axicon

An axicon is a type of optical element that is used to convert a Gaussian beam into a Bessel beam. This conversion is achieved through the use of a conical lens, which is a lens with a conical shape. The axicon is typically made of a transparent material, such as glass or plastic, and is designed to have a specific angle of the cone, which determines the properties of the resulting Bessel beam.

The axicon works by diffracting the incoming Gaussian beam, which is a type of laser beam with a Gaussian intensity profile. The diffraction occurs at the conical surface of the axicon, and the resulting beam is a Bessel beam, which has a unique intensity profile that is characterized by a series of concentric rings. The Bessel beam has the property of being non-diffracting, meaning that it maintains its shape over long distances, which makes it useful for a variety of applications, such as optical trapping, microscopy, and laser machining.

The axicon is a relatively simple and inexpensive optical element, and it can be easily integrated into existing optical systems. However, the performance of the axicon depends on the quality of the conical surface, and any imperfections or deviations from the ideal shape can lead to a degradation of the resulting Bessel beam. Therefore, it is important to ensure that the axicon is manufactured to a high standard to achieve the desired performance.