Experimental investigation of a passively mode-locked fiber laser based on a symmetrical NOLM with a highly twisted low-birefringence fiber

• Published in: Laser physics Vol. 18; no. 7; pp. 914 - 919
• Main Authors: Ibarra-Escamilla, B., Pottiez, O., Kuzin, E. A., Grajales-Coutiño, R., Haus, J. W.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.07.2008; Springer
• Subjects: Exact sciences and technology; Fiber lasers; Fundamental areas of phenomenology (including applications); Laser optical systems: design and operation; Lasers; Modulation, tuning, and mode locking; Nonlinear optics; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Ultrafast processes; optical pulse generation and pulse compression; 42.65.-k; 42.55.Wd; 42.81.-i; Output power; Laser mode locking; Circular polarization; Mode locked laser; Linear polarization; Birefringent fiber; Autocorrelations; Experimental study; Nonlinear optics; ps range; Fiber lasers; Non linear loop mirror
• ISSN: 1054-660X; 1555-6611
• DOI: 10.1134/S1054660X08070177

We experimentally investigate the passive mode-locking operation of a figure eight-fiber laser based on a symmetrical nonlinear optical loop mirror (NOLM) with a highly twisted low-birefringence fiber in the loop. NOLM switching is achieved by the polarization asymmetry between the counterpropagating beams in the loop. The most efficient switching is obtained when we have linear polarization for one of the beams and the circular polarization for the other. We used a quarter-wave retarder (QWR) in the NOLM loop to break the polarization symmetry. Through the QWR position, it is possible to adjust the transmission behavior from a maximum to a minimum at a low input power. With our configuration, it is possible to get self-starting mode-locking operation at a specific position of the QWR. This QWR position corresponds to a value close to the minimal transmission. The pulse repetition frequency was 0.8 MHz. The mode-locked laser ran in a stable operation for hours. We achieved a stable generation of picosecond pulses with milliwatts of an average output power.