Generation of high-energy soliton-like pulses in 1.9–2.5 µ m spectral domain

Abstract: We experimentally demonstrate the generation of soliton-like pulses with 195–230 fs duration and energy up to 20 nJ in the spectral region of 1.9–2.5 µm directly from the Tm-doped all-fiber MOPA laser. The emerged Raman solitons generated directly in the fiber amplifier exhibit unusual dynamics and spectral properties forming a supercontinuum without conventional gaps between Stokes pulses. Namely, at the output powers above 2 W, in addition to conventional soliton spectral peaks beyond 2.3 μm, we observe high spectral density over an extended range of 1.95–2.23 μm corresponding to a coherent structure that to the best of our knowledge differs from any previously observed supercontinuum regimes. The average optical power of the fiber laser is at the 3-W level, whereas the estimated peak power reached the 80-kW level. Such a relatively simple laser system with high spectral density is a promising light source for various applications ranging from advanced comb spectroscopy to ultra-fast photonics

All-fiber optical supercontinuum sources in 1.7-3.2 μm range

We report supercontinuum generation in the 1.7-2.9 μm range with up to 3.08 W of output power and in the range of 1.93-3.18 μm with up to 3.8 W of output power from all-fiber MOPA pulsed systems with Tm-doped fiber mode-locked seed laser. Supercontinuum generation was demonstrated in nonlinear germanate fibers and fluoride (ZBLAN) fibers. The supercontinuum bandwidth reached 1250 nm at -10 dB level

Broadband dispersion measurement of ZBLAN, germanate and silica fibers in MidIR

We report the first ultra-broad band dispersion measurements in short-length ZBLAN, germanate and silica-based optical fibers in the near- and midIR wavelength ranges between 1.7 and 2.0 μ m and from 2.3 to 2.45 μm, using two ultra-broadband light sources: a broadband superluminescent Tm-doped fiber source and a novel femtosecond pulsed mode-locked Cr:ZnS oscillator. The measured second order dispersion characteristics of the fibers correspond to the theoretical predictions (numerical calculations)

Nonsaturable absorption in alumino-silicate bismuth-doped fibers

We report an experimental and theoretical investigation of fluorescence decay and transmission coefficient at ∼1 μm pumping for a series of bismuth (Bi) doped alumino-silicate fibers with different concentrations of Bi centers. By modeling the experimental data, we show that the excited-state absorption (ESA) and up-conversion (UC) processes are responsible for a growth of nonsaturable absorption and deviation from exponential the fluorescence decay in the fibers with an increase in Bi centers content. Assuming that Bi centers ensemble is composed of subsystems of single and paired centers, and an increase in partial weight of the latter with a Bi centers concentration growth, we can successfully explain the experimental data. Also, these assumptions allow us to estimate the constants characterizing the ESA and both homogeneous and inhomogeneous UC processes in the fibers

YDFL operating in 1150-1200-nm spectral domain

A family of high-power Yb-doped fiber lasers operated in the range of 1150-1180 nm with output powers of up to 35 W and optical efficiencies up to 60% is realized. Operation at 1200 nm is also demonstrated. Amplified spontaneous emission increase with output power increase is analyzed in frames of the inhomogeneous broadening concept

Flat-top supercontinuum and tunable femtosecond fiber laser sources at 1.9-2.5 μm

We report the high-energy flat-top supercontinuum covering the mid-infrared wavelength range of 1.9-2.5 μm as well as electronically tunable femtosecond pulses between 1.98-2.22 μm directly from the thulium-doped fiber laser amplifier. Comparison of experimental results with numerical simulations confirms that both sources employ the same nonlinear optical mechanism - Raman soliton frequency shift occurring inside the Tm-fiber amplifier. To illustrate that, we investigate two versions of the compact diode-pumped SESAM mode-locked femtosecond thulium-doped all-silica-fiber-based laser system providing either broadband supercontinuum or tunable Raman soliton output, depending on the parameters of the system. The first system operates in the Raman soliton regime providing femtosecond pulses tunable between 1.98-2.22 μm. Wide and continuous spectral tunability over 240 nm was realized by changing only the amplifier pump diode current. The second system generates high-energy supercontinuum with the superior spectral flatness of better than 1 dB covering the wavelength range of 1.9-2.5 μm, with the total output energy as high as 0.284 μJ, the average power of 2.1 W at 7.5 MHz repetition rate. We simulate the amplifier operation in the Raman soliton self-frequency shift regime and discuss the role of induced Raman scattering in supercontinuum formation inside the fiber amplifier. We compare this system with a more traditional 1.85-2.53 μm supercontinuum source in the external highly-nonlinear commercial chalcogenide fiber using the Raman soliton MOPA as an excitation source. The reported systems1 can be readily applied to a number of industrial applications in the mid-IR, including sensing, stand-off detection, medical surgery and fine material processing

Waveguide-saturable absorber fabricated by femtosecond pulses in YAG:Cr4+ crystal for Q-switched operation of Yb-fiber laser

A waveguide-saturable absorber with low propagation loss is fabricated by femtosecond pulses in YAG:Cr4+ crystal. Q-switch operation of a Yb fiber laser with the new saturable absorber having absorption saturation parameters similar to the bulk YAG:Cr4+ crystal is demonstrated

Novel Y2O3-codoped Yb/Tm-doped picosecond fiber laser

We demonstrate the novel picosecond mode-locked Y2O 3-codoped Yb/Tm-doped fiber lasers, operating at 1950 nm and producing pulses of up to 1 nJ energy, using a SESAM and an Er-doped pump fiber laser operating at the wavelength 1590 nm or a semiconductor pump laser operating at the wavelength of 1560 nm. We also report on the spectroscopic characterization of these new fibers with various compositions, identifying the optimum one for the maximum Yb/Tm energy transfer, the latter increasing with the increase of the Y concentration. The observed energy transfer between Yb and Tm makes this laser promising also for direct diode-pumping with most advanced and low cost 975 nm diodes, making this laser attractive for compact low cost picosecond Tm-doped fiber laser systems

QoT Evaluation of Optical Line System Transmission with Bismuth-Doped Fiber Amplifiers in the E-Band

We numerically investigate E-band quality of the transmission using an ex- perimentally characterized bismuth-doped fiber amplifier, demonstrating its impact on de-ployed C+L system