Grzegorz Sobon

Graphene Oxide vs. Reduced Graphene Oxide as saturable absorbers for Er-doped passively mode-locked fiber laser

In this work we demonstrate comprehensive studies on graphene oxide (GO) and reduced graphene oxide (rGO) based saturable absorbers (SA) for mode-locking of Er-doped fiber lasers. The paper describes the fabrication process of both saturable absorbers and detailed comparison of their parameters. Our results show, that there is no significant difference in the laser performance between the investigated SA. Both provided stable, mode-locked operation with sub-400 fs soliton pulses and more than 9 nm optical bandwidth at 1560 nm center wavelength. It has been shown that GO might be successfully used as an efficient SA without the need of its reduction to rGO. Taking into account simpler manufacturing technology and the possibility of mass production, GO seems to be a good candidate as a cost-effective material for saturable absorbers for Er-doped fiber lasers.

Mode-locking in Er-doped fiber laser based on mechanically exfoliated Sb 2 Te 3 saturable absorber

We demonstrate the usage of a new saturable absorber material – antimony telluride (Sb2Te3) for efficient mode-locking of an Erbium-doped fiber laser. The Sb2Te3 layers were obtained by mechanical exfoliation and transferred onto the fiber connector tip. The all-fiber laser was capable of generating optical solitons with the full width at half maximum of 1.8 nm centered at 1558.6 nm, with 4.75 MHz repetition rate. The pulse energy of the generated 1.8 ps pulses was at the level of 105 pJ.

Black phosphorus saturable absorber for ultrashort pulse generation

Low-dimensional materials, due to their unique and versatile properties, are very interesting for numerous applications in electronics and optoelectronics. Recently rediscovered black phosphorus, with a graphite-like layered structure, can be effectively exfoliated up to the single atomic layer called phosphorene. Contrary to graphene, it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, black phosphorus is now intensively investigated and can complement or replace graphene in various photonics and electronics applications. Here, we demonstrate that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ∼300 nm thick layers of black phosphorus were transferred onto the fiber core, and under pulsed excitation at 1560 nm wavelength, its transmission increases by 4.6%. We have demonstrated that the saturable absorption of black phosphorus is polarization sensitive. The fabricated device was used to mode-lock an Er-doped fiber laser. The generated optical solitons with the 10.2 nm bandwidth and 272 fs duration were centered at 1550 nm. The obtained results unambiguously show that black phosphorus can be effectively used for ultrashort pulse generation with performances similar or even better than currently used graphene or carbon nanotubes. This application of black phosphorus proves its great potential to future practical use in photonics.

Passive harmonic mode-locking in Er-doped fiber laser based on graphene saturable absorber with repetition rates scalable to 2.22 GHz

Passive harmonic-mode locking of erbium-doped fiber laser with atomic multilayer graphene is presented. The laser could operate at several harmonics (from 2nd to 21st) of the fundamental repetition frequency of the ring resonator (106 MHz). The highest achieved repetition rate was 2.22 GHz (which corresponds to the 21st harmonic) with sub-picosecond pulse durations and over 40 dB of the supermode noise suppression. The saturable absorber was formed by multilayer graphene, mechanically exfoliated from pure graphite block through Scotch-tape and deposited on the fiber ferrule.

Sub-130 fs mode-locked Er-doped fiber laser based on topological insulator

In this work we present for the first time, to the best of our knowledge, a stretched-pulse mode-locked fiber laser based on topological insulator. As a saturable absorber (SA) a ~0.5 mm thick lump of antimony telluride (Sb2Te3) deposited on a side-polished fiber was used. Such a SA introduced 6% modulation depth with 43% of non-saturable losses, which is sufficient for supporting stretched-pulse mode-locking. The ring laser resonator based on Er-doped active fiber with managed intracavity dispersion was capable of generating ultrashort optical pulses with full width at half maximum (FWHM) of 30 nm centered at 1565 nm. The pulses with duration of 128 fs were repeated with a frequency of 22.32 MHz.

Mode-locked erbium-doped fiber laser based on evanescent field interaction with Sb2Te3 topological insulator

In this Letter, we demonstrate a mode-locked Er-doped fiber laser incorporating antimony telluride (Sb2Te3) topological insulator (TI) as a saturable absorber (SA). The laser was capable of generating 270 fs-short soliton pulses at 1560 nm wavelength, which are the shortest solitons generated with a TI-based saturable absorber so far. In order to form a saturable absorber, a bulk piece of Sb2Te3 was deposited on a side-polished single-mode fiber with the presence of a low refractive index polymer. Such saturable absorber exhibits modulation depth at the level of 6% with less than 3 dB of non-saturable losses. Our study shows that TI-based saturable absorbers with evanescent field interaction might compete with SAs based on carbon nanomaterials, like graphene or nanotubes. Additionally, thanks to the interaction with the evanescent field, the material is not exposed to high optical power, which allows to avoid optical or thermal damage.

Thulium-doped all-fiber laser mode-locked by CVD-graphene/PMMA saturable absorber

We report an all-fiber Tm-doped fiber laser mode-locked by graphene saturable absorber. The laser emits 1.2 ps pulses at 1884 nm center wavelength with 4 nm of bandwidth and 20.5 MHz mode spacing. The graphene layers were grown on copper foils by chemical vapor deposition (CVD) and transferred onto the fiber connector end. Up to date this is the shortest reported pulse duration achieved from a Tm-doped laser mode-locked by graphene saturable absorber. Such cost-effective and stable fiber lasers might be considered as sources for mid-infrared spectroscopy and remote sensing.

Harmonically mode-locked Er-doped fiber laser based on a Sb2Te3 topological insulator saturable absorber

In this letter we present for the first time, to the best of our knowledge, a harmonically mode-locked Er-doped fiber laser with antimony telluride (Sb2Te3) topological insulator material used as a saturable absorber (SA). The SA was prepared via mechanical exfoliation of the bulk material. The 80 nm thick Sb2Te3 layers transferred onto fiber ferrule entirely cover the fiber core. The Er-doped fiber mode-locked laser based on such SA generated optical pulses was centered at 1558 nm with 1.9 ps duration and a fundamental repetition rate of 3.75 MHz. Increasing the pump power results in stable harmonic mode-locked operation up to the 81st harmonic at 304 MHz repetition frequency. The laser was capable of generating optical solitons with 2.2 ps duration. The number of generated harmonics could be tuned only by changing the pump power injected into the laser cavity.

Simultaneous mode-locking at 1565 nm and 1944 nm in fiber laser based on common graphene saturable absorber

We present for the first time to the best of our knowledge an all-fiber thulium (Tm) and erbium (Er) doped fiber laser simultaneously mode-locked by a common graphene saturable absorber. The laser consists of two ring resonators combined with a common saturable absorber (SA). The generated optical solitons have a full width at half maximum (FWHM) of 3.9 nm and 4.2 nm for Tm- and Er-doped laser, respectively. The used graphene layers were grown on copper foils by chemical vapor deposition (CVD) and transferred onto the fiber connector end. Broadband and flat absorption spectrum of used SA supports mode-locked operation at 1565 nm and 1944 nm. The repetition frequency of the resonator with Er-doped fiber was 20.19 MHz while the Tm-doped resonator was around 1 m longer and resulted with repetition rate of 18.43 MHz. The reported experiment unambiguously confirms one of the biggest advantage of the carbon nanomaterial (in this case graphene) SAs over semiconductor saturable absorption mirrors (SESAM), which is broadband operation range, allowing to mode-lock two lasers spectrally separated by almost 400 nm.

Linearly polarized, Q-switched Er-doped fiber laser based on reduced graphene oxide saturable absorber

We demonstrate generation of linearly polarized pulses from a passively Q-switched Erbium-doped fiber laser. The cavity was designed using only polarization maintaining fibers and components, resulting in linearly polarized output beam with degree of polarization at the level of 97.6%. Reduced graphene oxide was used as a saturable absorber for Q-switched operation. The laser was capable of delivering 1.85 μs pulses with 125 nJ pulse energy at 115 kHz repetition rate.