Abstract
We report on manufacturing of a compact beam homogenizer module including two lens arrays and an aperture. Lens arrays are fabricated by an all laser-based technology employing a precise femtosecond pulsed laser ablation and a CO2 laser polishing step. Each lens array is processed revealing a high contour accuracy and a roughness of 25 nm. The 8x8 lens arrays are designed to have a square footprint to generate a quadratic Top-Hat beam profile and focal length of 10 mm to realize compact packaging. Firstly, the lens arrays are tested in an experimental setup using commercial lens holders with their functionality being demonstrated by shaping a uniform 4.5 mm squared Top-Hat beam profile, as being calculated. Afterwards, a 3D printer is used to additively manufacture the housing for the beam homogenizer module having a length of only 16 mm. After assembling the laser-fabricated lens arrays and a laser-cutted aperture into the housing, the functionality of the miniaturized module is proven.
Highlights
Lens arrays have been demonstrated to be applied in numerous fields of optics such as, e.g., in sensor applications as in Shack-Hartman sensors for wave front detection [1], in imaging systems as for microscopy [2] or photolithography [3] or for increasing the light extraction efficiency in organic light-emitting diodes/devices [4,5]
The individual lenses reveal a square footprint for both, resulting in a fill factor of 100% and required to generate square shaped Top-Hat beam profiles when used in a beam homogenizer setup
The lens array consists of uniform lenses, while the magnification exemplarily shows the contour of a single lens
Summary
Lens arrays have been demonstrated to be applied in numerous fields of optics such as, e.g., in sensor applications as in Shack-Hartman sensors for wave front detection [1], in imaging systems as for microscopy [2] or photolithography [3] or for increasing the light extraction efficiency in organic light-emitting diodes/devices [4,5]. Hua et al [12] demonstrated the usage of the femtosecond laser in a backside wet etching process for geometry generation, which is followed by thermal annealing to smoothen the surface to fabricate microlens arrays in silica. Pan et al [13] and Zhang et al [14] showed the microlens array fabrication by femtosecond laser production of microholes and a subsequent wet etching step forming the lens geometry on silicon as well as silica and sapphire, respectively. Modified photosensitive glass with a femtosecond laser which is further processed via thermal treatment, wet etching and annealing to fabricate the finalized optic. Applied the femtosecond laser to fabricate periodic microstructures in fused silica and soda lime glass, respectively, which are further polished and reshaped by a CO2 -laser step to polish the preform and form the desired geometry. The most standard lens array fabrication processes use polymer substrates or include an etching step, while our process offers the fabrication of glass lens arrays without using polymer substrates or etching
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