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Q-switched Fiber Laser
Published in Johan Meyer, Justice Sompo, Suné von Solms, Fiber Lasers, 2022
Johan Meyer, Justice Sompo, Sune von Solms
Most recently, nanostructured material showed saturable absorption properties. This was first reported in 2002 on carbon nanotubes (Sakakibara et al. 2003; Y.-C. Chen et al. 2002) (single-walled carbon nanotubes SWNT). These nanotubes present the advantage of being capable of being used at different wavelength depending on their diameters. Also, before 2010, graphene showed absorption properties at large band (Dawlaty et al. 2008) and becomes rapidly used as a saturable absorber (Kim et al. 2015; Z. Sun et al. 2010). These absorption properties are independent of frequency and only depend on the fine-structure constant of the graphene. This absorption can be saturated under strong optical power density by a Pauli blocking effect preventing multiplicity of electrons states. Similar properties have been demonstrated on graphene oxide (Liu et al. 2013; Wang et al. 2011) and reduced graphene oxide (Sobon et al. 2012; He et al. 2012) at different wavelengths and in different configurations like end-butting (He et al. 2012), with an insulator clamped between two fibers terminated by connectors (Y Chen et al. 2013), another insulator (Y.-J. Sun et al. 2015), the graphene deposited on a tapered fiber (Liu et al. 2013), insulator put in contact with a side polished fiber (Lee et al. 2015), and finally, graphene deposited by a vapour deposition technique on a planar waveguide of Yb: KYW (Kim et al. 2015).
Techniques of Measurements of Linear and Nonlinear Optical Properties of Layered Nanomaterials for Applications in Photonics
Published in Tarun Kumar Gangopadhyay, Pathik Kumbhakar, Mrinal Kanti Mandal, Photonics and Fiber Optics, 2019
Pathik Kumbhakar, S. Biswas, A. K. Kole
Nanosecond lasers are now being widely used in many areas of science and technology. As all photonic sensors and devices, including the eye, have a specific intensity level above which damage occurs, it is becoming necessary to protect these expensive instruments from laser related damages [129,130]. In many optical systems such as telescopes, gun sights, night vision, etc., direct viewing is essential, so one of the most important applications for OL is eye and sensor protection in optical systems. Moreover, the use of OL before the sensors enhances the capability of operating in harsh conditions. On the other hand, in photothermal spectroscopy [131], OL has interesting applications. Here, OL is used to reduce the large background signal and hence enhances the fast transient signals of interest. However, such application requires an OL with very slow response time. OL is also used in various laser pulse reshaping applications [132]. If the materials show saturable absorption, then it can be used for pulse compression, Q switching and mode locking purposes [133]. On the other hand, materials with reverse saturable absorption find passive mode locking application [134].
Basic Photon and Quantum Optics
Published in Daniel Malacara-Hernández, Brian J. Thompson, Fundamentals and Basic Optical Instruments, 2017
Passive mode-locked continuous lasers involve a very different physics of pulse formation from that of giant pulse lasers. Random noise fluctuations due to longitudinal mode beating occur in the laser until one of the noise spikes is large enough to saturate the absorber. This pulse sees an increased transmission through the absorber jet due to this saturation and then encounters the gain jet. Here, it saturates the gain slightly and reduces the gain for the noise spikes that follow. This selection process continues until only one pulse survives. The pulse then shortens further due to the same saturable effects. Saturable absorption selectively removes energy from the leading edge of the pulse, while saturable gain steepens the trailing edge. The pulse continues to shorten until a pulse-broadening effect, such as dispersion, can balance it [85].
Doubly Q-switched tape casting YAG/Nd:YAG/YAG ceramic laser
Published in Journal of Modern Optics, 2018
Yufei Ma, Ying He, Zhenfang Peng, Renpeng Yan, Xudong Li, Xin Yu, Yao Tong, Lin Ge, Jiang Li, Frank K. Tittel
The pulse width at a repetition rate of 10 and 20 kHz as a function of absorbed pump power is shown in Figure 4. For the doubly Q-switched laser using both active and passive Q-switches in the cavity simultaneously, the output characteristics such as the pulse repetition rate and pulse width were mainly controlled by the active Q-switch. The passive Q-switch saturable absorber is only used to generate short laser pulses as a result of normal saturable absorption characteristics [18]. From Figure 4, we can see that the pulse width of doubly Q-switched lasers was narrower than that of purely AO Q-switched lasers, especially for low absorbed pump power levels. For example, when the absorbed pump power was 3.3 W and the repetition rate was 20 kHz, the pulse width was 46.7 and 42 ns for AO Q-switched and doubly Q-switched lasers, respectively.
Intensity-dependent optical nonlinearities of composite materials made of ionic liquid crystal glass and bimetallic nanoparticles
Published in Liquid Crystals, 2023
V. Rudenko, A. Tolochko, D. Zhulai, S. Bugaychuk, G. Klimusheva, G. Yaremchuk, T. Mirnaya, Yuriy Garbovskiy
The results of the open aperture Z-scan experiment carried out for the CdC8+Ag/Au (1:1) sample (Figure 2) demonstrate the presence of two nonlinear absorption mechanisms. At lower input intensities (I0 = 2.21–8.76 MW/cm2), a competition between the saturable absorption (SA) and reverse saturable absorption (RSA) takes place. At higher values of intensity (I0 = 9.44 MW/cm2), the SA process completely dominates. And at even higher intensity, the nonlinearity of the absorption decreases, which can be a consequence of some degradation of the sample. The values of the calculated nonlinear optical parameters for the CdC8+Ag/Au (1:1) sample are listed in Table 2.