Ultra long high resolution beam by multi-zone rotationally symmetrical complex pupil filter

Area of Science:

• Optics and Photonics
• Diffraction Optics

Background:

• Achieving high resolution and extended depth of focus (DoF) simultaneously in optical beams is challenging.
• Traditional focusing systems often face trade-offs between transverse resolution and axial DoF.

Purpose of the Study:

• To demonstrate an ultra-long, high-resolution optical beam with an extended depth of focus.
• To investigate the use of a complex pupil filter for beam shaping.

Main Methods:

• A seven-zone rotationally symmetrical complex pupil filter was designed and applied to a focusing lens aperture.
• The filter modulates both amplitude and phase of transmitted light across different zones.
• Scalar diffraction theory was employed to optimize the pupil filter parameters.

Main Results:

• The demonstrated beam achieved an extended depth of focus (DoF) 16 times greater than conventional beams.
• The spot size at the beam waist was reduced to 0.7 times, indicating improved transverse resolution.
• The complex pupil filter effectively controlled light propagation for enhanced beam characteristics.

Conclusions:

• A complex pupil filter is an effective method for generating optical beams with simultaneous high transverse resolution and extended axial DoF.
• This technique offers a promising approach for applications requiring precise focusing over a large range.