We report here a monolithic all-fiber laser oscillator with femtosecond-written FBGs and side-pumping coupler. The splice-free resonant cavity is realized by directly writing a pair of fiber Bragg gratings (FGBs) into an ytterbium-doped fiber (YDF) based on the femtosecond laser phase mask scan method. Furthermore, a (2+1)×1 side-pumping coupler is fabricated in the same YDF by the taper-fused method. When pumping with two 976 nm laser diodes (LD), a maximum output power of 1218 W is realized at the 1070 nm, corresponding to the optical-optical conversion efficiency of about 71%. This work displays an extremely compact and stable fiber laser oscillator, which is of great significance to the development of high power fiber lasers.
Mid-infrared fiber lasers have shown out standing prospects in many fields, so mid-infrared fiber Bragg grating (FBG) as the most essential component in mid-infrared fiber laser oscillators has attracted much attention. Here, we fabricated mid-infrared FBGs on ZBLAN fibers operating nearby 2.8-2.9 μm by femtosecond laser direct inscription technique, and measured their transmission spectra by all-fiber measurement system, which lays the foundation of high-power all-fiber mid-infrared laser oscillators near 2.8 μm.
Here, we use a compact gas cavity based on anti-resonance hollow-core fiber (HCF) for trace gas detection. Since there are lots of characteristic absorption lines (P and R branch) of CO2 molecule in 2 μm band, we used a self-made 2 μm fiber amplifier seeded by a precisely tunable narrow linewidth diode laser as the detection light source. The absorption characteristics of R(26), R(28), R(30) and R(32) at different CO2 pressure are measured and analyzed. This work provides a potential cost-effective method for the high-precision detection of trace gas.
In this paper, we fabricate FBGs-based FPCs using femtosecond laser and the temperature characteristics is studied. The FBGs are inscribed by line-by-line scanning technique, by which the FBGs can be limited to a specific area in the fiber core region. Besides, the grating length, the grating position and the distance between two successive FBGs can be precisely controlled to adjust bandwidth and free spectral range. FP interference is obviously seen in reflection and transmission spectrum. Line-by-line inscribed FPC is a good candidate for sensing application.
Chirped and tilted fiber Bragg gratings (CTFBGs) have attracted a lot of attention for stimulated Raman scattering (SRS) suppression in high-power fiber laser systems in past years. Here, we fabricate CTFBGs in large-mode-area double cladding fibers and demonstrate its application in a 2-kW fiber laser for SRS filtering at the system’s output. A maximum Raman suppression of about 17 dB is obtained at the central wavelength, and the insertion loss is smaller than 0.2 dB for signal laser. In addition, no obvious degradation of laser beam quality is observed. Better suppression effect could be achieved by broadening the rejection bandwidth of the CTFBGs in the future.
In this paper, mode distribution in large-mode-area (LMA) 25/400 fiber was investigated while attempts to recognize and sort different modes with their combination were carried out on a CNN net via Tensorflow. VGG16 model was chosen as the backbone net through several test to increase precision. The model was trained on a dataset including 6000 pictures in 15 categories. And the final accuracy was up to 0.98. It indicates that recognizing modes in high power fiber laser system based on a CNN net was a feasible plan in the mode control assignment.
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