El-Hang Lee

Design and fabrication of a significantly shortened multimode interference coupler for polarization splitter application

We report that we have successfully designed and fabricated a significantly shortened multimode interference coupler for application in polarization splitter, using a phenomenon that we termed quasi-state (QS) imaging effect. First, we identified and analyzed the QS imaging effect, and, based on the QS analysis, designed and fabricated a novel multimode interference (MMI) device with its split length shortened to 1/5 of a normally designed MMI split length. The fabrication is simple and cost effective and the fabricated device shows outstanding characteristics in extinction ratio, signal homogeneity, excess loss, and tolerance in the length of the splitter.

Resonance characteristics of waveguide-coupled polyimide microring resonator

We report for the first time on the resonance characteristics of a polyimide-based micro-ring resonator model. The resonator consists of a microring coupled to a pair of waveguides. Using the finite-difference time-domain method, we were able to obtain resonance peaks, from which the resonance wavelength could be identified. For a resonator with a microring of 10 μm diameter, known as the minimum for a lossless microring, we found the free spectral range of 46.65 nm, and quality factor of 588. These are excellent values strongly supporting the outstanding utility and quality of the microring resonators for wavelength-division multiplexing filter applications.

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.

Novel design of polarization splitter based on a quasi-state multimode interference coupler

Summary form only given. We introduced the quasi-state using four-mode interference in the multimode interference (MMI) coupler. For TE polarization, output powers at the bar and cross waveguides are shown as a function of the propagation length, and quasistates are depicted.

Microphotonics: physics, technology, and an outlook toward the 21st Century

This paper presents an overview of our study on the study on the subject that is categorically termed <<microphotonics>>. Microelectronics, as we define it here, is an area of scientific and technological study concerning the miniaturization, interconnection, and integration of photonic devices, circuits, and systems in micron or submicron scale. We examine the scientifc and technological issues relating to these matters and discuss the challenges that the microphotonics faces toward the information technology in the 21st century. In the course of this study, we closely follow the experiences of microelectronics side by side, so that they can provide lessons, learnings, and insights that microphotonics can rightfully benefit from in a complementary form. Similarities, dissimilarites, advantages, and disadvantages, merits and demerits of the two technologies are explored in such a way that they can be more effectively utilized by mutual support.

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.

Polarization-insensitive design and fabrication of hybrid sol-gel arrayed waveguide gratings

Summary from only given. The influences of the sol-gel process conditions on the optical property are described in detail in a previous work. Here, we report on the design and fabrication of a polarization-insensitive 5-channel arrayed waveguide grating (AWG) device.

Micro/nano-scale integrated photonic devices and circuits: issues and challenges

This paper presents an overview of our study on approaching and achieving micron-scale or nano-scale integrated photonic devices and circuits. We examine the scientific and technological issues and challenges concerning the miniaturization and integration of photonic devices and circuits in micron or submicron scale. We will discuss the size effects, quantum effects, high-field effects, proximity effects, optical interference effect, nonlinear effects, and thermal effects in the process of miniaturization and integration of photonic devices and arrays. Models of our study include the devices and arrays of vertical cavity surface emitting microlasers, microdisk lasers, arrayed waveguides, micro-ring resonator devices and arrays and directional couplers, multi-mode interference devices, and spot-size converters. Issues and challenges for two-dimensional integration and three-dimensional integration are discussed based on realisitic examples. We will also discuss similar effects in micro/nano-scale electronics, so that they can provide the lessons from which the micro/nano-photonics can benefit in a complementary manner.

Planar Waveguide Type Temperature-Insensitive Refractive Index Sensor

This paper reports numerically analyzed results on temperature independent performance of planar-type long period waveguide gratings (LPWGs) for potential temperature-insensitive refractive index sensor applications. A polymer based waveguide structure with an optimized thermo-optic coefficient of core layer is designed for a stable and sensitive refractometer under temperature variation.

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.