Multi-kW cw fiber oscillator pumped by wavelength stabilized fiber coupled diode lasers

Abstract

High power Yb doped fiber laser sources are beside CO 2 -and disk lasers one of the working horses of industrial laser applications. Due to their inherently given robustness, scalability and high efficiency, fiber laser sources are best suited to fulfill the requirements of modern industrial laser applications in terms of power and beam quality.Pumping Yb doped single-mode fiber lasers at 976nm is very efficient. Thus, high power levels can be realized avoiding limiting nonlinear effects like SRS. However the absorption band of Yb doped glass around 976nm is very narrow. Therefore, one has to consider the wavelength shift of the diode lasers used for pumping.The output spectrum of passively cooled diode lasers is mainly defined by the applied current and by the heat sink temperature. Furthermore the overall emission line width of a high power pump source is dominated by the large number of needed diode laser emitters, each producing an individual spectrum.Even though it is possible to operate multi-kW cw single-mode fiber lasers with free running diode laser pumps, wavelength stabilizing techniques for diode lasers (e.g. volume holographic gratings, VHG) can be utilized in future fiber laser sources to increase the output power level while keeping the energy consumption constant.To clarify the benefits of wavelength stabilized diode lasers with integrated VHG for wavelength locking the performance of a dual side pumped fiber oscillator is discussed in this article. For comparison, different pumping configurations consisting of stabilized and free-running diode lasers are presented.

Development and thermal management of 10kW CW, direct diode laser source

“…This is mainly driven by the significant advantages of diode lasers over their CO 2 laser counterpart, including the high material absorption and electro-optical conversion efficiency, etc. [4][5][6]. The output wavelengths of 9xx nm highpower diode lasers are shorter than that of CO 2 lasers.…”

A 3kW single-mode continuous laser based on multi-stage amplifiers fiber system

“…In recent years, with the improvement of Large Mode Area (LMA) gain fiber technology, high brightness semiconductor pump sources, and high-power fiber coupler devices, fiber lasers have continuously developed towards higher power and beam quality. The Yb-doped fiber (YDF) with LMA has shown tremendous progress in attaining kilowatt and even multi-kilowatt with near diffraction-limited beam quality [2][3][4][5]. Fiber lasers are widely used in industrial manufacturing, scientific research, national defense and military industry due to their high electro-optical conversion efficiency, good beam quality, simple thermal management, and ease of integration.…”

Theoretical study of the effect of pump wavelength drift on mode instability in a high-power fiber amplifier

“…Because it has such a far-reaching impact, signal/pump wavelength [15][16][17][18][19][20][21], fiber coiling [22][23][24][25] and fiber parameters such as core/cladding size [19,[25][26][27][28][29] have been investigated to gain a deeper insight into MI. It has been reported theoretically and experimentally that the MI threshold is reduced when the total pump absorption is reduced by shortening the fiber length [21,28], which is one of the ways to suppress the pump power noise [14] and nonlinear effects [30].…”

“…It has been reported theoretically and experimentally that the MI threshold is reduced when the total pump absorption is reduced by shortening the fiber length [21,28], which is one of the ways to suppress the pump power noise [14] and nonlinear effects [30]. Previous research has confirmed that without accurate wavelength stabilization technology the pump wavelength changes during operation [31,32], which affects the optical-to-optical efficiency by changing the pump absorption [20]. For a fiber laser system pumped with an unstabilized laser diode, the pump…”