We report the passive phase locking of an array of four fiber amplifiers in a unidirectional ring cavity. The feedback loop consists of a single-mode fiber that filters intracavity the far-field pattern of the four emitted beams. The pointing of the laser output can be managed by the intracavity filtering.
"The system analyzed in this paper is that of a ring laser cavity consisting of an array of fiber amplifiers used as gain media. A fraction of the amplifiers' output is spatially filtered by a singlemode feedback fiber, the output of which is coupled to the input end of the amplifier array by a 1-to-N splitter –. This arrangement is similar to other external cavity reimaging techniques based on the Talbot ,  and self-Fourier  cavities, in which the power in unwanted higher order modes is removed by spatial filtering. "
[Show abstract][Hide abstract] ABSTRACT: In this paper, a formulation of the cavity mode structure, loss, and beam quality of a ring-cavity fiber laser beam combining apparatus is developed, which shows that the resonator is rigorously single mode. The passive phasing property is clearly understood on the basis of the theory, and conditions are specified for a cavity that permits the attainment of optimum phasing conditions. An important result is that reduction of over-all cavity loss must be achieved at the price of reduction of maximum array size, although mitigated by the property that this loss occurs in the low-power feedback leg. Application of the analysis to specific examples gives the dependence of cavity loss and Strehl ratio on fiber and cavity properties.
IEEE Journal of Selected Topics in Quantum Electronics 05/2009; 15(2-15):320 - 327. DOI:10.1109/JSTQE.2008.2011999 · 2.83 Impact Factor
"Active phase controlling techniques require complicated phase detection and correction for each element of the array. To obtain easy and practical phase locking array of fiber lasers, developing these schemes with all-fiber arrangement, multiports output, and without active phase correction, are one of the current interests in coherent combining fields  . "
[Show abstract][Hide abstract] ABSTRACT: Passive phase locking of multiple fiber lasers by using a common all-fiber ring cavity is proposed and demonstrated. The cavity is chiefly composed of multiple 2×2 fiber couplers, which are insets of component fiber lasers of an array. The common ring cavity not only acts as a ring filter for mode selection and stabilization of component fiber lasers, but also provides a common channel for mutual injection coupling among them. We have demonstrated efficient phase locking of multiple Erbium-doped fiber lasers with linear and ring resonators based on the common ring cavity configuration, and obvious interference patterns and stable coherent output have been observed in experiment. The power transmission and resonance properties of the ring cavity are investigated theoretically by the intensity and amplitude addition methods. The research results indicate that increasing the coupling ratio of fiber couplers can increase the coupling strength, and decreasing the loss of the common ring cavity can increase both the coupling strength and combining efficiency. Finally, the phase locking mechanism of the presented scheme is discussed, and we believe that the phase locking array forms a composite resonator on account of the common ring cavity, and the array achieves phase locking states through mutual injection coupling among component lasers.
Proceedings of SPIE - The International Society for Optical Engineering 12/2008; 7158. DOI:10.1117/12.807042 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Coherent combining of two fiber lasers has been experimentally demonstrated by using a ring coupled cavity and single-mode
fiber filtering technique. Their phases are primarily synchronized due to mutual injection coupling introduced by a common
ring coupled cavity, and efficient phase locking is realized by utilizing a single-mode feedback fiber to filter the far-field
pattern. The detailed experimental investigations indicate that the stability of phase locking can be improved significantly
by this spatial filtering technique, and the far-field intensity distribution can be manipulated by controlling the position
of the filtering fiber.
Applied Physics B 10/2009; 97(2):469-473. DOI:10.1007/s00340-009-3655-0 · 1.86 Impact Factor
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