Microfiber assisted bidirectional wavelength-locked ultrafast erbium-doped fiber laser

Abstract

Bidirectional mode-locked fiber lasers are promising media to implement intracavity phase interferometry (IPI) due to the ability to produce ultrashort pulses in a compact design. A typical bidirectional ultrafast fiber laser will generate counter-propagating pulses with different repetition rates due to the asymmetric constructure. In this paper, by using the filtering effect of microfiber, an asymmetric bidirectional fiber laser that emits two pulses with same operation wavelength is demonstrated. The utilization of microfiber in locking output wavelength from two directions may directly simplify the design of laser cavity suitable for IPI applications. Moreover, continuous wavelength tuning in a single-cavity bidirectional ultrafast fiber laser has been realized for the first time by applying strain on the microfiber. In the clockwise (CW) direction, wavelength tuning ranges from 1558.96 nm to 1567.3 nm and from 1558.93 nm to 1567.25 nm in the counter clockwise (CCW) direction. The counter-circulating pulses maintain spectral locking state during the whole wavelength tuning process with a good linear sensitivity of 0.2 nm/µm. Such features may further expand the scope and field of fiber lasers for sensing.