Abstract

An optical vortex, e.g., Laguerre-Gaussian mode, has been widely applied to a variety of research activities, such as super resolution microscopes, spatial division multiplexing telecommunications, and microfabrications, because it carries an annular spatial form and orbital angular momentum characterized by lℏ per photon (where l is an integer defined as the topological charge) associated with its helical wavefront [1]. Broadband tunable optical vortex laser sources, whose lasing wavelength matches the absorption bands of the materials being studied, are highly required in the aforementioned applications. In fact, we have successfully demonstrated a tunable optical vortex laser source by employing an optical vortex pumped LiB₃O₅ (LBO, 30 mm long) optical parametric oscillator. However, this system was pumped by a 532nm green laser with a pulse duration of 25 ns, and thus, its pulse energy was limited to be >0.2 mJ within a wavelength range of 735-1903 nm owing to a relatively low parametric gain; it also had a ‘frequency gap’ within a wavelength region of 990-1130 nm (the vortex mode generation was inhibited within this wavelength region) arising from a double resonance of the signal and idler outputs [2, 3].

© 2017 IEEE