# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 6 Laser-Processed Smart Materials in Photonics and Optoelectronics  
The application of laser processing in the development of smart materials for photonics and optoelectronics has opened up new frontiers in advanced technology. This innovative approach involves utilizing laser irradiation to induce controlled changes in the properties of materials, enabling precise modifications tailored to specific optical and optoelectronic requirements [166]. In the field of photonics, smart materials created by using laser processing are applied in the development of reconfigurable photonic devices. As a result of laser-induced heating, materials can undergo controlled and reversible phase transitions, enabling the development of materials with dynamic optical properties that respond to external stimuli such as temperature, light, or magnetic fields. Promising phase-change materials (PCMs) include chalcogenide compounds and transition-metal oxides [167]. Chalcogenide vitreous semiconductors find applications in integrated optics, memory cells, and diffractive-optical elements due to their low absorption in the near and mid-infrared range and reversible phase transitions from amorphous to crystalline states when exposed to short-wavelength radiation. The study in [168] presented an approach for accurately predicting the microstructure and optical response of such phase-change materials during laser-induced heating. This method is crucial for designing programmable photonic devices, particularly for applications like all-optical neural networks and PCM-programmable perceptrons. The samples consisted of 50 nm-thick silicon nitride membrane windows on a 0.5 mm thick silicon substrate, with a 30 nm amorphous Ge\({}_{2}\)Sb\({}_{2}\)Te\({}_{5}\) film deposited using radio frequency magnetron sputtering. The simulation of crystallization and melting processes in amorphous Ge\({}_{2}\)Sb\({}_{2}\)Te\({}_{5}\) involved utilizing a focused Gaussian laser beam. The beam radius (1/e\({}^{2}\) intensity) was fixed at 600 nm, while the peak power was adjusted within the range up to 5.0 mW, and pulse durations varied from 10 ns to 1000 ns. These choices of parameters were determined based on the capabilities of the laser testing system. A nanosecond laser was employed for processing. Figure 12 illustrates the results of partial crystallization by changing the laser pulse width from 10 ns to 60 ns at 5.4 mW. In this range, controllable reflectivity is observed, and longer pulses inducing melting and subsequent recrystallization, with forming larger grains in the center and smaller grains around the perimeter. Experimental data align well with simulation results. In [169], it was demonstrated that subablative ultrashort laser pulses effectively generate well-organized surface nanostructures in chalcogenide glasses. Irradiation utilized ultrashort pulses from the Yb:KGW femtosecond laser system at a 1030 nm wavelength, featuring a pulse duration of 185 fs and a frequency of 200 kHz. The incident laser beam, normally oriented and linearly polarized, was focused through a lens with a 75 mm focal length, resulting in a beam spot diameter on the sample's surface of approximately 70 \(\upmu\)m (1/e\({}^{2}\)). Femtosecond laser exposure was employed to create structured patterns in mid-IR materials, particularly chalcogenide glass (Ge\({}_{23}\)Sb\({}_{7}\)S\({}_{0}\)), with a focus on developing photonic devices, including applications in spectroscopy [170]. Three distinct femtosecond laser systems were employed, each emitting pulses with varying durations. The first system generated 50 and 100 fs pulses at 850 nm using a Yb-doped fiber. The second system produced 150 fs pulses at 1030 nm through a Regen amplifier, while the third system delivered 270 fs pulses, also at 1030 nm, using a Yb-doped femtosecond fiber laser.