No abstract

Flattop beams are in high demand for a variety of applications, including uniform surface treatment, interference laser processing, repairing and skin therapy. In this experiment, we optimized the direction of phase grating to spatially separate the beam into extracted and residual components in the Fourier plane, and spatially filtered the components to form a square or hexagonal flattop beam with no wave-like structure inside and high edge steepness.

A chiral structure is formed by the optical radiation force induced by a circularly polarized light that has spin angular momentum; chiral structures are expected to be used for light control devices and molecular chirality discrimination devices. In this paper, we clarify the relationship between the differences in the distributions of the optical radiation force and the possibility of formation of chiral structures. We first simulate the optical radiation force distribution in the case of a Gaussian beam that successfully forms a chiral structure. Given a vector $${\varvec{r}}$$ r with a centre of the light spot $$\mathrm{O}$$ O and polar coordinates $$R(\left|{\varvec{r}}\right|, \theta )$$ R ( r , θ ) , and an optical radiation force vector $${\varvec{F}}$$ F at $$R$$ R , the angle $${\theta }^{\mathrm{^{\prime}}}=\mathrm{\angle }({\varvec{r}}, {\varvec{F}})$$ θ ′ = ∠ ( r , F ) and $$\left|{\varvec{F}}\right|$$ F must be constant with respect to the declination angle $$\theta$$ θ for a chiral structure to form. These conditions are fulfilled in the case of a 6-beam interference pattern, but not in the case of a 4-beam interference pattern, which is consistent with the result that no chiral structure is formed in the latter case. The equations derived for simulation of optical radiation force distribution can be used for any optical intensity distribution, and will be of great help in the research of any dielectrics deformation.