  Laser beams carrying orbital angular momentum (OAM) provide an additional
degree of freedom and have found wide applications ranging from optical
communications and optical manipulation to quantum information. The efficient
generation and operation of ultra-intense OAM beams is a big challenge that has
to be met, currently setting a limit to the potential applications of
ultra-intense OAM beams in high-energy-density physics studies. Here, we
theoretically and numerically demonstrate for the first time that a pump beam
with a new OAM state is generated by coupling of the seed pulse with OAM
Langmuir waves arising from both backward and forward stimulated Raman
scattering mechanisms. Advantage is taken of the high energy transfer
efficiency from pump to amplified seed beams by operating in the non-linear
regime, as this significantly reduces the size of amplification system and
promotes access to high-intensity OAM laser beams for scientific and industrial
applications.
