Completely monolithic linearly polarized high-power fiber laser oscillator

Abstract

We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M² < 1.2). Pump power is delivered via a high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers.Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed 1 . Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

13 kW monolithic linearly polarized single-mode master oscillator power amplifier and strategies for mitigating mode instabilities

“…Many applications, such as coherent lidar system, nonlinear frequency conversion, coherent beam combining architectures, require high power linearly-polarized laser sources with single mode operation or near-diffraction-limited beam quality [1,2]. Recently, linearly-polarized fiber laser with 1kW output power has been achieved in a monolithic fiber Bragg grating (FBG)-based Fabry-Pé rot cavity [3], which employed a pairs of high power FBGs. It is a technological challenge to design FBG that can withstand multi-kilowatt power, and further power scaling may confront with some technological difficulties.…”

“…Recently, linearly-polarized fiber laser with 1kW output power has been achieved in a monolithic fiber Bragg grating (FBG)-based Fabry-Pé rot cavity [3], which employed a pairs of high power FBGs. It is a technological challenge to design FBG that can withstand multi-kilowatt power, and further power scaling may confront with some technological difficulties.…”

15 kW ytterbium-doped single-transverse-mode, linearly polarized monolithic fiber master oscillator power amplifier

“…Employing this scheme, output power from several tens of watts [15] to kilowatt level has been demonstrated. In 2014, Belke et al announced a 1 kW single-transverse-mode linearly polarized all-fiber oscillator, which was the highest linearly polarized output power reported to date [16]. Increasing the output power may eventually be limited by the pump brightness and the optical power the gratings can endure [17].…”

Mitigating of modal instabilities in linearly-polarized fiber amplifiers by shifting pump wavelength

“…High-power linearly polarized (LP) fiber sources are required in many applications, such as a coherent lidar system, nonlinear frequency conversion, and coherent beam-combining architectures [1][2][3][4]. An LP fiber laser with 1 kW output power was achieved recently [5], which employed a pair of highpower monolithic fiber Bragg grating (FBG) in a Fabry-Pérot cavity. It is a technological challenge to design an FBG that can withstand multi-kilowatt power, and further power scaling through oscillators may confront some technological difficulties.…”