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Ultraviolet coherent light source

Ultraviolet coherent light source will be developed by third harmonic generation of a near-infrared fibre laser. The development will be based on novel methods for frequency tripling in a compact and efficient manner.

Compact, efficient and coherent ultraviolet (UV) sources are required for many important industrial applications - printing, semiconductor wafer inspection and micro-lithography, writing of fibre Bragg grating, bio-sensing, etc. In particular, a very promising field of application is related to the use of conventional plates, sensitive to UV radiation, in computer to plate (CtP) machines. Existing laser sources in this range include either bulky inefficient lasers such as Ar-ion, dye and excimer lasers or low power GaN (Gallium-Nitride) diode laser, and HeCd gas lasers (see example http://www.rp-photonics.com/ultraviolet_lasers.html). An alternative approach is to up-convert the frequency of diode-pumped solid-state or fibre lasers. This approach can provide an all-solid-state compact device with high reliability. Significant progress was made in the last years in near-infrared solid state lasers, in term of power level, reliability and commercial availability, but these sources typically operate around 1 micron. Conversion to the ultraviolet by quadratic nonlinear harmonic generation is a two-step process, in which the first stage is frequency doubling to the green, followed by sum-frequency generation of the fundamental and second harmonic. This allows for generating radiation around approximately 355 nm from a 1,064 nm source. These conversions have been traditionally done by birefringent phase matching in crystals such as KTP and LBO. These crystals are widely used in pulsed lasers, both Q-switched and mode-locked. The conversion efficiency with these crystals, however, is insufficient for many applications when CW pump sources are used. The goal of this project is to generate a compact ultraviolet CW source by third harmonic generation of a near infrared laser. This source will then be used for CtP applications. Presently one of the most promising markets for CtP is the printing of conventional plates, sensitive to UV radiation. Those plates, in fact, are the most widely diffused and are much cheaper than the digital ones, although less sensitive. Andromeda, which is the end user of the UV laser, already manufactures CtP machines working with sources in the IR (infrared) and violet spectral region for digital plates, and will extend its product portfolio with this UV source. The novelty is the improvement of the harmonic generation process using new nonlinear crystals that can be quasi-phase matched, and the use of novel designs of the nonlinear conversion process. The nonlinear crystals, in particular stoichiometric LiTaO3, are made by the Israeli partner, RAICOL CRYSTALS. The improvement in conversion efficiency and ultraviolet power will allow for pursuing new opportunities that have not been possible so far. Keywords: Ultraviolet coherent source; nonlinear crystal; nonlinear frequency conversion.
Acronym: 
UVICOLS
Project ID: 
4 556
Start date: 
01-09-2008
Project Duration: 
12months
Project costs: 
450 000.00€
Technological Area: 
Apparatus Engineering
Market Area: 
Laser Related

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