The Axicons in Optical Systems

Axicons, or conical lenses, are unique optical components with a conical surface that plays a crucial role in shaping light beams into ring-shaped patterns. These lenses are widely used in various applications, including laser processing, microscopy, and medical aesthetics, due to their ability to create uniform ring-shaped illumination and precise beam shaping.

A typical axicon consists of a conical surface and a flat base. Depending on their design, axicons can be used to either converge or diverge light beams, transforming a collimated beam into a donut-shaped or ring-shaped pattern.

Types of Axicons: Convergent and Divergent

Axicons can be broadly classified into two categories based on their behavior:

Convergent Axicons: These axicons focus a collimated light beam into a ring-shaped pattern. The ring has a sharp inner edge and a gradually fading outer edge.

Divergent Axicons: These axicons spread a collimated beam into a wider ring pattern. The ring diameter increases as the distance from the axicon increases.

The critical parameter in axicon design is the apex angle (α), which determines the behavior of the light beam after passing through the axicon.

When a collimated beam of light passes through an axicon, it undergoes refraction at the conical surface, causing the light to bend and form a ring-shaped pattern. The behavior of the ring beam depends on the apex angle (α) and the refractive index (n) of the axicon material.

For Small Apex Angles (α < 10°): The deflection angle (β) of the light beam is approximately proportional to the apex angle and the refractive index.

Focus Position Calculation: The focal position of the ring beam can be calculated using the relationship between the height of the beam (h), the apex angle (α), and the refractive index (n).

One of the most intriguing features of axicons is their ability to generate Bessel rings. As the observation screen is moved farther from the axicon, the diameter of the ring increases while its width remains constant. This characteristic makes axicons ideal for applications requiring stable and uniform ring-shaped illumination.

Applications of Axicons in Optical Systems

Axicons are versatile optical components with a wide range of applications. Their ability to generate ring-shaped beams makes them indispensable in fields such as laser processing, medical aesthetics, and microscopy.

Transmissive Axicons: Generating Ring Light Sources

Transmissive axicons are used to create uniform ring light sources, which are preferred over point sources for their even illumination. By combining an axicon with a converging lens, a ring-shaped source can be generated at the focal plane of the lens.

Ring Diameter Calculation: The radius of the ring (R0) can be calculated using the focal length of the lens (f) and the parameters of the axicon.

Divergent Axicons for Larger Rings: Divergent axicons allow for larger ring diameters by preventing the light beams from intersecting, resulting in a more spread-out ring pattern.

Reflective Axicons: Advanced Beam Shaping

Reflective axicons are used to achieve specific beam shaping effects by reflecting light off their conical surfaces. When a collimated beam is reflected by an axicon, it forms a ring-shaped pattern with a width that remains constant as the beam propagates.

Double Apex Angle Effect: The deflection angle of the ring beam is twice the apex angle (α) of the axicon.

Daisy-Chain Configuration: By using two axicons with the same apex angle, a collimated beam can be split into multiple parallel ring beams, each with half the diameter of the original beam. This configuration allows for precise control over the ring diameter by adjusting the distance between the axicons.

Axicons are remarkable optical components that enable precise control over light beams, transforming them into stable and uniform ring-shaped patterns. Their applications span across diverse fields, from laser processing and microscopy to medical aesthetics, making them indispensable tools in modern optical systems.

Bena Optics specializes in the design and manufacturing of high-quality axicons tailored to meet the specific needs of optical systems. Our axicons are engineered for precision, durability, and efficiency, ensuring optimal performance in a wide range of applications.

With a commitment to innovation and quality, Bena Optics is at the forefront of optical component development, providing reliable solutions for the most demanding optical challenges.