Vector soliton dynamics in a high-repetition-rate fiber laser

Abstract

The existence of vector solitons that arise from the birefringence nature of optical fibers has been increasingly of interest for the stability of mode-locked fiber lasers, particularly for those operating in the high-fundamental-repetition-rate regime, where a large amount of fiber birefringence is required to restore the phase relation between the orthogonally polarized vector solitons, resulting in stable mode-locking free of polarization rotation. These vector solitons can exhibit diverse time-varying polarization dynamics, which prevent industrial and scientific applications requiring stable and uniform pulse trains at high fundamental repetition rates. This pressing issue, however, has so far been rarely studied. To this end, here we theoretically and experimentally dissect the formation of vector solitons in a GHz-repetition-rate fiber laser and investigate effective methods for suppressing roundtrip-to-roundtrip polarization dynamics. Our numerical model can predict both dynamic and stable regimes of high-repetition-rate mode-locking by varying the amount of fiber birefringence, resulting in the polarization rotation vector soliton (PRVS) and linearly polarized soliton (LPS), respectively. These dynamic behaviors are further studied by using an analytical approach. Interestingly, our theoretical results indicate a cavity-induced locking effect, which can be a complementary soliton trapping mechanism for the co-propagating solitons. Finally, these theoretical predications are experimentally verified, and we obtain both PRVS and LPS by adjusting the intracavity fiber birefringence.

Nonlinear chirped pulse amplification for a 100-W-class GHz femtosecond all-fiber laser system at 1.5 m

“…The RF spectrum is acquired at a resolution bandwidth (RBW) of 10 Hz, as shown in Figure 4(b), wherein a 10.6-GHz fundamental frequency and an 89-dB signal-to-noise ratio (SNR) are indicated, implying a good short-term mode-locking stability. Over a wider frequency span (i.e., 25 GHz), no sidelobe or satellite peak in the RF domain is observed, as shown in Figure 4(c), confirming a stable operation without polarization rotation [ 40 ] . Such a stationary state of polarization is particularly important for PM-fiber amplifiers [ 41 ] .…”

“…Over a wider frequency span (i.e., 25 GHz), no sidelobe or satellite peak in the RF domain is observed, as shown in Figure 4(c), confirming a stable operation without polarization rotation [40] . Such a stationary state of polarization is particularly important for PM-fiber amplifiers [41] . Figure 4(d) presents the oscilloscopic trace of the seed that exhibits good intensity uniformity, wherein a temporal period of 94 ps is indicated, in accordance with the repetition rate of approximately 10.6 GHz.…”

Unveiling Laser Radiation of Multiple Optical Solitons by Nonlinear Fourier Transform

“…Numerical Simulation of Multiple Solitons Drifting: To better understand the multiple solitons drifting in mode-locked fiber lasers, the split-step Fourier method was adopted to solve the coupled nonlinear Schrödinger equations (NLSE) in a lumped propagation model [45,46] ) v…”

Modulating dual-wavelength optical fiber vector solitons

“…level in a time domain can often be observed in modelocked fiber lasers because many different kinds of soliton parameters (such as second-order and higher-order fiber dispersion, self-phase modulation, linear birefringence, crossphase modulation, spectral filtering bandwidth, and so on) can be managed to meet specific conditions and finally achieve the output of different types of optical fiber vector solitons. Group-velocity locked optical fiber vector soliton [10,11], polarization-locked optical fiber vector soliton [12][13][14], and polarization-rotated optical fiber vector soliton [15,16] are three forms of optical fiber vector solitons that are often observed in the experiment. In the construction of vector soliton fiber lasers, an all-fiber circular laser oscillator cavity structure is usually employed because of its stability and relatively simple structure.…”