Comprehensive investigation on producing high-power orbital angular momentum beams by coherent combining technology

Abstract

High-power orbital angular momentum (OAM) beams have distinct advantages in improving capacity and data receiving for free-space optical communication systems at long distances. Utilizing the coherent combination of a beam array technique and helical phase approximation by a piston phase array, we have proposed a generating system for a novel high-power beam carrying OAM, which could overcome the power limitations of a common vortex phase modulator and a single beam. The characteristics of this generating method and the orthogonality of the generated OAM beams with different eigenstates have been theoretically analyzed and verified. Also a high-power OAM beam produced by coherent beam combination (CBC) of a six-element hexagonal fiber amplifier array has been experimentally implemented. Results show that the CBC technique utilized to control the piston phase differences among the array beams has a high efficiency of 96.3%. On the premise of CBC, we have obtained novel vortex beams carrying OAM of $\pm 1$ by applying an additional piston phase array modulation on the corresponding beam array. The experimental results agree approximately with the theoretical analysis. This work could be beneficial to areas that need high-power OAM beams, such as ultra-long distance free-space optical communications, biomedical treatments, and powerful trapping and manipulation under deep potential wells.

Reflection of vortex beam from relativistic flying mirror

“…In this study, inspired by the flying mirror and the generation of relativistic vortex beams 23 – 29 with a large OAM, we re-examined the behavior of an intense vortex beam reflected by a relativistic flying mirror in the case of oblique incidence. In addition to the frequency and emission angle of the reflected beam, the OAM also changes.…”

Reconfigurable structured light generation in a multicore fibre amplifier

“…In this approach, the active beam control element(s) can be positioned before the amplifier(s) (where the power levels are relatively modest) to provide the control needed for active phase locking between the multiple output beams at the (higher power) system output. Such master oscillator power amplifier (MOPA) based configurations might provide significant scope for power scaling of beam-shaped fibre lasers 41 . In addition, CBC from MCF amplifier/lasers has previously been successfully demonstrated as an effective way for power scaling of simple Gaussian beams 42 – 44 .…”

“…Alternatively, adaptive spatial mode shaping has been achieved in large mode area fibre amplifiers by employing fibre-based photonic lanterns and deformable mirrors as beam shaping elements for high power operation, enabling efficient generation of scalar linearly polarized (LP) modes [30][31][32][33][34] . Similarly, coherent beam combination (CBC) using signals from multiple (independent) parallel laser sources has recently been proposed as a promising way to form exotic beams that avoids the low damage threshold problem of such flexible and scalable beam shaping elements and has been investigated theoretically and experimentally [35][36][37][38][39][40][41] . In this approach, the active beam control element(s) can be positioned before the amplifier(s) (where the power levels are relatively modest) to provide the control needed for active phase locking between the multiple output beams at the (higher power) system output.…”

Deep-learning-based phase control method for tiled aperture coherent beam combining systems

“…Tiled aperture coherent combining has advantages in the development of combined numbers, and has achieved remarkable results in the past [9, 10] . It also shows great potential in new frontiers such as high-power structured light generation [11] . In high-power tiled aperture CBC systems, especially during operation with serious thermal and experimental fluctuations, dynamic phase noise always occurs and affects the performance of the combined beam.…”