From spectral broadening to recompression: dynamics of incoherent optical waves propagating in the fiber

Abstract

Interplay between dispersion and nonlinearity in optical fibers is a fundamental research topic of nonlinear fiber optics. Here we numerically and experimentally investigate an incoherent continuous-wave (CW) optical field propagating in the fiber with normal dispersion, and introduce a distinctive spectral evolution that differs from the previous reports with coherent mode-locked fiber lasers and partially coherent Raman fiber lasers [Nat. Photonics 9, 608 (2015).]. We further reveal that the underlying physical mechanism is attributed to a novel interplay between group-velocity dispersion (GVD), self-phase modulation (SPM) and inverse four-wave mixing (IFWM), in which SPM and GVD are responsible for the first spectral broadening, while the following spectral recompression is due to the GVD-assisted IFWM, and the eventual stationary spectrum is owing to the dominant contribution of GVD effect. We believe this work can not only expand the light propagation in the fiber to a more general case and help advance the physical understanding of light propagation with different statistical properties, but also benefit the applications in sensing, telecommunications and fiber lasers.

Brightness enhancement on random-distributed-feedback Raman fiber lasers pumped by multimode diodes

“…When the signal optical power exceeds 276W, the higher-order Stokes light disappears. The observed changes in the spectral characteristics are closely related to the distinctive half-open cavity structure of the random laser [32,42,43].…”

“…In cavity-free Random Fiber Lasers, incident photons propagating through a long passive fiber a can be backscattered by the random refractive index, inhomogeneity induced weak Rayleigh scattering and amplified by the SRS. At the same time, the acoustic field generated by electrostriction induces moving, random density gratings, a process defined as Stimulated Brillouin Scattering (SBS) [42,43]. Then, photons experiencing a frequency down-shift due to the Doppler Effect are excited by the transient temporal characteristics.…”

“…This NSTD decreases as the power is scaled up to higher levels, indicating a progressive improvement in the temporal stability of the signal laser. Although there have been reports discussing the temporal fluctuations [42], the precise dynamics underlying these processes remain somewhat unclear and necessitate further analysis by researchers.…”

Evanescent Field Controllable MZ Sensor via Femtosecond Laser Processing and Mechanic Polishing

“…From Equation ( 6), it can be inferred that the output light intensity varies with the effective refractive index. We used Rsoft software to simulate the function of the proposed device [24][25][26][27]. The device structure was modeled as shown in Figure 2a, and the beam propagation method was used to simulate the light transmission in the sensor.…”

Room-Temperature Fiber-Coupled Single-Photon Sources based on Colloidal Quantum Dots and SiV Centers in Back-Excited Nanoantennas

“…We attribute this difference to imperfect alignment, mode mismatch between the free space and the MM fiber, and dielectric reflection from the uncoated fiber facet. The apparent spectral broadening in Figure c is visible due to plasmon radiation caused by high-intensity excitation that was used for back-excitations (Appendix D) and also partially attributable to MM fiber spectral broadening . The plasmon emission can be filtered using temporal filtering with pulse excitation as evidenced in ref .…”