Wavelength-agile fiber laser using group-velocity dispersion of pulsed super-continua and application to broadband absorption spectroscopy

A swept-wavelength source is created by connecting four elements in series: a femtosecond fiber laser at 1.56 mum, a non-linear fiber, a dispersive fiber and a tunable spectral bandpass filter. The 1.56-mum pulses are converted to supercontinuum (1.1-2.2 mum) pulses by the non-linear fiber, and these broadband pulses are stretched and arranged into wavelength scans by the dispersive fiber. The tunable bandpass filter is used to select a portion of the super-continuum as a scan-wavelength output. A variety of scan characteristics are possible using this approach. As an example, an output with an effective linewidth of approximately 1 cm(-1) is scanned from 1350-1550 nm every 20 us. Compared to previous scanning benchmarks of approximately 1 nm/mus, such broad, rapid scans offer new capabilities: a gas sensing application is demonstrated by monitoring absorption bands of H2O, CO2, C2H2 and C2H6O at a pressure of 10 bar.