Mode-locking features in a sub-200-fs erbium-doped all-fiber laser based on high-density well-aligned single-walled carbon nanotubes

High-Density Well-Aligned Single-Walled Carbon Nanotubes for Application as a Saturable Absorber with a High-Pass Filter Effect in an Erbium-Doped Ultra-Short-Pulse Fiber Laser

“…It is worth noting that the operating range of carbon nanotubes with a diameter of up to 1.2 nm corresponds to the absorption of the E 11 passband at the central wavelength of 1550 nm. This is consistent with the experimentally measured absorption range of HDWA-SWCNTs (1–1.6 μm) shown in our previous work, which limits their performance in higher wavelength lasers.…”

“…In this case, as seen in the laser scheme, we used two polarization controllers (PC) to adjust the mode-locking and an isolator–polarizer to achieve the NPE effect. The second regime achieved by the hybrid mode-locking mechanism, a film of high-density well-aligned single-walled carbon nanotubes (HDWA-SWCNTs) was introduced into the laser cavity, which was located between two FC/APC connectors and played the role of a slow saturable absorber. , The Raman spectrum and SEM of the nanotubes used are shown in Figure a,b, respectively. The HDWA-SWCNTs remained after treatment with a diameter of up to 1.2 nm, corresponding to the 225.7 cm –1 radial breathing mode of the Raman spectra.…”

“…Passive stabilization methods address the more fundamental causes of noise and are based on optical principles . When talking about passive methods to reduce intensity noise, saturable absorbers play a significant role not only in the formation of mode-locking but also in the stabilization of output pulse characteristics. − To date, in order to achieve a stable mode-locking in USP lasers, various SAs have been developed such as SA based on the nonlinear polarization evolution (NPE), − as well as SESAM saturable absorbers, carbon nanotubes, ,, and films of transition metal dichalcogenides. − Furthermore, it is especially worth highlighting hybrid mode-locking methods, which means the use of two saturable absorbers in the same cavity, for example, the use of NPE and carbon nanotubes SA . Hybrid mode-locking simplifies the mode-locking process in the cavity by taking advantage of two saturable absorbers with different characteristics.…”

Analysis of the Passive Stabilization Methods of Optical Frequency Comb in Ultrashort-Pulse Erbium-Doped Fiber Lasers

“…The resonator scheme, which includes carbon nanotubes and the NEP mechanism, is shown in Figure 25a [189]. In this scheme, the pulse duration was sub-200 fs, and the RIN value did not exceed −135.4 dBc/Hz (30 Hz-1000 kHz) at a repetition rate of 42.2 MHz with an SNR of ~64 dB (at a resolution of ~300 Hz).…”