Maximizing power output from continuous-wave single-frequency fiber amplifiers

Abstract

This Letter reports on a method of maximizing the power output from highly saturated cladding-pumped continuous-wave single-frequency fiber amplifiers simultaneously, taking into account the stimulated Brillouin scattering and transverse modal instability thresholds. This results in a design figure of merit depending on the fundamental mode overlap with the doping profile, the peak Brillouin gain coefficient, and the peak mode coupling gain coefficient. This figure of merit is then numerically analyzed for three candidate fiber designs including standard, segmented acoustically tailored, and micro-segmented acoustically tailored photonic-crystal fibers. It is found that each of the latter two fibers should enable a 50% higher output power than standard photonic crystal fiber.

Experimental Investigations on TMI and IM-FWM in Distributed Side-Pumped Fiber Amplifier

“…[43] (the V-value of gain fiber is 5.7735). On the other hand, when the bending diameter decreases, the bend-induced mode coupling becomes serious which means the higher-order mode can be excited and the higher power ratio of the HOMs account for [16] (see Fig. 10).…”

“…[8], [9] revealed that a small frequency shift (about kHz) between the fundamental and highorder modes should be indispensable for the presence of TMI. Some measures for improving the TMI threshold (i.e., the output power corresponding to the presence of TMI) have been presented such as increasing the power of single-mode seed light [10], [11], increasing the linewidth of seed light [12], [13], increasing the loss of high-order modes (e.g., realized by coiling fiber [14], [15]), optimizing the doping of the core [11], [16], shifting the pump or signal wavelength [17], [18] and so on.…”

Transverse mode instability mitigation in a high-power confined-doped fiber amplifier with good beam quality through seed laser control

“…The TMI effect has now become one of the major limiting factors for the power scaling of high-brightness fiber lasers. In order to mitigate the TMI effect, various methods have been proposed, including but not limited to increasing the loss of high-order modes [6], shifting the pump or signal wavelength [7][8][9], employing the counter/bi-directional pumping scheme [10,11], increasing the ratio of cladding diameter to core diameter [12], exploiting specialty optical fiber design [13][14][15][16][17], etc. Among these solutions, adopting the specialty optical fibers, such as distributed mode filtering fiber [18], large-pitch fiber [19], tapered fiber [20], and confined-doped fiber [21], is an effective approach to solving the contradiction between the high output power and good beam quality.…”

Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

“…After TMI is commonly observed in the experiment, researchers have delivered huge efforts to mitigate this effect, for example, by modifying the fiber parameter [7][8][9], using different-linewidth seed lasers [10,11], and optimizing the pump direction or its wavelength [12][13][14]. These methods mainly focus on passive optical devices, but they cannot change the inherent mechanism which causes TMI.…”