# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 7 Computer-Generated Diffractive Optical Elements for Laser-Processed Smart Materials
The utilization of computer-generated DOEs facilitates laser heating, the preferred method for creating local processing zones, significantly enhancing the properties of the pseudo-alpha titanium alloy Ti-2 Al-1.5 Mn [49]. The annealing zone exhibits a granular structure comprising the \(\alpha\)-phase and a small amount of the \(\beta\)-phase. The fibrous structure formed by plastic deformation was eliminated through this laser annealing, forming a well-defined grain structure. The laser power was set at 450 W, and the processing speed is maintained at 6 mm/s. For redistribution of the power density in the focal spot of the laser beam, subsequently shaped by a DOE, a telescopic system consisting of two lenses was used. Figure 17 illustrates the microstructure of the cross-section of the Ti-2 Al-1.5 Mn rolled sheet titanium alloy after laser annealing. Research demonstrated that laser annealing augmented ultimate tensile strain and reduced the minimum bend angle for cold deformation, presenting opportunities to forming options for Ti-2 Al-1.5 Mn with higher accuracy and without additional heating. Computer-generated DOEs offer innovative possibilities for tailoring material characteristics and performance with exceptional precision. In this way, for example, their applications facilitate the development of more sensitive optical sensors for a wide range of applications, including medical diagnostics, environmental monitoring, and security  
Figure 17: Microstructure of Ti-2 Al-1.5 Mn rolled sheet titanium alloy after laser annealing using DOEs, highlighting the annealing zone (1) and initial structure (2). Laser heating enhanced pseudo-alpha titanium alloy properties, fostering a granular structure with improved ultimate tensile strain and reduced minimum bend angle for cold deformation [49]. technologies [204]. In [205], DOEs enabled high spatial multiplexing of femtosecond laser pulses with a sub-MHz repetition rate, showcasing a single-step, cost-effective, and versatile lithographic tool that does not require a mask. This advancement facilitated ultrahigh micropatterning rates and the creation of mm-sized surface-enhanced infrared absorption sensors. The experimental setup utilized fundamental-harmonic pulses generated by a laser with a central wavelength of 1030 nm and a duration of 300 fs. These pulses were generated with an energy of around 5 \(\upmu\)J and a frequency ranging from 0 to 2 MHz. The optical configuration included not only lenses and a galvanometric scanner but also a DOE made of fused silica. An encouraging application of computer-generated DOEs involves the precise fabrication of nanostructures in the form of porous and oxide-metallic materials. Manipulating nanostructure morphology within specific regions of the laser-affected zone can be effectively addressed by modifying the laser beam's shape and redistributing its energy, particularly power density [206; 207; 208]. For the processing tasks, a CO\({}_{2}\) laser with diffusion cooling and radio frequency excitation was utilized. The laser generated pulses with durations ranging from 0.026 to 125 ms, and the average power of the laser beam was adjusted within the range of 200 W to 330 W. Using a laser beam modulated within the range of 3 Hz to 5 kHz, studies have revealed that the collaborative impact of thermal influences originating from laser pulses and laser-induced vibrations, specifically within the sound frequency spectrum, leads to a significant enhancing in the diffusion coefficient within materials. The crucial element for enhancing mass transfer in the solid phase of metallic materials, whether of the heated in an oxidation-free environment or selectively oxidable metallic materials, was recognized as the dynamic stress-strain state caused by laser-induced vibrations. This innovative approach involves the use of computer-generated DOEs for shaping the laser beam, enhancing the precision of energy transmission onto material surfaces, even those with intricate shapes.