Fiber amplifiers

All-fiberized very-large-mode-area Yb-doped fiber based high-peak-power narrow-linewidth nanosecond amplifier with tunable pulse width and repetition rate*

“…When the forward output power exceeds 17.8 W, the peak at 1064.2 nm grows rapidly. The frequency difference of these two peaks is calculated to be 15.8 GHz, which is coincident with the Brillouin frequency shift in silica fiber at 1064 nm, [25] and thus indicating the onset of the SBS. The corresponding temporal features of backward output pulses are shown in Fig.…”

“…When operating in continuous-wave and assuming that the pump wave is linear polarized and undepleted, the threshold of the SBS can be evaluated by [25]…”

“…where K is the polarization factor, G is the amplification factor of the fiber amplifier, and ∆v p and ∆v B are the spectral linewidths of the pump wave and Brillouin gain spectrum, respectively. [25][26][27] When operating in the pulsed regime, L eff can be obtained from [28] L…”

“…Figure 7(a) shows the output spectrum at the maximum output power of 30.8 W. We observe a pedestal with 3-dB spectral bandwidth of ∼ 12 nm, located at the bottom of the peak wavelength of ∼ 1064 nm, which is attributed to the growth of in-band ASE leaked out by the pre-amplifiers and the gain-induced broadening of the signal laser. According to the Raman frequency shift of ∼ 13 THz (∼ 49.1 nm at 1064 nm) in silica fiber, [25] the envelope centered around 1114 nm is Stokes waves generated by the nonlinear effect of the SRS. The onset of the SRS is probably caused by the above-mentioned pedestal, which has a broad spectral bandwidth of ∼ 12 nm.…”

Engineering Waveguide Nonlinear Effective Length via Low Index Thin Films

“…To fully appreciate the reported results, we start by considering a set of underpinning materials in integrated photonics and their fundamental nonlinear figure of merit FoM = n 2 /α, where n 2 is the nonlinear Kerr coefficient and α represents the propagation loss coefficient. [ 21 ] In Table 1 , associated results are reported for the following material systems: graphene [ 22,23 ] (representative for 2D materials), gold [ 24,25 ] (representative for noble metals), ITO [ 26 ] (representative for low‐index compounds), silicon nitride [ 27,28 ] (representative of nonlinear‐absorption‐free integrated systems), silicon [ 29 ] (most established photonic platform), and silica [ 30 ] (cornerstone of long‐haul optical data transmission). From the reported data it is immediately apparent how this FoM is limiting and at times misleading in describing nonlinear performances.…”