1. 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
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9. 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
22. 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
23. 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
24. Taper drawing of silica fibers L. Tong et al., Nature 426 , 816 (2003). 2. Fabrication of Nanofibers
25. 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
26. 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
27. 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
28. More than 30% of the total energy is guided outside the core Field distribution in the sub-wavelength fiber x (µm) y (µm) Sz
29. 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
30. 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
31. (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
32. 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
34. 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
35. 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).
36. 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
37. Potential applications C. Girard, “Near fields in nanostructures”, Rep. Prog. Phys. 68, 1883-1933(2005)] Nanofiber is a promising solution for future photonic devices
38. 5. Outlook Nanofiber research is among the “TOP FIVE IN PHYSICS” J. Giles, Nature 441, 265 (2006)
39. A 450-nm diameter silica wire wraps on a hair and guides light around it. 100µm
41. 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.
42. PC in the nature world Sea mouse spine hair Butterfly
43. Properties of PC Photonic band gap Transparent Polarization Isotropy Super dispersion Band edge effect DFB
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48. 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.
49. 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
50. 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
51. 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%
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53. 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.
54. 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,
55. 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
56. 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
57. Negative dispersion (Air/ (HL) 6 (4L)(LH) 6 /Glass) ， incident angle=50°for air At the wavlength=747.57nm
58. Numerical simulation a) At 747.57nm b) at 747.3nm At 747.3nm, dispersion +9.75μm, at 747.57nm dispersion is － 151.5μm 。
59. Reflective beam separation For F-P filter, with incident angle of 30.26° ， from air, at the wavelength of 747.57nm 。
66. 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
67. Sub-wavelength imaging At the distance of the surface of 0.68a, two point sources, with interval of 0.83 λ
68. 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
69. 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
70. 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
77. Time domain OCT Mirror Source Detector Pre - amp Band - pass Filter Demodulator AD Converter Interferometer Output Signal
78. 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
83. 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.
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