Optically induced angular alignment of birefringent micro-objects by linear polarization

Fluorinated polyimide micro-objects having large birefringence of Δn=−0.13 (refractive index n1=1.62, n2=1.49 for the wavelength λ=1.06 μm), which were fabricated by reactive ion etching and suspended in water (n=1.33), were trapped and angularly aligned in a single Gaussian laser beam (λ=1.06 μm, power P>3 μW). The optically induced angular alignment effect is caused by the transfer of spin angular momentum due to the interaction between their birefringence and the linearly polarized light.