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High Harmonic Generation
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
THG finds application in the production of high-power laser sources and in nonlinear microscopy. In high-power laser interaction such as inertial confinement fusion, THG is used to convert the laser light into ultraviolet light. The most common way to generate ultraviolet light is by using an Nd:YAG laser with a wavelength of 1064 nm. The generated light has a wavelength of 355 nm by the third-harmonic process. The schematic diagram for this is shown in Figure 8.6. We can use two LBO (Lithium Triborate: LiB3O5) crystal or LBO and BBO crystals. The first case is the frequency doubler, which gives second-harmonic light. The second case is the sum frequency generation, which gives the third-harmonic light.
Laser Sources Based on Semiconductor Media and Nonlinear Optic Phenomena
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
In principle, nonlinear response to strong laser radiation occurs in nearly all media, and very often is unwanted and uncontrolled. It is nonlinear processes in ordered crystalline media that allow for the real beneficial exploitation of the effects. The most common commercially used frequency conversion crystal materials are β-barium borate (BBO), monopotassium phosphate (KDP), potassium titanyl phosphate (KTP), lithium triborate (LBO), and lithium niobate (LN). If a medium is subjected to a strong electromagnetic (radiation) field, E, its macroscopic polarization, P(t), associated with the nonlinear susceptibility, χ, can be approximated as a power series expansion in terms of the said incident light field:
Light Propagation in Anisotropic Crystals
Published in Glen D. Gillen, Katharina Gillen, Shekhar Guha, Light Propagation in Linear Optical Media, 2017
Glen D. Gillen, Katharina Gillen, Shekhar Guha
In a biaxial crystal, nX, nY, and nZ are all unequal. Some examples of biaxial crystals of importance in nonlinear optics are Lithium Triborate (LiB3O5 or LBO), Potassium Niobate (KNbO3), Potassium Titanyl Phosphate (KTiOPO4 or KTP), Potassium Titanyl Arsenate (KTiOAsO4 or KTA), alpha Iodic acid (α HIO3), etc.
General theory of light propagation and triplet generation for studies of spin dynamics and triplet dynamic nuclear polarisation
Published in Molecular Physics, 2023
Yifan Quan, Nemanja Niketic, Jakob M. Steiner, Tim R. Eichhorn, W. Tom Wenckebach, Patrick Hautle
Two laser systems have been used for photo-excitation. The light of both systems can be coupled with high efficiency into a high numerical aperture multi-mode fibre that transports the light over long distances (up to 20 m), allowing to conveniently separate the laser system from the rest of the apparatus. The fibre is attached at the other end to an optical stage at the bottom of the cryostat, which collimates the unpolarised light in vertical direction onto the sample along the crystal b-axis. In addition, the fluorescence spectrum emitted by the sample is monitored with a photo spectrometer (Avantes AvaSpec-2048) with a wavelength long pass filter to block the transmitted laser light. The line broadening of the fluorescence spectrum by crystal phonons allows a determination of the actual sample temperature during laser irradiation. In the first laser system to be shortly denoted as the 515 nm laser, the output of a diode pumped Yb:YAG disk laser (Jenlas disk IR50) is doubled in a lithium triborate (LBO) non-linear crystal. It operates at a fixed wavelength of 515 nm and is used for photo-excitation into a vibronic excited singlet state. The second system to be shortly denoted as the 556 nm laser consists of a diode pumped Nd:YAG laser (CNI HPL-556-Q 50) using the 1112 nm line that is then frequency doubled with an LBO. It operates at a fixed wavelength of 556 nm and is used for photo-excitation into a lower vibronic excited singlet state than the former. The pulse shapes of these laser systems operating at 1 kHz were measured using a diode detector (Alphalas UPD-300-UP, rise time ps) and shown in Figure 2. The pulses are scaled according to the integrated pulse energy illuminating the sample as measured by a power meter. For the 515 nm laser the pulse energy was 0.9 mJ lasting for about 0.4 μs with an estimated beam spot at the sample position of A = 36 mm. The pulse energy of the 556 nm laser was determined to be about 3.2 mJ over roughly 3.2 μ s with a slightly larger beam waist and a corresponding estimated spot size of A = 60 mm.