Fabrication of silica microspheres

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Table of contents

Introduction
1 Whispering gallery mode microcavities
1.1 General properties of WGMs
1.1.1 A simple approach for WGMs
1.1.2 WGMs theory in microspheres
1.1.2.1 Solution of electromagnetic field
1.1.2.2 Resonance positions and spacing
1.1.2.3 Mode splitting due to small ellipticity
1.1.2.4 Optical field distribution
1.1.2.5 Quality factor
1.1.2.6 Mode volume
1.1.3 FEM simulations of silica microtoroids
1.1.3.1 Mode volume
1.1.3.2 Higher order modes
1.2 Fabrication of silica microspheres
1.2.1 CO2 laser source
1.2.2 Experimental setup
1.2.3 Results
1.3 Fabrication of on-chip microtoroids
1.3.1 Fabrication of microdisks
1.3.2 Fabrication of microtoroids
2 WGM excitation with tapers
2.1 Tapered fiber couplers
2.1.1 Introduction
2.1.2 Taper fabrication
2.1.3 Results and discussion
2.2 Modeling the Coupling
2.2.1 Description of the model
2.2.1.1 Equations of the fields
2.2.1.2 Effects of the coupling gap g adjustment
(a) The critical coupling region: C = I or g = gc
(b) The undercoupled region: C I or g > gc
(c) The overcoupled region: C I or g < gc
2.2.2 WGM Doublets
2.3 Excitation of WGMs in microspheres
2.3.1 Experimental setup
2.3.2 Excitation mapping of WGMs in a microsphere
2.4 Excitation of WGMs in microtoroids
2.4.1 Experimental setup
2.4.2 Typical WGM resonance spectra
2.4.3 The impact of the gap
2.4.4 Excitation mapping of toroid WGMs
3 Microlaser characterization
3.1 Thermal bistability
3.1.1 Theoretical model
3.1.2 Numerical and experimental results
3.2 Experimental setup and method
3.2.1 Experimental setup
3.2.2 Step-by-step recording method
3.3 Results
3.3.1 Evidence of lasing
3.3.2 Real-time laser characteristic measurement
4 Nd3+:Gd2O3 based lasers
4.1 Photoluminescence of a doped sphere
4.1.1 General properties of Nd3+:Gd2O3 nanocrystals
4.1.2 Photoluminescence in the WGM
4.2 Lowest threshold recording
4.2.1 Q factors
4.2.2 Power calibration
4.2.3 Evidence of lasing
4.2.4 Threshold and slope efficiency
4.3 Sub-μW threshold single-mode microlaser
4.3.1 Fundamental polar mode q = 0 for pumping
4.3.2 Emission spectra and threshold
4.3.3 Laser performance vs coupling conditions
4.3.4 Microlaser characterization using scanning Fabry-Perot interferometer
5 Other results in microlasers
5.1 Microsphere lasers using Yb3+:Gd2O3 nanocrystals
5.1.1 General properties of Yb3+ ions
5.1.2 Q factors of the active microsphere
5.1.3 Laser results
5.2 Neodymium implanted silica microtoroid lasers
5.2.1 Fabrication of a rolled-down microtoroid
5.2.2 Q factors
5.2.3 Emission spectra
5.2.4 Single mode lasing threshold
Conclusion
Bibliography