Maria Michalska

A continuous-wave (CW) multi-watt-level 1.76-μm all-fiber Tm-doped laser resonantly pumped at 1.56 μm is presented. To mitigate long-wavelength amplified spontaneous emission (ASE), an in-house-drawn depressed-cladding Tm-doped fiber (dc-TDF) was used as an active medium. In a linear cavity, an output power of 2.47 W, with an optical signal-to-noise ratio (SNR) exceeding 65 dB and a high slope efficiency of 75.8% relative to the launched power, was demonstrated. Furthermore, bidirectional pumping enabled output power scaling over 4 W with a slope efficiency of 66%. To our knowledge, this is the first demonstration of 1.7-μm laser operation using dc-TDFs.

The dynamics of semiconductor lasers are modelled in the time domain using a pair of differential equations known as rate equations. The analysis, based on temporal solutions of these equations, yields practical results utilised in various applications. Alternatively, an analysis employing the phase space method, a well-established analytical tool in applied mathematics, provides a more comprehensive perspective on semiconductor laser dynamics. The main purpose of this paper is to provide a detailed and intuitive introduction to phase space analysis in the context of semiconductor laser dynamics. The goal is to offer an easily comprehensible description of the mentioned method, placing emphasis on the graphical representation and physical interpretation of the results. The method effectiveness is shown through its application to selected practical problems. Furthermore, semiconductor laser dynamics can be treated as an illustrative example, showcasing the applicability of the method, which can be readily extended to other types of lasers or even more advanced dynamic systems.

New construction of a silica-based multi-ring profile of Tm ³⁺ doped fiber laser is presented. Optimisation of both multi-ring refractive index profile and active ions distribution towards high beam quality mode propagation is a new approach in developing active fiber constructions. Using a system of layers forming the core allows controlling the dopant profile and, consequently, the emission properties of fiber lasers (power density, beam profile shape etc.). The preform fabricated using MCVD technology is presented. The refractive index profile (Δn = 9·10 ⁻³ ), EPMA-EDS analysis (Tm ₂ O ₃ and Al ₂ O ₃ concentration 0.56 and 5.2 wt% respectively), and excited state ( ³ F ₄ ) decay time are shown. The double-clad fiber laser based on the Fabry-Perot resonator construction (17/240 μm core/cladding) was used for single-mode laser beam generation at a wavelength of 1938.8 nm (exc. @ 790 nm) with an FWHM bandwidth of 0.17 nm (1.68 W output power, M ² _x = 1.10, M ² _y = 1.23). For the optimized gain fiber (25/330 μm core/cladding diameters) length, the laser provided an output power of >5 W with a slope efficiency of ∼26%, determined to the absorbed pump power.

We report on high-power thulium-doped fiber amplifiers built using a nanoparticle-doped double-clad, pedestal-style large mode area fiber. The applied nanoparticle doping technique allowed achieving uniform high doping concentrations of Al ₂ O ₃ and Tm ₂ O ₃ across the fiber core. The fiber outer layer was fluorine-doped providing a decrease in pump radiation interaction with the coating, thereby enhancing the reliability of the entire laser system under high-power operation. The laser system operating at a wavelength of 2034 nm delivered an output power of up to 441 W with a slope efficiency of 57.4%, and the electro-optical conversion efficiency of the amplifier was 25%. The 1940-nm-wavelength all-fiber amplifier seeded with a narrowband Tm-doped fiber laser provided an output power of up to 273 W with a slope efficiency as high as 61.8%. In both cases the output spectrum was characterized by a 3-dB spectral bandwidth below 160 pm. Moreover, a special splicing procedure for large mode area fibers transmitting high power radiation was proposed and successfully demonstrated.

Fiber laser sources operating in the 2 µm wavelength region have gained extensive attention due to their wide range of applications, including in medicine, remote sensing, spectroscopy, plastic material processing, and mid-infrared generation

We demonstrate a thulium-doped, mode-locked, all-fiber laser capable of operating in two generation regimes: dispersion-managed soliton and noise-like pulse (NLP). Employing a nonlinear optical loop mirror as an artificial saturable absorber, the oscillator generated optical pulses with a fundamental pulse repetition frequency of ~15.795 MHz. The total net dispersion of the laser cavity had a slightly anomalous group delay dispersion value of −0.016 ps². After appropriate adjustment of a polarization controller, bound states of a dispersion-managed soliton composed of three pulses with fixed soliton separations were also observed. NLP generation, tunable over 35 nm from 1943.5 to 1978 nm, was also presented in the same laser setup. To our knowledge, this is the first report of the generation of tunable NLPs in a mode-locked thulium-doped fiber laser based on a nonlinear loop mirror saturable absorber.

We report the generation of a spectrally flat supercontinuum in a fluoroindate ( I n F 3 ) fiber with a maximum time-averaged output power of 1.14 W and a spectrum extended to 4.75 µm. The pump source was a fast gain-switched and semiconductor saturable absorber mirror mode-locked thulium Tm-doped fiber laser followed by a cascade of two Tm-doped fiber amplifiers. The repetition rates of the gain-switched pulses and mode-locked sub-pulses were 50 kHz and 111 MHz, respectively, whereas the duration of sub-pulses recorded within a gain-switched pulse envelope was ∼ 110 p s . This home-built pump laser system provided an output average power of 2.45 W at a central wavelength of 2 µm. To the best of our knowledge, this is the first paper on supercontinuum generation in an I n F 3 fiber pumped by a fast gain-switched and mode-locked laser system. This approach is promising for further efficient continuum generation in the mid-infrared region.

We investigate a noise-like pulse (NLP) generation in an all-PM-thulium-doped fiber laser. An NLP with a coherence spike width of 232 fs was generated at 1993.6 nm with a 3-dB bandwidth of 32.6 nm.

In this work, sub-kilowatt, compact thulium-doped fiber laser systems, operating at a wavelength of 1940 nm, have been presented. The continuous-wave laser power generated out of a single oscillator was 90 W with a slope efficiency of 56.7%. Applying a master oscillator – power amplifier configuration, an output power of 120.5 W with a slope efficiency of 58.2% was demonstrated. These are the first results of the works aimed at developing kW-class “eye-safe” laser systems in Poland. Full Text: PDF ReferencesZ. Liu, et al., "Implementing termination analysis on quantum programming", Sci. China Inf. Sci. 62, 41301 (2019) CrossRef S. D. Jackson, A. Sabella, D.G Lancaster, "Application and Development of High-Power and Highly Efficient Silica-Based Fiber Lasers Operating at 2 μm", IEEE J. Sel. Top. Quantum Electron. 13, 567, (2007). CrossRef E. Russell, N. Kavanagh, K. Shortiss, and F. C. G. Gunning, "Development of thulium-doped fibre amplifiers for the 2μm waveband", Proc. SPIE 10683, 106832Q (2018) CrossRef P. Peterka, B. Faure, W. Blanc, M. Karásek, and B. Dussardier, "Theoretical modelling of S-band thulium-doped silica fibre amplifiers", Opt. Quantum Electron. 36, 201 (2004) CrossRef M. Eichhorn, "Pulsed 2 μm fiber lasers for direct and pumping applications in defence and security", Proc. SPIE 7836, 78360B (2010). CrossRef O. Traxer and E. X. Keller, "Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser", World J. Urol. 2019 Feb 6. doi: 10.1007/s00345-019-02654-5 CrossRef S. Das, "Optical parametric oscillator: status of tunable radiation in mid-IR to IR spectral range based on ZnGeP2 crystal pumped by solid state lasers", Opt. Quant. Electron. 51, 70 (2019) CrossRef M. Michalska, P. Hlubina, and J. Swiderski, "Mid-infrared Supercontinuum Generation to ∼4.7 μm in a ZBLAN Fiber Pumped by an Optical Parametric Generator", IEEE Photon. J 9, 3200207 (2017) CrossRef https://www.ipgphotonics.com DirectLink M.D. Burns, P. C. Shardlow, P. Barua, T. L. Jefferson-Brain, J. K. Sahu, and W. A.Clarkson, "47 W continuous-wave 1726 nm thulium fiber laser core-pumped by an erbium fiber laser", Opt. Lett. 44, 5230 (2019) CrossRef S.D. Jackson, "Cross relaxation and energy transfer upconversion processes relevant to the functioning of 2 μm Tm3+-doped silica fibre lasers", Opt. Commun. 230, 197 (2004). CrossRef X. Wang, P. Zhou, X. Wang, H. Xiao, and L. Si, "102 W monolithic single frequency Tm-doped fiber MOPA", Opt. Express 21, 32386 (2013) CrossRef K. Yin, R. Zhu, B. Zhang, G. Liu, P. Zhou, and J. Hou, "300 W-level, wavelength-widely-tunable, all-fiber integrated thulium-doped fiber laser", Opt. Express 24, 11085 (2016) CrossRef G. D. Goodno, L. D. Book, and J. E. Rothenberg, "600-W, single-mode, single-frequency thulium fibre laser amplifier", Proc. SPIE 7195, 71950Y (2009). CrossRef T. Ehrenreich, R. Leveille, I. Majid, K. Tankala, G. Rines, and P. Moulton, "1-kW, all-glass Tm: fiber laser", Proc. SPIE 7580, 1 (2010) DirectLink M. Michalska et al., "Highly stable, efficient Tm-doped fiber laser—a potential scalpel for low invasive surgery", Laser Phys. Lett. 13, 115101 (2016). CrossRef