Transverse mode instability threshold enhancement in Yb-doped fiber lasers by cavity modification

Abstract

To enhance the transverse mode instability (TMI) threshold of a fiber oscillator, a novel configuration is presented. In this configuration the oscillator cavity length is considerably reduced and the remaining active fiber is released out of the cavity to absorb the rest of the pump power and amplify the output signal of the cavity. In fiber oscillators, the index gratings generated by both forward and backward propagating signals can interact with light propagating in the backward and forward directions and degrade the output beam quality. In the proposed modified configuration, due to lower intra-cavity forward and backward signal power the index grating is smoothed and the TMI threshold is increased. Experimental results indicate that this modified configuration has a higher TMI threshold than a conventional fiber oscillator. Finally a higher TMI threshold is achieved in the bidirectional pumping scheme of the modified configuration.

A Novel Bidirectional Output Oscillating-Amplifying Integrated Fiber Laser With 2 Ports × 2 kW Level Near-Single-Mode Output

“…However, both OC-FBGs structure in the bidirectional fiber laser resonator led to less round-trips times of laser in the cavity, finally resulting in low utilization of pumping. In order to increase the transverse mode instability (TMI) threshold and pumping utilization of fiber laser oscillators, Hejaz et al proposed the oscillating-amplifying integrated fiber laser (OAIFL), which increased the TMI threshold by about 26% [15]. Fig.…”

A 3.7-kW Oscillating-Amplifying Integrated Fiber Laser Featuring a Compact Oval-Shaped Cylinder Package

“…In some application scenarios, fiber lasers are challenged by harsh environments and/or strong reflecting light. Recently, an oscillating-amplifying integrated fiber laser has been proposed [ 13 , 14 , 15 , 16 ], which has the advantages of high efficiency, environmental robustness, and anti-reflection [ 13 , 14 ]. A 5-kW oscillating-amplifying integrated fiber laser has previously been demonstrated in [ 16 ], which presents a new high-power laser structure for use in industrial applications.…”

Theoretical demonstration of a novel bidirectional output oscillating-amplifying integrated fiber laser

“…In 2022, Zhong et al achieve a 2×2kW near-singlemode bidirectional output with an all-fiber linear cavity fiber laser structure [5] . In 2018, Hejaz et al proposed the oscillating-amplifying integrated fiber laser to achieve the further utilization of the pump light [6] . Enlightened by the advantages of these two structures, a novel bidirectional output oscillating-amplifying integrated fiber laser (B-OAIFL) is proposed and studied theoretically for the first time, the influences of the relevant parameters on the characteristics of the output laser are preliminarily studied in theory, and the feasibility of the B-OAIFL is theoretically demonstrated.…”