Above figure shows a beam expander made with two co axial

Last updated: 6/9/2023

Above figure shows a beam expander made with two co axial converging lenses of focal length f and f and separation d f f Parallel light rays incident on lens 1 will form image I at the focus of lens 1 This image will act as object for lens 2 Second lens is placed that I is at its focus so that its image will be at infinity and the rays refracting from it will be parallel rays In this way the device can expand a laser beam while keeping the light rays in the beam parallel to the central axis through the lens Suppose uniform laser beam of width W 2 5mm and Intensity I 9 0kw m enter a beam expander for which f 12 5cm and f 30 0cm 1 What is the width of final beam W ii What is the value of d for the above beam expander iii If f is increased then what adjustment is required in the beam expander