Method of controlling focal point position through phase plate

Abstract

The invention relates to a method of controlling focal point position through a phase plate, wherein any light beam at polarization state is converted into a parallel incident light beam through a single-objective lens focusing optical system, the incident light beam is subjected to wavefront phase modulation by a special phase plate with phases distributed along poloidal cosine, and the incident light beam is focused by an objective lens after passing a high pass filter, and the facula of the focused incident light beam can freely move on a focal plane by adjusting two parameters of the phase plate. The incident light beam can be any light beam at polarization state, and the method is effective to objective lenses with any apertures. Besides, the method avoids the adoption of a 4pi double-objective lens focusing optical system, and only the single-objective lens focusing optical system is used for realizing the free movement of the focal point on the focal plane, thereby greatly improving the flexibility and maneuverability of experiment and application.

Description

technical field [0001] The invention relates to an applied optical technology, in particular to a method for controlling the focus position by using a phase plate. Background technique [0002] The light intensity distribution in the focal area has been a research hotspot because its nature greatly affects the performance of the optical system. With the increase of the numerical aperture of the objective lens, due to the increasing influence of the vector characteristics of the beam, it presents special properties in the focal area, and has been widely used in optical information storage, optical microscopy, lithography, laser processing, and optical micromanipulation. , super-resolution, light-matter interaction and other optical systems. [0003] In 1986, Ashkin experimentally used a linearly polarized Gaussian beam to control particles after being focused by a high numerical aperture objective lens, and proposed the concept of optical tweezers. Since then, researchers h...

AI Technical Summary

Problems solved by technology

However, the above two methods have three shortcomings: first, this method only focuses on the spot after the incident light is radially polarized, and does not work for other polarization beams; second, in the 4pi optical system The movement of the spot increases the difficulty of adjusting the optical path, reduces the flexibility of the experiment, and limits the scope of application of the method; third, the position of the spot cannot be controlled simply by changing a certain parameter of the pupil filter. Recalculate the transmittance of the pupil filter, which is not conducive to continuous control of the focus point

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