Self-aligned dual-beam superresolution laser direct writing with a polarization-engineered depletion beam

A fiber-based, self-aligned dual-beam laser direct writing system with a polarization-engineered depletion beam is designed, constructed, and tested. This system employs a vortex fiber to generate a donut-shaped, cylindrically polarized depletion beam while simultaneously allowing the fundamental mode excitation beam to pass through. This results in a co-axially self-aligned dual-beam source, enhancing stability and mitigating assembly complexities. The size of the central dark spot of the focused cylindrical vector depletion beam can be easily adjusted using a simple polarization rotation device. With a depletion wavelength of 532 nm and an excitation wavelength of 800 nm, the dual-beam laser direct writing system has demonstrated a single linewidth of 63 nm and a minimum line spacing of 173 nm. Further optimization of this system may pave the way for practical superresolution photolithography that surpasses the diffraction limit.