In conclusion, a fast fine single-mode and coarse double-mode widely wavelength-tunable ECDL is demonstrated. A double-wavelength coarse tuning range of 120 nm for the spectral range between 1470 and 1590 nm is achieved by rotating the diffraction gratings. Double-mode laser sources are attractive for many applications, such as optical sensing, THz wave generation and imaging, dual-wavelength interferometry, optical switching, wavelength division multiplexing. In order to increase the coarse tuning range, a gain chip with a wider gain bandwidth should be used. A piezo fast fine tuning range of 7 cm 1 (210 GHz) is de-monstrated by scanning the external cavity length. Fast (kHz) scan
rates and wide fi ne tuning ranges are needed to perform spec-troscopic investigations of turbulent media and short-living molecules. A piezo element with higher displacement and/or a faster
scan rate using the lighter and stabler components can increase
the fast fi ne tuning range