Laser emissions from buried depressed-cladding waveguides inscribed in Nd³⁺:CLNGG laser crystals by picosecond-laser beam writing

Picosecond (ps-) laser systems can be successfully employed in ultrafast micromachining due to some specific characteristics such as extended system stability, reduced costs, increased laser pulse energies, and higher repetition rates. However, there are only a few reports in the literature regarding the fabrication of waveguides in glasses and crystalline materials with laser systems delivering pulses of few ps-pulse duration [1]. In general, such waveguides are realized with femtosecond (fs-) laser sources and by using a line-by-line translation inscription technique along a defined shape [2].

In this work, we are reporting on the fabrication of buried depressed-cladding waveguides in a 0.7-at.% Nd:CLNGG disordered crystal by ps-laser beam writing. The laser emission performances were characterized under the pump at 807 nm with a fiber-coupled diode laser. For a quasi-continuous-wave pumping regime, a waveguide with 100 mm diameter (circular cross-section) delivered laser pulses at 1.06 mm with energy E_p= 0.35 mJ for a pump pulse energy of E_pump= 13.3 mJ (corresponding to an overall optical-to-optical efficiency h_o= 0.03), with a slope efficiency of h_s = 0.04. Such waveguides are good candidates for the realization of integrated laser sources consisting of cladding waveguides pumped by diode lasers and for the generation of ultra-short laser pulses at 1 mm.

Funding: This work was financed by the postdoctoral project PD 63/2022, code PN-III-P1-1.1-PD-2021-0522 and partially supported by the program NUCLEU-LAPLAS VII 30N/2023, Ministry of Research, Innovation and Digitization, Romania. The support of the National Interest Infrastructure facility IOSIN - CETAL at INFLPR is acknowledged.

1. Corbari, C.; Champion, A.; Gecevičius, M.; Beresna, M.; Bellouard, Y; Kazansky, P.G. Femtosecond versus picosecond laser machining of nano-gratings and micro-channels in silica glass. Opt. Express 2013, 21, 3946-3958.
2. Okhrimchuk, A.; Mezentsev, V.; Shestakov, A.; Bennion, I. Low loss depressed cladding waveguide inscribed in YAG:Nd single crystal by femtosecond laser pulses. Opt. Express 2012, 20, 3832-3843.