Pure transverse spin perpendicular to wave propagation in multiple plane waves

Transverse spin, an intriguing aspect of spin angular momentum, has gained considerable attention in recent years. However, transverse spin is typically accompanied by longitudinal spin in electromagnetic fields. This work aims to generate a series of optical fields with pure transverse spin. We present analytical and numerical demonstrations showing that when multiple linearly polarized plane waves interfere in the same plane, the longitudinal spin vanishes, leaving only the transverse spin, which is perpendicular to both the wave propagation and the inhomogeneous field plane. This transverse spin is demonstrated to be related to the imaginary part of the complex Poynting momentum. Furthermore, we show that pure transverse spin is also observed in the interference of multiple Gaussian beams, offering practical applications in optical field preparation and enhancing our understanding of spin-related physics.