Title Page
Abstract
Contents
1. Introduction 17
1.1. Background and Motivation 17
1.2. Overview of the Dissertation 23
2. Fundamentals of Optical Fiber and Fiber Lasers 25
2.1. Optical Fibers 25
2.1.1. Step-index Optical Fiber 25
2.1.2. Propagation Modes in Optical Fibers 29
2.2. Rare-earth-doped Fiber 33
2.2.1. Erbium-doped Fiber 35
2.2.2. Ytterbium-doped Fibers 37
2.2.3. Thulium-doped Fibers 39
3. Pulsed Fiber Lasers 41
3.1. Pulsed Laser Operation 41
3.2. Q-switched Fiber Laser 43
3.3. Mode-locked Fiber Laser 47
3.3.1. Active Mode-locked Fiber Laser 51
3.3.2. Passive Mode-locked Fiber Laser 53
4. Pulse Amplification 56
4.1. Master Oscillator Power Amplifier (MOPA) 57
4.2. Chirped Pulse Amplification (CPA) 62
5. Measurement of Nonlinear Optical Properties 66
5.1. Chacterization of Nonlinear Absorption 68
5.2. Characterization of Nonlinear Refraction 70
5.3. Experimental Results of Z-scan Measurements 73
5.3.1. Nonlinear Optical Characteristics of V₄C₃ MXene 76
5.3.2. Nonlinear Optical Characteristics of Cr₂Te₃ TMC 84
5.3.3. Nonlinear Optical Characteristics of SnTe TCI 90
6. Experimental Results of Pulsed Fiber Lasers 96
6.1. Passively Mode Locked Pulse Generation by V₄C₃ MXene SA 97
6.2. Passively Q-switched Pulse Generation by Cr₂Te₃ TMC SA 105
6.3. Passively Mode-locked Pulse Generation by SnTe TCI SA 110
7. Four-wave Mixing in Optical Fiber 115
7.1. Intermodal Four-wave Mixing (IMFWM) 119
7.2. Pump laser for IMFWM Processes at Visible Wavelengths 121
7.3. Photon-pair Generation by IMFWM Process 125
7.4. Coincidence Detection of Photon-pairs 132
8. Polarization-entangled Photon-pair Generation in Optical Fibers 137
8.1. Polarization Entangled Photon-pairs 140
8.2. Two-photon Interference Measurement 145
8.3. Reconstruct of Density Matrix 150
9. Conclusion 156
9.1. Topics for Further Studies 160
References 161
Publication Lists 178
국문초록 182
Table 5.3.1.1. Nonlinear absorption coefficient and nonlinear refractive index of 2D V₄C₃ MXene nanosheets at 1560 and 1910 nm wavelengths. 83
Table 5.3.1.2. Comparison of nonlinear absorption coefficient and nonlinear refractive index of renowned 2D nanomaterials obtained through Z-scan measurement at SWIR wavelengths. 83
Table 5.3.2.1. Nonlinear optical coefficients and nonlinear refractive index of PVD-grown Cr₂Te₃ film measured at different input intensities. 88
Table 5.3.2.2. Comparison of nonlinear absorption coefficient and nonlinear refractive index of 2D nanomaterials obtained by Z-scan measurement. 89
Table 5.3.3.1. Nonlinear absorption coefficient and nonlinear refractive index of SnTe TCIs obtained through Z-scan measurement. 95
Table 5.3.3.2. Comparison of Nonlinear absorption coefficient and nonlinear refractive index of 3D materials obtained by Z-scan measurement. 95
Table 6.1.1. Comparison of pulse characteristics of MXene-based SAs at SWIR wavelengths. 104
Table 6.2.1. Summary of Q-switched fiber lasers with SAs fabricated by bottom-up synthesis method. 109
Table 7.2.1. Optical parameters of SMF-28 at 532 nm wavelengths. 128
Table 7.2.2. Analytically calculated optical parameters for Equation 7.3.1. 128
Table 7.2.3. Possible IMFWM processes estimated from analytical calculation. 128
Table 7.2.4. Possible IMFWM processes estimated from numerical calculation. 128
Table 8.3.1. Quantum state tomography set of 16 measurements. 152
Figure 2.1.1.1. (a) Cross-section and (b) refractive index profile of step-index optical fiber. 26
Figure 2.1.1.2. Schematic of ray propagation in optical fiber. 27
Figure 2.1.2.1. Mode field profiles of several LPlm modes in step-index optical fibers.[이미지참조] 32
Figure 2.1.2.2. Effective refractive index as a function of V-number for several LP modes. 32
Figure 2.2.1.1. (a) Energy band diagram of EDF. (b) Absorption and emission cross section of EDF. 36
Figure 2.2.2.1. (a) Energy band diagram of YDF. (b) Absorption and emission cross section of YDF. 38
Figure 2.2.3.1. (a) Energy band diagram of thulium-doped fiber. (b) Absorption and emission cross section of thulium-doped fiber. 40
Figure 3.1.1. (a) Schematic of pulsed laser with extra-cavity modulator. (b) Pulse evolution of extra-cavity modulator. (c) Schematic of pulsed laser with intracavity modulator. (d) Pulse evolution of intracavity modulator. 42
Figure 3.2.1. (a) Schematic of switch-off operation and (b) energy state diagram and when the loss of the modulator is high. (c) Schematic of switch-on operation and (d) energy state diagram and when the... 44
Figure 3.2.2. Schematic of the basic principle of a Q-switching operation as a function of time. 44
Figure 3.3.1. (a) Intensity of 100 longitudinal modes with randomly varying phases. (b) Intensity of 5 longitudinal modes with randomly varying phases. (c) Intensity of 100 longitudinal modes with locked phases. 49
Figure 3.3.2. Schematic of mode-locked pulse generation within the optical cavity. 50
Figure 3.3.1.1. Temporal evolution of actively mode-locked pulses and modulation losses. 52
Figure 3.3.2.1. Illustration of the saturable absorption of nonlinear optical material. 54
Figure 3.3.2.2. Change of transmission of SA as a function of incident peak intensity. 55
Figure 4.1.1. Schematic of typical MOPA fiber laser system. 58
Figure 4.1.2. Schematic of MOPA fiber laser system. 60
Figure 4.1.3. (a) Optical spectrum and (b) oscilloscope trace of output of MOPA fiber system. 61
Figure 4.2.1. Schematic of chirped pulse amplification. 62
Figure 4.2.2. Schematic of all-fiber chirped pulse amplification system. 65
Figure 4.2.3. (a) Optical spectrum, (b) oscilloscope trace, and (c)autocorrelation trace of seed laser. (d) Optical spectrum, (e) oscilloscope trace, and (f) autocorrelation trace of CPA output. 65
Figure 5.1.1. (a) Schematic of OA Z-scan measurement. (b) Typical OA Z-scan trace. 69
Figure 5.2.1. (a) Schematic of CA Z-scan measurement. (b) Typical CA Z-scan trace. 71
Figure 5.3.1.1. (a) SEM image of V₄C₃ MXene bulk powder. (b) SEM and (c) AFM image of exfoliated V₄C₃ MXene. (d) Measured AFM profile (Corresponding points are marked in (c)). (e) XPS spectrum of... 78
Figure 5.3.1.2. Schematic of simultaneous detection of Z-scan signals. 79
Figure 5.3.1.3. Experimental results in (a) OA arm and (b) CA arm with respect to input laser intensities measured at 1560 nm wavelengths. (c) Experimental results in OA arm and (d) CA arm with respect to... 81
Figure 5.3.2.1. (a) TEM image. (b) Magnified view of TEM image. (c) FFT image. (d) XRD data. (e) XPS spectrum of chromium and telluride. (f) Raman spectrum, and (g) Measured UV-VIS spectrum. 86
Figure 5.3.2.2. (a) Schematic of simultaneous detection of Z-scan signals for Cr₂Te₃ film at 1560 nm. Experimental results in (b) OA arm and (c) CA arm with respect to input laser intensities. 88
Figure 5.3.3.1. (a) SEM image. (b) AFM image. (c) Height of SnTe TCI used in the experiment. (d) EDS mapping image of (d) tin and (e) telluride. XPS spectrum of (f) tin and (g) telluride. (h) Raman spectrum... 92
Figure 5.3.3.2. (a) Experimental Schematics. Experimental results in (b) OA arm and (c) CA arm with respect to input laser intensities. 93
Figure 6.1.1. (a) Experimental setups for measuring nonlinear optical performance. Transmission change as a function of an incident peak intensity measured at the wavelength of (b) 1560 and (c) 1910 nm. 98
Figure 6.1.2. Schematic of rare-earth-doped fiber ring cavity. Different optical components were used at the wavelength of 1560 and 1910 nm except for V₄C₃ MXene-based SA. 101
Figure 6.1.3. Output characteristics of mode-locked pulses from V₄C₃ MXene-based SA incorporated EDF cavity. (a) Optical spectrum, (b) oscilloscope trace, (c) autocorrelation trace, and (d) RF spectrum. 101
Figure 6.1.4. (a) Optical spectrum of mode-locked pulses from V₄C₃ MXene-based SA incorporated THF cavity. (b) Repetition rate and (c) pulse width of mode-locked pulses. (d) RF spectrum measured at... 102
Figure 6.1.5. Optical spectrums measured at every 30 min. for consecutive 3 hours for (a) 1560 and (b) 1900 nm operation. 103
Figure 6.2.1. Schematic for the measuring the performance of Cr₂Te₃-film-based SAM. (b) Change of reflection as a function of incident peak intensity of the Cr₂Te₃-film-based SAM. 106
Figure 6.2.2. Experimental schematic fiber ring cavity with Cr₂Te₃-film-based SAM. 107
Figure 6.2.3. (a) Measured oscilloscope trace at different pump power. (b) Measured optical spectrum at a pump power of 130 mW. (c) Measured repetition rate and pulse width. (d) Measured output power and... 109
Figure 6.3.1. (a) Schematic and (b) photo of SnTe TCI-based SAs (D-shaped fiber). 110
Figure 6.3.2. (a) Schematic of measuing nonlinear transmission of fabricated SA. (b) Nonlinear optical transmission change of SnTe TCI-based SA with increased optical intensities. 111
Figure 6.3.3. (a) Schematic of fiber ring cavity with SnTe-based SA. (b) Oscilloscope traces (inset: single mode-locked pulse), (c) optical spectrum, (d) measured optical spectrum at 30 min. for 3 h, (e)... 114
Figure 7.1 Schematic of (a) spontaneous parametric down-conversion and (b) spontaneous four-wave mixing. 116
Figure 7.2.1. (a) Schematic of SHG of amplified mode-locked pulses. (b) Measured optical spectrum and (c) oscilloscope trace of SHG signal. 123
Figure 7.2.2. (a) Beam profile of output of MOPA system. Measured D4σ in (b) horizontal and (c) vertical axis. 124
Figure 7.3.1. (a) neff, (b) β⁽⁰⁾, (c) β⁽¹⁾, and (d) β⁽²⁾ of different LP modes calculated in commercially available single-mode fiber in visible wavelength region.[이미지참조] 127
Figure 7.3.2. (a) Phase-matching curve of IMFWM processes. (b) Relative efficiency of generated signal and idler photons from Equation 7.1.3. 129
Figure 7.3.3. (a) Optical spectrum of generated IMFWM processes. (b) Optical spectrum of generated IMFWM processes with different pump configuration. 131
Figure 7.4.1. Schematics of coincidence detection of two SPCM. 133
Figure 7.4.2. Schematics of voltage divider for DE-115 board. 134
Figure 7.4.3. Coincidence window of 26.44 ns, (b) 12.66 ns, (c) 8.90 ns, and (d) 4.90 ns. 134
Figure 7.4.4. Photo image of coincidence counter based on FPGA and voltage divider. 135
Figure 7.4.5. Screen capture of LabVIEW program of coincidence counter. 136
Figure 8.1. Schematic of time-bin entangled photon-pair source generated in optical fiber. 139
Figure 8.2. Schematic of polarization-entangled photon-pair source generated in the optical fiber. 139
Figure 8.2.1. (a) Experimental schematic polarization-entangled photon-pair generated from IMFWM process. (b) Detection of spectral properties of IMFWM processes. (c) Post-selection of entangled... 146
Figure 8.2.2. TPI fringe measured in polarization basis of (a) horizontal and (b) diagonal. 148
Figure 8.3.1. (a) Real and (b) imaginary parts of reconstructed density matrix of polarization entangled photon-pairs. 155