Optical Trapping by a Light Intensity Gradient

Why a tightly focused laser beam creates a stable trap that pulls a small object toward the point of highest light intensity, holding it there without any physical contact.

References

• Ashkin, A., Dziedzic, J.M., Bjorkholm, J.E., Chu, S. "Observation of a Single-Beam Gradient Optical Trap." Optics Letters 11, no. 5 (1986): 288–290.