A Q-switched mode-locked (QML) laser at 2 μm waveband is demonstrated with with a maximum average power of watts. Graphene oxide are prepared by the vertical growth method and employed as a saturable absorber for passively QML operation. The stable QML pulses at 1897 nm are obtained with pulse width of 5.04 ns. The maximum output power of the laser is 1050 mW with a pump power of 20 W for an output coupler of 9%. The repetition frequency and width of QML pulses are 53.19 MHz and 5.04 ns, respectively. The modulation depth reach almost 100%. The Watt level QML all-solid-state Tm, Ho:LLF ceramic laser has broad application prospects in space target detection, environmental detection, and nonlinear optical research.
Eccentric fiber Bragg gratings (EFGBs) in standard single-mode optical fiber by using point-by-point direct writing technique with 800 nm femtosecond laser. The experimental results show that the transmission spectrum amplitude is coupled by Bragg and cladding mode resonance over a wide spectrum range. Meanwhile, the spectral characteristics of EFBGs were studied by adjusting grating period, grating length, laser power and eccentric distance. The eccentric distance is the most essential parameter in terms of inscribing gratings. It can break up the original structural symmetry of the fiber by changing the offset of grating in the fiber core. This change will bring great opportunities and breakthroughs to the application of EFGBs.
The effects of pulse power, filling ratio, number of period and period on the long-period fiber gratings (LPFGs) by using radiation of femtosecond laser. The results show that the strong resonance peaks of LPFGs can be induced and the resonant peaks have different degrees of offset. When the parameters of the LPFG are set to be number of grating period of 70, filling ratio of 0.5, pulse power of 2.0 mW and period of 500 μm, the first resonance peak of LPFG has a blue-shift of 147.3 nm. Furthermore, the size of first resonance peak of LPFG is -19.4 dB. These characteristics of LPFGs provide a favorable opportunity for in-depth research of late-model sensing devices.
In this paper, the fabrication mechanism of Fiber Bragg Gratings (FGBs) in standard SMF-28 telecommunication fibers without hydrogen loading were explored by using point-by-point (PBP) direct writing method based on femtosecond laser with pulse duration of 100fs, 1kHz repetition rate, a central wavelength of 800nm. And more, a series of FBGs were successfully fabricated. The spectral characteristics of FBGs were explored by adjusting grating period, grating length and laser power. And the FBGs with different center wavelengths and periods were fabricated in order to obtain optimal spectral properties. The result shows that the resonant peak intensity is strengthen when the grating length and laser power was improved. This research will demonstrate the potential application of the developed FBGs for use in multi-wavelength fiber lasers and a variety of high temperature applications.
In this paper, the long period fiber gratings (LPFGs) in standard SMF-28 telecommunication fibers without hydrogen loading were inscribed by using point-to-point direct writing method of femtosecond laser pulses with pulse duration of 100 fs, repetition rate of 1kHz and a central wavelength of 800 nm. The LPFGs with different spectral characteristics were fabricated by adjusting grating period, grating length and duty ratio. The results show that the resonant peak wavelengths shift to the long-wave direction with the increase of the grating length increasing. The variations of duty ratio will lead to the generation of resonance rejection band of LPFGs from singlepeak to multi-peak plus lesser out-of-band loss.
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