Mode-locked ytterbium-doped all-fiber lasers based on few-layer black phosphorus saturable absorbers

Solution-processed two-dimensional materials for ultrafast fiber lasers (invited)

“…The broadband non-linear optical response of BP was confirmed by the wideband open-aperture Z-scan measurement technique from the visible to mid-infrared region [208]. Since the first demonstration of BP-based passively mode-locked fiber lasers [209], BP has been used to mode lock fiber lasers in the 1-μm [42,131], 1.5-μm [119-121, 125, 197], and 2-μm regions [122,144] by the solution-processing method, as well as to Q-switch fiber lasers [116,123,126,127,130,132,210]. For example, Qin et al reported on BP fabricated by LPE for the Q-switched Er:ZBLAN fiber laser at 2.8 μm, where the maximum average power of 485 mW with pulse energy of 7.7 μJ was achieved [117].…”

“…The most popular exfoliation method used to fabricate SAs is ultrasonication, in which ultrasound waves are employed to disrupt the weak inter-layer van der Waals forces within the 2D crystal ( Figure 1A, B). Ultrasonication has proved effective for most 2DM-based SAs, including graphene [36,41,[62][63][64][65][66][67]133], TIs [16, 59, 89, 91, 105, 107-111, 114, 136-138], TMDs [19, 39, 60, 74, 83-89, 91, 92, 96, 97, 99-104, 135, 139-142], and BP [42,[116][117][118][119][120][121][122][123][124][125][126][127][128][129][130][143][144][145]. Its popularity arises from the ease of use, low cost, and immediate availability across most laboratories [55,146,147].…”

“…Other solvents used for graphene were ortho-dichlorobenzene [168] and perfluorinated aromatic solvents [169]. Among the solvents used for fabricating SAs, NMP is the most popular [61, 67, 88, 103, 116, 117, 119-129, 144, 145], while other solvents used are DMF [85][86][87][88] and isopropyl alcohol (IPA) [42,89,104,[116][117][118]. While the main advantage of using solvents is the high purity of the final material, there are also several drawbacks.…”

“…While other solvents with lower boiling points have been proposed, like acetone, acetonitrile, 1-propanol, or IPA, their solubility parameters were not as good as those for NMP and DMF and their use was not as successful [170][171][172][173][174]. Despite this, there are a number of reports on SAs made from IPA-based 2DM solutions, particularly MoS 2 [89], PtTe [104], Bi 2 Se 3 [16,89,110,111,137,138], and BP [42,[116][117][118].…”

“…60 and 266 MW/cm 2 [40,41]). Moreover, black phosphorus (BP) with a large span of bandgap and controllable band energy (0.3 eV for bulk BP and 2 eV for monolayer BP) that can be controlled by the number of layers has also proved to be a broadband SA up to the mid-infrared band [42].…”