Waveguide fabrication in lithium-niobo-phosphate glasses by high repetition rate femtosecond laser: route to non-equilibrium material’s states

Abstract

Abstract:We study waveguide fabrication in lithium-niobo-phosphate glass, aiming at a practical method of single-stage fabrication of nonlinear integrated-optics devices. We observed chemical transformations or material redistribution during the course of high repetition rate femtosecond laser inscription. We believe that the laser-induced ultrafast heating and cooling followed by elements diffusion on a microscopic scale opens the way toward the engineering non-equilibrium sates of matter and thus can further enhance Refractive Index (RI) contrasts by virtue of changing glass composition in and around the fs tracks. References and links1. H. Misawa and S. Juodkazis, eds., 3D Laser Microfabrication. Principles and Applications (Wiley-VCH, Weinheim, 2006). 2. R. Osellame, G. Cerullo, and R. Ramponi, Femtosecond Laser Micromachining: Photonic and Microfluidic Devices in Transparent Materials, SpringerLink : Bücher (Springer Berlin Heidelberg, 2012).

Ultrafast Laser Direct Writing in Glass: Thermal Accumulation Engineering and Applications

“…For example, ion migration induced enrichment of network modifiers, such as Ca, Al, La, and K ions, is demonstrated to cause positive index change and migration of glass former of silicon ions leads to a negative index change. [21,71,75,81,82] Other distinct contributions, such as the optical Kerr effect, the thermooptical (TO) effect and finally the influence of trapped electrons or holes may also affect the energy distribution deposited in the focal volume, which modify the local structures with RI change. [39] Furthermore, as all the structure reorganization and ion migration occur in the temperature field generated by ultrafast laser pulses with high repetition rate, the temperature gradient can be an important contributor to drive the matter flow, and finally modify the local structures and elementary composition.…”

Radiation effects on phosphate glasses: Review

“…Lines of KSm(PO 3 ) 4 crystals were locally precipitated in phosphate glass in the K 2 O·Sm 2 O 3 ·P 2 O 5 system using Nd:YAG laser with a power of 0.8 W and a moving speed of 0.5 μm.s −1 . A similar approach was used by Dubov et al to fabricate high contrast waveguide in lithium‐niobo‐phosphate glass using femtosecond laser at high repetition rate . The laser at high repetition rate leads to ultrafast heating and localized melting and so to local atoms/ions diffusion, nonlocal material transformations, and/or chemical changes in material.…”

“…65 A similar approach was used by Dubov et al to fabricate high contrast waveguide in lithium-niobo-phosphate glass using femtosecond laser at high repetition rate. 66 The laser at high repetition rate leads to ultrafast heating and localized melting and so to local atoms/ions diffusion, nonlocal material transformations, and/or chemical changes in material. It is this diffusion of the chemical elements, which is thought to be the main mechanism for the refractive index contrast.…”

Thermodiffusion of alkali ions in alkali niobophosphate glasses

“…The study of thermodiffusion processes in solid ionic electrolytes provides the fundamental basis for creating gradient structures inside glass samples through local changes in the chemical composition by femtosecond laser radiation, 1–5 continuous wave (CW) laser, 6–8 by means of thermal poling, 9–11 and thermally activated ion‐exchange 12,13 …”

“…The study of thermodiffusion processes in solid ionic electrolytes provides the fundamental basis for creating gradient structures inside glass samples through local changes in the chemical composition by femtosecond laser radiation, [1][2][3][4][5] continuous wave (CW) laser, [6][7][8] by means of thermal poling, [9][10][11] and thermally activated ion-exchange. 12,13 In case of femtosecond laser radiation, depending on the parameters of the irradiation and the glass-forming matrix, the temperature at the center of the laser spot can range between a thousand and several thousands degrees Celsius.…”