A femtosecond soliton source with fast and broad spectral tunability has been developed by researchers in Argentina. The source, which comprises a Ti:sapphire laser and a highly nonlinear photonic-crystal fibre, can be tuned from 850 nm to 1000 nm with nearly constant pulse width and average power (Optics Letters 34 842).
The key to the laser's tuning performance is the use of solitons generated in the photonic-crystal fibre. At the low-power coupling regime, solitons can be tuned over a broad range of wavelengths from 850 to 1000 nm. The solitons generated in the fibre maintain almost constant pulse and spectral widths regardless of input power.
In the set-up, a photonic-crystal fibre measuring 75 cm in length is pumped with a Ti:sapphire laser that provides 37 fs pulses at a repetition rate of 94 MHz and a wavelength of 830 nm. Average power ranging from 1 to 10 mW is pumped into the fibre, controlled by an acousto-optic modulator (AOM).