optical characterisation of rare-earth doped fluoride and phosphate ...

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xiv1.6 Fundamental light-matter interactions in a two level system. The notationJ and J 0 designate the upper and lower energy levels respectively. 251.7 Population of each of the Stark levels for the 1.5 m lasing transition( 4 I 13=2 ! 4 I 15=2 ) in Er 3+ . . . . . . . . . . . . . . . . . . . . . . . . . . 252.1 Microsphere fabrication with a microwave plasma chamber. A bulksample is rst ground into a powder and then injected through a quartztube to a ame, where microspheres form under surface tension. Themicrosphere can later be mounted on the end of an optical bre formanipulation (see bottom right image). . . . . . . . . . . . . . . . . . 302.2 Scanning Electron Microscope image of a silica microsphere fabricatedby melting the end of a tapered optical bre. The electrons penetrateinto the microsphere, revealing the bre core in the centre and claddingin the outer region, where the WGM should propagate. . . . . . . . . 312.3 Schematic of (a) tapered bre-microsphere and (b) angle-polished bremicrospherecoupling schemes. . . . . . . . . . . . . . . . . . . . . . . 322.4 Calculated polish angle as a function of sphere radius for a wavelengthof 980 nm for the fundamental n = 1 mode, and the n = 2 mode. . . 342.5 (a) Propagation constant for the fundamental HE 11 mode at 980 nm,and (b) phase matching condition at 980 nm in a silica microsphere. . 372.6 Poynting vector for a 0.5 m radius bre taper for light with a wavelengthof 1.5 m. The boundary of the bre wall shows a discontinuityin the vector eld causing a large power density. The evanescent eldis quasi linearly polarised. . . . . . . . . . . . . . . . . . . . . . . . . 382.7 Schematic of the taper fabrication rig. Dashed lines indicate controllines or data transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 422.8 Taper prole for a 3 m diameter taper. The pull length is 40 mm, thescan length is 7 mm, and the initial taper diameter is 125 m. Theinset shows an SEM image of a section of the taper with a diameter of5.9 m. The inset bar in the lower right is 1.0 m. . . . . . . . . . . 44
xv2.9 Approximated length-scale delineation curves for three taper fabricationtechniques - direct CO 2 heating, indirect micro-furnace heating,and a 2-step process employing both techniques. The green trace representsthe delineation between guidance and non-guidance of light. . 452.10 Optical micrograph of a bottle resonator with a diameter of 12 m anda length of 300 m. The bar is 10 m. . . . . . . . . . . . . . . . . . 483.1 The theoretical absorption loss of ZBLAN is compared to that of experimentallyrealised bres from the visible to the near infra-red [23].The attenuation in silica is higher by a factor of about 10 or more. . . 533.2 Absorption spectra for 0.2 mol% Er 3+ doped ZBLALiP bulk glass atoptical and IR wavelengths. . . . . . . . . . . . . . . . . . . . . . . . 553.3 Er 3+ energy level diagram with radiative (solid lines) and non-radiativetransitions for a 976 nm pump. The thick, black line at 1540 nmindicates the C-band lasing transition. . . . . . . . . . . . . . . . . . 563.4 Theoretical refractive index variation as a function of wavelength inZBLALiP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573.5 The experimental setup schematically represents how the microsphereis excited with a 980 nm diode laser (DL) and the emissions are collected.The uorescence is collected on a CCD spectrometer, and thelasing emission is collected in an optical spectrum analyser (OSA). Legend:OI - optical isolator, VA - variable attenuator, WDM - wavelengthdivision multiplexer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 593.6 66 m diameter microsphere lasing spectrum about 1.5 m showingwhispering gallery mode structure. Inset: microsphere and bre taperwith a green WGM. The FSR is 7.8 nm. . . . . . . . . . . . . . . . . 603.7 Absorption and emission cross-sections for 0.2 mol% Er 3+ doped bulkZBLALiP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Page 1 and 2: OPTICAL CHARACTERISATION OF RARE-EA
Page 3: Table of ContentsAcknowledgementsLi
Page 6 and 7: AcknowledgementsThe work in this th
Page 8 and 9: viiiList of Publications[1] J. Ward
Page 10 and 11: xTo the best of our knowledge, this
Page 12 and 13: xiiWDMWGMZBNAZBLALiPZBLANWavelength
Page 16 and 17: xvi3.8 Gain coecient for dierent po
Page 18 and 19: xviii4.9 Fluorescence slopes and sp
Page 20 and 21: xxList of Tables1.1 Rigorous select
Page 22 and 23: 2device size (typically < 200 m dia
Page 24 and 25: 4a wider range of materials can exh
Page 26 and 27: 6in Chapter 2: angle-polished bres
Page 28 and 29: 81.2 Whispering Gallery ModesWhispe
Page 30 and 31: 10where j l (h (1)l) are spherical
Page 32 and 33: 12(a)(b)Figure 1.2: Calculated inte
Page 34 and 35: 14parameter, x nl , up to order =
Page 36 and 37: 16coecient of water. There is an a
Page 38 and 39: 18(a) Silica glass(b) ZBLALiP glass
Page 40 and 41: 20eld (Eqn. 1.2) over a quantisatio
Page 42 and 43: 221.7 Spectroscopy of Rare Earth Io
Page 44 and 45: 241.9 Radiative Emission RatesIn th
Page 46 and 47: 261.10 Material Loss Mechanisms in
Page 48 and 49: 28Chapter 2Fabrication of and Coupl
Page 50 and 51: 30Figure 2.1: Microsphere fabricati
Page 52 and 53: 32Figure 2.3:Schematic of (a) taper
Page 54 and 55: 34Figure 2.4: Calculated polish ang
Page 56 and 57: 36bre, the exact electric eld equat
Page 58 and 59: 38Figure 2.6: Poynting vector for a
Page 60 and 61: 40a few dozen tapered bres.As an al
Page 62 and 63: 42Figure 2.7: Schematic of the tape
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44Figure 2.8: Taper prole for a 3 m
Page 66 and 67:
46taper angle, the light in the pro
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48Figure 2.10: Optical micrograph o
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50controlled. The discrete step-siz
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52In recent years, much eort has be
Page 74 and 75:
543.2 ZBLALiP Material PropertiesWe
Page 76 and 77:
56Figure 3.3: Er 3+ energy level di
Page 78 and 79:
58(Avanex, 1998 PLM) with a spectra
Page 80 and 81:
60Figure 3.6: 66 m diameter microsp
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62(a) C-band(b) Pump bandFigure 3.7
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64as Judd-Ofelt (JO) analysis [72]-
Page 86 and 87:
66The total spontaneous radiative t
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68Table 3.2: Predicted radiative tr
Page 90 and 91:
70Figure 3.9: Observed Er 3+ :ZBLAL
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72pumping at 637 nm [77]. The same
Page 94 and 95:
74Figure 3.10: Calculated fraction
Page 96 and 97:
76Figure 3.11: Light in-Light out l
Page 98 and 99:
78representing the Q of the cavity.
Page 100 and 101:
80Figure 3.13: Quality factor measu
Page 102 and 103:
82Chapter 4Thermally Induced Optica
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84especially benecial for C-band la
Page 106 and 107:
86note three distinct emission band
Page 108 and 109:
88therefore a combination of the in
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90This is close to the value of 2.1
Page 112 and 113:
92Figure 4.4: Lasing spectrum for a
Page 114 and 115:
94Figure 4.6: Intensity bistability
Page 116 and 117:
96Figure 4.7: Chromatic switching f
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98equation, given byl = 2n s d 1 +
Page 120 and 121:
100Figure 4.9: Fluorescence slopes
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102and the Kerr eect immediately, b
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104a precise setting for each spher
Page 126 and 127:
106Figure 4.11: Graphical descripti
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108explanation for the peak in the
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110and the associated wheatstone br
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112performance have made them an in
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114laser slightly above threshold.
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116range is shown in Fig. 5.3(a). S
Page 138 and 139:
118Chapter 6ConclusionsThis project
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120work. The reason for choosing 80
Page 142 and 143:
122Appendix ASpectral Characterisat
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In this paper we will give an overv
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1.:1.21.21.11.10.90.60.70.60.90.60.
Page 148 and 149:
⎥⎦2.2 Mode matching between a m
Page 150 and 151:
Puill lengtln (iuniuncurrents or ot
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1.6x10 -71.4x10 -7IOG-2intensity (a
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134Appendix BA Heat-and-Pull Rig fo
Page 156 and 157:
083105-2 Ward et al. Rev. Sci. Inst
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083105-4 Ward et al. Rev. Sci. Inst
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140Appendix CUpconversion Channels
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2 The European Physical Journal App
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150
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152
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JOURNAL OF APPLIED PHYSICS 102, 023
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023104-3 Ward et al. J. Appl. Phys.
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162
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164
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166
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168
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Figure F.1: Electrical wiring diagr
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172[9] J. Z. Zhang and R. K. Chang.
Page 194 and 195:
174[28] C. C. Lam, P. T. Leung and
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176[45] F. Le Kien, J. Q. Liang, K.
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178[63] M.-F. Joubert. \Photon aval
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180[81] A. Biswas, G. S. Maciel, C.
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182[98] M. Ajroud, M. Haouari, H. B
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184[116] L. Ricci, M. Weidemuller,
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