Optical solitons have emerged as a highly active research domain in nonlinear fiber optics, driving significant advancements and enabling a wide range of practical applications. This study investigates the dynamics of dark solitons in systems governed by the resonant nonlinear Schrödinger equation (RNLSE). For the RNLSE with third-order (3OD) and fourth-order (4OD) dispersions, the dark soliton solution of the equation in the (1+1)-dimensional case is derived using the F-expansion method, and the analytical study is extended to the (2+1)-dimensional case via the self-similar method. Subsequently, the nonlinear equation incorporating perturbation terms is further studied, with particular attention given to the dark soliton solutions in both one and two dimensions. The soliton dynamics are illustrated through graphical representations to elucidate their propagation characteristics. Finally, modulation instability analysis is conducted to evaluate the stability of the nonlinear system. These theoretical findings provide a solid foundation for experimental investigations of dark solitons within the systems governed by the RNLSE model.

The bandwidth of the ±1-order Kelly sidebands of mode-locking fiber lasers is investigated for narrow terahertz (THz) signal generation. Four key factors influencing the bandwidth of Kelly sidebands are found and analyzed in detail. Then, a numerical model is presented for manipulating the parameters of the mode-locking fiber laser. Two mode-locking fiber lasers are designed for generating narrow sidebands. The bandwidth of the ±1-order Kelly sidebands is reduced to 0.041 nm and 0.021 nm for the sidebands with different spacings. Using the data obtained from the optical spectra with narrow bandwidth Kelly sidebands, the frequency spectra of the generated THz signals are obtained. Finally, the bandwidth of the generated THz signals is reduced to 7.16 GHz and 3.4 GHz, respectively.

This report describes the generation of acoustic signals via laser-interference-based heating. Sound signals of varying intensities were generated by modulating two continuous-wave (CW) laser beams interfering in air. In this study, we discovered that the acoustic signals generated by two spatial-frequency-modulated CW lasers scanning in air are significantly stronger than those of a single CW laser. The intensity of photoacoustic signals is proportional to the diameter of the laser beam. Furthermore, our investigation showed that modulating the spatial frequency of the two laser beams can change the intensity of the acoustic signal. In addition, we found that the two beams stack better against a single beam when scanned vertically in three dimensions.