Influence of laser amplitude and beam waist radius on attosecond pulse trains in a cross-collision tightly focused circularly polarized field

Radiation from nonlinear Thomson scattering (RNTS) has emerged as an important mechanism for generating highly directional and broadband attosecond emission. However, the influence of laser-field structure on electron dynamics and the resulting radiation characteristics has not yet been systematically explored. In this work, we employ a tightly focused circularly polarized Gaussian laser model that incorporates high-order field components to investigate the trajectory evolution and radiation features of high-energy electrons in a cross-collision geometry under the coupled variation of laser amplitude <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:msub> <mml:mi>a</mml:mi> <mml:mrow> <mml:mn>0</mml:mn> <mml:mtext> </mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> (normalized laser amplitude <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:msub> <mml:mi>a</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:math> )and beam waist radius <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"> <mml:mrow> <mml:msub> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mrow> <mml:mfenced open="(" close=")" separators="|"> <mml:mrow> <mml:mtext>normalized beam waist </mml:mtext> <mml:msub> <mml:mi mathvariant="normal">b</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>=</mml:mo> <mml:msub> <mml:mi mathvariant="normal">ω</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi mathvariant="normal">λ</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:mfenced> </mml:mrow> </mml:mrow> </mml:math> . The results show that <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"> <mml:mrow> <mml:msub> <mml:mi>a</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:math> predominantly governs longitudinal acceleration and spectral broadening, while <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"> <mml:mrow> <mml:msub> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:math> modulates the interaction length and strongly affects radiation directivity. Together, these parameters determine the spatial peak position, beam collimation, and structural features of the emitted attosecond pulses. This study reveals the regulatory role of laser-field structure in RNTS and provides theoretical guidance for optimizing high-directionality and broadband attosecond light sources.