152 fs nanotube-mode-locked thulium-doped all-fiber laser

Abstract

Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps2, and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials.

Soliton Mode-Locked Large-Mode-Area Tm-Doped Fiber Oscillator

“…We note that the Kelly sidebands in the optical spectrum which is similar to that of Ref. [28], are much stronger than previously reported soliton mode-locked fiber lasers [6][7][8][9]. This is due to the fact that the amplitude of soliton pulse circulating in this laser cavity experiences strong periodic perturbations induced by the significantly discrete losses mentioned above and rapidly variable gain across the bent active fiber [29].…”

“…Thulium (Tm) -doped fibers (TDFs) are one of the most successful gain media in the fiber laser family that have a wide gain bandwidth of about 300 nm centered at ~1.9 μm, capable of supporting sub-100 fs pulse generation and amplification. However, due to the inherently large negative material dispersion of silica fiber at 2 µm, most of ultrafast Tm-doped fiber oscillators operate in the soliton regime, with pulse energy typically limited to < 1 nJ [6][7][8][9]. Intra-cavity dispersion engineering can be utilized to break through this barrier and boost the energy to few nJ level [10], in which the output typically requires complex pulse compression technique to get bandwidth-limited pulses.…”

CNT-based saturable absorbers with scalable modulation depth for Thulium-doped fiber lasers operating at 1.9 μm

“…The Authors in ref. 21 report 10% of modulation depth, but also in their case the sample was not fully saturated due to not enough pumping power. Modulation depth of 18% was reported in ref.…”

Large-area highly crystalline WSe_2 atomic layers for ultrafast pulsed lasers

“…Furthermore, as we change the polarization of input light passing through microfiber-based WSe 2 SA, the polarization dependent loss (PDL) maintains in a small range of 60.72%~62.84% at 1550 nm with 3.21 mW input power, which confirms the PDL could be ignored in the microfiber based WSe 2 SA to avoid undesired NPE effect. Moreover, it is well known that the stable and ultrashort pulse trains can be generated in a passively mode-locked laser after achieving the balance between the self-phase modulation (SPM) and negative group velocity dispersion (GVD) in laser cavity [39]. The WSe 2 SA has normal dispersion, but the accurate value could not be calculated yet because of the hybrid structure of microfiber and WSe 2 film.…”

“…As we increase the cavity length up to 80 m, the pulse duration was in this case 1.23 ps. Worth noting that shorter pulse width can be realized by further optimizing the cavity length with approximate zero dispersion in cavity [39]. Recent demonstrations indicated that several kind of 2D materials, like graphene [33], black phosphorus [34], WS 2 [35], and MoSe 2 [36], show broadband nonlinear optical absorption, which have been used as SA for mode-locking operation.…”