Modeless operation of a wavelength-agile laser by high-speed cavity length changes

An external cavity laser has been designed for rapid but stable wavelength-tuning. To enhance the tuning stability, cavity modes are suppressed by rapidly changing the cavity length as part of the wavelength-scanning mechanism. The ~ 27 cm cavity length is modulated at speeds up to 1190 m/s, corresponding to ~ 90% of one wavelength in an optical round-trip time. The laser scans from 1370-1464 nm and back at a rate of 15.5 kHz with a measured instantaneous linewidth of ~ 0.3 nm. This high speed modeless laser has several advantages over traditional designs which will be discussed here.