# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 6 Laser-Processed Smart Materials in Photonics and Optoelectronics
In [178], experimental studies involving bi-layer Si/Ti films were conducted using the circular laser writing system equipped with a continuous-wave DPSS laser, operating with a wavelength of 532 nm and a maximum power of 2 W. The linear scanning speed of the focused laser spot is determined by the radial position of the lens, measuring 0.7 \(\upmu\)m during experimental studies. For example, when dealing with a Ti film thickness of approximately 60 nm, the maximum scanning speed during laser writing reached around 200 mm/s. Laser ablation offers precise material removal, enabling the creation of microchannels or cavities with sub-micron accuracy. Direct laser writing, recognized for its versatility and efficiency in producing intricate photonic devices through localized adjustments in the refractive index of bulk dielectric materials, was widely employed. It accommodated various transparency ranges, including the visible, near, or mid-infrared range [46]. In [179], the femtosecond laser system employed in the investigation had a central wavelength of 800 nm, a frequency of 1 kHz, and a pulse width of approximately 35 fs. A polarized laser beam was generated using a half-wave plate polarizer. An objective lens with a numerical aperture of 0.7 and a magnification of 50\(\times\) was focused on the core of the TCF. The fiber grating was created by periodically scribing lines along the parallel direction of the core, employing a laser energy setting of 0.3 \(\upmu\)J and a platform with a scanning speed of 20 \(\upmu\)m/s. The line length and the period of the fiber grating were determined by the exposure time. In [180], experimental investigations were carried out using laser thermochemical recording on a thin metal film, specifically an ultrathin 10-nm titanium film deposited on a BK7 glass substrate. The experiments utilized a continuous-wave Yb-fiber laser operating at a wavelength of 1070 nm and featuring a Gaussian distribution. The laser source was coupled with an optical module that facilitated the control of scanning speed and allowed for the adjustment of the laser beam diameter to 35 \(\upmu\)m at the focal plane. During the track recording, a beam diameter of 85 \(\upmu\)m and a scanning speed of 1 mm/s were used. This technology expedites the production of sophisticated optical chips by integrating photonic functions, material ablation, and electrode patterning, simplifying the process by eliminating the need for multiple lithography steps. Laser annealing plays a pivotal role in modifying the crystal structure of materials, especially semiconductors, to improve their optical and electronic properties, aiding in the development of photovoltaic devices and optoelectronic circuits. Integrating 2D materials into silicon photonic devices holds the promise of significantly enhancing optoelectronic device performance, leading to reduced response times, reduced energy consumption, and a simplified fabrication process. In [181], laser processing emerged as a powerful tool for enhancing 2D material-based photonic devices, unlocking advanced design possibilities for silicon photonic integrated circuits. In [182], laser recrystallization was utilized to produce ultralong single-crystal SnSe wires with a structure conducive to high thermoelectric performance at micro- to nanoscale diameters, presenting potential applications in optoelectronic devices like photodetectors and other components with specific electronic and optical properties. Laser doping utilizes laser treatment to introduce specific impurities into materials, enabling the customization of their electrical and optical characteristics for various optoelectronic applications [183]. The experimental investigations utilized the second harmonic of a nanosecond-pulsed Nd-laser with a wavelength of 532 nm. Employing two beam splitters in the experimental setup, the energy density was selected within the range of 0.1-0.9 J cm\({}^{-2}\).