Coherent beam combination of two nanosecond fiber amplifiers by an all-optical feedback loop

Abstract

A passive coherent beam combination of two nanosecond amplifiers is realized by using an all-optical feedback loop. The width of the combined pulses is 9.7 ns, and the pulse repetition frequency is 2.023 MHz. With the least mismatch between pulse period and time of the cavity round trip in our loop, the visibility of far-field coherent patterns is more than 71%. The dynamics of passive phase locking is studied, and the established time of phase locking of two pulsed amplifiers is at least 10 cavity round trips in the all-optical feedback loop.

Experiments and Perturbative Analysis of Dammann-Grating-Based Aperture Filling in a Passive Coherent Beam Combination

“…On the other hand, shorten the length of the all-optical feedback loop will reduce the residual phase error contribute to the stimulated Brillouin scattering and the fourwave mixing. This method can also reduce the establish time of passive phase-locked and enhance robustness to environmental perturbations [12]. Moreover, this aperture filling technology could apply to other CBC methods, which have less residual phase error.…”

“…The other is achieving a power scaling of each amplified channel can be realized by multistage amplification. Moreover, because of the passive CBC all-optical phasing mechanism, the complicated electronic servo systems often used for active phase-locked counterparts are not required [12]. However, in CBC technology, too much energy resides in undesired side lobes of the far field of a phase-locked fiber laser array.…”

Passive Coherent Polarization Beam Combination of a Four-Fiber Amplifier Array

“…Coherent beam combination (CBC) of fiber lasers/amplifiers has attracted intensive attention due to its advantageous aspect of brightness scaling [1]- [16]. Generally speaking, CBC can be classified into two categories, CBC of fiber amplifiers seeded by a common oscillator with active phasing technique [1]- [5] and passive phasing of a fiber laser/amplifier array without external control phase differences among the amplifier chains [7]- [16].…”

“…Generally speaking, CBC can be classified into two categories, CBC of fiber amplifiers seeded by a common oscillator with active phasing technique [1]- [5] and passive phasing of a fiber laser/amplifier array without external control phase differences among the amplifier chains [7]- [16]. However, in order to further boost the coherent output power by CBC configuration, the power enhancement of the individual amplifier chain should be considered significantly.…”

Dammann-grating-based passive phase locking by an all-optical feedback loop

“…Figure 3(b) shows the in-phase mode, which is stable and robust, and the visibility of it is up to 88.7%. We define the visibility by the formula V I max − I min ∕I max I min , in which I max and I min are the maximum intensity and the adjacent minimum intensity of the primary maximum on the intensity distribution pattern, respectively [18]. The high number of sidelobes in the in-phase mode is due to the poor fill factor (∼0.6) in the near field.…”