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Innovative method for cost-efficient optical device manufacture

A newly developed, rapid, inexpensive and versatile method offers manufacture of aspherical optical devices that are of particular interest for emerging optic technologies.
Innovative method for cost-efficient optical device manufacture
The use of conventional spherical lenses in laser technologies may cause significant problems with the strong focus location, which could lead to extensive fabrication and production costs and times. To answer this need, a Spanish research group focused on the generation of aspherical lenses (axicons) by exploiting sulphur alloys. Axicons feature high lateral resolution of the light beam along user defined distances and large focal length. For this reason, they have been proven very advantageous when used in optical traps or confocal microscopy and 3D imaging.

Common methods for axicon fabrication involve polishing conventional optical glasses, or photolithographic techniques, which are extremely slow or costly. Unlike these, the new method is conducted through laser-assisted deposition of a semiconductor alloy onto a transparent substrate. At the same time, the deposited material is irradiated through the increasing thickness of the material deposited onto the transparent surface.

The desired optical function of the device is highly dependant on the profile of the deposited material and can be easily set through manipulation of specific parameters. These concern the laser ablation of a starting material, the substrate's location, the laser-assisted process environment, and the intensity distribution of the light field relative to the deposited material's increasing thickness. The latter parameter is responsible for the specification of the diffractive pattern to be recorded in the material.

Characterised by low cost and reduced manufacture time, the patented method could be used for producing advanced optical devices. Such devices come from arsenic sulphide semi-conducting alloys and display a wide range of refractive profiles from flat to aspherical. Therefore, they can be easily employed, either as a single optical element or as part of an array. Additionally, the method allows the development of devices with optical diffractive functions superimposed to its refractive performance, thus offering more complex mixed performances using a simple fabrication method.
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