Creating a nondiffracting beam with sub-diffraction size by a phase spatial light modulator

Area of Science:

• Optics and Photonics
• Applied Physics

Background:

• Nondiffracting beams offer unique properties like self-healing and localized intensity, making them valuable for microscopy and materials processing.
• Conventional methods for generating nondiffracting beams are limited by the diffraction limit, restricting their transverse size.

Purpose of the Study:

• To overcome the diffraction limit in generating nondiffracting beams.
• To design and create a phase mask mirror capable of producing sub-diffraction nondiffracting beams.

Main Methods:

• Utilized super-oscillation and the vectorial angular spectrum method to design a phase mask mirror.
• Fabricated the phase mask mirror using a phase spatial light modulator with specific optical parameters (focal length 1 m, radius 5 mm, NA ~0.005, wavelength 632.8 nm).
• Illuminated the mirror with a linearly polarized Gaussian wave.

Main Results:

• Successfully generated a nondiffracting beam with a sub-diffraction transverse size.
• The beam's maximum transverse size was smaller than the diffraction limit (0.5λ/NA) for propagation distances exceeding 43.3 mm.
• Demonstrated that increasing the numerical aperture (NA) can further reduce the transverse size of the nondiffracting beam.

Conclusions:

• The developed phase mask mirror effectively generates nondiffracting beams that surpass the conventional diffraction limit.
• This technique offers a pathway to create highly localized optical fields for advanced scientific and technological applications.
• Future work can focus on increasing the NA to achieve even smaller transverse beam sizes.