Femtosecond-laser micromachined Pr:YLF depressed cladding waveguide: Raman, fluorescence, and laser performance

Abstract

We report on the fabrication of channel waveguide by a femtosecond laser (fs-laser) micromachining system in a Pr:LiYF4 (Pr:YLF) crystal. The micro Raman (μ-Raman) spectra and scanning confocal fluorescence imaging investigations of the depressed cladding structure indicated that slight changes (with respect to widths of the emission lines and spectral positions) have been generated in the laser-modification region. In the meantime, the possible relation of these changes with the waveguide formation was analyzed. The microphotoluminescence (μ-PL) experiment manifests an excellent preservation of the fluorescence properties of the Pr3+ ions in the guiding area. π-polarized waveguide lasers at wavelengths of 605 nm and 720 nm were achieved with a pumping laser at a wavelength of 444.5 nm. The maximum output power of the lasers achieved was 66 mW and 47 mW with slope efficiencies of 9.5% and 6.3%.