(INVITED) Determination of non-linear refractive index of laser crystals and ceramics via different optical techniques

• Published in: Optical materials. X Vol. 8; p. 100065
• Main Authors: Lamaignère, Laurent, Toci, Guido, Patrizi, Barbara, Vannini, Matteo, Pirri, Angela, Fanetti, Samuele, Bini, Roberto, Mennerat, Gabriel, Melninkaitis, Andrius, Lukas, Luise, Hein, Joachim
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2020; Elsevier
• Subjects: Degenerated four waves mixing; n2-parameter; Neodymium-doped Calcium Fluoride (Nd:CaF2) crystal; Time-resolved digital holography; Ytterbium-doped Yttrium Aluminium Garnet ceramic; Z-scan; Neodymium-doped Calcium Fluoride (Nd:CaF2) crystal; Ytterbium-doped Yttrium Aluminium Garnet ceramic; Degenerated four waves mixing; Time-resolved digital holography; Z-scan; n2-parameter
• ISSN: 2590-1478; 2590-1478
• DOI: 10.1016/j.omx.2020.100065

The exact knowledge of optical material parameters is crucial for laser systems design. Therefore, the work reported herein was dedicated to the determination of an important parameter that is typically not known or only known with insufficient precision: the Kerr coefficient determined by the third order non-linearity, also called the n2-parameter. The optical Kerr effect is responsible for the accumulated nonlinear phase (the B-integral) in high energy laser amplifiers, which often represents a serious limitation. Therefore, the knowledge of n2 is especially required for new types of laser materials. In this paper we report measurements carried out on the widely used optical material Ytterbium-doped Yttrium Aluminium Garnet (Yb:YAG) ceramics. Furthermore, the new Neodymium-doped Calcium Fluoride (Nd:CaF2) crystal was investigated. Specifically, three different approaches have been employed to determine experimentally the nonlinear refractive index of these materials. Thus classical Z-scan technique (at two different wavelengths), the degenerated four waves mixing and the time-resolved digital holography techniques, were compared. These different approaches have permitted the precise measurements of these parameters as well as their dispersion estimations. •Three different approaches have been used to determine experimentally the nonlinear refractive index of optical materials.•Four different set-ups have been developed with three different procedures: Z-scan, DFWM TRDH.•This comparison of experimental results using different facilities will increase the accuracy of n2 values determination.•Measurements carried out on Yb:YAG ceramics and on Nd:CaF2 crystal were investigated.