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Plano-Convex (PCX) Axicons feature one conical surface and one plano surface. They are used to produce a non-diffractive ring-shaped beam that increases in diameter over distance while retaining a constant ring thickness. When used with a collimated Gaussian beam, Plano-Convex (PCX) Axicons create an approximation of a Bessel beam ideal for a range of medical, research, measurement, and alignment applications. They feature a precision fused silica substrate and are available uncoated and with a wide selection of anti-reflection (AR) coating options.
A Bessel beam is a non-diffractive beam comprised of rings equal in power to one another. Although Bessel beams are only theoretically possible because they require an infinite amount of energy, the output of Plano-Convex (PCX) Axicons offer a good approximation by maintaining a high level of the non-diffractive Bessel beam properties.
The ring thickness (t) is easily defined by taking ½ of the beam diameter (db):
The diameter of the ring (dr) is defined using the length from lens output to image (L), the index of refraction of the lens material (n), and the angle a:
For optimum performance, we recommend using Plano-Convex (PCX) Axicons in conjunction with one of our beam expanders in order to ensure a beam diameter of at least 50% of the clear aperture.