High gain in a dual-pass rod-type fiber amplifier

Abstract

Single-pass amplification using rod-type fibers has become a common route to pulsed laser sources around 1030 nm with high average and peak power. Average-power scaling is currently limited by the dynamic thermooptic phenomenon of "transverse mode instability." In comparison, double-pass amplifier configurations have not been extensively studied. Recent theoretical and experimental work has shown both static and dynamic mode degradation phenomena, including an unexpected nonlinear polarization rotation effect. Here we present new results obtained with a modified setup using polarization filtering between the first and the second pass. We obtain up to 113 W output power, i.e., more than 40 dB of amplification from a single amplifier module seeded by 10 mW of 20 ps/20 MHz/1030 nm pulses. We observe excellent beam quality and polarization extinction ratio. Finally, we investigate a wide range of seed powers and report a strong increase in the static mode deformation threshold with decreasing seed power. The experimental results are corroborated by numerical simulations.

Photonic crystal rod-based high-performance ultrafast fiber laser system

“…In contrast with the previous reported experimental research on rod-fiber ultrafast laser systems [21][22][23][24] , in our work, in addition to the general concerned average power, pulse energy, and pulse duration, we have also directed our research towards a beam pointing stability promotion technique. Therefore, we innovatively implemented a research work on improving beam pointing stability performance of high-power femtosecond fiber CPA laser systems, and presented a photonic crystal rod-based high-performance femtosecond fiber CPA laser source.…”

“…The most successful attempt of MFA increment is the development and use of rod-type photonic crystal fibers. Exceptional performances in terms of average power and pulse energy have been demonstrated using photonic crystal rod [21][22][23][24] .…”

“…However, research into improving beam pointing stability has been rarely mentioned, such as in Refs. [21][22][23][24]. As a result, in order to meet the critical requirements of practical application, in femtosecond CPA laser systems with large dispersion manipulation, how to reasonably design and integrate the optical route of the compressor and simultaneously ensure the promotion of beam pointing stability remains an important research subject and of great significance.…”

Experimental investigations of seeding mechanisms of TMI in rod fiber amplifier using spatially and temporally resolved imaging

“…The spatial distributions of the three TMI peaks above 100 Hz show the same dynamics with different variations. A recent work regarding dual-pass rod-type fiber amplifiers [22] has shown that vectorial modes are needed to fully describe the mode properties of these large core rods, but in this work we use the LP-modes for simplicity. All the TMI fluctuations in Fig.…”