The removal of materials by ablation instead of melting is the key characteristic of ultrafast laser pulses which can carry it out without causing thermal damage despite the utilization of high power. This unique feature makes the ultrafast laser uniquely suited for a variety of manufacturing applications in a variety of industries. It also enables large substrates processing as well as provides a cost-efficient means of industrial micro-machining. Additionally, the formation of microtextured riblet to effectuate drag reduction on aluminum airfoils as well as bioinspired surface functionalization which aids in bringing the functionalization of laser surfaces to the mass production levels can be facilitated when high-speed scanning systems are combined with high-average power lasers that result in processing fast and accurate processing of large areas.
On the other hand, pico- and femtosecond fiber lasers have been making ripples in the space of ultrafast-laser materials processing. The characteristics of active fiber are the confines of higher pulse energies. Coupled with advances in beam handling, delivery, laser technology, and process development, and valued for extending virtually athermal materials processing, this class of lasers has paved for several industrial and scientific applications. In the past, the increment of fiber diameter has been the traditional enable of higher pulse energies. However, the quality of the beam of these LMA (large effective mode area) is extremely sensitive to any sort of fiber bending. Thus, the prospect of high power with excellent beam characteristics are offered by T-DCF (tapered double-clad fiber) amplifiers, which comprises a double-clad optical fiber. Developed by Finland based Ampliconyx Oy and Tampere University along with the consortium of European partners including Fiat Chrysler through the European PULSE project, these amplifiers have been developed by utilizing a fiber-drawing process that creates a taper along the length of the fiber. The T-DCF laser has been reported to deliver up to 2.5 kW with pulse durations as short as 100 fs and repetition rates up to 1 GHz.
With the cost of production being a wee bit above that of normal fibers, the T-DCF amplifiers offer the prospect of high power with excellent beam properties in a space-effective format. Further despite substantial advancements are being carried out solid-state high-power ultrafast technologies with the utilization of new configurations like the Amphos InnoSlab technology, the thermal management challenges and high cost of solid-state gain material has the potential deter the industry-wide adoption of such a technology, thus T-DCF laser is one such competitivetechnology that enables faster, more precise, and nonthermal laser manufacturing. While the aforementioned class of fiber lasers has several noteworthy characteristics, considering the highest-average-power ultrafast light bulk solid-state lasers are a viable solution that is worth a mention. Such developments have commercial potential which can augment the global ultrafast lasers market growth. While the earlier-mentioned pico- and femtosecond fiber lasers have many remarkable qualities and have found large scale applications in mobile device glass scribing, when the need for ultra-short pulse lasers arises in the area of high repetition rates and high power to achieve economically viable throughput, these lasers are quite limited.
To this end in January 2020, it was reported that the researchers at the CAPS (Fraunhofer Cluster of Excellence Advanced Photon Sources) aim not only to overcome the limitation of ultrafast laser power but also to facilitate the technologies development coupled with the development of process chain from pulse generation to process technology, and real-world applications. Utilizing a technique that primarily compromises a longitudinally pumped rectangular crystal by collimated laser diodes also known as the InnoSlab technique, an ultrafast amplifier has been created that emits compressed pulses that are just above 1 mJ energy at 500 kHz, resulting in an average power of 530 W. The demonstration of the reduction of pulse-duration from 590 to 30 fs with less than 5% of the energy loss has been demonstrated by the researchers who have utilized a gas-filled Herriott-type cell. The aim of the project is the fractioning ultrafast-laser average output powers of 10 – 20 kW.
On the other hand, mature technologies like Ti: sapphire amplifiers have enabled diverse applications in biology, chemistry, material sciences, and physics, because of the rare combination of high peak power and pulse energy as well as short pulse width. One such sophisticated application of the technology is attosecond physics where ultra-broadband pulses at XUV (extreme-ultraviolet) wavelength can be created to produce isolated attosecond-scale pulses by using HHG (high harmonic generation). Ti: sapphire amplifiers are also known to be uniquely suited for terahertz pulse generation that can be utilized in semiconductor materials interrogation. This technology is also used in 2D spectroscopy which comprises the recording of the optical signal as a function of the wavenumber of an ultra-broadband pulse from an OPA, resulting in a unique combination of structural and dynamic data. This facilitates the simultaneous recording of all frequencies. Applications of 2D spectroscopy can be exemplified by the University of California, Berkeley, where it is being used to probe the fundamental physics in perovskite films that has potential applications in next-generation solar cells, by the researcher.
Another example is that of the University of California, San Diego where a unique type of 2D spectroscopy is being used to study a CO2 reduction catalyst expected to be important for artificial photosynthesis. Conversely the Ytterbium (Yb) amplifiers which are comparatively more recent can be utilized as a dopant in gain fibers unlike Ti: sapphire amplifiers. This facilitates the spreading of the thermal load over a longer path with a much larger surface volume/area from the optical pumping. Yb amplifiers are also known to result in less energy wasted. This creates ample room for scaling Yb amplifiers to much higher average powers with a lower cost per watt, compared to Ti: sapphire amplifiers. Further tens of watts can be delivered by it from a footprint which is equivalent to that of the desktop computer. Yb amplifiers’ compact architecture also contributes to the further enhancement of n the overall amplified tunable system.