Mitigation of stimulated Raman scattering by polychromatic lasers with multiple orbital angular momenta

Abstract This work investigates the mitigation of stimulated Raman scattering (SRS) using polychromatic lasers with multiple orbital angular momenta (OAM). The transverse intensity of a Gaussian (GS) beam follows the GS distribution, which only develops a scattered light with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>l</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:math> . In contrast, a Laguerre–Gauss beam with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>l</mml:mi> <mml:mo>=</mml:mo> <mml:mo>+</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> predominantly generates scattered lights with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>l</mml:mi> <mml:mo>=</mml:mo> <mml:mo>+</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>l</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> through SRS, where the daughter waves with different OAM are decoupled. Three dimensional simulation results show that a polychromatic light with multiple OAM can reduce the SRS level and hot electron generation more effectively than a polychromatic light with the same average intensity, due to the mismatch of more daughter waves. Moreover, the introduction of OAM leads to spatiotemporal intensity smoothing, which can further reduce SRS.