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We experimentally studied the room-temperature polarization-resolved electrical conductance of multilayer graphene-based films using a home-made terahertz time-domain spectroscopic polarimetry system. The conductance increases nonlinearly with an increase in the graphene layer number and reaches, for ~76 layers, 0.06 S for the real, and 0.03 S for the imaginary part, respectively.

Long-cavity ytterbium-doped fiber laser operating in the hybrid mode-locked regime was demonstrated. Self-starting and self-similarity of the laser output were achieved. Experiments were performed from the amplifying and frequency doubling of hybrid mode-locked laser radiation.

Ultrafast fiber sources operating in the spectral range of 2–3 μm have attracted attention due to a number of possible applications, e.g. for perspective communications, gas sensing, nonlinear frequency conversion, and medicine. Holmium-doped fibers (HDF) are commonly used as a gain medium for 2 μm lasers due to their broad gain spectrum, extending from 2 to 2.2 μm.

We have investigated the laser radiation parameters of the hybrid mode-locked holmium-doped fiber laser. To realize this regime we have combined nonlinear polarization evolution (NPE) and carbon nanotubes (CNT) as an additional nonlinear saturable absorber.

Ultrashort pulse (USP) fiber lasers have become one of the most important instruments in various fields of science and industry during two past decades [1]. A number of applications requires stability of pulse duration, repetition rate and low intensity noise of an USP source. For example, stabilization of this parameters is in great demand in frequency metrology field, dual comb spectroscopy, THz pulse spectroscopy and etc. [2]. It should be noted, that hybrid Mode-locking (ML) for USP generation have attracted a great attention due to their capabilities of enhancing pulse quality and providing reliable ML startup by taking advantage of a co-action of two saturable absorbers (SA) — a slow SA such as SESAM, carbon nanostructures or graphene, and a fast absorber based on nonlinear polarization evolution (NPE) effect [3]. Recently Carbon:Boron Nitride Single-Walled Nanotubes(C:BNNTs) SA is proved to be reliable absorber with excellent saturation parameters for erbium-doped fiber laser ML [4]. In this paper we have obtained and measured stability of stretch pulse generation in the hybrid ML erbium-doped all-fiber ring laser by using C:BNNTs SA in the co-action with NPE effect. We have managed to realize two different types of stable single-pulse, self-starting stretch pulse generation at a repetition frequency of 42.2MHz with S/N ratio ∼ 63 dB. Note, that the total intracavity group velocity dispersion β 2 was −0.021 ps2 at 1550 nm. Obtained sech2-type spectrum has a FWHM of ≈ 4nm at the output average power of 16.7mW and the Gauss-type spectra has a FWHM of ≈ 56 nm at the same output power. Pulse width measured by intensity autocorrelator is 650 fs for both USP generation regimes. Note, that the time-bandwidth product for the sech2 pulse is TBP=Δ × τ min ≈ 0.322 and for the Gauss pulse TBP ≈ 4.45 (typical TBP for a Gauss pulse ≈ 0.44). Thus, the obtained sech2 pulse is close to the bandwidth-limit (TBP ≈ 0.315 for a classical soliton). It should be noted, that minimal Gauss pulse width (up to sub-100 fs duration) can be achieved simply by proper fiber length control at the laser output.

Ultra-short pulse (USP) fiber lasers have a great potential for their applications in various fields of science, industry and technology [1]. We have implemented MOPA (Master Oscillator Power Amplifier) configuration. Master oscillator (MO) is ring all-fiber laser with 92.6 fs parabolic spectra dechirped pulses at a central wavelength of 1560nm with 11.2mW average output power and 38.2MHz repetition rate [2]. The short pulses were realized with a hybrid mode-locking (ML) technique [3] that implies a co-action of two ML mechanisms — saturable absorber based on the Boron-Nitride-doped Single-Walled Carbon Nanotubes [4] and Nonlinear Polarization Evolution [5] in fibers. MO total cavity dispersion is D T ≈ +0.01 ps2 for the central wavelength λ 0 = 1560nm as it was estimated according to the measured dispersion of fibers. The pulse evolution in preamplifier and in MO ring cavity has a similar structure. Note that in preamplifier output average power was increased to 100mW with slight change of the pulse duration and spectrum shape after master oscillator. Thus, we suggest similariton generation in MO according to obtained measurements. For achieving high output power we used chirped pulse amplification technique and stretched the pulse in the high-power amplifier entrance. The active fiber of the high-power amplifier is single mode double-clad Er-doped (without Yb3+) fiber with mode field diameter ∼ 25 µm pumped at 980 nm. As a result, output power of 3.1W with a pulse duration ∼ 20 ps without compression was achieved after high power amplification corresponding to pulse energy of ∼ 80 nJ and peak power of ∼ 4 kW.

We report on the ultra-short dispersion-managed (DM) soliton generation in the erbium-doped all-fiber ring laser hybrid mode-locked (ML) with Carbon:Boron Nitride Single-Walled Nanotubes (C:BNNTs) in the co-action with a nonlinear polarization evolution (NPE).

We report for the first time, generation of dissipative soliton from a ring-cavity thulium fiber laser mode-locked with the use of a carbon nanotubes saturable absorber and a length of DCF producing 416pJ pulse energy.

We report on development of 1mkm master oscillator generating 6.6 ps, 250 pJ soliton-like pulses. The selfstarting CW mode-locking is realized in ytterbium all-fiber ring laser with PM architecture using specially designed saturable absorber based on single-wall carbon nanotubes. Keywords—mode-locking; SWNT; ytterbium; soliton I. INTRODUCTION Generation of high energy picosecond pulses at the wavelength of 1 mkm is a subject of intensive investigation due to its practical demands. Realization of such lasers in fiber format can be especially fruitful because of highly developed fiber technology. One of the most popular approaches is MOPA laser scheme with Master Oscillator based on passive mode locking (ML) with SESAM (1). Although huge progress has been made in improving quality and lifetime of SESAM, another saturable absorbers should be investigated. This paper briefly presents results of ytterbium picosecond pulse laser based on ML with Single-Wall NanoTubes (SWNT) as saturable absorbers.

We have obtained, for the first time to the best of our knowledge, sub-100 fs similariton generation in the erbium- doped all-fiber ring laser hybrid mode-locked with Carbon:Boron Nitride Single-Walled Nanotubes in the co-action with a nonlinear polarization evolution.

Single-walled carbon nanotubes (SWCNTs) are being widely investigated as saturable absorbers for initiating and maintaining mode-locking [1-3]. Among their advantages are low fabrication cost, a high damage threshold, sub-picosecond recovery times and a wide spectral range (1.0–2.5 µm). All mode-locked fibre laser systems based on SWCNT saturable absorbers, demonstrated to date, have used the first electronic transition of the nanotubes, known as E 11 , which corresponds to the single real gap in the electron density of states (DOS) of semiconducting nanotubes [4]. It was expected that only this transition could be used for saturable absorption. However, in a couple of recent papers [5,6], the mode-locking regime has been realized in bulk lasers at 1.06 µm with arc-synthesized nanotubes, but the authors did not pay much attention to the fact that this wavelength belongs to the second absorption band, corresponding to the E 22 pseudo-gap [4]. This means that after excitation the electron falls to the lower energy transition, corresponding to the real gap E 11 . In this work we clearly demonstrate saturable absorption on the E 22 transition by using it to mode-lock a fibre laser for the first time. This discovery should enable the use of SWCNT saturable absorbers at much shorter wavelengths, into the visible spectral region.