Axicon Lens
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Axicon Lens
Axicon lenses use interference to form a focal line along the optical axis and can transform a laser beam into a ring-shaped beam. Axicon lenses are mainly used as beam shapers for laser applications.
Understanding Axicon Lenses
To turn a collimated beam into a ring shape, you need to face the flat side of the axicon lens toward the incoming beam. When the beam hits the center of this flat surface straight on, the light travels along the optical axis of the axicon and then exits the lens in a cone shape. Once this conical beam hits a flat surface, it forms a ring of light. The closer the surface is to the lens, the smaller the diameter of the ring.
Unlike a Gaussian beam, which fades as it travels, the beam shape created by an axicon behaves more like a Bessel beam — meaning it keeps a steady intensity profile over a longer range. In fact, within a certain depth of focus, an axicon can create a beam that closely approximates a true Bessel beam. This depth of focus depends on the incoming beam’s radius, the refractive index of the axicon, and the angle α. If the angle is small, you can roughly estimate the depth of focus with the formula: radius / [(refractive index – 1) × α].
