Three-level filter for increased depth of focus and Bessel beam generation

Area of Science:

• Optics and Photonics
• Diffractive Optics

Background:

• Standard lenses have limited focal depth, restricting applications requiring extended imaging or manipulation.
• Generating Bessel beams, known for their non-diffracting properties, is crucial for various optical tasks.

Purpose of the Study:

• To propose a novel, axially-symmetric filter for enhanced focal depth and Bessel beam approximation.
• To demonstrate a design combining high transverse resolution with good efficiency.

Main Methods:

• Development of an axially-symmetric filter composed of rings with strengths -1, 0, and 1.
• Utilizing an analytic solution for the filter design.
• Comparison with standard lenses and other depth-of-focus enhancement techniques.

Main Results:

• The proposed filter design achieves an approximation to a Bessel beam.
• Demonstrated an increase in focal depth exceeding 30 times that of a standard lens.
• Achieved a very flat axial intensity distribution over the extended focal range.

Conclusions:

• The novel ring-based filter offers a significant advancement in extending focal depth.
• The design provides a practical method for generating Bessel-like beams with high performance.
• This approach presents a valuable alternative for applications demanding extended focal ranges and high resolution.