Advances in ultrafast laser inscription in optical materials: from fundamentals to technological applications

G.A TORCHIA; M.R. TEJERINA; D.BIASETTI; D. PRESTI; V.GUAREPI; R.PEYTON

Barcelona

Conferencia; Europhoton Conference Barcelona; 2018

European Physics Society

In this contribution, we would like to introduce some fundamental studies and technological developments in  integrated photonics fabricated  by   ultrafast laser inscription (ULI).  Two decades ago, a pioneer article written  by K. Hirao et al. [1], showed that using a femtosecond laser pulse systems it is possible to modify in a precise  and  permanent  way  the  optical  properties  of  a  transparent  material.  This  process  allows  the  direct  writing  of guiding structures in several optical materials, commonly known as of waveguides which are the base of optical  circuits. As it is well known, this technique presents very useful advantages over other methods, such as rapid prototyping, maskless, 3D architecture, low cost among others so many contributions of ULI applications were reported [2-5]. In this paper, on one hand, we present fundamentals studies related to the ultrafast laser- matter interaction with optical materials in order to fabricate suitable and efficient wave-guiding structures. We will discuss about micro-Raman  and  luminescence  experiments  used  to  link  these  results  with  the  optical  performance  of  the  written  waveguides.  Modeling  and  spectroscopic  analysis  have  been  used  to  support  the  experimental  data obtained in different optical material such as LiNbO3, Cr:LISAF, Er/Yb, LNbO3. Additionally, in order to reduce the propagation losses, a thermal annealing was carried in pure Lithium Niobate waveguides; this reduction was supported by a simulation model considering the material thermal expansion after laser interaction. On the other hand, suitable technological devices were developed by using this fabrication method. Mach Zehnder interferometer (MZI) made in Lithium Niobate wafers were implemented as amplitude modulator, so a suitable  connecterized  prototype  will  be  developed    in  this  work.  Ultra  compact  power  divisors  were  also constructed follow the coherent coupling approach by using laser writing approach. Finally, we will present an  integrated directional coupler, the design of this optical circuit  was made by taking into account the coupling length for the evanescent modes in two closer type I waveguides obtained by ULI.