Ultrashort-pulse lasers with spectral tuning capability have widespread applications in fields such as spectroscopy, biomedical research and telecommunications1–3. Mode-locked fibre lasers are convenient and powerful sources of ultrashort pulses4, and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths5. Semiconductor saturable absorber mirrors are widely used in fibre lasers4–6, but their operating range is typically limited to a few tens of nanometres7,8, and their fabrication can be challenging in the 1.3–1.5 mm wavelength region used for optical communications9,10. Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness11–16. Here, we engineer a nanotube–polycarbonate film with a wide bandwidth (>300 nm) around 1.55 mm, and then use it to demonstrate a 2.4 ps Er31-doped fibre laser that is tuneable from 1,518 to 1,558 nm. In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems.
- ultrashort-pulse lasers
- spectral tuning capability
- mode-locked fibre lasers
- broadband saturable absorber
- semiconductor saturable absorber mirrors
- carbon nanotubes
Wang, F., Rozhin, A., Sun, Z., Scardaci, V., White, I. H., Hennrich, F., Milne, W. I., & Ferrari, A. C. (2008). Wideband-tuneable, nanotube mode-locked, fibre laser. Nature Nanotechnology, 3(2 November 2008), 738-742. https://doi.org/10.1038/nnano.2008.312