Passively harmonic mode-locked erbium-doped fiber laser at a 580 MHz repetition rate based on carbon nanotubes film

We propose and demonstrate a passively harmonic mode-locked erbium-doped fiber laser (EDFL) using carbon nanotubes polyvinyl alcohol (CNTs-PVA) film. The laser allows generation of the pulses with a repetition rate of 580 MHz, which corresponds to the 22nd harmonics of a 26.3 MHz fundamental repetition rate under 323 mW pump power. A particularly noteworthy feature of the pulses is the super-mode suppression ratio (SMSR), which is over 40 dB, indicating a stable operation

Single/dual-wavelength switchable bidirectional Q-switched all-fiber laser using a bidirectional fiber polarizer

A single/dual-wavelength switchable bidirectional Q-switched fiber laser using a bidirectional fiber polarizer is demonstrated. A 45° tilted fiber grating is used as a bidirectional fiber polarizer to induce a bidirectional intracavity birefringence filter in both clockwise (CW) and counter-clockwise (CCW) directions. A carbon nanotube saturable absorber is employed to produce Q-switched pulses. Through adjusting polarization states, switchable single/dual-wavelength lasing at 1551 and 1560 nm can be achieved in both CW and CCW directions. To the best of our knowledge, this is the first demonstration of a wavelength switchable bidirectional passively Q-switched fiber laser

High power Q-switched thulium doped fibre laser using carbon nanotube polymer composite saturable absorber

We have proposed and demonstrated a Q-switched Thulium doped fibre laser (TDFL) with a ‘Yin-Yang’ all-fibre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear amplified loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped fibre laser

Emergence of additional visible range photoluminescence due to aggregation of cyanine dye:astraphloxin on carbon nanotubes dispersed with anionic surfactant

Self-organization of organic molecules with carbon nanomaterials leads to formation of functionalized molecular nano-complexes with advanced features. We present a study of physical and chemical properties of carbon nanotube-surfactant-indocarbocyanine dye (astraphloxin) in water focusing on aggregation of the dye and resonant energy transfer from the dye to the nanotubes. Self-assembly of astraphloxin is evidenced in absorbance and photoluminescence depending dramatically on the concentrations of both the dye and surfactant in the mixtures. We observed an appearance of new photoluminescence peaks in visible range from the dye aggregates. The aggregates characterized with red shifted photoluminescence peaks at 595, 635 and 675 nm are formed mainly due to the presence of surfactant at the premicellar concentration. The energy transfer from the dye to the nanotubes amplifying near-infrared photoluminescence from the nanotubes is not affected by the aggregation of astraphloxin molecules providing important knowledge for further development of advanced molecular nano-complexes. The aggregation with the turned-on peaks and the energy transfer with amplified photoluminescence create powerful tools of visualization and/or detection of the nanotubes in visible and near-infrared spectral range, respectively, boosting its possible applications in sensors, energy generation/storage, and healthcare

Self-Assembly for Two Types of J-Aggregates: Cis-Isomers of Dye on the Carbon Nanotube Surface and Free Aggregates of Dye Trans-Isomers

Development of novel nanoscale devices requires unique functional nanomaterials. Furthermore, chemical design of different nanoparticles in one unit is a complex task, particularly the application of self-assembly J-aggregates, which can substantially advance the nanomaterial's properties due to resonant delocalization of excitons. Here, we have demonstrated for the first time formation of resonantly coherent J-aggregates on carbon nanotubes with highly efficient energy transfer from the aggregates to the nanotubes. All the energy of photons absorbed by the aggregates is conveyed to the nanotubes, completely quenching the J-band emission and photosensitizing the nanotubes. Overall, we discovered formation of two types of J-aggregates, where one type is related to self-assembly of cis-isomers on the nanotube surface and the second type is associated to self-organizing trans-isomers into free J-aggregates without the nanotubes. Importantly, the J-aggregates on carbon nanotubes with strong energy transfer peaks of photoluminescence in the near infrared range are of high interest for practical applications on biomedical imaging and nanoscale optoelectronic and nanophotonic devices