Laguerre-Gaussian modes selection in diode-pumped solid-state lasers

Abstract

Over the last twenty years, diode pumping of solid-state lasers has opened new prospects for the mode control and formation of Laguerre-Gaussian (LG) beams, enabling a large variety of applications. Experiments on scalar and vector LG modes selection in Nd 3þ -and Yb 3þ -doped ceramics and crystal lasers carried out at the Institute for Laser Science, Tokyo are reviewed. Selection of LG modes from low to high orders using intra-cavity elements, polarization-selective mirrors, or shaping the pump beam profile, is considered. Illustrations of record-high-order LG hollow modes, multiring modes with highly directional propagation properties, characteristics of cw and pulsed lasers with radially or azimuthally polarized beams of high polarization purity are presented. General solutions of the wave equation for the axi-symmetric electric field, which describe LG beams of various profiles, are proposed for data analysis. In parallel, a short review on LG modes selection studies carried out at other laboratories is given.

Role of cavity degeneracy for high-order mode excitation in end-pumped solid-state lasers

“…Hence many experimental works aiming at the excitation of high-order Laguerre-Gaussian (LG) modes in diodepumped solid-state lasers have already been realized. The first observation of high-order LG mode excitation in an end-pumped laser was done by Flood et al [7], and a comprehensive review of subsequent reports on LG mode excitation is given in [8]. More recently, Ince-Gaussian (IG) solutions to the paraxial wave equation [9] have attracted considerable attention.…”

Coupled counterrotating polariton condensates in optically defined annular potentials

“…In lasing systems with an imposed circular symmetry, an annulus of lasing spots can sometimes form along the perimeter of the structure (1)(2)(3)(4)(5)(6). Such transverse modes are often referred to as "petal states" (1) or "daisy modes" (2) and are interpreted as annular standing waves (3), whispering gallery modes (4), or coherent superpositions of Laguerre-Gauss (LG) modes with zero radial index (5,6).…”

“…Their circular symmetry makes them interesting for numerous applications such as free space communication or fiber coupling (7), and their LG-type structure suggests implementations using the orbital angular momentum of light (8), such as optical trapping (9) or quantum information processing (10). Petal states have been reported for various conventional lasing systems, including electrically and optically pumped vertical cavity surface-emitting lasers (VCSELs) (2,4), as well as microchip (6) and rod lasers (1).…”

“…Such transverse modes are often referred to as "petal states" (1) or "daisy modes" (2) and are interpreted as annular standing waves (3), whispering gallery modes (4), or coherent superpositions of Laguerre-Gauss (LG) modes with zero radial index (5,6). Their circular symmetry makes them interesting for numerous applications such as free space communication or fiber coupling (7), and their LG-type structure suggests implementations using the orbital angular momentum of light (8), such as optical trapping (9) or quantum information processing (10).…”

Vortex Laser based on III-V semiconductor metasurface: direct generation of coherent Laguerre-Gauss modes carrying controlled orbital angular momentum

“…On the other side, generation of OAM inside a laser cavity is complex and comes with both technical and fundamental challenges. Nevertheless, it is a very promising approach to obtain high power, highly pure, coherent Laguerre-Gauss vortex mode and has been investigated through several experimental works242526272829303132. Yet, a fundamental limitation for OAM handedness control arises from orbital degeneracy and symmetry of wave-functions with opposite orbital number ± l as in the hydrogen atom: in conventional optical cavities, the obtained OAM handedness is very often not controlled in a deterministic manner.…”