Direct generation of an optical vortex beam in a single-frequency Nd:YVO_4 laser

Abstract

A simple method for generating a Laguerre-Gaussian (LG) mode optical vortex beam with well-determined handedness in a single-frequency solid state laser end-pumped by a ring-shaped pump beam is reported. After investigating the intensity profile and the wavefront helicity of each longitudinal mode output to understand generation of the LG mode in a Nd:YVO4 laser resonator, selection of the wavefront handedness has been achieved simply by inserting and tilting an etalon in the resonator, which breaks the propagation symmetry of the Poynting vectors with opposite helicity. Simple calculation and the experimental results are discussed for supporting this selection mechanism.

Controlled generation of higher-order Poincaré sphere beams from a laser

“…Such beams have found many applications in diverse fields such as optical manipulation [38,39], and optical free space communication [40]. While many attempts have been made to generate these modes inside a laser cavity [41][42][43][44][45] the degeneracy in the handedness of the azimuthal modes means that standard laser cavities cannot distinguish them: the spatial intensity distribution of laser modes with opposite azimuthal handedness (such as + and − ) are identical, they have identical radii of curvature on the wavefront and identical Gouy phase shifts. Consequently their intra-cavity losses are identical and thus very often uncontrolled helicities, coherent, or incoherent superpositions of modes with opposite handedness are produced [45].…”

Controlling light’s helicity at the source: orbital angular momentum states from lasers

“…The creation of vortex beams has now been extended from free-running, continuous wave lasers to pulsed lasers, with Q-switched [36,37] and mode locked [38] lasers already demonstrated, as well as to single-frequency lasers [39]. In the case of the latter, a simple method to control the helicity of the light was introduced in the form of a tilted etalon, appropriately aligned to introduce high loss for one handedness and low loss for the other by noting that the skew angle differs for the two due to the twist on the wavefront (figure 5).…”

“…(Online version in colour. )˜0 (a) Schematic of the concept to use the Poynting vector skew angle as a means to select modes via reflection losses with a tilted etalon[39]. With this approach, the handedness of the output could be controlled, shown here as spiral interference images for (b) = +1, (c) = −1, (d) = −2 and (e) = +2.…”

Generation and Thermal Properties of a Dual-Transverse-Mode With Dual-Polarization and Dual-Frequency by a Dual-Medium Microchip Laser

“…Using a hollow pump beam to achieve the DHB generation in microchip cavity was studied [13], [14], however, to obtain the hollow pump beam is also not easy. Recently, direct DHB generations by laser cavity without special pump design are achieved [15]- [17], while the DHB is not stable enough or the cavity design is quite complex. When the DHB is designed to be generated with DMML, the properties of the output beam are dual-transverse-mode, dual polarization and dual-frequency, which is quite special compared with the ordinary laser beams.…”