Laser Processing Architecture for Improved Material Processing

Abstract

This chapter presents a novel architecture and software-hardware design system for materials processing techniques that are widely applicable to laser directwrite patterning tools. This new laser material processing approach has been crafted by association with the genome and genotype concepts, where predetermined and prescribed laser pulse scripts are synchronously linked with the tool path geometry, and each concatenated pulse sequence is intended to induce a specific material transformation event and thereby express a particular material attribute. While the experimental approach depends on the delivery of discrete amplitude modulated laser pulses to each focused volume element with high fidelity, the architecture is highly versatile and capable of more advanced functionality. The capabilities of this novel architecture fall short of the coherent spatial control techniques that are now emerging, but can be readily applied to fundamental investigations of complex laser-material interaction phenomena, and easily integrated into commercial and industrial laser material processing applications. Section 9.1 provides a brief overview of laser-based machining and materials processing, with particular emphasis on the advantages of controlling energy deposition in light-matter interactions to subtly affect a material's thermodynamic properties. This section also includes a brief discussion of conventional approaches to photon modulation and process control. Section 9.2 comprehensively describes the development and capabilities of our novel laser genotype pulse modulation technique that facilitates the controlled and precise delivery of photons to a host material during direct-write patterning. This section also reviews the experimental design setup and synchronized photon control scheme, along with performance tests and diagnostic results. Section 9.3 discusses selected applications of the new laser genotype processing technique, including optical property variations and silicate phase fractionation in a commercial photosensitive glass ceramic and pyroelectric phase transitions in a perovskite

Local Modification of Speed of Sound in Lithium Alumino-Silicate Glass/Ceramic Material by Pulsed Laser Irradiation and Thermal Processing

“…Furthermore, by altering the protocol of the crystalline growth process, we have shown that a different phase of the lithium silicate could also be formed that show velocity changes (i.e., Δυ S , Δυ L ) of over 11% and 9%, respectively. Finally, by implementing laser amplitude modulation and the use of specific pulse sequence profiles, it becomes possible to pattern both the LMS and LDS phases on the same sample and thereby allow sections to be removed by chemical etching and sections to remain for controlling the propagation of ultrasonic waves. It also becomes feasible to engineer the propagation of mechanical force through a material where Poisson’s ratio can be varied locally.…”

“…Variability of exposure, resulting from the changing velocity of the motion stages, is reduced because the prescribed exposure dose is defined in terms of net distance traveled rather than specific time duration. 23 Each 1 cm × 1 cm pattern is exposed at constant laser power even though it is possible to vary this by amplitude modulating the EO crystal. However, laser power changes between square pattern exposures are automatically changed by altering the voltage amplitude on the EO crystal (i.e., the light valve).…”

“…With this approach, it is possible to controllably deliver a specific number of laser pulses per spot size while traversing at an average velocity of 3 mm/sec. Variability of exposure, resulting from the changing velocity of the motion stages, is reduced because the prescribed exposure dose is defined in terms of net distance traveled rather than specific time duration . Each 1 cm × 1 cm pattern is exposed at constant laser power even though it is possible to vary this by amplitude modulating the EO crystal.…”

“…Moreover, there is evidence that with pulsed UV laser exposures it is also possible to affect the growth of a particular crystalline phase. 23 While most research has focused on the properties of the crystalline matter with regards to its chemical solubility, optical transparency, and structural stiffness, we present initial experimental results in this article on the change in the ultrasonic wave velocity as a result of changes in the crystalline density. Applications and use of ultrasonics are on the increase.…”

Utility of optical heterodyne displacement sensing and laser ultrasonics as in situ process control diagnostic for additive manufacturing

“…A solution to this third problem, which surprisingly has not been implemented, is the synchronous amplitude modulation of the laser/energy source with the motion platform. 9 Moreover, the development of an optical spectroscopy system can be complex if information on the scale of tens of microns is necessary from a distance of tens centimeters.…”