McCormack O, Giudicotti L, Fassina A, Pasqualotto R
Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti 4, 35127 Padova, Italy.
Rev Sci Instrum. 2021 Jul 1;92(7):073001. doi: 10.1063/5.0056614.
A novel method for the path combination of two lasers with very similar wavelengths has been implemented to enable the evaluation of a dual-laser calibration Thomson scattering (TS) technique. The first experimental test of this TS technique has been performed in a RFX-mod plasma device, where, due to experimental constraints, the combination of a Nd:YAG (λ = 1064 nm) and a Nd:YLF (λ = 1053 nm) laser system was the only viable choice available. The method requires that the beam path of both lasers be combined into a single path with the same polarization. This presents a unique challenge due to the small difference between the two laser wavelengths. In this paper, we describe two methods for beam combination: first via a prism, eventually dismissed as unpractical, and second via a polarizing beam splitter in reverse with a dual-wavelength waveplate. We detail the optical setup, waveplate design, and successful implementation of this second method.
