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Effective, high energy ultrafast laser systems for practical applications requires laser sources with low and tunable repetition rate. Intrinsically, a mode-locked fiber laser operates at relatively high and fixed repetition rates (at the order of MHz). Such a high repetition rate limits the achievable pulse energy from an amplifier. To overcome this limitation, we demonstrate a fast, compact, and fully automatic custom made pulse picking system for operation with femtosecond lasers with repetition rates up to 50 MHz. It employs custom electronics with FPGA based signal processing unit and a fast 200 MHz acousto-optic modulator. Proposed solution is flexible and it can be used with various lasers, modulators and detectors. Therefore it is possible to operate e.g. at 1.55 Μm and 2 μm wavelengths. Moreover, the unit can automatically adopted to different repetition rates of seed lasers by adjustable time delay, to be in phase with optical signal. FPGA based signal processing unit can be reconfigured by a microcontroller to deliver several triggering options, digital delay line and frequency meter unit.

We report our observations of both fundamental and bound soliton states generated in all-polarization maintaining (all-PM) fiber laser mode-locked by graphene saturable absorber. The laser can generate fundamental soliton pulses with 312 fs duration, centered at 1560 nm. For higher pumping power the laser operates in bound soliton state. Stable 460 fs pulses with equal intensities and 9.4 pulse-to-pulse separation.

In this paper we demonstrate a preliminary work done on employing antimony telluride (Sb2Te3) topological insulator as a saturable absorber for Yb-doped fiber lasers. The material was deposited onto a side-polished fiber by means of a pulsed magnetron sputtering technique. Fabricated absorber was implemented in an all-normal dispersion cavity and allowed for self-starting dissipative soliton generation. The laser emitted stable pulse train at a repetition rate of 17.07 MHz with 4.25 nm broad output spectrum centered around 1039.4 nm. Average output power amounted to 0.54 mW with 32 pJ pulse energy.

In this work, we present experimental results of characterization of the developed holmium-doped silica-based optical fibers with holmium ions concentrations in the range from 1000 to 10000 ppm. The fibers were fabricated by the modified chemical vapor deposition and solution doping method. They were characterized in terms of their spectral attenuation, refractive index profile, and especially performance in fiber laser. Simultaneously, two different fiber laser setups were tested. In the first one, holmium-doped fiber in Fabry-Perot configuration was pumping by in house developed thulium-doped fiber laser in ring arrangement. In the second one, bulk-optic pump-coupling configuration, consisted of a commercially available thulium fiber laser emitting at 1940 nm and system of lenses and mirrors was used. We have focused on comparison of laser output powers, slope efficiencies, and laser thresholds for individual holmiumdoped fiber in these different laser arrangements. Finally, the application of the developed fiber in subpicosecond fiber laser with graphene-based saturable absorber for mode-locking operation was investigated.

In this work, we demonstrate a high-pulse energy, fiber-based chirped pulse amplification (CPA) setup utilizing Er- and Er/Yb-doped fibers, operating at 1555 nm central wavelength. The integrated pulse-picker allows to reduce the repetition frequency down to the kHz-range, which enables generation of sub-picosecond pulses with energies above 2 μJ and pulse peak power exceeding 1 MW. The system utilizes an Er/Yb co-doped large mode area fiber in the final amplification stage. Thanks to the used mode-field adaptors, the setup is almost fully fiberized, except the bulk grating pulse compressor.

We present an Er-doped fiber mode-locked laser based on an evanescent field interaction with the Sb2Te3 topological insulator. The saturable absorber (SA) consist of a bulk piece of Sb2Te3 material placed on the side-polished fiber in the presence of UV curable polymer. The measured SA optical parameters like: linear absorption, modulation depth and non-saturable loses were of 50%, 6% and 43%, respectively. The SA was spliced into the ring laser cavities characterized by the all-anomalous, all-normal and balanced dispersion. Such laser resonators allowed for optical solitons, dissipative solitons and Gaussian pulses generation with 3dB bandwidth of 8.5 nm, 37 nm and 17 nm, respectively.

In this work, femtosecond pulse generation in Er-doped fiber laser using graphene oxide (GO) paper based saturable absorber (SA) is presented. The article includes the characterization of optical properties of prepared SA material and detailed description of the laser performance. Stable mode-locking operation was achieved, with 515 fs soliton pulses centered at 1559 nm. The GO paper SA is characterized by 5.4% modulation depth and 155 MW/cm 2 of saturation intensity. The nearly wavelength-independent linear absorption combined with straightforward fabrication process make it a suitable material for application as a SA in low-power mode-locked fiber lasers operating in various spectral ranges.

We present first to our knowledge self-starting graphene-chitosan based ultrafast fiber laser setup. Graphene-chitosan composite placed between two fibres connectors is saturable absorber in demonstrated setup and is responsible for modelocking operation. Laser is built with polarization maintaining fibres which grants self-start feature. Laser produces ~300 fs soliton pulses centered at 1566 nm with 10 nm FHWM optical bandwidth. Time bandwidth product of demonstrated laser is 0.37. Repetition rate of 42 MHz and average output power of 1.2 mw corresponds to pulse energy and peak power of 20 pJ and 62 W, respectively. As an active media in laser Erbium-doper fiber was used. Presented setup proves graphene is novel promising material for ultrafast lasers production at worldwide scale.

In this paper we present a dual-wavelength fiber mode-locked laser based on CVD-graphene saturable absorber (SA). The laser setup is based on two ring cavities connected by a common branch with a graphene SA. As a gain media erbium (Er) and thulium (Tm) doped active fiber were used. The laser generate optical pulses centered at 1558.5 nm and 1937 nm. The repetition rates and pulse durations were of 23.2 MHz, 16.42 MHz and 0.95 ps, 1.03 ps for the solitons generated in Er- and Tm-doped cavities, respectively.

We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm 3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm 3 , are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003oC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3⋅10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.

In this work we present our results on supercontinuum (SC) generation using a photonic crystal fiber (PCF) fabricated from lead-bismuth-gallium-oxide glass (PBG-08). Due to high refractive index, high nonlinearity and high transmittance, the PBG-08 glass-based fibers seem to be excellent media for broad supercontinuum generation in the infrared spectral region. In our experiment, a short-length piece of PCF (6 cm) is pumped by a femtosecond fiber laser system, delivering 540 fs pulses at 60 MHz repetition rate and 2.75 W of maximum average power. This compact and cost-effective system allows to generate supercontinuum spanning from 900 to 2400 nm.

Supercontinuum generation (SG) in photonic crystal fibers (PCFs) usually takes advantage of soliton dynamics, when pump wavelength is located in the anomalous dispersion region near the zero-dispersion wavelength of the fiber. This results in broader bandwidth than pumping in the normal dispersion region (NDR). SG in NDR is of interest, because of its potential for high degree of coherence and low intensity fluctuations. It was experimentally demonstrated in silica fibers and PCFs pumped around 1000 nm, covering the visible and near-infrared. We developed an all-solid PCF with hexagonal lattice made from N-F2 capillaries, with lattice constant Λ=2.275 μm, filling factor d/Λ=0.9, and a solid N-F2 core with 2,5μm diameter. The capillaries were filled with thermally matched borosilicate glass rods with lower refractive index. The PCF has all-normal dispersion, flattened within 1400- 2750 nm (-35 to -29 ps/nm/km) and a local maximum of -29 ps/nm/km at 1550 nm. Measured attenuation in 1500-1600 nm is around 3.2 dB/m. Nonlinear coefficient calculated at 1550 nm is 17/W/m. We numerically investigate the evolution of supercontinuum formation with a maximum bandwidth of 900-2400 nm. Considered pump pulse lengths were between 1 ps and 50 fs, with corresponding peak powers from 20 kW to 200 kW. Measured coupling efficiency using 20× microscope objective was 50%. One-photon-per-mode noise was used to simulate pump noise and multi-shot SG spectra were calculated. Preliminary experimental results are in good agreement with developed model.

We present a method of generating mid-IR radiation by means of nonlinear difference frequency generation (DFG) effects occurring in periodically polled lithium niobate (PPLN) crystals using an all-fiber dual-wavelength amplifier. The presented mid-IR laser source incorporates an unique double-clad (DC) Erbium and Ytterbium (Er-Yb) doped amplifier stage capable of simultaneous amplification of both wavelengths required in the DFG process - 1064 nm and 1550 nm. The amplifier delivered more than 23.7 dB and 14.4 dB of amplification for 1550 nm and 1064 nm wavelength, low power, off-the-shelf, fiber pigtailed, distributed feedback (DFB) laser diodes, respectively. The dual-wavelength amplifier parameters crucial for the DFG process were investigated, including long-term power and polarization instabilities and optical spectrum characteristics of both amplified wavelengths. The DFG setup used a single collimator radiation delivery scheme and an 40 mm long MgO doped PPLN crystal. In effect the DFG source was capable of generating 1.14 mW of radiation centered around 3.4 μm. The overall performance of the mid-IR source was elaborated by performing sensitive Tunable Diode Laser Absorption Spectroscopy (TDLAS) detection of methane (CH4) in ambient air on an free-space optical path-length of 8 m. The measured detection limit of the sensor was 26 ppbv with a 1σ SNR of 69.

For the last few years we were elaborating the laser-fiber vibrometer working at 1550 nm. Our main stress was directed towards different aspects of research: analysis of scattered light, efficient photodetection, optimization of the fiber-free space interfaces and signal processing. As a consequence we proposed the idea of a multichannel fiber vibrometer based on well developed telecommunication technique – Wavelength Division Multiplexing (WDM). One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. We present the results of finished project “Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objects” where we have constructed a 4-channel WDM laser-fiber vibrometer.

In this paper we present a device - fiber based coherent light source operating at 1550 nm wavelength and 5 W of the output power. It is made completely of the fiber elements without any bulk optics therefore it is stable and resistant to the environmental conditions. The main idea was to use so called MOPA (Master Oscillator Power Amplifier) configuration to obtain universal design. Thus the device can be easily configured to work in couple different operation regimes.

In this work we demonstrate a harmonically mode-locked Er-doped fiber laser utilizing graphene saturable absorber. The laser could operate at various harmonics of the fundamental repetition frequency, depending on the launched pump power. The highest obtained repetition rate was 2.22 GHz, which corresponds to the 21st harmonic of the resonator mode-spacing. At this harmonic, the laser generated sub-picosecond pulses with over 40 dB of supermode noise suppression. Multilayer graphene was obtained by mechanical exfoliation and deposited onto a fiber connector tip, forming a saturable absorber.

A new design of an erbium-ytterbium doped fiber amplifier is demonstrated. The amplifier contains a wavelength-tuned loop resonator for the 1 μm signal. The amplified spontaneous emission (ASE) from Yb ions is used to stimulate a laser emission at several wavelengths from the 1 μm band in the 1550 nm amplifier. The wavelength of this lasing is selected by introducing a spectral filter. The results show, that the efficiency of the amplifier at nominal 1550 nm wavelength can be increased by introducing a feedback loop with 1040 nm and 1050 nm filters. This loop also protects the Er-Yb amplifier from parasitic lasing and allows output power scaling without risk of self-pulsing at 1 μm.

Mechanically exfoliated graphene saturable absorber based all-polarization maintaining passively mode-locked erbium doped fiber laser is presented. The laser consists of fully polarization maintaining (PM) fibers and components, providing linear output polarization state. The saturable absorber was formed by mechanical exfoliation of graphene flakes from pure graphite and deposited on a fiber connector. It was characterized using atomic force microscopy and Raman spectroscopy. Laser resonators with repetition frequency of 45.88 MHz and 114.1 MHz were investigated. The soliton pulses at 1555 nm were achieved with duration around 600 fs. The splicing procedure of PM-fibers was also optimized which results in improvement of degree of polarization (DOP).

In this work we present a new design of Er/Yb co-doped fiber amplifier with controlled amplified spontaneous emission (ASE) at 1 μm. The Yb-ASE is controlled by stimulating a laser emission at 1064 nm in the amplifier, by providing a positive 1 μm signal feedback loop. The results were discussed and compared to a conventional amplifier setup without 1 μm ASE control. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output power at 1550 nm and provide stable operation without parasitic lasing at 1 μm.

In this work we present a high-power laser source developed in Master Oscillator Power Amplifier (MOPA) configuration. Presented MOPA source consists of three amplifying stages: pre-amplifier based on erbium-doped fiber, medium-power stage based on double-clad Er/Yb co-doped fiber and the power stage, based on Er/Yb co-doped doubleclad LMA fiber. Whole system is set up in All-In-Fiber technique, without any bulk, free-space optical elements. It provides over 20W of output power in the eye-safe 1550 nm band.

The WDM fiber transmission technique was used to measure vibration parameters of four points of a vibrating object. The 4-independent laser diodes form a WDM system according to the rule 'one wavelength-one analyzed point'. Keywords: laser Doppler vibrometry, fibre vibrometry, heterodyne detection, multichannel vibrometry.