Report In Japan 20060613 Liuxu

Department of Optical Engineering Zhejiang University, Hangzhou, China 2006. 10. 12 The New Developments on Optical and Photonic Technology in Zhejiang University Professor Xu LIU

Contents: 1. Brief Introduction of ZJU and OED 2. New Development in the Research of Optical Engineering Nano-photonics Photonic Crystals (PC) and Thin film devices Optical Coherent Tomography (OCT) and applications 3. Conclusion

1. Brief Introduction of ZJU Locate in Hangzhou one of the most beautiful cities at east coast of China 100 miles south-west of Shanghai. Zhejiang University

Zhejiang University -- ranked among the top 3 Chinese universities 6 campuses in City of Hangzhou 30,000 undergraduate students 12,000 graduate students 5,000 PhD candidates 8,000 faculty and staff members

Dept. of Optical Engineering 1952 ： The first division of optical engineering in China 1960 ： The first Dept. of Optical Engineering in China 1984: Ph.D Programs 1986: Post-doctoral Programs 1988 ： Selected National Key Academic Discipline 1990 ： State Key Lab. of Modern Optical Instrumentation 1993: National E&T Center of Optical Instrumentation 1995: International Joint Laboratory of Photonics with Hamamatsu Photonics 2002: Selected National Key Academic Discipline 2005 ： No:1 Discipline in China

Education: Undergraduate program: ( 4 year program) 720 students Optical Engineering Program for MS degree: ( 2~2.5 year program) 219 students Optical Engineering Instrumentation Science and Technology Program for Ph.D: ( 3 year program) 107 students Optical Engineering Instrumentation Science and Technology Faculty and staff members: Total 98 faculty/staff in the department Including: 28 professors, 37 associate professors 16 Post doctors & assistant professors

Constitution State Key Lab. of Modern Optical Instrumentation International Joint Laboratory of Photonics National R&D center of Optical Instrumentation For technical development and transform For bio-optics and bio-photonics For applied science researches

The State Key Laboratory of Modern Optical Instrumentation Lab of optical instrumentation Lab of optical thin films and display Lab of opto-electronics Lab of opto-electric information detection Center for optics and electromagnetic wave Cover all the Department

History of Education In past 50 years, the Department has brought up 4800 Bachelors 850 Masters 200 Ph.Ds In the same time, more than 300 engineers have also been trained by continuing education programs. The Cradle of Chinese optical Engineers

Annual Funds for Research: Million yuan RMB

Publications in the last years Totally 196 papers on scientific journals and 2 books are published SCI collected ： 73 papers EI collected ： 125 papers Foreign journal ： 51 papers 23 patents opened

Research fields in the Optical Engineering Department

A. Precision detection and instrumentation Precision optical detection Position detection Wave-front & Surface roughness testing Optical coherent tomography (OCT) Nano-scale detection & metrology AFM Nano-scale probe Near field detection Fiber sensor and application Fiber grating Nano-fiber and application

B. Imaging Techniques and Hybrid optical imaging system Diffractive component CAD Laser direct writing system Digital image processing Imaging systems and techniques High resolution imaging Auto focus for digital imaging Dynamic range expending

C. Projection display Transmit liquid crystal projection display Reflective liquid crystal projection display Helmet display system LED based display technique Volumetric 3D display

D. Photonics Technology Photonic crystal design Photonic crystal antenna Photonic crystal wave-guide Metamaterials design and development Left hand materials Negative refractive index effect in optical region Passive integrated optical circuit on silicon Optical system on chip Integrated optical circuit

E. Laser and nonlinear optics technology Fiber laser technique Phase conjugation technique Nonlinear optics Semiconductor laser pumping New type organic dye tunable laser

F. Optical Thin film Techniques Optical thin film coatings for extreme cases Thin film coatings based on 1D PC “ Thin film Grating” super-prism effect Structured thin film devices Tunable thin film devices

G. Optical radiation and color detection Optical radiation metrology technique Color matching model and instrumentation Spectrometry

2. The New Development in the Research of Optical Engineering Nanometer optical fiber and new potential application Photonic Crystal and potential application OCT techniques & application Lab 浙江大学光学工程

Micro- and Nano-fibers for Micro- and Nano-photonics

Shrinking optical fibers into nanofibers 4- μ m diameter 150-nm diameter L. Tong et al., Nanotechnology 16, 1445 (2005). Micro- and Nanofibers Standard optical fibers 9 μ m 125 μ m

a. Laser-assisted VLS growth 1-2. Morales, A.M. & Lieber, C.M. A laser ablation method for the synthesis of crystalline semiconductor nanowires. Science 279 , 208–211 (1998). b. Photolithographic or electron beam lithography problems: Surface roughness Optical lose Nano wire situation Lab 浙江大学光学工程

Taper drawing of silica fibers L. Tong et al., Nature 426 , 816 (2003). 2. Fabrication of Nanofibers

we developed a simple method to fabricate sub-micrometer- or nanometer-diameter silica wires with extraordinary uniformities. The principal motivation for studying these optical- quality wires is their usefulness as low-loss optical waveguides for future micrometer- or nano-scale photonics, and as tools and materials for many other researches. 20um SEM of a 560-nm diameter silica wire Optical micrograph of a 360-nm diameter silica wire guiding He-Ne light Lab 浙江大学光学工程

Diameter: 50 nm  several micrometers Length: L ~ 1 mm (D < 100 nm) L can go up to 100 mm for D > 200 nm D ~ 50 nm Lab 浙江大学光学工程

SEM images Silica nanofibers D = 50 nm D = 70 nm D = 450 nm D = 260 nm Nature 426 , 816 (2003) Nature 426 , 816 (2003) D = 480 nm Small dimension Uniform diameter Large length Circular cross section 2. Fabrication of Nanofibers

More than 30% of the total energy is guided outside the core Field distribution in the sub-wavelength fiber x (µm) y (µm) Sz

Light coupling between the nano-fibers Light is sent into a silica wire by means of evanescent coupling. As shown here, He-Ne laser (633-nm wavelength) transfers from a 390-nm diameter wire to a 450-nm diameter wire. 100µm 100µm 390-nm diameter wire 390-nm diameter wire 450-nm diameter wire 450-nm diameter wire

More recently  < 0.01dB/mm L. Tong et al., Nature 426 , 816-819 (2003). G. Brambilla et al., Opt. Express 12 , 2258-2263 (2004). 3. Optical wave guiding with nanofibers Loss measurement Light launching ： Evanescent coupling Loss measurement Optical microscope image of coupling light from a 390-nm-diameter wire to a 450-nm-diameter wire. Schematic diagram for loss measurement of nanofibers

(D=360 nm, λ = 633 nm) L. Tong et al., Nano Lett. 5 , 259 (2005) Optical wave guiding along silica nanofibers on aerogel substrate Optical wave guiding with nanofibers 100µm

633-nm-wavelength light guided along a 260-nm-diameter tellurite nanofiber on a MgF 2 substrate with guiding loss <0.1 dB/mm Optical wave guiding along typical glass nanofibers L. Tong et al., Opt. Express 14 , 82 (2006). Optical wave guiding with nanofibers Up-conversion photoluminescence in a 320-nm-diameter Er-doped ZBLAN nanofiber excited by a 975-nm-wavelength light

Light propagation in fiber bending Minimum bending radius ~ 5.6 µm 100µm Minimum bending radius ~ 9.0 µm Light output

4. Micro- and nanofibers for photonic devices Fiber diameter ： 350&450 nm Wavelength ： 633 nm Transfer length ：＜ 5 μm Microcoupler assembled with tellurite nanofibers Ultra-compact photonic integration and devices Substrate: Silica No excessive loss! L. Tong et al., Opt. Express 14, 82 (2006). 3-dB splitter

Micro- and nanofibers for photonic devices High-quality microfiber knot resonators (2) Knot resonators in air Transmission spectra of a 850- μ m-diameter microfiber knot assembled using a 1.73-μm-diameter microfiber. The inset shows a single resonance peak. Transmission spectra of a microfiber knot with diameter of (a) 1.84 mm, (b)1.38 mm, (c) 1.08mm, (d) 239μm and (e) 196μm. The knot is assembled with a 2.5-μm-diameter microfiber and is freestanding in air during the test. High quality factor (Q=57,000) Changing FSR with knot diameter X. Jiang et al., Appl. Phys. Lett. 88, 223501(2006).

Micro- and nanofibers for photonic devices High-quality microfiber knot resonators (4) Microfiber knot lasers Laser emission spectrum of a 2-mm-diameter microfiber knot. The knot is assembled with a 3.8-μm-diameter microfiber. (a) Laser emission spectrum with pump power around threshold. (b) Laser emission spectrum with pump power much higher than threshold. Optical microscope image of the green up-converted photoluminescence from a 5.74-mm-length microfiber knot. The knot is assembled with a 2.7-μm-diameter Er:Yb-doped phosphate glass microfiber. Optical microscope image Laser emission spectrum

Potential applications C. Girard, “Near fields in nanostructures”, Rep. Prog. Phys. 68, 1883-1933(2005)] Nanofiber is a promising solution for future photonic devices

5. Outlook Nanofiber research is among the “TOP FIVE IN PHYSICS” J. Giles, Nature 441, 265 (2006)

A 450-nm diameter silica wire wraps on a hair and guides light around it. 100µm

Photonic Crystal & Optical Thin films devices

Photonic Crystal The concept was proposed by E.Yablonovitch and S.John in 1987 independently （ Phys.Rev.Lett,1987,58,2059 Phys.Rev.Lett,1987,58,2486 ） PC is an artificial material with periodic refractive index distribution in the scale of wavelength.

PC in the nature world Sea mouse spine hair Butterfly

Properties of PC Photonic band gap Transparent Polarization Isotropy Super dispersion Band edge effect DFB

Applications of PC super dispersion Reflector & filter PC waveguide PC lens PC fiber Recent development ： Nonlinear PC device Out coupling devices …… ..

Fabrication methods Film adding+ hole etching Self-assembly Pulse laser machine Holographic imaging

Thin film techniques for PC Self clone films by Tohoku Univ. Film micro column structure by Robbie. K &. Brett.M.J

Omni-directional reflector in visible or violet region Dispersion equation of 1D PC 1 D photonic crystal

1D PC Band width Ratio of refractive index Relative band wide vs. index ratio PC frequency vs. wave vector In case of low index ratio <3, no perfect band gap ， only exits partial gap for certain incident angle.

Superposition of angular band PC PC1 ， PC2 with periods of 106.11nm and 118.84nm From λ1 ＝ 328.95nm to λ2 ＝ 352.11nm ， relative bandgap reach to6.80% 。 Bandgap shematic

1D photonic crystal Omni-directional mirror Angular Zone overlap to increase the frequency range, decrease the condition of the big refractive index ratio in PC Biqin Huang, Peifu Gu, Ligong Yang, Construction of one-dimensional photonic crystals based on the incident angle domain, Physical Review E, 2003, Vol.68, No.4, 046601 Lab 浙江大学光学工程

The design of reflector  0 =365nm ， Sub/(HL) 20 (1.12H1.12L) 20 /Air ， n sub =1.416 0˚ ～ 56˚ ， PC1 band 332.0 ～ 345.6nm ； 56˚ ～ 80˚ ， PC2 band 335.2 ～ 351.2nm ； PC1/PC2 band 332.0nm~350.4nm. Relative wide 5.39%

“ Thin film grating” superprism effect Group delay GD ： Spatial dispersion ：

For high reflection coatings High reflector mirror coating: Glass/(HL) 30 /Glass ， n 0 =1.52 ， angle of incident of θ 0 =39° ， n 1 =2.0 、 n 2 =1.5,d 1 =225nm ， d 2 =300nm 。 For TE light form 800nm to 1315nm is pass band, and for region >1315nm is rejection band, the superdispersion effect appears at the edage of the pass band.

Examples Glass/(LH) 30 /Glass,39°incident angle Glass /(LH) 30 / Air, 39°incident angle There exists negative group delay, means negative spatial dispersion. And the superdispersion is sensitive for the incident media,

For Thin film F-P filter Glass/ H （ LH) 5 (6L) （ HL) 5 H /Air, H － TiO 2 , L － SiO 2 , thickness105nm, n glass =1.52, TE wave, incident angle=30.26° At the wavelength of minimum reflectance, maximum phase change

Positive spatial dispersion At wavelength of 747.57nm and 745nm ， incident angle=30.26° ， g=600μm At the wavelength of 747.57nm and 745nm ，入 z ＝ 0 surface light distribution

Negative dispersion (Air/ (HL) 6 (4L)(LH) 6 /Glass) ， incident angle=50°for air At the wavlength=747.57nm

Numerical simulation a) At 747.57nm b) at 747.3nm At 747.3nm, dispersion +9.75μm, at 747.57nm dispersion is － 151.5μm 。

Reflective beam separation For F-P filter, with incident angle of 30.26° ， from air, at the wavelength of 747.57nm 。

Reflective light beam separated (a) At 747.57nm ， (2) at 745nm

Potential application “Thin film grating” Very narrow band filter Possible used in some fluorescence spectra analysis In DWDM system 

Dielectric thin film polarizer

Bend gap TE mode form0.208 to 0.291exist rejected band ； and TM mode does not exist band ， relative band wide is 33.1 ％ .

spectra At normal incident, infect for TE mode is always reflected

Thin film imaging effect Grating period Lx ＝ a ＝ 0.44 μ m ， thin film period Lz ＝ Lx ， Si thick T ＝ 0.14 μ m ， 45° At the wavelength λ=1533nm

Sub-wavelength imaging At the distance of the surface of 0.68a, two point sources, with interval of 0.83 λ

MicroDisplay devices based on MOEMS Based on the induced admittance concept, the thin film device has admittance Z=X+iY: the reflectance of Air|Ag Airgap is X->0 、 Y->0 ， R->0 ， Max abs. X->∞ 、 Y->∞ ， R->1 ， Max refl. The center reflection wavelength input  /4 SiN x Silicon PSG reflect transmit V drive

scheme of the device 诱导反射光谱的色品图插入 Si3N4 后不同空气腔高度下的反射率曲线

Process (1) 硅基板准备 (2) 热氧化 100nm SiO 2 作为绝缘层 (3) 沉积 1.3 μ m 厚的多晶硅作牺牲层 (4) 沉积 250nm 厚的氮化硅作结构层 (5) 离子束刻蚀氮化硅 (6)KOH 溶液腐蚀释放氮化硅粱 (7) 电子束蒸发 50nm 的 Al

Dynamic performance 在 100Hz 的方波驱动下的光学响应上：电压驱动信号，下：光学响应信号响应时间 1~2 ms 。电容 C= ε 0 ε rS/d=6.941 ×10 -9 F ，电阻 R=105KΩ ，电容充放电常数 0.73 ms ，限制了器件的动态性能。 (a)250Hz 方波； (b)200Hz 正弦波 (b) (a) 器件的频率响应，方波电压保持 20V

Devices testing wyko 白光干涉仪的测试图，测得腔长 1.512 μ m CCD 拍摄图

Optical Coherent Tomography and application

OCT system & Michelson interferometer

Cross-sectional imaging Axial Scanning (Depth) Backscattering Intensity

Time domain OCT Mirror Source Detector Pre - amp Band - pass Filter Demodulator AD Converter Interferometer Output Signal

Spectrum domain OCT S pectrum A mplitudes F FT Source Sample Static reference mirror Diffractive Grating (1200lp/mm) Detector Array VR eg. L103K-2K （ BASLER ） 2048pixels 10um×10um 40Mhz 18.7Khz I(k) k a(z) z

The retina cross-section of a rabbit

Esophagus‘s （食道） image 超生波 Ultrasonic OCT

4. Conclusion Optical techniques have developed so fast, that lots of new techniques have bean demonstrated, the Nanophotonic, Photonic Crystal, and so call optical meta － materials will bring us lots of new possibilities, including new imaging technique, new optical devices, etc. Optics has shown most important role in the future.

Report In Japan 20060613 Liuxu

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