Field effect relies on the nonlinear current-voltage relation in semiconductors; analogously, materials that respond nonlinearly to an optical field can be utilized for optical modulation. For instance, nonlinear optical (NLO) materials bearing a saturable absorption (SA) feature an on-off switching behavior at the critical pumping power, thus enabling ultrafast laser pulse generation with high peak power. SA has been observed in diverse materials preferably in its nanoscale form, including both gaped semiconductor nanostructures and gapless materials like graphene; while the presence of optical bandgap and small carrier density have limited the active spectral range and intensity. We show here that solution-processed plasmonic semiconductor nanocrystals exhibit superbroadband (over 400 THz) SA, meanwhile with large modulation depth (∼7 dB) and ultrafast recovery (∼315 fs). Optical modulators fabricated using these plasmonic nanocrystals enable mode-locking and Q-switching operation across the near-infrared and mid-infrared spectral region, as exemplified here by the pulsed lasers realized at 1.0, 1.5, and 2.8 μm bands with minimal pulse duration down to a few hundreds of femtoseconds. The facile accessibility and superbroadband optical nonlinearity offered by these nonconventional plasmonic nanocrystals may stimulate a growing interest in the exploiting of relevant NLO and photonic applications.
We demonstrate a passive mode-locked Er:Yb doped double-clad fiber laser using a microfiber-based topological insulator (Bi(2)Se(3)) saturable absorber (TISA). By optimizing the cavity loss and output coupling ratio, the mode-locked fiber laser can operate in L-band with high average output power. With the highest pump power of 5 W, 91st harmonic mode locking of soliton bunches with average output power of 308 mW was obtained. This is the first report that the TISA based erbium-doped fiber laser operating above 1.6 μm and is also the highest output power yet reported in TISA based passive mode-locked fiber laser.
Soliton explosions are among the most intriguing nonlinear dynamics in dissipative systems, manifesting themselves as a self-recovered localized structure when suffering explosive instabilities. Herein, we report on the investigation of soliton explosions in an ultrafast fiber laser operating in the multi-soliton regime. It is demonstrated that explosion of one soliton could be induced by another one through the soliton interactions mediated by the transient gain response of an erbium-doped fiber. We denote this phenomenon as "mutually ignited soliton explosions" when referring to the multi-soliton regime. The results provide the first investigation of soliton explosions in the multi-soliton regime and, therefore, will enhance a more comprehensive understanding of the soliton exploding phenomenon.
We report the first, to the best of our knowledge, demonstration of
Grüneisen relaxation photoacoustic microscopy (GR-PAM) of lipid-rich
tissue imaging at the 1.7 µm band, implemented with a high-energy
thulium-doped fiber laser and a fiber-based delay line. GR-PAM
enhances the image contrast by intensifying the region of strong
absorbers and suppressing out-of-focus signals. Using GR-PAM to image
swine-adipose tissue at 1725 nm, an 8.26-fold contrast enhancement is
achieved in comparison to conventional PAM. GR-PAM at the 1.7 µm band
is expected to be a useful tool for label-free high-resolution imaging
of lipid-rich tissue, such as atherosclerotic plaque and nerves.
Here, we show that solution-processed Cu-Sn-S semiconductor nanocrystals (NCs) demonstrate a tunable localized surface plasmon resonance band in the near infrared region, where strong saturable absorption occurs. A saturable absorber based on these plasmonic NCs enables the construction of a stable mode-locked femtosecond fiber laser operating at the telecommunication band.
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