Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: Fabrication, fluorescence imaging and laser performance

Abstract

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

Femtosecond laser induced phenomena in transparent solid materials: Fundamentals and applications

“…1-to-2, 1-to-3 and 1-to-4 splitters are also produced with the adjustable splitting ratio. High contrast cladding waveguides are also fabricated in various types of nonlinear crystals with different configurations by Chen group [327,[329][330][331][332][333][334]. Laser oscillations at different wavelengths and SHG are realized using the cladding waveguides by this group.…”

Crystalline Waveguide Lasers in the Visible and Near-Infrared Spectral Range

“…This results in a positive refractive index difference between n 2 and n 1 and allows for waveguiding in the unmodified core. The tracks of Type III structures can be arranged in various ways thus nearly arbitrary and relatively large cross sections of the waveguiding core can be realized [43], [44]. The cross section of the waveguiding region can be adapted to the cross section of multi mode diode bars or fiber coupled laser-diodes [45], [46].…”

Fluorescence imaging of lattice re-distribution on step-index direct laser written Nd:YAG waveguide lasers

“…4 DLW has been found especially appropriate for the local modification and controlled fabrication of laser waveguides in rare earth doped YAG crystals and ceramics. [5][6][7][8][9][10][11][12] In the simplest channel waveguide fabrication scheme (in which waveguides are constituted by either a single or double laser-written line tracks), waveguiding is produced at the stress affected volume (generally called Type II stress-induced waveguides) where the refractive index changes are produced through the piezo-optic effect. 10 In other cases, waveguiding is produced by a low-index cladding.…”

“…4 I 11/2 transition of Neodymium ions). 7,8,15 One of the main drawbacks of Nd:YAG DLW waveguides fabricated with low repetition rate lasers is the unavoidable damage and stress, as well as the impossibility of writing increased step-index type waveguides. The importance of being able to inscribe step-index increased waveguides (Type I WGs in the following), relies on the fact that these type of waveguides (step-index direct written cores) could exhibit superior light confinement and lower bend losses, as well as much more controllable mode dispersion properties, than stress-induced waveguides.…”