Converting Gaussian to line beams with high efficiency by flat liquid crystal optical elements

Line-shaped laser beams are desired for applications ranging from ultrafast laser processing to metrology. Here we demonstrate that line-shaped laser beams with diffraction-limited line widths can be generated from Gaussian beams with high efficiency by using flat liquid crystal optical elements. The liquid crystal optical elements are designed based on the Pancharatnam-Berry (PB) geometric phase acquired by light passing through a half waveplate and fabricated by using a high-resolution molecular orientation photopatterning technique. We show that these liquid crystal PB optical elements can achieve a diffraction efficiency over 99%, yielding no zero-order light leakage. We further demonstrate beam shaping devices for converting Gaussian beams into crosshair-shaped beams. The design and fabrication methods presented in this paper are general and can be extended to meet other complex beam shaping needs.