Improved Intrapulse Raman Scattering Control via Asymmetric Airy Pulses

We experimentally demonstrate the possibility of tuning the frequency of a laser pulse via the use of an Airy pulse-seeded soliton self-frequency shift. The intrinsically asymmetric nature of Airy pulses, typically featured by either leading or trailing oscillatory tails (relatively to the main lobe), is revealed through the nonlinear generation of both a primary and a secondary Raman soliton self-frequency shift, a phenomenon which is driven by the soliton fission processes. The resulting frequency shift can be carefully controlled by using time-reversed Airy pulses or, alternatively, by applying an offset to the cubic phase modulation used to generate the pulses. When compared with the use of conventional chirped Gaussian pulses, our technique brings about unique advantages in terms of both efficient frequency tuning and feasibility, along with the generation and control of multicolor Raman solitons with enhanced tunability. Our theoretical analysis agrees well with our experimental observations.

Figure 1

(a),(b) The typical shape of a nonchirped and a chirped Airy pulse, respectively. (c) Asymmetry degree ($A_{\text{whole}}$) and peak power for the Airy pulse shown in (a) resulting from different linear chirps, where $C$ is a chirp parameter defined in the text.

Figure 2

Theoretical (a-d) and experimental (e-f) results showing the SSFSs associated with tail-leading (left) and tail-trailing (right) asymmetric Airy pulses. (a),(b) The nonlinear propagation and the insets plot the profiles of the inputs for each case. (c)–(f) The simulated and the experimental output spectra, for both input Airy pulses propagating along a 625-m-long LEAF fiber. The dotted red curves in (d) and (f) are the copies of the corresponding primary SSFS from (c) and (e), allowing for a better comparison between the two cases.

Figure 3

Experimental observations of the dependence of the Raman soliton self-frequency shift upon the linear prechirp coefficient $C$, obtained by using (a) a tail-leading and (b),(c) a tail-trailing Airy pulse, respectively, for different input powers. In (d), a Gaussian-like pulse is presented for comparison. Each spectral pattern is obtained by imposing different linear chirps at the input. The white circles in (b) and (c) trace out the peak of the primary SSFS of tail-leading Airy pulses for 18- and 22-mW input powers, respectively.

Figure 4

(a),(b) Experimental results showing the power-dependent control of multicolor Raman soliton generation via the use of (a) a nonchirped tail-trailing Airy pulse and of (b) a chirped tail-leading Airy pulse. (c) Simulation results showing SSFS tuning obtained by applying a linear chirp $C$ to the tail-leading Airy pulse.