China
Africa
Explore chapters and articles related to this topic
Fibre Lasers
Published in Yu. N. Kulchin, Modern Optics and Photonics of Nano and Microsystems, 2018
The generation of laser radiation in the form of short pulses is an extremely important problem. The significance of this problem is due to two reasons. First, the pulse duration determines the time interval for the interaction of laser radiation with the medium, which is extremely important in the study of fast processes. Secondly, the energy of laser radiation, being concentrated in a short laser pulse, causes a large pulse power and high intensity of the electromagnetic field of its light wave. At present, lasers, including fibre ones, are capable of generating ultrashort pulses with a duration of only a few femtoseconds. During this time, the pulse can pass a very short distance of several micrometers in length. But even small changes in its energy during this time can lead to significant changes in the power and strength of the pulse field.
Introduction to lasers and optical amplifiers
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
William S. Wong, Chien-Jen Chen, Yan Sun
Two common operation modes of solid-state lasers are the CW mode and the pulsed mode. In the CW operation, solid-state lasers generate monochromatic, highly coherent, and high-intensity light. A widely used mechanism to produce pulses in solid-state and other lasers is the Q-switching method [19,20]. By changing the cavity Q mechanically, electrically, or optically, the stored energy in the laser gain medium can be released with a short time period to generate a pulse (in the order of nanoseconds) with a high peak intensity [10,11,21] (see also Section 6.1.3 for a description of Q switching). Short pulses provide advantages in manufacturing and in medical applications such as micromachining/microfabrication and laser ablation since the size of the heat-affected zone can be reduced. As the demand on shorter pulse duration and higher peak intensity increases, different techniques such as mode-locking techniques [22,23] and chirped pulse amplification (CPA) techniques [24] were applied on solid-state lasers to generate ultrashort pulses (down to sub-picosecond ranges). In fact, solid-state lasers, due to their wide bandwidth and excellent optical properties, generated many of the record-breaking short pulses. These ultrashort pulses are suitable for applications in the study of ultrafast phenomena, spectroscopy, and telecommunication.
Mode-locking Techniques and Principles
Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
In most cases, ultrashort light pulses are generated with mode-locking techniques, where one obtains regular trains of usually coherent ultrashort pulses with relatively low energy, rather than single pulses. Pulse repetition rates are typically in the region of many megahertz or even gigahertz. There are various techniques for picking a single pulse out of such a pulse train (or making a pulse train with much lower pulse repetition rate), and then amplifying such pulses to much higher energy levels. That area, however, goes beyond the scope of this chapter.
Temporal contrast improvement by a self-diffraction process for a petawatt-class Ti:sapphire laser
Published in Journal of Modern Optics, 2020
Na Xie, Xiaojun Huang, Xiaodong Wang, Kainan Zhou, Li Sun, Yi Guo, Jingqin Su
Ultraintense and ultrashort pulse lasers can create extreme conditions in laboratories and have applications in various research fields. With the development of ultraintense and ultrashort laser pulses, laser intensity as high as 1022 W/cm2 [1] and petawatt-class peak power have been achieved [2–8]. The laser temporal contrast, defined as the ratio of the peak intensity of the main pulse to that of the prepulse, must be high for plasma-creating laser pulses in laser-matter interactions. If the prepulse intensity is above the ionization threshold (∼1011 W/cm2 for most materials), preplasma is generated by the prepulse before the main pulse reaches the target and affects the interaction between the main pulse and target. With the increase of peak power of ultraintense lasers, the requirement for the temporal contrast becomes higher. The temporal contrast is generally limited by two major types of prepulses: one is the amplified spontaneous emission (ASE) background in chirped pulse amplification (CPA) or the parametric fluorescence in optical parametric chirped pulse amplification (OPCPA), and the other is satellite pulses before the main pulse. For lasers aimed at petawatt-class, tens-of-petawatt, or higher peak power, techniques need be employed to generate laser pulses with ultrahigh temporal contrast.
Impact of the Oil Temperature on the Frictional Behavior of Laser-Structured Surfaces
Published in Tribology Transactions, 2019
Andreas Janssen, Mohammad Dadgar, Wolfgang Wietheger
Microstructures can be manufactured on surfaces by various methods. LST or laser structuring is an accurate method for microstructuring that is based on ablation of material by means of laser radiation. Duration of the pulses is important in laser materials processing. The laser used in this work is an ultrashort pulse laser and delivers pulses with a pulse duration of only a few picoseconds. The ultrashort pulse laser process provides a high degree of structural flexibility and precision in terms of manufacturing technology because no melt and heat-affected zone is generated. Although this view is physically not correct, it practically can be assumed as shown in Weikert (15). This enables the surface structures to be produced with less construction time and cost compared to alternative manufacturing processes. Additionally, postprocessing is not necessary when using an ultrashort pulse laser. The characteristics and phenomenology of ultrashort pulse laser ablation and its separation from other forms of laser ablation have been discussed in the literature (Momma, et al. (16); Janssen (17); Nolte (18)).
Chirped bright and double-kinked quasi-solitons in optical metamaterials with self-steepening nonlinearity
Published in Journal of Modern Optics, 2019
Abdel Kader Daoui, Houria Triki, Anjan Biswas, Qin Zhou, Seithuti P. Moshokoa, Milivoj Belic
To improve the capacity of high-bit-rate transmission systems, it is essential to use ultrashort pulses whose durations are shorter than 100 fs (4). In this case, the nonlinear susceptibility will produce higher order nonlinear effects like the Kerr dispersion (i.e. self-steepening), the delayed nonlinear response and even the third-order dispersion.