Anatoly S. Pozharov

Thulium-doped mode-locked all-fiber laser based on NALM and carbon nanotube saturable absorber.

We report on a thulium-doped fiber laser mode-locked with a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes. Laser system based on the nonlinear amplifying loop mirror generates 450 fs pulses with 18 mW maximum average power.

SESAM and SWCNT Mode-Locked All-Fiber Thulium-Doped Lasers Based on the Nonlinear Amplifying Loop Mirror

We report on thulium-doped all-fiber lasers based on the nonlinear amplifying loop mirror and mode-locked with a semiconductor saturable absorber (SESAM) or single-walled carbon nanotubes (SWCNTs). An intracavity and external dispersion management was realized with the aid of a passive germanium-silicate fiber. The SESAM mode-locked laser generates as short as 230-fs pulses with a maximum average output power of 106 mW, corresponding to a 3.7 kW peak power and almost 2 nJ pulse energy. In contrast to the SESAM-based laser, the SWCNT mode-locked laser generates 450-fs pulses of mW-level average output power.

Ultra-short pulse generation in the hybridly mode-locked erbium-doped all-fiber ring laser with a distributed polarizer

We report for the first time to the best of our knowledge on the ultra-short pulse (USP) generation in the dispersion-managed erbium-doped all-fiber ring laser hybridly mode-locked with boron nitride-doped single-walled carbon nanotubes in the co-action with a nonlinear polarization evolution in the ring cavity with a distributed polarizer. Stable 92.6 fs dechirped pulses were obtained via precise polarization state adjustment at a central wavelength of 1560 nm with 11.2 mW average output power, corresponding to the 2.9 kW maximum peak power. We have also observed the laser switching from a USP generation regime to a chirped pulse one with a corresponding pulse-width of 7.1 ps at the same intracavity dispersion.

Arc-synthesis of Single-walled Carbon Nanotubes in Nitrogen Atmosphere

Synthesis of single‐walled carbon nanotubes by arc‐discharge technique has been realized in nitrogen atmosphere with Ni:Y2O3 catalyst. Presence of carbon nanotubes in the synthesized material has been confirmed by a Raman spectroscopy and by a transmission electron microscopy. The synthesis parameters (gas pressure, arc current) have been optimized.

Transform-limited pulse generation in normal cavity dispersion erbium doped single-walled carbon nanotubes mode-locked fiber ring laser

We demonstrate an erbium doped fiber ring laser mode-locked with a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes (SWCNT). The laser with large normal net cavity dispersion generates near bandwidth-limited picosecond inverse modified soliton pulses at 1.56 µm.

Performance peculiarities of carbon-nanotube-based thin-film saturable absorbers for erbium fiber laser mode-locking

We have studied the saturation behavior of single-walled carbon-nanotube-based saturable absorbers (SWCNT-SAs) at different temperatures and SWCNT concentrations in the polymer matrix and tried to relate it to the mode-locked erbium-doped fiber laser performance. It has been observed that a modulation depth of SWCNT-SA transmission which we relate to the ground state recovery time monotonically decreases upon temperature growth. Comparing laser performance with different SWCNT-SAs, we suppose that the defects in the CNT lattice promote recovery acceleration resulting in shorter pulse generation as obtained for boron-nitride-doped SWCNTs. Moreover, for the first time, to the best of our knowledge, we have observed and studied the long-term relaxation of SWCNT-SA saturated transmission exhibiting temperature-dependent behavior.

Hybrid mode-locked erbium-doped all-fiber soliton laser with a distributed polarizer

A soliton-type erbium-doped all-fiber ring laser hybrid mode-locked with a co-action of arc-discharge single-walled carbon nanotubes (SWCNTs) and nonlinear polarization evolution (NPE) is demonstrated. For the first time, to the best of our knowledge, boron nitride-doped SWCNTs were used as a saturable absorber for passive mode-locking initiation. Moreover, the NPE was introduced through the implementation of the short-segment polarizing fiber. Owing to the NPE action in the laser cavity, significant pulse length shortening as well as pulse stability improvement were observed as compared with a SWCNTs-only mode-locked laser. The shortest achieved pulse width of near transform-limited solitons was 222 fs at the output average power of 9.1 mW and 45.5 MHz repetition frequency, corresponding to the 0.17 nJ pulse energy.

Generation regimes of bidirectional hybridly mode-locked ultrashort pulse erbium-doped all-fiber ring laser with a distributed polarizer

We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications.

Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E11 M , to the background absorption and to the absorption band of semiconducting nanotubes E11 S , respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E11 M ) and 1745 nm (E11 S ).

Stable similariton generation in hybrid mode-locked erbium-doped all-fiber ring laser for application in optical frequency standard

Recently similariton (or self-similar pulse) fiber lasers have attracted great attention due to their capabilities of highenergy pulse generation that could find different applications in science and industry. Moreover it is very important to reach stable pulse generation for the application as a frequency divider in optical frequency standard. Hybrid modelocking mechanism was used for obtaining stable similariton generation at 38 MHz pulse repetition frequency. It involves two types of mode-locking mechanisms in the cavity - saturation of carbon nanostructures absorber (recovery time Trt ~ 500 fs) and nonlinear polarization evolution based on the nonlinear Kerr-effect (Trt ~ 10 fs). It was shown that total intracavity dispersion should be slightly positive for generating stable similaritons with duration of less than 90 fs and spectral bandwidth of more than 50 nm at 11.2 mW output average power that could be further applied in an all-fiber MOPA setup.