Broadband and ultrafast response of plasmonic nanoparticles offer a significant advantage in optical modulation and allow ultrashort pulse generation from visible to mid‐infrared (MIR) region. However, many of the materials exhibit limited saturable absorption bandwidth in MIR spectral region, which limits the MIR pulses generation and the relative applications. Herein, it is shown that solution‐processed silver nanowires (AgNWs) exhibit an ultrabroadband localized surface plasmon resonance (LSPR) from 0.3 to over 25 μm, which contributes to wideband nonlinear optical response in the whole MIR region. Using those AgNWs as saturable absorbers (SA), all‐optical modulation in near infrared and MIR region is demonstrated. Mode‐locked lasers are realized at 1, 1.5, and 2 μm bands with minimal pulse duration down to a few hundreds of femtoseconds, and a Q‐switched laser at 3 μm band is achieved. The results show that AgNWs SA has the potential for constructing pulsed lasers in the MIR or even longer wavelength region.
We demonstrated a mode-locked erbium doped fiber laser (EDFL) operating at 1558 nm by exploiting ferroferric-oxide nanoparticles (FONPs) as the saturable absorber (SA) material. FONPs, with an average diameter of ~20 nm, were prepared by a thermal decomposition method, then mixed with sodium carboxymethylcelluose to form an FONP film. The FONP SA was fabricated through a sandwiched FONP film between two fiber connectors. By inserting the FONPs SA into an EDFL cavity pumped by a 980 nm laser diode, stable passive mode-locking was achieved with a threshold pump power of ~120 mW. The obtained modelocked laser had a central wavelength of ~1558 nm, a spectral bandwidth of ~0.8 nm, a pulse width of ~4.35 ns, and a repetition rate of ~37.32 MHz. Furthermore, a maximum average power of ~17 mW was obtained for a pump power of 340 mW. To the best of our knowledge, this is the first time that it has been demonstrated that FONPs can be used for constructing mode-locked fiber lasers.
We demonstrate passively mode-locked erbium/thulium doped fiber lasers (TDFLs) operating at 1560/1950 nm by using a common gold nanorods (GNRs)/D-shaped fiber as saturable absorber (SA). The SA is prepared by the composite of GNRs with an average aspect ratio of 5.3 and D-shaped fiber, which has broadband absorption from 1000 nm to 3000 nm. By inserting the same SA into an erbium or thulium doped fiber laser cavity, stable passively mode-locked laser at 1560 or 1950 nm is achieved, respectively. A 1560 nm laser with a pulse width of 590 fs and a repetition frequency of 25.72 MHz is obtained for the erbium doped fiber laser (EDFL), and a 1950 nm laser with a pulse width of 373 fs and a repetition rate of 27.66 MHz is also obtained for the TDFL. Our results show that the GNRs/D-shaped fiber SA could be used for constructing broadband femtosecond fiber lasers.
Ultrathin gold nanowires (UGNWs) with a diameter of ⩽2 nm have attracted much attention because of their high aspect ratios, unusual physical properties and potential applications in nanoelectronics, sensors and photonics. Despite recent advances on UGNWs and the related devices, nonlinear optical properties of UGNWs and their application on photonic devices (e.g. ultrashort pulsed lasers) remain largely unexplored. Here we show that UGNWs can be used as broadband saturable absorbers (SAs) for constructing ultrashort pulsed lasers with an operating wavelength range from near-infrared to mid-infrared (MIR). UGNWs are prepared by using a silane-mediated approach, and then mixed with polyvinyl alcohol to form the UGNWs film. The UGNWs film not only show strong absorption from visible to MIR spectral region (over 25 μm), but also possess the nonlinear saturable absorption properties in the spectral region. As the UGNWs film SA is inserted into an erbium or thulium doped silica fiber laser cavity, stable passively mode-locked lasers at 1562.2 or 1970 nm with a pulse width of a few hundreds of femtoseconds is obtained, respectively. Especially, by inserting the UGNWs film SA into a holmium/praseodymium codoped fluoride fiber laser cavity, stable passively mode-locked laser at 2864 nm is achieved. Our results show that the UGNWs film are promising SAs for constructing broadband ultrashort pulsed lasers.
We report a dual-wavelength erbium-doped fiber laser (EDFL) with a tunable wavelength spacing from ~9 to 58 nm based on a single multimode interference filter (MMIF). The MMIF has a simple structure of single mode fiber (SMF)-multimode fiber-SMF and two main transmission peaks at 1537 and 1565 nm, which are located in the gain spectrum of the EDF. The wavelength spacings of these two transmission peaks were tuned from 7.8 to 58.5 nm, owing to the multimode interference effect by mechanically bending the MMIF. By adding the MMIF into the EDFL cavity, dual-wavelength lasers were obtained and the corresponding wavelength spacing was tuned from 9 to 58 nm by adjusting the MMIF. To the best of our knowledge, this is the first time an all fiber dual-wavelength EDFL with a tunable wavelength spacing using a curved MMIF has been reported.
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