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Latest News

  Beginning August 1^st, 2007, Professor Sheng-Lung Huang will succeed the position of GIEOE Chairman

Beginning August 1st, 2007, Professor Sheng-Lung Huang will succeed the position of GIEOE Chairman. Current GIEOE Chairman C. C. Yang’s two consecutive terms, totaling six years, will have come to an end. Professor Huang has been GIEOE Vice Chairman since February 2006, and has made great contributions to the Institute. Professor Huang’s professional experiences is as follows:

  Starting August 1^st, 2007, the Institute’s English name has been changed into “the Graduate Institute of Photonics and Optoelectronics”, “GIPO” for short, or “the Institute of Photonics and Optoelectronics”, “IPO” for short.

  GIEOE and Department of Electronics, Moscow State Technical University of Radio Engineering, Electronics and Automation signed Agreement for Cooperation

Through Professor Peng, Lung-Han’s arrangement and negotiation, the Agreement for Cooperation signed by GIEOE and Department of Electronics, Moscow State Technical University of Radio Engineering, Electronics and Automation, was approved by College of EECS in the end of January. The agreement signing would later be officially completed through air mail in February of 2007. This document outlines the reciprocal exchange program of cooperation and coordination in academic teaching and research.

  GIEOE academic visiting highlights

March “Photonics Forum” Lecture Highlights Time: March 9th, 2007, 4:30 pm Speaker: Professor Chen, Tai-Jen George (Vice President for Academic Affairs of National Taiwan University; Professor of Department of Atmospheric Sciences, National Taiwan University) Topic: The Story of Spring Rain—Things Most Worth Remembering From Student Life Until Now
Professor Chen, Tai-Jen George visited GIEOE on March 9th, 2007, and lectured at room 105, the EE Building II. The lecture “The Story of Spring Rain—Things Most Worth Remembering From Student Life Until Now” was attended with enthusiasm by GIEOE professors and students.
Time: March 23rd, 2007, 4:30 pm Speaker: Doctor Liou, S.W. (Vice Superintendent, Taipei City Hospital; Director-general, Laser and Photonics Medicine Society of the R.O.C.) Topic: The Application of Lasers in Ophthalmology Doctor Liou, S.W., Vice Superintendent of Taipei City Hospital visited GIEOE on March 23rd, 2007 to give a lecture. The humorous and amiable Doctor Liou spoke with wit and wisdom. GIEOE professors and students attended the lecture with enthusiasm and learned much.
March GIEOE Lecture Highlights Time: March, 8th, 2007, 12 pm Speaker: Professor Cheng, I-Chun (Professor of GIEOE, National Taiwan University) Topic: Thin Film Electronic Backplanes for Flexible Displays
Professor Cheng, I-Chun, a new member of the GIEOE faculty, gave a lecture to help GIEOE faculty and students understand her research and area of specialization. The lecture took place in room 142, the EE Building II. The lecture topic, “Thin Film Electronic Backplanes for Flexible Displays”, attracted many professors and students of GIEOE, and elicited animated discussion.
Time: March 12th, 2007, 10 am Speaker: Professor Connie J. Chang-Hasnain (EECS Department, University of California, Berkeley) Topic: Nano-optoelectronics For Communications Professor Connie J. Chang-Hasnain from EECS Department, University of California, Berkeley, is an academic with international renown. Responding to an invitation, she visited Taiwan to attend a workshop and gave a lecture at GIEOE to
help everyone understand her research and area of specialization. The lecture took place on March 12th, 2007, 10pm at room 142, the EE Building II. The topic of the lecture was “Nano-optoelectronics For Communications.” Faculty and students attended with enthusiasm.
April “Photonics Forum” Lecture Highlights Time: April 13th, 2007, 4:30 pm Speaker: Dr. Jyuo-Min Shyu (Vice President of the Industrial Technology Research Institute/Director of the Electronics and Opto-electronics Research Laboratories) Topic: Research & Developments of the Industrial Technology Research Institute in the Field of Optoelectronics and Electronics
Dr. Jyuo-Min Shyu visited GIEOE on April 13th, 2007 (Friday), and gave a lecture at lecture theater 101, Barry Lam Hall. Dr. Jyuo-Min Shyu presented his lecture “Research & Developments of the Industrial Technology Research Institute in the Field of Optoelectronics and Electronics” with wit and wisdom, and GIEOE faculty and students participated with enthusiasm.
Time: April 27th, 2007, 4:30 pm Speaker: Director Chang , Yia-Chung (Director, Research Center for Applied Sciences, Academia Sinica) Topic: Optical Nanometrology of Au Nanoparticles on a Multilayer Film For the April 27th, 2007 “Photonics Forum”, we invited Dr. Chang , Yia-Chung, Professor, Dept.of Physics, UIUC, and Director, Research Center for Applied Sciences, Academia Sinica, to speak at GIEOE. GIEOE faculty and students participated with enthusiasm and learned much.
May “Photonics Forum” Lecture Highlights Time: May 18th, 2007, 4:30 pm Speaker: Professor Bau ,Tzong-Ho (Vice President for Administrative Affairs of National Taiwan University, Professor of Department of Political Science, National Taiwan University) Topic: ~The Reflection Between Humanities and Society~ What is the Meaning of Rational Policy-making?
Vice President Bau, Tzong-Ho visited GIEOE on May 18th, 2007, and gave a lecture in lecture theater 101, Barry Lam Hall. The topic was, “The Reflection Between Humanities and Society~ What is the Meaning of Rational Policy-making?” and the lecture drew enthusiastic participation from GIEOE faculty and students.
Time: May 25th, 2007, 4:30 pm Speaker: Professor Klaus Ploog (Paul-Drude-Institut für Festkörperelektronik) Topic: Ferromagnetic Semiconductors for Spin Injection  For the May 25th (Friday), 2007 “Photonics Forum”, GIEOE invited Professor Klaus Ploog (Paul-Drude-Institut für Festkörperelektronik) to lecture. Professor Klaus Ploog spoke with wit and wisdom, and GIEOE faculty and students participated with enthusiasm, learning much in the process.

Special Report

  GIEOE, National Taiwan University visited

Universities and Research Institutes in Beijing and Nanjing, China

--Visiting date: March 31 to April 8, 2007--

I. Preface

In order to familiarize GIEOE faculty and staff with developing China’s most advanced research and higher education system, and increase exchange between institutes, GIEOE organized a visiting party. From March 31 (Saturday) to April 8 (Sunday) this year, the party has visited Peking University; Tsinghua University (Beijing); Institute of Semiconductors, Institute of Physics, Chinese Academy of Sciences; Nanjing University. Through campus tours and exchanges between faculty and directors, the members of the visiting party increased their understanding of related areas in China’s well-known universities. Participants exchanged opinions and ideas concerning relevant topics, building interchange between both parties.

II. Members

III. Member’s Thoughts and Reflections

Chairman C.C. Yang:

1. China’s top universities and research institutes are all investing heavily in optoelectronics and related fields. For example, Tsinghua University’s Department of Electronic Engineering (mainly comprised of optoelectronics and communications; microelectronics is its own independent department) is constructing a new building 216, 000 square feet large, half of which will be provided for optoelectronics research (including a large-scale clean room). Department of Physics (including certain electrical engineering and optoelectronics areas), Nanjing University is also constructing a new building that is several thousand ping (equal to 36 square feet) large, to be mostly used for optoelectronics-related research. Also, the Institute of Semiconductors, Chinese Academy of Sciences has built a 14, 400 square feet clean room for crystal growth and device process, advanced and impressive in size and scale. In contrast, NTU’s optoelectronics infrastructure and facilities still have much room for improvement.

2.  Students of China show greater drive for knowledge and advancement. For instance, about 50 graduate students of Department of Physics, Nanjing University came voluntarily to hear the speech delivered by our visiting party. Furthermore, the students eagerly posed questions that were perceptive and insightful. In comparison, Taiwanese students’ ability to compete becomes a cause for concern. 

Vice Chairman Huang, Sheng-Lung:

During this visit to China, we were left with deep impressions of the three universities’ research teams, each comprised of outstanding professors. With integrated resources, research is more in depth, simultaneously developing basic theory, experiments, and numerical simulation. The research team of Professor Ming, N. B.  at Nanjing University has published three papers in Science in recent years. This achievement is not without reason.

In addition, the representative students that received us were knowledgeable and cultured, each working to the best of his or her ability. They voluntarily participated during our speech and raised questions with confidence. These students of China are an amazing group.

Professor Liu, Chee-Wee:

Students of China are admitted into university through examination. Those from agricultural villages or those with financial difficulties have an opportunity to enter university or graduate school, and through this, improve their financial and social status. Thus, they are motivated to work hard. This visit allowed both parties to better understand each other. With this improved understanding, we can help students find suitable work and guide their research subject to fit industry needs. This allows Taiwan’s entrepreneurs to gain excellent employees and increases opportunities for collaborative projects, improving the development of the academic and industrial sectors for both sides.

Professor Peng, Lun-Han:

My deepest impression was formed while visiting Nanjing University’s nonlinear photonic crystal laboratory. Its scale (small area, old process instruments), cannot compare with the advanced and expensive core facilities of Institute of Physics, Chinese Academy of Sciences, or with its class 100 clean room of the Institute of Semiconductors. Yet how did such a primitive institute receive China’s top honor in natural science? How did such a department manage, in one year, to publish three papers in Science?

When everyone works toward a common goal, their strength is limitless.

IV. Future Exchange Agreements

GIEOE’s visit to China’s well-known universities and research institutes allowed both parties to improve their mutual understanding, and allowed us to learn from their experience. Furthermore, we have reached four concrete exchange agreements:

1.  An agreement was reached with Department of Electronics Engineering (mainly comprised of optoelectronics and communications), Tsinghua University (Beijing). Graduate students will be exchanged annually. Ph.D. candidates will conduct workshops together and collaborate on research. Further details will be settled at a later time.

2.  An agreement was reached with Department of Physics (including certain electrical engineering and optoelectronics areas), Nanjing University. Graduate students will be exchanged annually. Ph.D. candidates will conduct workshops together and collaborate on research. Further details will be settled at a later time.

3.  "The Cross-strait Symposium on Optical Micro-structure and Laser Technology 2007" is confirmed to take place on September 10^th to 15^th, 2007 at Nanjing University. Both parties have begun preparations.

Professor Yi Luo, Tsinghua University (Beijing) and members of the GIEOE visiting party dine together

Members of the GIEOE visiting party in front of the College of Physics, Peking University

Members of the GIEOE party visit Professor Jun-Ming Zhou, Institute of Physics, Chinese Academy of Sciences

Members of the GIEOE visiting party with Qiming Wang, Fellow of the Institute of Semiconductors, Chinese Academy of Sciences

Members of the GIEOE visiting party with Professor You-Dou Zheng, and others in front of the Physics building, Nanjing University

Research Result Column for the Program of “Aiming for Top University”

Electroluminescence from zinc oxide nanoparticles/organic nanocomposites

Professor Ching-Fuh Lin

Graduate Institute of Electro-Optical Engineering, National Taiwan University

Zinc oxide (ZnO) is attractive for optoelectronics applications due to its wide bandgap and high exciton binding energy.  Most ongoing works for ZnO-based electroluminescence (EL) devices involve the epitaxial growth of ZnO thin film by metalorganic chemical vapour deposition. Here we employ ZnO nanoparticles to prepare an inorganic-organic nanocomposite film by spin-coating method, and achieve   ultraviolet-blue EL emission.

The hybrid nanocomposite film is composed of ZnO nanoparticles, N,N’–diphenyl-N,N’–bis(3-methylphenyl)-1,1’-biphenyl-4,4’-diamine (TPD) and polymethyl methacrylate (PMMA).  Utilizing the fact that the solubility of ZnO nanoparticle is different from that of TPD: PMMA, we investigate the phase-segregation between TPD: PMMA and the ZnO nanoparticles upon spin-coating. With proper parameters for phase segregation, the ZnO nanoparticles and the TPD: PMMA, the organic hole-transporting layer, can be divided into two layers. The hybrid nanocomposite with phase-segregation is then sandwiched between indium tin oxide (ITO) and aluminum (Al) electrode. Holes are injected from the ITO contact into the highest occupied molecular orbital of the TPD matrix, and are transported towards the valance band of the ZnO nanoparticles. Similarly, electrons are injected from the Al cathode to the conduction band of the ZnO nanoparticles. Thus our ZnO-based device exhibits defect-free emission, as shown in Figures 1 and 2.  The narrow emission peak at 392 nm well corresponds to the ZnO bandgap energy. The phase-segregation condition enhances electron and hole recombination in the ZnO nanoparticles and also the emission. Our method has the prominent advantage of lowering the fabrication cost of ZnO–based devices.

Figure 1 Blue emission from ZnO: TPD/PMMA nanocomposite.	Figure 2 Electroluminescence spectrum from ZnO: TPD/PMMA nanocomposite.

Generation of tunable blue/green light using ZnO:PPLN crystal fiber by self-cascaded second order nonlinearity

Professor Sheng-Lung Huang’s Group

Graduate Institute of Electro-Optical Engineering, National Taiwan University

(e-mail) slhuang@cc.ee.ntu.edu.tw

Blue/green light sources are desired for many applications, such as projection television, satellite communication, underwater communication, and biomedical analysis. Many approaches have been attempted for the generation of tunable blue/green coherent light sources. A novel self-cascaded first-order second harmonic generation (SHG) and third-order sum frequency generation (SFG) in a ZnO:PPLN crystal fiber was proposed. This cascaded process is similar to c ³ process, so the third-harmonics can be generated using this scheme. The simulated SHG and self-cascaded SHG + SFG efficiencies are shown in Fig. 1. A PPLNCF with a pitch of 15.45 mm was successfully fabricated. Its cross section after etched by HF solution is shown in Fig. 2(a). At this domain pitch, the SHG signal and its fundamental signal at 1423.9 nm can satisfy the third-order SFG quasi-phase matching (QPM) condition. The measured SHG power at 714.2 nm was 12.25 mW under 100-mW input power, and the effective nonlinear coefficient achieved was 25.3 pm/V. The self-cascaded SHG + SFG power measured at 477.1 nm was about 700 mW under 350-mW input power. The maximum internal efficiency of the SHG is 14.84%. The tuning range of the self-cascaded SHG and SFG generated tunable blue-green light was more than 40 nm. When the input laser was tuned from 1414 nm to 1545 nm, the self-cascaded SHG + SFG generated tunable blue-green light was from 471.3 to 515 nm as shown in Fig. 2(b). The maximum simulated 3-dB bandwidth achieved using a gradient-period QPM structure is 196 nm, which is from 1476 nm to 1672 nm.

This work has been collaborated with Dr. A. H. Kung’s group at the Institute of Atomic and Molecular Sciences, Academia Sinica.

Fig. 1. The simulated SHG and self-cascaded SHG + SFG efficiencies. The inset is an expanded view.

Fig. 2. (a) The HF etched Y-face image of a poled sample with 15.45-mm domain pitch. (b) Blue/green light outputs by the self-cascaded SHG + SFG processes with wavelengths from 471.3 nm to 515 nm.

A Novel Analysis Method for Photonic Crystals Based on a Multidomain Pseudospectral Method

Professor Hung-Chun Chang

Graduate Institute of Electro-Optical Engineering, National Taiwan University

The proposed method for calculating the band diagrams of two-dimensional photonic crystals is shown to possess excellent numerical convergence behavior and accuracy, as compared with the conventional plane-wave expansion method. The proposed scheme utilizes the multidomain Chebyshev collocation method. By applying Chebyshev-Lagrange interpolating polynomials to the approximation of spatial derivatives at collocation points, the Helmholtz equation is converted into a matrix eigenvalue equation that is then solved for the eigen frequencies. Suitable multidomain division of the computational domain is performed to deal with general curved interfaces of the permittivity profile and field continuity conditions are carefully imposed across the dielectric interfaces. The proposed method shows uniformly excellent convergence characteristics for both the transverse-electric (TE) and transverse-magnetic (TM) waves in the analysis of different structures. The analysis of a mini band gap is also shown to demonstrate the extremely high accuracy of the proposed method (Fig. 3). For details, please refer to the article: Physical Review E, vol. 75, 026703 (2007).

Low Blur Effect and High Light Extraction Efficiency Enhancement of Organic Light Emitting Displays with Novel Microstructure Attachment

Associate Professor H. Y. Lin’s Group

Graduate Institute of Electro-Optical Engineering, National Taiwan University

(e-mail) hylin@cc.ee.ntu.edu.tw

Micro-structured film attachment and surface roughing techniques have long been utilized to improve the light extraction efficiency from a light source with a high refractive index. In our research, we have systematically studied the light extraction efficiency as functions of coverage ratio and height ratio of micro-lens arrays (Fig. 1). Instead of merely concerning the efficiency for lighting purposes, we must take both the light extraction efficiency and image quality into account for display applications. The image blur was observed to decrease the contrast ratio and thus lower the image quality. In our research, we apply an innovative microstructure array arrangement to planar light emitting device, i.e., organic light emitting display (OLED), to reduce the image blur effect and keep almost the same light extraction efficiency as that obtained by applying a conventional micro-structured film attachment (Fig. 2).

Fig. 1 The power and luminance enhancement ratio as functions of area ratio and height ratio.

Fig. 2 The 3-sub-pixel images for the original OLED device, the one with a conventional microlens array attachment,  and the one with a novel microlens array attachment, respectively (from left to right).

Ferroelectric Domain Engineering for White Light and Digital Processing

Professor Lung-Han Peng’s Group

Graduate Institute of Electro-Optical Engineering, National Taiwan University

(e-mail) peng@cc.ee.ntu.edu.tw

We apply the techniques of dielectric coating and self-assembled lithography with high pulsed field poling to achieve electrostatic control of the ferroelectric domain motion down to the submicron regime.  Figure 1 illustrates a poling of a f=10mm LiNbO₃ cylinder on whose perimeter existing a periodically poled domain structure with periodic sign change in the c⁽²⁾ nonlinear susceptibility at a periodicity ~2mm.  The latter structure constitutes a quasi-phase-matching (QPM) mechanism to facilitate efficient energy exchange in the nonlinear optical processes such as harmonic and parametric generation.  Figure 2(a)~(d) illustrate the micrographs and the far field pattern of CCD intensity image of the array generation of QPM-SHG red (630nm), green (532nm), and blue (465nm) lasers that were wavelength converted from fundamental IR pump sources using our 2D nonlinear photonic crystals (NPCs) made on 6mm-long´0.5mm-thick LiNbO₃ and LiTaO₃ chips.  Figure 3(a) and (b) illustrate the wavelength bandwidth measured under the condition of single pass and pulsed excitation of the QPM-SHG red and blue lasers.  The data support the use of 2D NPCs to increase the wavelength bandwidth and to maintain a reasonable conversion external efficiency (~30%) for applications in digital light processing.  This work has been collaborated with Dr. A. H. Kung at IAMS, Academia Sinica and supported by the NSC.

Fig1: +Z face micrographs showing (a) periodically poled submicron domains along the perimeter  of a LiNbO3 ring of 10mm diameter.

Fig. 2 (a)~(c) micrographs of 2D periodically poled LiNbO3 and LiTaO3 for red, green, and blue QPM-SHG. The pitch density of the inverted domains in (a)~(c) are 12, 7.8, and 5.3mm, for (d) QPM-SHG at wavelength of 630, 532, and 465nm, respectively.

Fig.3 wavelength acceptance bandwidth for (a) 2D PPLN at red SHG and (b) 2D PPLT at blue SHG.

Profiles--Faculty Members

Laboratory Descriptions

I. Overview

In this laboratory, there are three major research topics: Integrated photonics devices and systems, Display technology, and Lighting applications. For the research activities, the facilities in the laboratory include: (1) Simulation software tools such as BeamPROP, Fullwave, LightTools, etc. for the design and analysis of electromagnetic/optical devices and systems, and (2) Hardware equipment, such as optical table, visible laser, IR tunable laser, optical power meter, microscope, visible/IR optical spectrum analyzer, PC and high precision optical fiber/waveguide alignment station.

II. Recent research topics

(1) Integrated Photonic Devices and Systems

The Silicon on Insulator (SOI) wafer is used as the substrate, on which the miniature silicon optical waveguide devices with a cross section smaller than 400 nm Í400 nm, and a bending radius less then 40 μm are implemented as optical signal processors. Compared to the conventional weakly confined waveguide devices, the entire dimensions of such SOI-based waveguide devices can be 100 times smaller. The recent research topics include: low-loss silicon photonic wires, the optimal design of the fiber coupler on the miniature silicon photonics wires, miniature Arrayed Waveguide Grating (AWG) devices, miniature polarization splitters, etc. In addition, by integrating the silicon optical waveguide devices with MOSFET structure on a single SOI wafer, silicon optical modulators and switches can also be implemented.

(2) Display Technology: Color Science and Image Quality

Based on the visual perception of human, we can study the preference for the color and image quality of any dynamic and static pictures shown on a display. The result of this study can be used as a tool to improve the image quality of the display. The research topics include: Preferred color, the discrimination of the image quality with the quantization of Color space, the study of the relationship between the eye gaze behavior and the discrimination of image quality, the image processing algorithm for image quality improvement, optimal colorization of gray-scale images, etc.

(3) Lighting Applications

The solid-state light emitting devices are used for various lighting applications, including the design and implementation of solid-state lighting apparatus, the automatic color calibration of lighting apparatus, the technology for creating dynamic lighting scenarios on demand, lighting technology for therapy, operative field-emitting lighting sources, etc.

Professor Snow H. Tseng         Virtual Optical Laboratory

Research objectives:

Due to the extreme complexity involved, the optical characteristics are conventionally studied using heuristic approximations, including the diffusion approximation, Monte Carlo simulation, etc.  However, the validity of such approximations has not been determined.  By employing a novel numerical technique, the pseudo-spectral time-domain method, combined with parallel computing technology, this problem can now be accurately studied by solving Maxwell's equations.  Based upon fundamental electromagnetic principles, we establish a virtual optical experiment platform capable of simulating optical experiments in a practically noiseless environment where optical characteristics can be accurately determined.

Specifically, we are interested in the research of biomedical optics.  Optical techniques are assuming greater importance in medicine, mainly due to its non-invasive characteristics.  Effective optical diagnostic techniques depend upon a thorough understanding of the optical characteristics of biological tissue, therefore, our research focus is to simulate and determine the optical characteristics of macroscopic biological random media.  By means of a virtual optical experiment platform, our goal is to accurately determine the optical characteristics of biological structures.  On a broader scope, our research will help advance the development of innovative optical diagnostic and imaging techniques.

In addition, there are several ongoing research projects, including the photonic nanojet, Monte Carlo simulation of light scattering by random media, Negative Refractive index super lens, and flexible display simulation analysis.    Each of the research is conducted by an individual master-level student. As a result, each student can learn to conduct research and become independent researchers.

Currently, we are recruiting new group members.  The only requirement is: “diligent, willing to learn.”  Programming experience would be better, though not necessary.  Prof. Tseng believes that graduate students should be capable of learning whatever necessary skills on his/her own (where there is a will, there is a way.)

Our Vision:

With the advance of computing technology, it is becoming more and more feasible to analyze electromagnetic problems accurately with computers.  The simulation we use in our lab includes: the finite-difference time-domain (FDTD) method, the pseudospectral time-domain (PSTD) method, and the Monte Carlo method.  By means of simulations, our goal is to analyze and predict the outcome and foresee possible problems.  Furthermore, by accurately determining the optical characteristics of biological tissues, we hope to help advance the optical diagnostic techniques.  Ultimately, we anticipate optical diagnostic to be done in real-time economically (say, at a convenient store), so that diseases can be early detected to facilitate early treatment.

Ongoing research topics:

(1) NANOJET

Light scattering through a semi-cylinder in 2D is modeled using the FDTD method. Illuminated by a plane wave, the localized nanojets are generated at the shadow-side surface of the semi-cylinders. The nanojets have waists smaller than the diffraction limit and propagate over several optical wavelengths without significant diffraction.

Fig. 1 light scattering by a semi-cylinder of n = 2.2

(2) Monte Carlo Simulation of Light Scattering by Multi-Spheres

Using Monte Carlo method in light scattering through a uniformly distributed system with multiple spheres has been done.  Without directly solving Maxwell’s equations in such a complicated system, we transform the system through Mie scattering theory to a random-walk photon model to get the scattering pattern.  By this heuristic approximation, the influence of variable particle sizes can be studied in the random media.

Fig. 2.  Monte Carlo simulation of light scattering by biological tissue.

(3) SURFACE PLASMON

The local field enhancement and surface plasmon resonance of metallic nanoparticles were used to focus and to manipulate light.  We investigated the local field enhancement of symmetric silver nano-cylinder pairs by using the FDTD method.  The intensity of local field enhancement is found to depend on separation distance, radius ratio, and numbers of nano-cylinder.

Fig. 3.  The magnetic field of a single Ag cylinder of radius r = 25nm and l= 344 nm.

(4) PHOTONIC CRYSTALS

Lens of negative refractive index, was proposed by J. B. Pendry in 2000. Negative refraction index is based upon Snell’s law. The refractive wave propagates forward to the same side relative to the normal as incident wave.  In photonic crystals, it seems to the light group velocity propagate to a negative refractive material by Snell’s law, when the ratio between the light frequency and the lattice constant is particular.  We investigate the focusing effect in 2D hexagonal photonic crystal(PhC) slabs by the FDTD method.

Fig 4.  Negative refraction makes a slab lens.

Laboratory equipment

Since our laboratory is newly born, our equipment are far from complete.  We recently purchased a parallel computing cluster consisting of 32 computing core.  This computer cluster enables complex light scattering simulations of macroscopic dimensions.

Fig. 5.  A new 32-core Computing Cluster

I. Overview

The major research areas in Advanced Optoelectronic Devices Lab focus on the design and fabrication of InGaN-based light-emitting devices. At the same time, since LED-based solid state lighting technology is very promising, we also focus on multi-LED white light source for illumination, so called “Smart Lighting” technology. The tunable spectrum of multi-LED white light sources not only can drastically increase luminous efficiency but also for different applications with different color temperatures and color rendition capability.

II. Current research topics

a.       III-nitride based LEDs with different doping profile

b.      High color-rendering white light LEDs

c.       Thin-film varistor for LED ESD protection

d.      Sapphire wet-etching

III. Equipments in Lab

a.       Integrating sphere

b.      LED electrical characterization

         ● Keithley source meter and Probe station

c.       High temperature furnace and oven

Please send any comment to eoe5@cc.ee.ntu.edu.tw 

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Graduate Institute of Electro-Optical Engineering, National Taiwan University

 http://eoe.ntu.edu.tw/