Jaroslaw Sotor

Fundamental and harmonic mode-locking at 21 μm with black phosphorus saturable absorber

We report mode-locking in holmium-doped all-fiber laser based on black phosphorus saturable absorber. The generated solitons are centered at 2094 nm with bandwidth reaching 4.2 nm and pulse duration of 1.3 ps. In harmonic mode-locking, up to 10th harmonic (290 MHz) was obtained. Properties of black phosphorus saturable absorber are investigated. Our findings validate black phosphorus suitability for ultrafast applications in mid-infrared.

All-polarization-maintaining, stretched-pulse Tm-doped fiber laser, mode-locked by a graphene saturable absorber

In this Letter, we demonstrate an all-polarization-maintaining, stretched-pulse Tm-doped fiber laser generating ∼200  fs pulses centered at 1945 nm. As a saturable absorber, a graphene/poly(methyl methacrylate) composite was used. To the best of our knowledge, this is the first demonstration of stretched-pulse operation of a graphene-based fiber laser at 2 μm.

Tm:GdVO4 microchip laser Q-switched by a Sb2Te3 topological insulator

We report on the first application of a topological insulator based on antimony telluride (Sb2Te3) as a saturable absorber (SA) in a bulk microchip laser. The transmission-type SA consisted of a thin film of Sb2Te3 (thickness: 3 nm) deposited on a glass substrate by pulsed magnetron sputtering. The saturable absorption of the Sb2Te3 film was confirmed for ns-long pulses. The microchip laser was based on a Tm:GdVO4 crystal diode-pumped at ∼802 nm. In the continuous-wave regime, this laser generated 3.54 W at 1905-1921 nm with a slope efficiency η of 37%. The Q-switched laser generated a maximum average output power of 0.70 W at 1913 nm. The pulse energy and duration were 3.5 μJ and 223 ns, respectively, at a repetition rate of 200 kHz. The Sb2Te3 SAs are promising for passively Q-switched waveguide lasers at ∼2 μm.

Stretched-pulse Ho-doped fiber laser mode-locked by graphene based saturable absorber

In this work we propose a simple, all-fiber dispersion managed Ho-doped laser mode-locked with graphene saturable absorber (SA). Dispersion compensating fiber was used to balance the anomalous dispersion of the active and standard single mode fibers, which allows to overcome the limitations set by soliton area theorem. The laser was pumped by a custom-made 1940 nm thulium-doped fiber laser delivering up to 3 W of power. Graphene/PMMA composite sandwiched between fiber connectors serves as a fully fiberized SA. The generated Gaussian pulses centered at 2059 nm reached 53.6 nm of bandwidth. Compressing the pulses by guiding it through SMF-28 fiber yields pulse durations of 190 fs. We also compare the graphene-based laser with a setup mode-locked with nonlinear polarization rotation - an artificial SA. To the best of our knowledge, this is a first demonstration of a nanomaterial-based stretched pulse fiber laser operating beyond 2 μm. The all-fiber cavity is a more robust alternative to setups that include bulk optics, and requires significantly less alignment compared to lasers mode-locked with real SAs

Sn-doped Bi 2 Te 2 Se as a broadband saturable absorber for Q-switched fiber lasers

Passively Q-switched fiber lasers based on low-dimensional saturable absorbers have been extensively developed due to their efficiency, robustness and great simplicity [1]. However, an environmentally stable, industrial class lasers are still lacking. Here, we present a new material for the application as a broadband saturable absorber for large-energy Q-switched ytterbium- and erbium-doped fiber lasers. Bi2Te2Se:Sn is a small band gap semiconductor and ternary topological insulator [2]. It is characterized by broadband saturable absorption [3].

Ultrashort pulse generation in 2.1 μm spectral range using black phosphorus based saturable absorber

Lasers emitting ultrashort optical pulses beyond 2 μm have found numerous applications in e.g. spectroscopy, telecommunications and medicine [1]. Such wavelengths typically can be reached by Ho-doped active fibers and broadband nanomaterials based saturable absorbers (SA) [2], which are recently intensively developed. Here, for the first time, we demonstrate a black phosphorus (BP) SA used as a mode-locker in an all-fiber Ho-doped laser. The generated solitons were centered at ∼2090 nm with FWHM of 4.2 nm and pulse duration of ∼1.3 ps.

SESAM-assisted Kerr-lens mode-locked YbiCaF 2 oscillator pumped by a single-mode fiber-coupled laser diode

Femtosecond 1 μm lasers are widely used in numerous scientific and industrial applications [1, 2]. Such oscillators are intensively developed and ultrafast sub-100 fs operation has been already demonstrated in several ytterbium-doped active media. One of the most interesting among them and relatively shortly investigated is Yb:CaF2. This is a simple cubic crystal, with very broadband emission spectrum extending over 50 nm [3]. Although the gain bandwidth of the crystal supports generation of ultrashort pulses, design of an appropriate cavity is nontrivial due to a strong tendency for Q-switched mode-locking. The shortest pulse duration achieved with this gain medium so far is 48 fs by exploiting Kerr-lens mode-locking [4]. Until now this regime was demonstrated only with high power pumping due to the relatively low nonlinear refractive index of CaF2. On the other hand, single-mode pumping is beneficial with regard to suppression of parasitic thermal effects while keeping laser setup compact. Recently, an Yb:CaF2 laser emitting 65 fs pulses based on SESAM was demonstrated [5]. Since a low power single-mode diode pumping scheme was employed, only 35 mW of output power was obtained.

Numerical simulations of sub-100 fs soliton fiber laser mode-locked by graphene

We demonstrate the generation of 98 fs soliton pulses in all-polarization maintaining fiber laser mode-locked by graphene saturable absorber. The experimental results are supported by detailed numerical simulations. We confirmed soliton-like pulse shaping in the cavity with strong dispersion-management. The developed computer model was used to study the intra-cavity pulse dynamics. These are the shortest soliton pulses generated in a fiber laser with graphene-based saturable absorber up to date (with the broadest optical spectrum).

An all-PM fiber source generating 5.4 nJ, 95 fs laser pulses in the 2 μm spectral range

We demonstrate an all-polarization maintaining (PM) fiber laser systems which allows for generation of ultrashort laser pulses in 2 μm spectral range. The developed laser setup is very compact and reliable. The average output power of the laser pulses centered at 1975 nm was 244 mW. While the pulse duration and energy were of 95 fs and 5.4 nJ, respectively.

Exploiting nonlinear properties of pure and Sn-doped Bi 2 Te 2 Se for passive Q-switching of all-polarization maintaining ytterbium- and erbium-doped fiber lasers

Due to their broadband nonlinear optical properties, low-dimensional materials are widely used for pulse generation in fiber and solid-state lasers. Here we demonstrate novel materials, Bi2Te2Se (BTS) and Sn-doped Bi2Te2Se (BSTS), which can be used as a universal saturable absorbers for distinct spectral regimes. The material was mechanically exfoliated from a bulk single-crystal and deposited onto a side-polished fiber. We have performed characterization of the fabricated devices and employed them in polarization-maintaining ytterbium- and erbium-doped fiber lasers. This enabled us to obtain self-starting passively Q-switched regime at 1 µm and 1.56 µm. The oscillators emitted stable, linearly polarized radiation with the highest single pulse energy approaching 692 nJ. Both lasers are characterized by the best performance observed in all-polarization maintaining Q-switched fiber lasers with recently investigated new saturable absorbers, which was enabled by a very high damage threshold of the devices. This demonstrates the great potential of the investigated materials for the ultrafast photonics community.