Abstract
An Erbium-doped fibre ring laser hybrid mode-locked with single-wall carbon nanotubes (SWNT) and nonlinear polarisation evolution (NPE) without an optical isolator has been investigated for various cavity conditions. Precise control of the state of polarisation (SOP) in the cavity ensures different losses for counter-propagating optical fields. As the result, the laser operates in quasi-unidirectional regime in both clockwise (CW) and counter-clockwise (CCW) directions with the emission strengths difference of the directions of 22 dB. Furthermore, by adjusting the net birefringence in the cavity, the laser can operate in a bidirectional generation. In this case, a laser pumped with 75 mW power at 980 nm generates almost identical 790 and 570 fs soliton pulses with an average power of 1.17 and 1.11 mW. The operation stability and pulse quality of the soliton pulses in both unidirectional regimes are highly competitive with those generated in conventional ring fibre lasers with isolator in the cavity. Demonstrated bidirectional laser operation can find vital applications in gyroscopes or precision rotation sensing technologies.
Highlights
Since their first demonstration, the ultrafast fibre lasers have been an object of continuous scientific and industrial research interest thanks to the highly integrated design and as a consequence compact size, lower cost, and excellent robustness against environmental exposure
We propose isolator-free ultrafast erbium-doped fibre laser, operating in both CW and CCW unidirectional and bidirectional regimes
Laser tends to operate in a counter-clockwise (CCW) direction
Summary
The ultrafast fibre lasers have been an object of continuous scientific and industrial research interest thanks to the highly integrated design and as a consequence compact size, lower cost, and excellent robustness against environmental exposure. All these practical advantages are highly desirable in the broad variety of the continuously developed application fields. The nonlinear optic Kerr-effect, i.e. the dependence of the refractive index on the intensity (peak power), has established another type of effective modulators with femtosecond time response They are NPE [6], nonlinear optical and amplifying loop mirrors (NOLM and NALM) [7,8]. The benefits of the simultaneous use of two SAs with a different recovery time for the creation of hybrid mode-locking have been recently proved in several works [9,10,11], by demonstrating generation of ultrashort pulses with higher average power, temporal purity, and higher frequency stability
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
