Title Page

Abstract

Contents

1. Introduction 14

2. Characteristics of a post-compressed beam 17

3. Spatial filtering system for post-compression 37

3.1. Spatial filtering of the pump laser 38

3.1.1. Experimental setup 38

3.1.2. Results and discussion 39

3.2. Spatial filtering for a 100-TW laser 40

3.2.1. Experimental setup 40

3.2.2. Results and discussion 42

3.3. Conclusion 43

4. Post-compression of a high power femtosecond laser 45

4.1. Experimental setup for characterizing the post-compressed beam 45

4.2. Spectral broadening with respect to the number of plates 48

4.3. Post-compression result 49

4.4. Spatial characteristics of a spectrally broadened pulse 50

4.5. Peak-power enhancement after post-compression 54

4.6 Conclusion 57

5. Wavefront-corrected post-compression 59

5.1. Experimental setup 59

5.2. Measurement and correction of the wavefront of post-compressed pulses 62

5.3. Intensity enhancement of post-compressed pulses 64

5.4. conclusion 66

6. Summary 68

Bibliography 71

Curriculum Vitae 80

Figure. 2.1. Characteristics of the spectral broadening of a femtosecond laser pulse induced by the self-phase modulation. (a) Spectra with respect... 19

Figure. 2.2. Beam profiles with respect to the number of fused silica plates as a sample (horizontal axis) and the ratio of input laser energy of 3.2 J... 23

Figure. 2.3. Temporal and spectral characteristics of a femtosecond Gaussian laser pulse after the self-phase modulation in the case of the B-... 26

Figure. 2.4. Temporal and spectral characteristics of a femtosecond Gaussian laser pulse after the self-phase modulation in the case of the B-... 28

Figure. 2.5. (a) Self-steepened pulse (blue dotted line) by intensity dependent group velocity in the case of the B-integral of 8 and the... 29

Figure. 2.6. Laser spectra measured with different initial GDD values of incident laser pulses. The spectrum in the center of the figure, taken as the... 30

Figure. 2.7. Laser spectra measured with different initial TOD values of incident laser pulses. The spectrum in the center of the figure, taken as the... 31

Figure. 2.8. Intensity-dependent spectral characteristics of 100-TW laser pulses measured after the two chirped mirrors. The output beam profiles... 33

Figure. 3.1. Schematics of the experimental setup for spatial filtering of the 1.5 J pump laser. L1: Cylindrical lens, L2: spherical lens, L3, L4: imaging... 39

Figure. 3.2. Spatial characteristics of the pump laser. The beam profiles (a) without and (b) with the spatial filters are compared. 40

Figure. 3.3. System configuration of the 100-TW Ti:Sapphire laser 41

Figure. 3.4. Schematics of the experimental setup for spatial filtering of the 100-TW laser. L1: Cylindrical lens, L2: spherical lens, L3, L4: imaging... 42

Figure. 3.5. Spatial characteristics of the 100 TW laser. The beam profiles (a) without and (b) with the spatial filters are compared. 43

Figure. 4.1. Schematics of the experimental setup for post-pulse compression and characterization. M1: dielectric mirror, FS: fused silica... 47

Figure. 4.2. Spectral broadening after propagating through 0.5-mm fused silica plates: 1 plate (a), 2 plates (b), and 3 plates (c). Measured spectra are... 49

Figure. 4.3. (a) Broadened laser spectrum obtained from the experiment (solid line) and the simulation (dashed line) after propagating through a... 50

Figure. 4.4. Spatial characteristics of post-compressed laser pulses measured after going through a 1.5-mm fused silica plate. The beam... 53

Figure. 4.5. Spatial characteristics of the spectral broadening after propagating through a 1.5-mm fused silica. (a) Pulse duration map of the... 55

Figure. 4.6. Spectral broadening after propagating through fused silica plates: (a) 1.5-mm-thick plate, (b) 1.5-mm and 1.0-mm-thick plates, and (c) 0.5-... 57

Figure. 5.1. Schematics of the experimental setup for the post-compression with wavefront correction. M1: dielectric mirror, FS: fused silica plates for... 60

Figure. 5.2. (a) Broadened spectrum (red line) after three 0.5-mm fused silica plates, shown along with the input spectrum (black line). (b)... 61

Figure. 5.3. Beam profile and wavefront measured after propagating through three 0.5-mm fused silica plates. (a) Beam profile and (b)... 64

Figure. 5.4. Comparison of focal spot images: (a) at a low input energy (0.03 J), (b) at a high input energy (2.5 J), and (c) at the high input energy... 66