Description
Ultrashort pulsed fibre lasers operating at 2.3 µm offer opportunities in environmental sensing, biomedical technologies, and next-generation telecommunications. This wavelength range is particularly attractive for gas spectroscopy due to strong absorption features of atmospheric species including hydrogen fluoride, carbon monoxide, formaldehyde, and methane. In optical communications, sources operating beyond the conventional silica transmission window may help overcome future capacity limitations in fibre networks by exploiting the theoretically up to 40× lower minimum transmission loss of fluoride glass fibres compared with silica around 2.3 µm. However, laser development at this wavelength remains challenging because of increasing infrared absorption in silica fibres beyond 2 µm.
This work presents progress towards a 2.3 µm fibre laser based on thulium-doped ZBLAN (ZrF₄–BaF₂–LaF₃–AlF₃–NaF), a heavy metal fluoride glass with favourable mid-infrared transmission. Previous demonstrations achieved efficient continuous-wave (CW) operation using up-conversion pumping at 1050 nm and reached watt-level output powers. Our current laser configuration demonstrated CW operation at 2330 nm using a 29 cm length of 1.3 mol.% thulium-doped ZBLAN fibre pumped at 1050 nm. The system delivered 38 mW output power with 8% slope efficiency and a lasing threshold of 70 mW, with further CW power scaling underway.
Short-pulse operation in thulium-doped ZBLAN at 2.3 µm has so far been limited to passive Q-switching, and mode-locked operation has not yet been reported. This work therefore focuses on achieving passive mode-locking using carbon nanotubes as saturable absorbers. Our previous investigation, independent of the laser system, demonstrated efficient saturable absorption at 2.3 µm with low non-saturable loss.
We will present ongoing work on CW power scaling and progress towards ultrashort pulse generation through carbon nanotube-enabled mode-locking.
| I am the presenting author | No |
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| If you are not the presenting author, please give the presenting author's name: | ehab.salih@adelaide.edu.au |