Transmission of Q-switched erbium: YSGG (λ=2.79 μm) and erbium: YAG (λ=2.94 μm) laser radiation through germanium oxide and sapphire optical fibres at high pulse energies

The erbium:YSGG and erbium:YAG lasers are used for tissue ablation in dermatology, dentistry and ophthalmology. The purpose of this study was to compare germanium oxide and sapphire optical fibres for transmission of sufficient Q-switched erbium laser pulse energies for potential use in both soft and hard tissue ablation applications. Fibre transmission studies were conducted with Q-switched (500 ns) Er:YSGG (λ=2.79 μm) and Er:YAG (λ=2.94 μm) laser pulses delivered at 3 Hz through 1-m-long, 450-μm germanium oxide and 425-μm sapphire optical fibres. Transmission of free-running (300 μs) Er:YSGG and Er:YAG laser pulses was also conducted for comparison. Each set of measurements was carried out on seven different sapphire or germanium fibres, and the data were then averaged. Fibre attenuation of Q-switched Er:YSGG laser energy measured 1.3 ± 0.1 dB/m and 1.0 ± 0.2 dB/ m for the germanium and sapphire fibres, respectively. Attenuation of Q-switched Er:YAG laser energy measured 0.9 ± 0.3 dB/m and 0.6 ± 0.2 dB/m, respectively. A maximum Q-switched Er:YSGG pulse energy of 42 mJ (26-30 J/cm²) was transmitted through the fibres. However, fibre tip damage was observed at energies exceeding 25 mJ (n = 2). Both germanium oxide and sapphire optical fibres transmitted sufficient Q-switched Er:YSGG and Er:YAG laser radiation for use in both soft and hard tissue ablation. This is the first report of germanium and sapphire fibre optic transmission of Q-switched erbium laser energies of 25-42 mJ per pulse.