S. G. Park

Design and fabrication of polarization-insensitive hybrid solgel arrayed waveguide gratings

We report on the successful design and fabrication of a polarization-insensitive arrayed waveguide grating (AWG), using solgel-derived silica glass films formed on fused-silica substrates. By controlling the waveguide width and making the propagation constants of the polarizations equal, we have found it possible to fabricate polarization-insensitive solgel-based AWGs. Polarization-insensitive design improves the cross talk by approximately 10 dB in the dynamic range.

Control of multimode effect on an arrayed waveguide grating device

We report on the method of successfully controlling the multimode effect in an arrayed waveguide (AWG) grating-device, in which the propagation modes of the optical waves are determined by the waveguide structure. As the grating order (m) changes, the imaging profiles for the other modes also change and can be effectively controlled. We found optimized values of order m for a given InP-ridge-type waveguide that can minimize the channel crosstalk. We compared the results of our simulation study with the experimental results that we obtained from the AWG device that we designed and fabricated by controlling various grating orders of m.

Design, fabrication, and integration of micro/nano-scale photonic crystal devices and plasmonic devices for VLSI photonic integration application

We present on the design, fabrication and integration of micro/nano-scale photonic crystal devices and plasmonic optical devices for VLSI photonic integration application. Using photonic crystals, we design and fabricate nanoscale directional couplers, multimode interference devices, power splitters, wavelength splitters, triplexers, filters, and develop their integration and interconnection schemes and technology. Using plasmonic structures, we design and fabricate horizontal directional couplers, vertical directional couplers, and chirped grating plasmonic structures to generate subwavelength lightwaves to be focused onto nano-potonic devices and modules. We examine scientific and technological issues concerning the miniaturization, interconnection, and integration of these nano-scale photonic devices for applications toward functional VLSI integrated circuits and systems.

Fabrication and integration of micro/nano-scale photonic devices and optical waveguide arrays for optical printed circuit board (O-PCB) and VLSI photonic applications (Invited Paper)

We report on the recent progresses of our work on the design, fabrication and integration of micro/nano-scale photonic devices and optical waveguide arrays for optical printed circuit boards (O-PCBs) and VLSI photonic applications. The waveguides are designed and fabricated by thermal embossing and ultraviolet (UV) radiated embossing of polymer materials. The photonic devices include vertically coupled surface emitting laser (VCSEL) microlasers, microlenses, 45-degree reflection couplers, directional couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors in micro/nano-scale. These de-vices are optically interconnected and integrated for O-PCB assembly and VLSI micro/nano-photonics. De-tailed procedures of fabricating and implementing these devices and assembly of O-PCB are described. The O-PCBs are to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or substrates. We report on the result of the optical transmission performances of these as-sembled O-PCBs up to 2.5 Gbps and 10 Gbps. For the design, fabrication, and VLSI integration of nano-scale photonic devices, we used photonic crystal structures. Characteristics of these devices are also described.

Fabrication and integration of micro/nano-scale optical wire circuit arrays and devices for high-speed and compact optical printed circuit board (O-PCB) and VLSI photonic applications

We report on the design, fabrication and integration of micro/nano-scale optical wire circuit arrays and devices for high-speed, compact, light-weight, low power optical printed circuit boards (O-PCBs) and VLSI photonic applications. The optical wires are formed in the form of waveguides by thermal embossing and ultraviolet (UV) radiated embossing of polymer materials. The photonic devices include vertically coupled surface emitting laser (VCSEL) microlasers, microlenses, 45-degree reflection couplers, directional couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors. These devices are optically interconnected and integrated for O-PCB assembly and VLSI micro/nano-photonics. The O-PCBs are to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or substrates. We report on the result of the optical transmission performances of these assembled O-PCBs. For the design, fabrication, and VLSI integration of nano-scale photonic devices, we used photonic crystal structures and plasmonic metallic waveguide structures. We examined the bandwidth, power dissipation, thermal stability, weight, and the miniaturization and density of optical wires and the O-PCB module. Characteristics of these devices are also described.

Integration of micro/nano-scale optical waveguide arrays and devices for optical printed circuit board (O-PCB) and VLSI photonic application

We report on the design, fabrication and integration of micro/nano-scale optical waveguide arrays and devices for optical printed circuit board (O-PCB) and VLSI photonic applications. The O-PCBs perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or chips in a manner similar to the electrical printed circuit boards (E-PCBs). The photonic devices include microlasers, microlenses, micro-reflectors, couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors. For VLSI micro/nano-photonics we used photonic crystals and plasmonic metal waveguide structures. We also describe device characterization using near filed scanning microscopy. We examine the scientific and technological issues concerning the miniaturization, interconnection, and integration of photonic devices, circuits and systems in micron or submicron scale. In miniaturization, the issues include size effect, proximity effect, energy confinement effect, microcavitiy effect, single photon effect, optical interference effect, high field effect, nonlinear effect, noise effect, quantum optical effect, and chaotic noise effect. In interconnection, the issues include homogeneous interconnection (between identical devices) and heterogeneous interconnection (non-identical devices). In integration, the issues of interfacing same kind of devices, two different kinds of devices, and several or many different kinds of devices are addressed. The discussion includes the nano-scale electron beam system and techniques to characterize nano-scale structures.

Optical printed circuit board (O-PCB) for VLSI micro/nano-photonic application

We present, in the form of review, the results of our study on the design, fabrication and assembly of optical printed circuit boards (O-PCBs) for VLSI micro/nano-photonic applications. The O-PCBs are designed to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards, substrates or chips, in a manner similar to the electrical printed circuit boards (E-PCBs). We have assembled and constructed O-PCBs using optical waveguide arrays and circuits made of polymer materials and have examined their information handling performances. We also designed power beam splitters and waveguide filters using nano-scale photonic band-gap crystals. We discuss scientific and technological issues concerning the processes of miniaturization, interconnection and integration of polymer optical waveguide devices and arrays for O-PCB and VLSI micro/nano-photonics as applicable to board-to-board, chip-to-chip, and intra-chip integration for computers, telecommunications, and transportation systems.

Tolerance design of optical micro-bench by statistical design of experiment

Design rule of optical micro-bench and tolerance of positional error of components assembled onto the bench are investigated in case of simple linear connections of incoming and outgoing optical fibers with and without ball lenses. Since there are many error variables with wide range of values that affects the optical coupling, the efficient array with reduced number of combinations is generated using statistical design of experiment and coupling efficiencies are calculated. From 3d B point, the tolerance of each position error is determined. For the fiber-to-fiber connection with ball lenses, the longitudinal and lateral positional errors have the strong interaction with each other to the coupling efficiency and thus should be be limited simultaneously.

SCH dependence of linewidth enhancement factor for high-speed 1.55-μm multiple quantum well laser diodes

The linewidth enhancement factor is the crucial design parameter with others, such as gain and refractive index changes for semiconductor laser diodes (LD). The changes of characteristics are measured according to the variation of the thickness of SCH (Separate Confinement Heterostructure, 1.24 micrometer p-InGaAsP). The gain spectra were obtained from the spontaneous emission for three LDs. The threshold current; Ith were about 15 mA. The optical field profiles for various SCH thickness was calculated from the effective index and transfer matrix method and the corresponding optical confinement factors are compared with the variation of measured (alpha) . It is meaningful to find the SCH thickness, SCH(Gamma max), of maximum confinement (Gamma) for given LD structure. Although the improvement of the linewidth enhancement factor ((alpha) ) in thicker SCH (greater than SCH(Gamma max)) has been known, it has not been measured for thin SCH (less than SCH(Gamma max)). Here, we compare the measured linewidth enhancement factors of three DFB-LDs with different SCH thickness of 500, 750, and 1000 angstrom, which are all smaller than the SCH(Gamma max) for given structure. It is shown that (alpha) would be improved as SCH thickness increases up to 1500 angstrom (approximately SCH(Gamma max)) for given structure if other design parameters permit.