Abstract

This study shows a method of calculating the geometrical dimensions of light concentrating cones. To produce the cone, which is to concentrate parallel beams, an appropriate length of the cone is computed for a certain half of apex angle and the radius of the bundle to be concentrated. This calculation of the ideal cone length can be done by a simple multiplication. Conventional calculation methods do not provide integers for the apex angle, which might be a disadvantage in the production of cones. The reflectance of the material used for the cone which is to concentrate the light allows calculation of the theoretical transmittance and the concentration factor. Both depend only on the reflectance and half of apex angle. Experiments confirmed the computed profile of energy density in the place of the highest concentration—the exit plane—for a homogeneous distribution of energy in the concentrated bundle. In addition the transmittance of a copper cone for the concentration of laser light (Nd:YAG laser, λ = 1064 nm, TEM₀₀) with Gaussian energy distribution was computed. The calculated values of transmission were verified in experiments for energies up to 15 mJ/pulse equaling a mean power of 0.5 MW/cm². Deviations from the computed values are mainly due to production deficiencies. With higher energies, laser-induced breakdowns on the inside of the cone consume a fraction of the energy.

© 1986 Optical Society of America

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