## 1 Introduction  
The rapid growth of the photovoltaics market requires advances in PV (photovoltaics) manufacturing and technologies that would translate into further cost reductions, as well as quality and efficiency increase of the solar cells [1]. Laser technology has already been widely applied in photovoltaic production for the last two decades, in many different ways (Figure 1) [2; 3].  
Among them, there are processes directly related to silicon wafers micromachining. Table 1 presents some examples of the femtosecond laser systems used for this purpose. They include dicing, nano and micro-structuration of the surface, and antireflection coating or nanoparticle absorbing [4; 5; 6; 7; 8; 9; 10; 11]. According to [PERSON] et al., a simple irradiation of the silicon surface with ultrashort laser pulses may improve the cell efficiency [4; 5; 6; 7; 8]. One of the common micromachining processes engaged in increasing the efficiency of the solar cells is the so-called junction isolation (laser edge isolation). During the manufacturing process, a conduction path is created between the front and back surfaces of the wafer, all around its edge. In that direct process, the laser scribes a groove on the top surface of the silicon wafer, around the cell's periphery [2; 12].  
speed due to an increased distribution of energy into the silicon. As a result, the process is more prone to thermal effects, such as melting, cracking, amorphization, and residual stress buildup [14]. The use of ultrashort laser pulses has eliminated most of these problems. The ability to process a wide range of materials with negligible thermal effects and without the necessity of post-processing tools, led to innovation in the area of micro and nanotechnology. Although companies like Coherent provide industrial solutions ready to use in production environments, femtosecond lasers are still considered not reliable enough for an efficient commercial use, which requires minimum complexity and maximum stability. Meanwhile, laser pulses with durations in the range of picoseconds are considered very well suited for micromachining of all types of materials and are often a first choice to achieve the desired quality and accuracy at industrial reasonable efforts and costs [15].  
The efficiency of the micromachining process depends on both: laser radiation parameters (pulse duration, wavelength, pulse energy, repetition rate) and target material properties (thickness, thermal conductivity, hardness, etc.) [16]. These parameters affect the course of laser ablation. The nature of the ablation process in the femtosecond regime is different and more complex than with longer, i.e., picosecond and nanosecond pulses [17; 18]. We found a range between picosecond and femtosecond laser pulses interesting for further investigation, since both short and long pulse types of laser-matter interactions appear. The prototype sub-picosecond laser demonstrated in this paper has already proven to be a sufficient tool for micromachining of thin metal foils and plastics [19] and its application is promising in the photovoltaic industry.  
The monocrystalline silicon used in this research is the base material for many types of electronic equipment, integrated circuits, and discrete components. It also serves as a photovoltaic, light-absorbing material in the manufacture of solar cells. According to a report [20], in 2018, laboratory results showed that the best performing modules were based on monocrystalline silicon with 24.4% efficiency. The best results demonstrate the potential for further efficiency enhancement desirable by the mass production level [20].