Narrow linewidth pulsed single-frequency fiber laser has the characteristics of excellent coherence and high peak power, and has been widely used in coherent LiDAR, precision measurement and nonlinear frequency conversion. In this work, energy scaling of single-frequency laser with long pulse duration and low repetition rate is demonstrated through leveraging an all-fiber amplifier based on polarization-maintaining (PM) large mode area tapered Yb-doped fiber. With dedicate synchronous pulse pumping for suppressing the inter-pulse ASE effect, and pre-shaping of the seed pulse for compensating the distortion of temporal profile, a 1064nm pulsed single-frequency laser output with an energy of 370mJ is realized with a repetition rate of 100Hz. In addition, the rectangle pulse shape is well maintained with a duration of 1.1ms. It is believed that the obtained result represents the highest energy ever reported for pulsed single-frequency fiber lasers.
A high-power linearly-polarized all-fiber single-frequency amplifier at 1064 nm based on tandem corepumping is demonstrated by adopting large-mode-area (LMA) fiber with core/cladding diameter of 20/130 μm. The output performance of the amplifier dependence on the input signal power has been investigated, and the results indicate that enhancing the injection signal power is advantageous in mitigating the amplified simultaneous emission (ASE) and increasing slope efficiency. A maximum output power of 252 W with corresponding slope efficiency of 85% is achieved with injection signal power of 7 W. At the highest output power status, a polarization extinction ratio (PER) of 17 dB and a beam quality of 1.15 are obtained respectively. In addition, by virtue of LMA fiber and tandem core-pumping, the amplifier exhibits good performance on thermal load, which in turn facilitate the maintenance of frequency noise and linewidth. To the best of our knowledge, this is the highest output power of single-frequency all-fiber amplifier based on core-pumping scheme.
A single-polarization single-frequency (SPSF) 1030 nm distributed feedback (DFB) fiber laser with mode switchable output is achieved. The DFB fiber laser is realized based on a 5 cm long π-phase shifted fiber Bragg grating (PS-FBG). A maximum output power of 84 mW with single-polarization operation is achieved. The polarization extinction ratio (PER) is around 17 dB and the linewidth is 18 kHz. The slope efficiency is 13% and the spectrum at the highest power shows an excellent optical signal to noise ratio of about 75 dB. Moreover, LP11 mode single-frequency lasing is achieved by adopting an acoustically-induced fiber grating (AIFG). The mode purity is estimated to be higher than 96%. These results, to the best of our knowledge, show the highest output power among the reports that achieve single-frequency 1030 nm DFB laser output with single-polarization operation. Furthermore, it is the first time to realize transverse mode switchable single-frequency fiber laser based on an AIFG. The high order mode single-frequency 1030 nm fiber laser has much potential to find applications in multiplexing system.
A high-energy, wavelength-tunable all-fiber picosecond MOPA laser is reported. The seed is provided by an active mode-locked oscillator which can be continuously tuned from 1030 nm to 1080 nm. The seed pulses with duration of 212 ps and average power of 3 mW are injected into a two-stage amplifier. The nonlinear effect in the main amplifier is alleviated by using a large mode area gain fiber, to avoid pulse distortion and spectral broadening. Over 10 W average output power ranged from 1030 nm to 1080 nm is achieved with the FWHM bandwidth and spectral signal-to-noise ratio of 0.2 nm and 30 dB, respectively. Measured pulse duration is less than 350 ps at repetition rate of ~536 kHz. The maximum peak power and single pulse energy reaches 54 kW and 18 μJ, respectively. The source is then used to pump a self-designed multi-core photonic crystal fiber (PCF) for supercontinuum generation. By tuning the wavelength of the laser to approach the zero-dispersion wavelength of the PCF, a broadband supercontinuum covering the wavelength range from shorter than 400 nm to longer than 2400 nm is achieved. The experimental results are in consistent with the theoretical analysis, which benefit from the wavelength continuously tunable property and the high peak power of the picosecond laser.
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