Sung-dong Suh

Bulk silicon photonic wire for one-chip integrated optical interconnection

We report a nano-sized silicon waveguide by forming partial silicon-on-insulator structure with SPE on bulk silicon substrate. The propagation loss is as low as 6.1 dB/cm, which is close to that of silicon-on-insulator based waveguide.

Development of Integrated Small-Form-Factor Optical Pickup with Blu-ray Disc Specification

In this study, a small-form-factor optical pickup (SFFOP), corresponding to the Blu-ray disc (BD) specifications has been developed. The developed SFFOP is composed of an integrated optical pickup and a swing-arm-type actuator. The integrated optical pickup has been developed in the form of an array using wafer-level fabrication technology. The developed SFFOP is composed of the fundamental optics which yields a numerical aperture (NA) of 0.85 and uses a blue laser diode having a short wavelength of 407 nm and a silicon optical bench, which consists of a laser diode, a photodiode and several mounts for the laser diode, an objective lens and mirrors. The micro objective lens is bonded to the lens holder on the SFFOP by an active alignment using a modified Mach–Zehnder interferometer. Also, a static focus error signal was detected to assemble a polarized holographic optical element. Through the measurement of the focus error signal with a swing-arm-type actuator, which was developed for the SFFOP, it is estimated that the developed SFFOP satisfies the BD specifications with the balance of the focus error signal below 10%.

Mach-Zehnder silicon modulator on bulk silicon substrate; toward DRAM optical interface

We present a Mach-Zehnder silicon modulator fabricated on a bulk silicon substrate featuring active length of 200 µm, modulation speed up to 5 Gb/s, power consumption of 2 pJ/bit, and extinction ratio of 10 dB.

Development of Microlens for High-Density Small-Form-Factor Optical Pickup

A microlens of numerical aperture (NA) 0.85 a small-form-factor optical pickup, following the specifications of the Blu-ray disc (BD), was designed, fabricated and evaluated. To avoid difficulties in the fabrication of a high-NA objective lens and to obtain a low chromatic aberration, a new hybrid lens unit was designed to have a refractive lens and a diffractive lens. The micro-plano-aspheric refractive lens was fabricated using glass molding technology, and the diffractive lens was fabricated in a two-dimensional array using the electron beam mastering and consecutive UV embossing process. For the evaluation of the developed lens unit, diffraction efficiency was measured with the proposed diffraction efficiency measurement method, and the wavefront error of the lens unit was evaluated using a modified Mach–Zehnder interferometer. The measured average efficiency of the diffractive lens was approximately 85% and the RMS wavefront error of the lens unit was 0.0376 λrms.

Si-based optical I/O for optical memory interface

Optical interconnects may provide solutions to the capacity-bandwidth trade-off of recent memory interface systems. For cost-effective optical memory interfaces, Samsung Electronics has been developing silicon photonics platforms on memory-compatible bulk-Si 300-mm wafers. The waveguide of 0.6 dB/mm propagation loss, vertical grating coupler of 2.7 dB coupling loss, modulator of 10 Gbps speed, and Ge/Si photodiode of 12.5 Gbps bandwidth have been achieved on the bulk-Si platform. 2x6.4 Gbps electrical driver circuits have been also fabricated using a CMOS process.

Polymeric light delivery via a C-shaped metallic aperture

A polymeric light delivery system with a C-shaped metallic nanoaperture is proposed for the heat-assisted magnetic recording. This light delivery system has high optical efficiency and easy fabricability in the low temperature process that is compatible with the conventional magnetic head. The light delivery characteristics are demonstrated analytically and experimentally. In particular, the near-field spot size of the light delivery system was measured using the virtual scanning near-field optical microscopy (VSNOM) method, in which the probe tip geometry is not reflected. The probable spot size of the developed light delivery is under 100 nm at a wavelength of 780 nm from a polymeric light delivery with the C-shaped metallic nanoaperture.

A Serial Optical Link Based Memory Test System for High-Speed and Multi-Parallel Test

A novel memory optical test solution is proposed and experimentally evaluated for at-speed DDR2-SDRAM test using a commercial automatic test equipment (ATE). Combination of an optical signal splitting scheme and SerDes (Serializer/De-Serializer) technique based on FPGA (Field programmable gate array) allows the high-speed multi-parallel memory test with reduced channel resources. Owing to the SerDes, optical fiber channels are reduced by more than 87 percent and the number of optical modules including transmitter/receiver dramatically decrease to 95 percent, compared with a conventional optical test interface system. Furthermore, the proposed system can optically expand the tester resource by 4 times using a 1 × 4 optical splitting scheme. We evaluated the signal integrity of 28 layer PCB operating at 3.125 Gbps with three-dimension electromagnetic simulation to obtain more reliable system for memory testing. Consequently, for the first time to the best of our knowledge, we realized an optical SerDes interconnect system for a memory test tester and demonstrated an actual write/read function test of DDR2-SDRAM.

10 Gb/s, 1×4 optical link for DRAM interconnect

We present a 10-Gb/s, 1×4 optical link based on a DRAM-integration-ready bulk-silicon modulator for multi-drop CPU-DRAM interconnects. The bulk-silicon modulator operated at 10 Gb/s on a die, and at 5 Gb/s in a QFP package. The 1×4 optical link was limited not by signal integrity but by optical power budget, demonstrating its scalable capacity for the future multi-drop memory bus.

90° bent metallic waveguide with a tapered C-shaped aperture for use in HAMR

An efficient and compact method of introducing light into a magnetic recording head for use in Heat Assisted Magnetic Recording (HAMR) is proposed. The technique uses a polymer waveguide to source light into a novel metallic structure consisting of a sub-wavelength C-aperture waveguide with a 90° bend and a tapered section. The structure is modeled using Finite Difference Time Domain (FDTD) simulations and it is shown that the 90° bend allows for low loss near-field optical access into a conventional magnetic recording head while the tapered C-waveguide allows for maximum input coupling and a minimum spot size at the recording media.

Super slim optical pickup for mobile storage device applications

This paper addresses the design, fabrication and packaging issues of SSOP(super slim optical pickup) module using blury technology. By using blu-ray technology, which uses a 407nm LD (Laser Diode) and an objective lens having NA (Numerical Aperture) 0.85, storage devices become miniaturized but have a high capacity. The developed prototype uses the integrated structure of a SiOB (Silicon Optical Bench) and a mirror substrate. The SiOB should be processed in order that a thin film PD(Photodiode) and interconnections, LD, Lens, QWP(Quarter Wave Plate) and HOE can be placed, and on the Silicon Substrate should Micromachined Silicon Mirror be formed. The SiOB is aligned and bonded with the wafer on which Silicon Mirror was formed. Then, it is diced. Because it is fabricated through this order, the super slim optical pickup can be fabricated by using wafer-level process. As a final step LD on the SiOB and HOE are mounted, assembled and bonded using an active alignment. The proposed SSOP was prototyped and characterized by measuring wavefront error and detecting static focusing and tracking error signals.