Multi-wavelength Q-switched Fiber Laser Research Articles

Characterization of multi-wavelength Q-switched fiber laser by changing wavelength separation of filter

Abstract In this paper, we present a simple compact and low threshold laser that has characteristics of Q-switched and multi-wavelength oscillation simultaneously. Multi-wavelength Q-switched oscillation is realized by inserting a Sagnac filter as a multi-wavelength filter and a section of unpumped erbium-ytterbium co-doped fiber (EYDF) into the laser cavity as a saturable absorber (SA). The characteristics of multi-wavelength Q-switched fiber laser affected by wavelength separation of filter and pump power are investigated. The number of Q-switched wavelengths increases and the wavelength separation of the laser reduces with wavelength separation of the filter decreasing. Stable multi-wavelength oscillations at wavelength separation of 0.4–0.8 nm were obtained by increasing the length of polarization maintaining fiber (PMF) in the Sagnac filter. Moreover, the number of wavelengths and wavelength separation are increased by increasing the pump power when the filter is fixed. Further, the multi-wavelength laser is verified to have Q-switched properties at each wavelength, which is filtered from laser output through a narrow-band tunable filter outside of the cavity.

Effects of dispersion on characterization of multi-wavelength Q-switched fiber laser

In this paper, a real-time switchable and reconfigurable multi-wavelength Q-switched fiber laser has been experimentally carried out, which is based on a real-time configurable filter (WaveShaper) and a section of unpumped erbium–ytterbium co-doped fiber (EYDF) as a saturable absorber (SA). The proposed multi-wavelength Q-switched laser has been demonstrated to generate different combination of wavelengths at 100 GHz and 200 GHz International Telecommunications Union (ITU) grids specifications. The WaveShaper not only acts as a multi-channel filter but also introduces wavelength-dependent loss (WDL) in the laser cavity. The WDL can effectively suppress the mode competition caused by homogeneous gain broadening of EDF. The attenuation at each wavelength is adjusted to equalize optical power of different channels. The effects of dispersion on the performance of multi-wavelength Q-switched fiber laser are investigated by introducing additional dispersion from WaveShaper. No significant wavelength drift was observed after monitoring of an hour, multi-wavelength Q-switched operation is clearly demonstrated with a good stability at room temperature.

Ni-NPs doped PVA: An efficient saturable absorber for generation multiwavelength Q-switched fiber laser system near 1.5 μm

We report on the use of Nickel nanoparticles (Ni-NPs) as saturable absorber (SA) to generate Q-switched fiber laser pulses in C-band. The Ni-NPs were incorporated in polyvinyl alcohol (PVA) to produce thin film-based saturable absorber (SA) and integrated into an erbium-doped fiber laser (EDFL) ring cavity to generate passively Q-switching. The Ni-doped PVA SA reveals modulation depth of 15% and a saturation intensity of 200 MW/cm2. Lasing in CW region begins at 77 mW pump power, whereas stable self-starting Q-switching with a central wavelength of 1563.1 nm begins at 85 mW. By fine adjustment of the laser diode pump power up to 236.4 mW dual-, and triple- lasing lines have been observed at 1563.1, 1563.3 and 1563.4 with side mode suppression ratio (SMSR) of more than 49 dB. The proposed laser is useful for generating pulse laser with a minimum pulse width of 1.5 μs and a maximum repetition rate of 56.79 kHz with a pulse energy of about 4.33 nJ at the maximum pump power of 275 mW. The stability of the pulse is verified from the radio-frequency (RF) spectrum with a measured signal-to-noise ratio (SNR) of 44 dB. The ability of Ni-PVA as an effective SA may lead to further development of pulsed fiber laser in the field of photonics.