Superdiffraction phase modulation film for three-dimensional compression of light spot and its processing method

Abstract

The invention provides a super-resolution phase modulation plate for 3D light spot compression and a processing method. The center of the modulation plate is a convex truncated cone or a circular flat-bottomed recess which are arranged at intervals; surfaces of the convex truncated cone, the circular flat-bottomed recess and a circular boss are in the same plane, and depths of various circular flat-bottomed recesses are identical. Structural parameters of the modulation plate are derived and determined according to an equation of Huygens-Fresnel principle. The super-resolution phase modulation plate for the 3D compression is obtained by a micro technological process, designed and mounted by combing parameters of a laser processing system, and used for the 3D compression of femtosecond laser light spots of a femtosecond laser processing system, which improves shape of light spots and improves the processing resolution. The phase modulation plate is made of optical glass materials, has the advantages of simple fabrication process, high precision, compact mounting structure, convenient operation and the like, and is widely applied to the laser micro / nano processing fields.

Description

Technical field: [0001] The invention belongs to the field of femtosecond laser micro-nano processing, and relates to an optical device design method and processing technology for achieving three-dimensional compression of a focused spot through super-diffraction phase modulation. Background technique: [0002] According to pages 353-355 of "Engineering Optics" (2nd Edition) published by the Mechanical Industry Press in 2006, due to the widespread existence of diffraction, in ordinary optical systems, a point object or a point light source is no longer an image. An ideal point, but expands into a certain spatial light field distribution near the image plane, that is, the imaging system creates a Fraunhofer diffraction pattern on the image plane of the point object. This diffraction pattern is called Airy spot. According to the Rayleigh criterion, the size of the Airy disk can reflect the resolution of the optical system. The radius of the Airy spot is directly proportional to th...

AI Technical Summary

Problems solved by technology

However, in actual use, reducing the wavelength of light is limited by luminescent materials and laser technology, and the increase in numerical aperture is restricted by optical materials and optical lens design, reducing the size of the diffraction spot is very limited

[0003] According to "Research on Femtosecond Laser Two-Photon Three-dimensional Microfabrication Technology" (Ph. The light intensity distribution of the converging spot is ellipsoidal, and the longitudinal (optical axis) size of the spot is about 3 times larger than the transverse (focal plane) size, which not only makes the processing resolution along the optical axis relatively low, but also makes it difficult to effectively apply For example, two-photon three-dimensional storage or processing of complex structures in the height direction

[0004] According to "APPLIED OPTICS" (Vol.43, No.22 August 2004 / p4233-4327) published by the "Optical Society of America" ​​in the United States in 2004, Colin J.R. Sheppard and others made use of phase and amplitude flat panel filters to The theoretical analysis is given, and preliminary conclusions are given to overcome the diffraction limit in the transverse or longitudinal direction, but the method of its practical application is not given.

[0005] According to "OPTICS LETTERS" (Vol.28, No.8 / April, 2003-p607-609) published by the "Optical Society of America" ​​in the United States in 2003, a series of annular binary phase pupil filters were designed, analytically The parameters that characterize the filter are deduced, and a super-diffraction continuous phase plate is proposed, in the hope that the high-resolution properties of its super-diffraction technology can be applied in many aspects. However, it is only a design analysis calculation, and no design results are given. and manufacturing applications

[0006] According to the introduction of "OPTICS LETTERS" (Vol.29, No.23 / December, 2004-p2746-2748) published by the "Optical Society of America" ​​in 2004, Zhou Changhe et al. The filter has obtained a lateral compression ratio of 0.8 and is applied in a single-layer high-density optical data storage, but it achieves super-diffraction in the lateral direction and fails to achieve three-dimensional super-diffraction resolution

[0007] According to "OPTICS EXPRESS" (Vol.13, No.16 / August 2005 / p6168-6174) published by the "Optical Society of America" ​​in the United States in 2005, Gibert Boyer et al. inserted a The three-ring amplitude filter obtains a quasi-spherical focal spot, and obtains the same imaging quality in three directions in three-dimensional imaging. However, its amplitude modulation is difficult to apply in laser micro-nano processing that requires high power.

[0008] According to "OPTICS LETTERS" (Vol.28, No.1 / January 1, 2003 / -p55-57) published by the "Optical Society of America" ​​in the United States in 2003 and "OPTICS EXPRESS" (Vol.13, No. .19 / September 2005 / p7288-7297), using a rectangular aperture in front of the focusing objective lens, and adjusting the size of the rectangular aperture to realize the three-dimensional spatial modulation of the focusing spot, but the amplitude modulation will seriously reduce the output The function of the spot is difficult to apply in femtosecond laser processing that requires high power

[0009] According to the "Journal of University of Science and Technology of China" (Vol.37, No.7, 2007, p748-752) published in China in 2007, a binary phase superdiffraction optical modulation element was theoretically obtained through optimized design. The change in the thickness direction of the optical modulation element is used to achieve super diffraction. However, the change in the thickness direction of several nanometers is difficult in the current manufacturing, measurement and evaluation, so it is difficult to manufacture it in the femtosecond laser processing system. to improve the super-resolution

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