Congratulations! Dr. Tingye Li, Distinguished Chair Professor of GIPO and Academician of Academia Sinica, receives the IEEE top honor gold medal.

The Institute of Electrical and Electronic Engineers (IEEE) awarded its top honor gold medal to our Distinguished Chair Professor, Academician Tingye Li, honoring him for his extraordinary contributions to fiber-optic communication technology. Congratulations on this great achievement!

Congratulations! GIPO Professor Hung-Chun Chang receives the title of “2010 OSA Fellow”.

Congratulations! GIPO Professor Ching-Fuh Lin receives the 2009 Outstanding Electrical Engineering Professor Award from the Chinese Institute of Electrical Engineering.

Professor Roel Baets visited GIPO on August 26^th (Wednesday), 2009, and lectured in Auditorium 105, EE Building 2. The lecture, “Silicon Photonics: Opportunities and Challenges” was attended with enthusiasm by GIPO professors and students, and everyone learned much from the lecture.

Professor Ray-Kuang Lee visited GIPO on October 23^rd (Friday), 2009, and spoke in Room 113, Barry Lam Hall. His lecture, “Light localization in classical and quantum worlds” was attended with enthusiasm by GIPO professors and students, and everyone learned a lot.

Vice Chairman Gong-Ru Lin (right), the host, and Professor R. K. Lee (left)

October 30^th (Friday), 2009 2:30 PM

Professor Chi-Chang Chen visited GIPO on October 30^th (Friday), 2009, and spoke about his France dream, his experiences in French life, culture, and study, at room 113, Barry Lam Hall. Chii-Chang Chen is a professor of the Department of Optics and Photonics, National Central University. In his youth, he gave up his original plan of studying in the U.S., and went to France instead to pursue further study. Living in a non English-speaking country for 5 years, the experience of life and the culture shock have greatly augmented his physical and spiritual strength. He believes that if one has a dream and pursues this dream earnestly, one is successful regardless of whether the goal of the dream has been achieved. GIPO students and teachers attended the speech with enthusiasm, and have benefited greatly.

Vice Chairman Gong-Ru Lin (right), the host, and Professor Chii-Chang Chen (left)

【Title】Summer Snow
【Photographer】Yi-Hao Pai, Chih-Hsien Cheng, and Chung-Lun Wu

【Title】Man's World
【Photographer】Po-Chun Yeh

【Title】Flame of Flowers
【Photographer】Chieh-Wei Huang

【Title】It Seems that a Nanometer Granule has a Life of Its Own
【Photographer】Ting-Ta Chi

【Title】 A Grain of Sand, A World
【Photographer】Szu-Yu Chen

【Title】Luxuriant Branches and Leaves
【Photographer】Shu-Ting Kuo

Miniature optical autofocus camera by micromachined fluoropolymer deformable mirror

Professor Guo-Dung Su

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

Along with the progress of image sensors in recent years, fix-focus cameras on mobile electronic devices do not fulfill consumer needs. With the size of mobile devices getting smaller and smaller, the displacement-to-thickness ratio is getting larger, and that makes mechanical motor systems difficult to be packaged inside cameras to achieve autofocus function.

We propose a design using micromachined fluoropolymer deformable mirrors rather than traditional mechanical motor. With low color dispersion and adjustable power range of 20-diopter, deformable mirrors can be integrated into optical module and are well suitable for miniature optical auto-focus camera. A polymer membrane works as a reflective mirror surface to focus the light variably by adjusting the voltage difference. Fig. 1 shows a schematic drawing and photograph of the fabricated device.

We conducted an experiment between optical power versus applied voltage. The polymer membrane was actuated by the electrostatic force and deformation of the polymer membrane can be adjusted by changing voltage difference continuously. The optical power and deformation versus the applied voltage is plotted in Fig. 2. The maximum optical power achieved is around 20-diopter when 160 volts is applied, corresponding to 27-μm deformation at the center of the membrane. The optical power of an organic deformable mirror could be adjusted continuously.

At the beginning, when the mirror was not actuated, the far object (the train) with “HARIBO” can be seen clearly while the near object, the name card with “Jen-Liang Wang”, is blurred as show in Fig. 3(a).  After applying voltage to the deformable mirror, the effective focal length of the system changes. The focal point moves forward so that the near object can be clearly seen. We can see that there are still some aberrations at the edge of the images. This can be fixed by custom-designing the lenses.  We demonstrate that the deformable mirror is feasible as vari-focus devices in camera lens module without moving component. This part is also shown in the video file submitted.

White Organic Light-Emitting Devices with Low Driving Voltage and High Efficiency

Professor Jiun-Haw Lee

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

By selectively doping yellow emitter in the ambipolar blue emitting layer (EML), white light organic light-emitting device (OLED) could be obtained and the driving voltage was reduced due to the recombination current increase. We doped rubrene near the maximum recombination zone of our OLED, 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl doped in 9,10-bis(2’-naphthyl) anthracene (DPAVBi:ADN), 2V reduction in driving voltage was achieved. Although electron and hole mobilities of ADN are comparable, we found the recombination zone is near the interface of hole-transport layer (HTL) and EML interface the injection barrier for the hole is higher than that for the electron.

Characterizations of GaN-Based LEDs Encompassed with Self-Aligned Nanorod Arrays of Various Distribution Densities

Professor Jian-Jang Huang

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

GaN-based LEDs encompassed with self-aligned nanorod arrays of three types of nanorod arrangement were fabricated by simply using spin-casting and dry etching.  Light diffraction behaviors are characterized by considering the radiation profiles of these structures.  The output power enhancement factor of the S-nanorod device over the conventional one is 27.25% in the vertical direction and 30.43% for the integrated intensity.  This enhancement is omni-directional because the less regular arrangement of S-nanorod structure results in a varying G and omni-directional distribution of radiation modes.  On the other hand, from the radiation profile, the D-nanorod device shows better directionality due to its relatively well-aligned nanorod arrays (and thus less varying lattice vector G) but with a less optical output enhancement.  The relatively well-arranged D-nanorods, especially in the first several columns facing p-mesa act as gratings with groove in the vertical direction and diffract laterally propagated light back toward the p-mesa, thus decreasing the amount of power enhancement.  Also, the existence of higher order diffraction modes enables the S-nanorod device to have a higher power enhancement factor.

Analysis of Highly Conducting Lamellar Gratings with Multidomain Pseudospectral Method

Professor Yih-Peng Chiou’s group

Graduate Institute of Photonics & Optoelectronics, National Taiwan University

Numerical modeling for grating structures plays an important role in their investigation and applications. The performance of the modeling is even essential, when grating periods become comparable to the wavelength and structures are involved with highly conducting materials. The rigorous coupled wave analysis (RCWA) is the most widely used spectral methods. But in recent years, numerical instability problem with TM polarization was discovered when the real part of the refractive index is very small (highly conducting gratings). Another common modal method is the classical modal method which is very powerful technique to approach this problem, but its complicate process to limit the further applications. Here we combine the features of these two numerical methods: the easily solved eigen equation in the grating of RCWA and the analytical mode profiles of modal method. The multidomain pseudospectral frequency method we adopted avoids classical modal methods from finding the roots of dispersion relation especially while complex roots are involved and avoids Runge phenomenon and Gibbs phenomenon to achieve uniform accuracy at the same time. The validity of numerical results by MDPS is compared with commonly used rigorous coupled wave analysis for TM polarization. The numerical evidence shows the developed method has not only better stability but also higher efficiency.

Y.-P. Chiou, W.-L. Yeh, and N.-Y. Shih, IEEE/OSA Journal of Lightwave Technology, 27,  Dec. 2009.

Experimental characterization of two-axis MEMS scanners with hidden radial vertical combdrive actuators and cross-bar spring structures

Professor Jui-che Tsai

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

We perform the experimental characterization of two-axis MEMS scanners driven by radial vertical combdrive actuators (Figure 1). The dc scan ranges are limited by the pull-in effect. Each scanner utilizes a cross-bar spring structure to achieve two rotational degrees of freedom (DOFs) without employing any gimbal. Both the actuators and torsion springs are hidden underneath the mirror to obtain a small form factor. The devices are fabricated by a five-layer polysilicon surface micromachining process (SUMMiT-V). Devices with different combinations of parameter values are experimentally characterized and compared.

The optimal design (S1) comes with a balanced cross-bar spring structure. The mechanical rotation angles are ±5.30° (50.2V) and ±6.04° (52.8V) for rotations about the x and y axes, respectively (Figure 2). For each rotational mode, a significant angle is obtained under a reasonable bias voltage. The resonant frequencies are 11.4 kHz and 11 kHz.

© 2009 Institute of Physics (IOP) and IOP Publishing Ltd

J. C. Tsai et al., “Experimental characterization of two-axis MEMS scanners with hidden radial vertical combdrive actuators and cross-bar spring structures,” J. Micromech. Microeng., Vol. 19, No. 4, 045002, Apr. 2009.