In this thesis, nanosecond pulsed lasers are used as the tools to generate microstructures on metal and glass. The applications of these structures are described too. The production of micro structures is demonstrated using diode-pumped solid state (DPSS) Nd:YVO4 lasers operating at wavelengths of 532nm or 1064 nm. The laser fluence and scanning speed are important parameters to control the results. The first part of thesis is on the laser generation of microstructures on metal surfaces. Copper (Cu) and titanium (Ti) have been studied. According to the reflectivity of metals, Cu is processed by a 532nm laser and Ti is processed by a 1064nm laser. It is shown that the periods of surface microstructures are highly dependent on the hatch distance (overlapping distance between laser scanning). Only if the laser fluence is greater than a threshold, may the microstructures on metals be induced. The thresholds are measured by the diameters of ablated areas at different fluence. Laser generated surface microstructures have been applied to modify the reflectivity of a Cu sample. It was found that laser induced surface microstructures on Copper can decrease the surface reflectivity by almost 97% between 250 nm and 700 nm. To find the mechanism of how to form microstructure on metal surface with laser, laser ablation and heating models have been studied. The 1D ablated numerical model is calculated in Matlab. The pressure of metal vapour is an important parameter, as it pushes the melted metal out of surface to form microstructures after re-solidification. The second part of thesis is on glass welding with microstructures on glass surfaces. The soda-lime glasses containing silver nanoparticles (from the company Codixx) have been studied and welded with Schott B270 glass. Compared with other techniques for welding glass, lasers offer the advantage of a relatively simple and flexible technique for joining the local area underneath the cover glass. Most of the laser energy is deposited in the Ag nanoparticle layer because of the large absorption coefficient at 532 nm. Expanded microstructures generated by the laser are applied to fill the gap between the glass surfaces. This is attributed to the formation of bubbles in the Ag nanoparticle layer after laser processing. The welded samples have the joint strength of 4.9 MPa and have great potential for industrial applications. A 3D analytical model is used to estimate the temperature of the glass after the laser pulse. The increase in temperature is about 129 °C. To induce the bubble in glass, many laser pulses are necessary. This is very different from the results for the metals.

Femtosecond laser direct writing in transparent materials such as glass and optical fibers has been used as a versatile tool in order to fabricate various 3-D photonic structures such as active and passive waveguides, couplers, gratings and diffractive optical elements (DOEs). This capability of patterning and refractive index modification in the bulk of transparent materials depends on the nonlinear absorption phenomenon. This practical technique has the potential to be used for cost effective and simplified manufacturing in various applications. This thesis examines three advanced manufacturing techniques that use ultrashort pulse filamentary propagation induced by nonlinear absorption in the transparent materials. First, a new gradient index lens fabrication method using femtosecond laser direct writing is introduced. Light that passes through the lens with refractive index change resulting from localized energy deposition is focused using a beam profiler. Second, wide welding area of glass samples are used to fabricate microfluidic devices with long channels by adopting customized fixture. The fixture making artificial pressure helps the two glass samples have wide optical contact area and the highly intensive pulse filamentation strongly joins glass slides. As an example of a more specific application, microfluidic samples with long grooves sealed by femtosecond laser welding were successfully fabricated as part of this project. Finally, a screw-shaped, long period grating sensor was fabricated by rotating the optical fiber. This technique enables the fiber core to have asymmetric refractive index change, resulting in higher sensitivity compared to conventional long period grating sensors. Also, a new long-period grating sensor with reverse bending effect has been demonstrated by producing complex pitches of refractive index change. / Graduate

Cette thèse porte sur l’assemblage de verres par impulsions laser femtosecondes. Une source laser femtoseconde à haute fréquence de répétition a été utilisée pour souder des lames de borosilicate de haute qualité de surface. La technique d’assemblage mise en œuvre diffère de la littérature par le système de focalisation utilisé. Un plan d’expériences a été réalisé afin de déterminer l’influence des différents paramètres laser sur les performances des soudures obtenues, démontrant que l’augmentation de la quantité d’énergie déposée améliore les performances mécaniques et thermiques. Les assemblages soudés peuvent atteindre une haute résistance mécanique supérieure à 25 MPa et supporter des chocs thermiques supérieurs à 300 ° C. L’adaptation des paramètres laser en fonction de la distance entre les lames de verre permet de souder des verres hors contact optique. Cette méthode a également été implémentée avec succès à l’assemblage de verre sur du silicium. / This PhD thesis is about glass bonding by femtosecond laser pulses. A femtosecond laser source generating high repetition rate laser pulses has been used to weld borosilicate glass plates with high surface quality. The method presented in this work differs from the literature by the focusing system implemented. The influence of the laser parameters on the bonded samples performances has been studied implementing a design of experiments, demonstrating that the mechanical and thermal resistance of the samples can be improved by increasing the amount of deposited. Thebonded samples provide high mechanical resistance, higher than 25 MPa, can held high thermal shock above 300 °C and present high transparency above 90 %. Glass bonding with a distance between the glass plates has been performed by adapting the laser parameters. Bonding of glass on silicon has also been performed successfully.