Transverse mode locking of different frequency-degenerate families based on annular beam pumping

Abstract

Optical vortex arrays have been achieved in an end-pumped N d : Y V O 4 laser pumped by an annular beam. Spontaneous transverse mode locking of Laguerre–Gaussian modes in different frequency-degenerate families has been obtained by merely adjusting the pump power. A maximum output power of 0.88 W and optical conversion efficiency of 13.6% are achieved for optical vortex arrays. Optical vortex arrays formed in different frequency-degenerate families of Laguerre–Gaussian modes can be actively controlled by the position of the axicon. This work provides a way to research transverse mode locking of Laguerre–Gaussian modes in different frequency-degenerate families based on annular beam pumping.

Generating Optical Vortex Array Laser Beams of Superimposing Hermite–Gaussian Beams with a Dual–Phase Modulation Digital Laser System

“…Optical vortices can also be generated directly in the laser system through in-cavity methods. However, compared to a single vortex beam, the laser configuration for generating vortex arrays is rare, including the superimposing of frequency-degenerate cavity modes [45][46][47][48][49][50][51][52], metasurfaces [53], and multiple microring lasers [54,55]. Although metasurfaces and multiple microring lasers can form many discrete singularities, and their topological charge can be tuned at will, these approaches require the manufacturing of optical elements through nano-technology.…”

“…Although metasurfaces and multiple microring lasers can form many discrete singularities, and their topological charge can be tuned at will, these approaches require the manufacturing of optical elements through nano-technology. In traditional laser systems, by utilizing a nonlinear process in the gain medium, the transverse mode locking of the same or different frequency-degenerated cavity modes such as Hermite-Gaussian (HG), Laguerre-Gaussian (LG) or Ince-Gaussian (IG) modes with π/2 phase shift forms an array of vortices with topological charge 1 in laser resonator [45][46][47][48][49][50][51][52]. These laser cavities with different schemes, such as off-axis pumping [45], shaped pumping [48][49][50], cavity elements misalignment [51], or cavity length [52] to select multi-modes simultaneously lasing, leading the change in the intensity distribution of the output vortex array.…”

“…In traditional laser systems, by utilizing a nonlinear process in the gain medium, the transverse mode locking of the same or different frequency-degenerated cavity modes such as Hermite-Gaussian (HG), Laguerre-Gaussian (LG) or Ince-Gaussian (IG) modes with π/2 phase shift forms an array of vortices with topological charge 1 in laser resonator [45][46][47][48][49][50][51][52]. These laser cavities with different schemes, such as off-axis pumping [45], shaped pumping [48][49][50], cavity elements misalignment [51], or cavity length [52] to select multi-modes simultaneously lasing, leading the change in the intensity distribution of the output vortex array. However, these approaches require mechanical adjustments, potentially limiting applications and necessitating fast and flexible control.…”

Conversion of Mode-Locked States within an Optical Cavity

“…Locking longitudinal modes of an optical resonator results in the generation of short laser pulses, whereas, locking its transverse modes results in a beam rapidly scanning the transverse plane. Common schemes for generating such transverse mode-locked beams involve off-axis pumping of a gain medium inside a resonator [1][2][3]. Which modes, and to what extent, are involved in the locking process has been analyzed [1] and controlled by simple means, e.g., by limiting the highest mode order with a slit [1], transversely displacing the pump spot [2] or varying the pump power [3].…”

“…Common schemes for generating such transverse mode-locked beams involve off-axis pumping of a gain medium inside a resonator [1][2][3]. Which modes, and to what extent, are involved in the locking process has been analyzed [1] and controlled by simple means, e.g., by limiting the highest mode order with a slit [1], transversely displacing the pump spot [2] or varying the pump power [3]. Here, we present the generation of transverse mode-locked beams with improved control over the modal amplitudes by longitudinal to transversal mode conversion.…”