Thus, the first-Stokes beam should lase at the first-order optical vortex mode. If the first-Stokes beam was l = 2, overlap ratio would be 78.2%. The overlap ratio between the pump and the first-Stokes of l = 1 was 94.6% on the calculation. In this experimental setup, the pump beam radius was observed to be 250um. The cavity mode of the Stokes beam could be calculated by using the ABCD matrix law. We theoretically analyzed the reason why the topological charge of 1 was generated for the first- and second-Stokes light by estimating the spatial overlap ratio between the pump and the Stokes output, because the Raman gain can be defined by the spatial intensity overlap between the pump and the Stokes light in Raman-active media. This indicates that the first- and the second-Stokes output beams had a topological charge of 1. A forked fringe having 2 legs was measured in both Stokes emissions. The topological charge of the first- and the second-Stokes waves were verified by the self-reference interferogram pattern. A lens with a focal length of 500 mm was inserted into the resonator to stabilize the cavity. M2 was the output coupler, which was a flat mirror with reflectivity of 99.1% at 532-nm, 38.3% at 563-nm, 55.7% at 599-nm, and 13.22% at 639-nm. A front mirror (M1) was flat and had a high transmissibility (T > 90%) at 532 nm and a high reflectivity (R > 99%) in the range of 560-660 nm. Because the Raman shift of a Ba(NO3)2 crystal is 1046 cm−1, the wavelengths of the Stokes light could be estimated to be 563 (first-Stokes), 599 (second-Stokes), and 639 nm (third-Stokes) from 532 nm as a fundamental wavelength. The 532-nm optical vortex beam was focused by a lens with a focal length of 500-mm, and inputted to a Raman-active medium that was a 60-mm long Ba(NO3)2 crystal. The 532-nm Gaussian beam was converted to an optical vortex beam with a topological charge of l = 2 through a spiral phase plate. A 532-nm pulsed laser was used as a pump beam. Interferogram patterns of the first- and second-Stokes waves were observed as optical vortices. The first- and second Stokes emissions that had an annular spatial profile were experimentally generated. In the present work, we pumped a Raman laser cavity by a 532-nm optical vortex with a topological charge of l = 2. However, to the best of our knowledge, the generation of a SRS vortex beam pumped by an optical vortex beam has not been achieved. Furthermore, various SRS vortex beams with a different order can be obtained by converting higher-order Herimite-Gaussian modes in the Stokes field via a π/2 cylindrical-lens mode converter. It has been demonstrated by using a cavity mirror that has a defect spot. An optical vortex beam at the first-Stokes wavelength has been directly created in a Nd:GdVO4 Raman laser. In addition to these processes, Stimulated Raman scattering (SRS) is also a well-known method for frequency conversion. Until now, frequency conversion of optical vortex beams has been demonstrated through various second-order nonlinear optical processes, for example second-harmonic generation, sum-frequency generation, and optical parametric oscillation. It is important that the wavelengths of solid-state lasers can be extended to new spectral lines for a number of useful applications. Recently, optical vortices have attracted intense attention, and have been widely employed for various applications, such as quantum entanglement, super-resolution microscopes, optical tweezers, trapping and guiding of cold atoms, optical testing, and material processing. Orbital angular momentum is characterized by lħ, where l is an integer, and is the so-called topological charge. This tax does not apply to children under 12 years of age.Optical vortices are beams that carry orbital angular momentum and exhibit an annular spatial profile. A tax is imposed by the city: From 1 October - 30 November, EUR 0.54 per person, per night for adults EUR 0.27 per night for guests aged 12-17 years old.This tax does not apply to children under 12 years of age. A tax is imposed by the city: From 1 June - 30 September, EUR 0.67 per person, per night for adults EUR 0.34 per night for guests aged 12-17 years old.A tax is imposed by the city: From 1 March - 31 May, EUR 0.54 per person, per night for adults EUR 0.27 per night for guests aged 12-17 years old.
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