The average diameter of PbSe quantum dots is ~5?nm and the average interparticle spacing distance is ~2.5?nm, characterized by transmission electron microscopy. The density of PbSe quantum dots in the single-arrayed layer is ~1.8 ? 1012?cm?2 and the density in the three-layered thin film of multi-stacked PbSe QDs is >1.6 ? 1013?cm?2. The peak intensities of absorption and photoluminescence were increased with increasing number of PbSe quantum dot layers. The time of luminescence decay to e?1 is 138?ns at room temperature. We investigated the structures of multi-layered and multi-stacked PbSe quantum dot thin films as well as their optical properties, and then suggested their photonic applications.