Effect of feedback elements on the phase locking properties of fiber lasers via mutual injection coupling

Coherent combining of several multi-wavelength fiber lasers is a promising approach to suppress the nonlinear effects and improve the output power. Passive phase locking of two multi-wavelength fiber lasers has been demonstrated by using mutual injection coupling and spatial filtering technique, and the effect of feedback elements on the phase locking properties has been investigated in detail. Three different kinds of feedback elements, fiber Bragg grating (FBG), fiber loop mirror (FLM) and fiber reflection mirror (FRM) are employed as the component laser’s high reflection mirror to construct the phase locking array respectively. Compared with the traditional feedback element FBG, the FLM is made of a 3dB fiber coupler and provide high reflection feedback in a wide spectral range for fiber laser, and the FRM is also a wide-band reflector with the fiber end coated by multilayer dielectric film. When the FLM and FRM are employed as the component laser’s feedback elements, a large number of longitudinal modes operate simultaneously and the spectra vary continuously. Fortunately, stable phase locking has been obtained as long as the single-mode filtering fiber is introduced into the feedback loop, and obvious interference patterns with high fringe visibility have been observed in far field. The phased array’s output power can also keep stable at the same time, and its amount is higher than the case of using FBG. In conclusion, the research results indicate that efficient phase locking of several multi-wavelength fiber lasers can also be achieved by passive self-adjusting method and higher output power can be obtained compared with the usual coherent combining of narrow-band laser beams, as long as necessary optical coupling is introduced among component lasers and proper spatial filtering measures are adopted.

[1]  Pu Zhou,et al.  Coherent beam combination of three two-tone fiber amplifiers using stochastic parallel gradient descent algorithm. , 2009, Optics letters.

[2]  Alain Barthélémy,et al.  Coherence properties of two fiber lasers coupled by mutual injection. , 2009, Optics express.

[3]  Philippe Roy,et al.  Coherent combining of fibre lasers , 2006 .

[4]  Mutual injection phase locking coherent combination of solid-state lasers based on corner cube. , 2013, Optics letters.

[5]  Tso Yee Fan,et al.  Beam combining of ytterbium fiber amplifiers (Invited) , 2007 .

[6]  Pu Zhou,et al.  Phase locking of a 275 W high power all-fiber amplifier seeded by two categories of multi-tone lasers. , 2011, Optics express.

[7]  Liu Zejin,et al.  Analysis of multiwavelength coherent beam combining effect. , 2012, Applied optics.

[8]  Pu Zhou,et al.  Mutual Injection-Locking and Coherent Combining of Two Individual Fiber Lasers , 2008 .

[9]  Bing Lei,et al.  Coherent combining of fiber lasers using a ring coupled cavity and single-mode fiber filtering , 2009 .

[10]  Pu Zhou,et al.  Coherent beam combining of high power fiber lasers: Progress and prospect , 2013, Science China Technological Sciences.

[11]  Pengfei Ma,et al.  Analysis of multi-wavelength active coherent polarization beam combining system. , 2014, Optics express.

[12]  Bing Lei,et al.  Phase locking of an array of three fiber lasers by an all-fiber coupling loop. , 2007, Optics express.

[13]  Asher A. Friesem,et al.  Passive phase locking of 25 fiber lasers. , 2010, Optics letters.

[14]  Jérôme Lhermite,et al.  Passive phase locking of an array of four fiber amplifiers by an all-optical feedback loop. , 2007, Optics letters.