| Introduction
There are over two dozen universities in China that have schools or colleges of optics or photonics. Zhejiang University (ZJU) is one of the leading Chinese universities in photonics, and has been ranked No. 1 in Optical Engineering (including optics and photonics) in the latest ranking made by Ministry of Education of China. The Centre for Optical and Electromagnetic Research (COER) is a dynamic photonic research center in Zhejiang University.
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Figure 1. COER research building, and a group photo of some local IEEE PS members with Dr. Rich Linke, the Executive Director of IEEE Photonic Society, when he visited COER and local IEEE PS chapter
in early November 2009. |
COER was started virtually from scratch in 1999, and since then has been growing very rapidly. Now it has a research building (see Fig. 1) with a lab space of over 2000 m2 and about 100 active researchers (including PhD and master students). Among its active faculty members, there are a national distinguished professor appointed by China’s central government (through “Qian-Ren” program), a “Chang-jiang” distinguished professor appointed by Ministry of Education, and a distinguished professor appointed by the university. The main photonics research areas of the center include subwavelength-structured metamaterials, integrated photonics, bio-photonics, optical sensing, optical signal processing and lasing, optical communication system/network, and microwave photonics. COER has published many papers in international top journals, and the citation number during a single year of 2009 is over 700 (according to ISI Web of Knowledge). Table 1 was received from NJTU (Taiwan) on publication in major all-optics journals in 2006 by some selected universities (ZJU’s data were added in the last column with COER’s contribution in the parentheses). Among ZJU’s 76 papers in these journals in 2006, COER has contributed 32 papers.
Table 1. Publication in major all-optics journals in 2006 by some universities selected by NCTU of
Taiwan (ZJU’s data were added in the last column with COER’s contribution in the parentheses).
COER is very active in international collaboration and has established joint research center/lab with the Royal Institute of Technology (Sweden) and Chinese University of Hong Kong. COER is active in photonics communities and has organized or co-organized some international conference/meeting in China each year during the past 5 years, such as The OSA Topical Conference on Nanophotonics (2007), I-CAMP (Inter-Continental Advanced Materials for Photonics, 2009). COER also plays a leading role in the Hangzhou Chapter of IEEE Photonics Society. COER is very serious about its team culture as well. “LOOK UP! LIFT UP!” is its motto, and “Zijin Guangdian” (meaning “Optoelectronics in Zijin campus” in Chinese) is its quarterly magazine recording each progress COER has made.
Below we describe some photonics research platforms and activities in COER.
Semiconductor Fabrication
Platform in COER’s Clean Room
COER has its own clean room of over 600 m2 with semiconductor fabrication equipment such as PECVD, ICP, and lithography (see Figure 2). This platform has been used for the fabrication of subwavelength-structured metamaterials (including photonic crystals) and planar lightwave circuits (including silicon-based integrated photonic devices and semiconductor lasers). The applications are in optical communications, optical sensing and optical interconnects. During the past years, COER has designed and fabricated ultra-high integration of photonic devices such as ultra-compact arrayed waveguide gratings (AWG), micro-ring resonators (MRR), Bragg gratings, multimode interference (MMI) couplers and hybrid integration of ultrahigh index contrast SOI nanowires and photonic crystals. COER has developed high-performance and low-cost integrated photonic devices used in FTTH system, such as triplexers and large bandwidth power splitters. The cross-order method to demultiplex 1310, 1490 and 1550 nm wavelengths with a single compact AWG triplexer has been introduced. Recently COER has collaborated with Ericsson on developing a special AWG used for upgrading 2.5 GHz GPON to 10 GHz GPON. COER has also introduced a novel open cavity formed by a photonic crystal with a negative effective refractive index, and a slow waveguide based on metamaterials of negative index.
Laser Microfabrication Platform
Laser microfabrication has become a key manufacturing technology for advanced photonic devices, particularly for those with submicron features. COER has several Argon ion lasers (from Coherent Ltd. and Spectrum Physics), 405 nm diode laser for laser direct writing (DWL 66FS, Heidelberg Instruments, Germany), and a femtosecond laser. The Argon lasers are used for applications including visible-light interference lithography for making large submicron periodic structures. The setup is in a multiple-beam interference configuration with multi-exposure capability, and SU8 photoresist with photosensitizer and photoacid generator is employed in the fabrication. Submicron patterns with area of around one square centimeter can be quickly fabricated in this platform. The diode pumped laser is utilized in the direct-writing laser system. Complex multi-dimensional photonic structures at the micrometer scale can be flexibly made.
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| Figure 2. Semiconductor fabrication platform in COER’s clean room. |
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| Figure 3. Laser microfabrication platform in COER. |
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| Figure 4. Biophotonics platform in COER. |
Biophotonics Platform
In COER, various types of nanoparticles with desired optical properties, such as gold nanorods (GNRs), quantum dots (QDs), and silica-coated nanoparticles, can be synthesized and surface functionalized for
in vitro or in vivo bio-imaging and bio-therapy as optical contrast agents. GNR-based sensors for the detection of DNA and protein have been fabricated. Recently, COER is applying surface enhanced Raman scattering (SERS) technology for tissue and in vivo Raman imaging. Other nonlinear optical imaging methods, such as two-photon excited fluorescence imaging and second harmonic generation imaging, are also studied with our fs-laser-combined confocal microscopy. Figure 4 shows a part of our biophotonics platform.
Collaborating with Philips Research, COER has worked on diffused optical tomography (DOT), which is a very powerful tool for early detection of human breast cancer. COER has also set up an ultra-sensitive surface plasmon resonance sensor, which is for sensing bio-molecules and environmental pollution.
Fiber-Based Lightwave Technology Platform
COER has a flexible fiber grating fabrication setup based on an Excimer laser and phase mask & point-by-point grating writing technology. Another grating fabrication setup based on two-beam interference technique is under construction. The new setup aims to make ultra-long fiber Bragg gratings (up to half meter) for manipulating fiber dispersion and fabricating special filters. Using this platform, COER has been working actively on the design and fabrication of fiber devices based on e.g. fiber gratings for communications and sensing applications. COER is also working on Fourier domain mode locking fiber lasers, data format conversion, nonlinear effects of optical fibers and their applications.
COER’s current research interests in optical networking and systems include OCDMA system, high-speed optical transmission, and various passive optical networks (PONs) such as WDM-PON, OCDMA-PON and GPON. Microwave photonics is a natural research activity for COER, which is well-equipped for microwave measurement.
In the area of fiber-based lightwave technology, COER is collaborating with many universities and corporations, such as the HongKong Polytechnic University, Queen’s University (Canada), Ericsson, and NEC America.
Summary
Here we have introduced briefly some main photonics research activities at Centre for Optical and Electromagnetic Research (COER) of Zhejiang University (China).
With world-class research facilities, excellent team culture, and active international collaborations, COER is becoming a research and education center of excellence in photonics. COER will make a continuous effort in the field of sub-wavelength photonics, biophotonics and fiber-based lightwave technologies in the future.
 This article was prepared with contributions from several staff members at COER and compiled by Academic Director Prof. Sailing He. Prof. He received his Ph.D. degree from the Royal Institute of Technology (KTH), Stockholm, Sweden, in 1992. Since then he has worked at KTH as an Assistant Professor, an Associate Professor, and a Full Professor. Currently he is also a national distinguished professor appointed by China’s central government (through “Qian-Ren” program) and a chief scientist for the Joint Research Center of Photonics of KTH (Sweden) and Zhejiang University (China). He has authored one monograph (Oxford University Press) and about 400 papers in refereed international journals. His current research interests include metamaterials, biophotonics, photonic integration technologies, fiber optical communication technologies, and optical sensing technologies. Prof. He is a Fellow of the Optical Society of America (OSA) and the International Society for Optical Engineering (SPIE).
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