High-power spectral beam combining of linearly polarized Tm:fiber lasers

Abstract

To date, high-power scaling of Tm:fiber lasers has been accomplished by maximizing the power from a single fiber aperture. In this work, we investigate power scaling by spectral beam combination of three linearly polarized Tm:fiber MOPA lasers using dielectric mirrors with a steep transition from highly reflective to highly transmissive that enable a minimum wavelength separation of 6 nm between individual laser channels within the wavelength range from 2030 to 2050 nm. Maximum output power is 253 W with M(2)<2, ultimately limited by thermal lensing in the beam combining elements.

Spectral beam combining of kW-class thulium-doped fiber lasers

“…To obtain diffraction-limited laser output powers in the multi-kW-regime, incoherent beam combination schemes such as spectral beam combination (SBC) could be utilized. Typically, dichroitic mirrors [5] and optical gratings [6] are common candidates for SBC. Yet, they have been (thermally) limited to a few hundred Watts of combined output power so far.…”

Emission Wavelength Limits of a Continuous-Wave Thulium-Doped Fiber Laser Source Operating at 1.94 µm, 2.09 µm or 2.12 µm

“…In these systems, the maximum output power reported in the literature was 567 W at 1.97 µm, achieved by Walbaum et al in 2016 [13]. Master-Oscillator Power Amplifier (MOPA) systems that are composed of a first low-power signal source (single-oscillator laser source or 2 µm diode) and one or more amplification stages were also studied in the literature (black dots in Figure 2) [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The highest output power generated in a monolithic MOPA source so far is 1100 W at 1.95 µm reported in 2021 [26].…”

Design and fabrication of dichroic filter with reduced absorption for spectral beam combining

“…Schmidt found the growth of temperature mainly as a function of transmitted power, meanwhile the decline of beam quality and the shift of focus position of the reflected beam that reflects from the thermal lensing area of the dichroic filter are functions of the transmitted laser beam powering up [4]. Shah ascribed the degradation beam quality of combined beam to the thermal effect in combination process, because of the higher asymmetry and astigmatism than the individual beams and the shifted location of the combined beam waist which not observed for individual beam [5]. Chen investigated the transversal beam profile in focal plane of combined laser beam, reflected beam, transmitted beam, transmitted beam without passing through the filter separately [6].…”