We present a hundred-watt-level linearly-polarized random fiber laser (RFL) pumped by incoherent broadband amplified spontaneous emission (ASE) source and prospect the power scaling potential theoretically. The RFL employs half-opened cavity structure which is composed by a section of 330 m polarization maintained (PM) passive fiber and two PM high reflectivity fiber Bragg gratings. The 2nd order Stokes light centered at 1178 nm reaches the pump limited maximal power of 100.7 W with a full width at half-maximum linewidth of 2.58 nm and polarization extinction ratio of 23.5 dB. The corresponding ultimate quantum efficiency of pump to 2nd order Stokes light is 86.43%. To the best of our knowledge, this is the first demonstration of linearly-polarized high-order RFL with hundred-watt output power. Furthermore, the theoretical investigation indicates that 300 W-level linearly-polarized single-mode 1st order Stokes light can be obtained from incoherently pumped RFL with 100 m PM passive fiber.

We demonstrate a random distributed feedback fiber laser at 2.1 μm. A high-power pulsed Tm-doped fiber laser operating at 1.94 μm with a temporal duty ratio of 30% was employed as a pump laser to increase the equivalent incident pump power. A piece of 150 m highly GeO₂-doped silica fiber that provides a strong Raman gain and random distributed feedbacks was used to act as the gain medium. The maximum output power reached 0.5 W with the optical efficiency of 9%, which could be further improved by more pump power and optimized fiber length. To the best of our knowledge, this is the first demonstration of random distributed feedback fiber laser at 2 μm band based on Raman gain.

We demonstrated a high-power continuous-wave (CW) dual-wavelength Ho-doped fiber laser (HDFL) at 2049 nm and 2153 nm with a simple coupled-cavity configuration. A ~100 W laser diode-pumped fiber laser at 1150 nm served as the pump source. The maximum output power reached ~22.3 W and the slope efficiency was 23%. By altering the incident pump power, the power ratio of two signal wavelengths could be tuned in a large range due to gain competition. As far as we know, this is the first CW dual-wavelength HDFL with the power exceeding ten-watt-level, and the first dual-wavelength HDFL with the central wavelengths exceeding 2.0 μm and 2.15 μm respectively.

We demonstrate a linearly polarized random distributed feedback Raman fiber laser with record 86.3 W output power with a piece of 157 m long polarization maintaining (PM) fiber. The maximum optical efficiency of first-order-Stocks light at 1120 nm reaches ~74% while pumping at 1070 nm. The full width at half maximum (FWHM) at maximum output power is ~2 nm and the polarization extinction ratio (PER) is measured to be as high as 22 dB. To the best of our knowledge, this is the highest output power for linearly-polarized random fiber laser.

In this paper, we proposed a temperature modulation technique for the suppression of stimulated Brillouin scattering (SBS). This technique can achieve different kinds of temperature distributions in a high-power laser system with compact design and safe operation. We built up an experiment platform and a theoretical model to evaluate the performance of the temperature modulation technique by applying different temperature distributions along the gain fiber. A total of 3.3 dB SBS suppression can be achieved with only a 70 °C temperature gradient at 36 W output power in this experiment. During the experiment, optical frequency domain reflectometry (OFDR) was used to measure the temperature distributions of the gain fiber core under the effect of the temperature modulation technique. By further simulating and optimizing the temperature distributions, we can see the potential of SBS suppression rise to 3.5 dB with this temperature modulation technique. Through these studies, we demonstrated our temperature modulation technique with high flexibility and great potential for SBS suppression in a high-power single-frequency laser system.

Understanding the laser-induced thermal damage mechanism is important to the development of high power continuous wave (CW) laser. In this paper, we monitor the evolution of damage via a self-build optical element testing platform and build a correspond theoretical model based on the temperature field and heat conduction theory. The waveband of optical coatings (ZnSe and YbF3) under test is dedicated for the mid-infrared. Using a 10 kW level mid-infrared CW laser, the thermal stress damage process of the optical coatings caused by surface contaminants is recorded. The Finite Element Method was employed to calculate the thermal damage mechanism of mid-infrared optical coatings. The calculated thermal damage mechanism agrees very well with our experiment. To the best of our knowledge, this is the first comprehensive study on thermal damage mechanism of mid-infrared coatings with surface contaminants induced by CW laser.

No abstract

No abstract