# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 6 Laser-Processed Smart Materials in Photonics and Optoelectronics
Figure 14d presents \(\theta\)-2\(\theta\) X-ray diffraction data, revealing the appearance of \(\{111\}\) GaSb reflections in the segregated fiber [185]. The study in [192] introduced a laser annealing process for crafting specialty optical fibers with a semiconductor silicon core encased in a glass shell. Figure 15 showcases the investigation of a silicon core fiber (SCF) using a CMOS camera positioned perpendicular to the laser beam. In Figure 15a,b, micrographs depict the SCF being heated by a CO\({}_{2}\) laser beam at different power levels. Real-time monitoring of the exposed fiber section is facilitated by the low emissivity of the transparent silica cladding compared to the silicon core. In Figure 15c, an intensity line scan along the fiber demonstrates the distinction between molten silicon and solid silicon based on their differing emissivities, with molten silicon exhibiting a clear dip in emissivity at the phase transition. Figure 14: Laser treatment of composite fibers: (**a**) Thermal emission images during initial heating, where solid Si is brighter than the liquid GaSb/Si alloy; (**b**) XCT of the fiber after heating and translation, showing GaSb accumulation (scale bar 350 \(\upmu\)m); (**c**) EDX elemental maps of silicon and GaSb regions after translation, with red arrows indicating cross-section locations; (**d**) \(\theta\)–2\(\theta\) X-ray diffraction data of the segregated fiber [191]. Similarly, in [193], the flux-assisted molten core method was employed for laser post-processing on a ZnSe core infused with Cu8 GeSe6. The extension of the molten core technique, introduced in [194], allowed the creation of glass-clad, crystalline gallium arsenide (GaAs) core fibers, a remarkable accomplishment given GaAs's challenges, with laser annealing to separate the Sn and GaAs phases. Lastly, the study in [195] demonstrated laser recrystallization following the thermal drawing of a fiber with a single-crystalline tellurium core. Two-photon lithography (TPL) serves as a versatile additive manufacturing technology for creating 2D and 3D micro- and nanostructures with sub-wavelength resolution [196]. Usually, a tunable femtosecond laser is employed as the excitation source, operating in a working range of 690-1040 nm, with a pulse width of 140 fs and a pulse frequency of 80 MHz. Ti:Sapphire-based oscillators are considered ideal for TPL applications due to their ability to provide a broad range of available wavelengths with ultrashort pulses. Also, these lasers meet the requirements for high intensity and temporal precision needed to initiate two-photon processes. Recent advancements in laser technology have broadened the application of TPL-fabricated structures in microelectronics, photonics, optoelectronics, microfluidics, and plasmonic devices. In [197], research focused on the controlled precipitation of metallic nanostructures into glassy matrices, offering efficient synthesis for applications in photonics, optoelectronics, and telecommunications. The second, third, and fourth harmonic of a Q-switched Nd:YAG laser, operating at wavelengths of 532 nm, 355 nm, and 266 nm, respectively were utilized to perform the laser irradiation. The laser pulses had an energy of approximately 40 mJ, corresponding to an energy density per pulse of about 0.36 J/cm\({}^{2}\), and a duration of around 10 ns, with a pulse frequency of 2 Hz. Throughout the experiments, the pulse energy density remained constant, while the number of laser pulses varied. This was achieved through the modification of silver nanoparticles within silicate glasses and size control via post-exchange treatments such as thermal annealing and laser irradiation. Thus, laser-processed smart materials represent a significant advancement in photonics and optoelectronics. Their ability to respond to external stimuli and adapt their optical  
Figure 15: (**a**) Micrographs of a silicon core fiber (SCF) being heated by a CO\({}_{2}\) laser beam. (**b**) Micrograph of the same SCF heated at a higher laser power.