Kerr nonlinearity and dispersion characterization of core-pumped thulium-doped fiber at 2  μm

Abstract

A nonlinear coefficient of 3.6-4.1 W −1 km −1 and group velocity dispersion of −20 ps 2 ∕km of a commercial corepumped thulium-doped fiber have been evaluated using degenerate four-wave mixing at 2 μm. The anomalous dispersion behavior of the fiber has been confirmed by linear measurements with an all-fiber Mach-Zehnder interferometer (MZI). Additionally, no pump-induced dispersion changes due to excitation of Tm 3 cations have been detected. These characteristics make these fibers attractive for pulsed fiber laser applications. A nonlinearpolarization rotation mode-locked laser involving nonlinear polarization evolution directly in the doped fiber is demonstrated. Thulium-doped fiber (TDF) lasers operating in the 2 μm spectral range have recently attracted significant interest for various applications, covering spectroscopy and atmospheric CO 2 monitoring, material and biological tissues processing, and telecommunications [1][2][3][4][5]. TDFs and a whole range of fiber optics components designed to operate around 2 μm have emerged during the past years and are now widely available, simplifying the implementation of lasers and amplifiers.Thulium-doped fibers can be purchased off the shelf, but some of their characteristics, namely, dispersion and nonlinearity, are rarely studied despite their impact on many applications. 2 μm pulsed lasers have undergone tremendous advances over the past few years, with continuous performance improvements in terms of pulse duration and peak and average powers [4]. Dispersion management of the fiber cavity enables the generation of soliton or similariton (parabolic) pulses [6] when a saturable absorber is included. Solid-state saturable absorbers (SESAMs [6], graphene [7]), or Kerr-nonlinear switching elements (nonlinear optical/amplifying loop mirrors [8]), or combinations of both of them [9], were used to modulate cavity losses. Particularly, nonlinear polarization rotation (NPR) is a straightforward and easy-to-implement effect to lock the cavity [10]. In any case, the dispersion and nonlinearity of the various fibers used in the cavity have a direct impact on the performance of the laser. Even though the realization of powerful lasers (over a few watts) requires the use of doubleclad fibers for pump coupling matters, the 2 μm mode propagates mostly in the core, the diameter of which can be compared to that of an SMF-28 (e.g., 10 μm for Nufern SM-TDF-10P/130-HE). It can therefore experience significant nonlinear effects due to the high field intensity in the doped fiber over a cavity round trip. TDF amplifiers have also become an active topic of research in the telecommunication field since the demonstration of long haul transmission at 2 μm in hollowcore fibers [5]. Due to the impressive bandwidth of such amplifiers (roughly from 1.8 to 2.1 μm [11]), this spectral band is seen as a potential solution to overcome the capacity limit of fiber networks. It is therefore crucial to study the nonlinear and dispersive properties of single core TDF, such as the standard TmDF200 by OF...

Mid-infrared continuous-wave parametric amplification in chalcogenide microstructured fibers

“…2. The 2 μm pump and signal lasers used in this experiment are custom built Tm-doped fiber lasers [9]. The pump wavelength was selected discretely with various fiber Bragg gratings, while the signal wavelength was selected by a tunable bandpass grating filter with a 1 nm linewidth.…”

“…We used an interferometric method [9] to characterize the dispersion of the untapered PCF. However, the phase delay contribution from the untapered and transition sections hinders this technique from directly yielding a reliable dispersion measurement of the tapered PCF.…”

Bi2Te3 Topological Insulator for Domain-Wall Dark Pulse Generation from Thulium-Doped Fiber Laser

“…The SA was located between the coupler and isolator. The total cavity length was measured as~9.5 m and its cavity group velocity dispersion (GVD) was calculated as -0.64 ps 2 according to the previously measured dispersion values [29,30] The nonlinear transmission of the prepared SA was also measured using lab-made, ~1.5 ps fiber laser with a repetition rate of 24 MHz at 1.93 μm. Figure 4 shows the measured nonlinear transmission with a fitted curve [27]:…”

“…The SA was located between the coupler and isolator. The total cavity length was measured as ~9.5 m and its cavity group velocity dispersion (GVD) was calculated as -0.64 ps 2 according to the previously measured dispersion values [29,30]. The laser output was measured by an optical spectrum analyzer (AQ6375, Yokogawa, Tokyo, Japan) a 500-MHz oscilloscope (6050A, Lecroy, Chestnut Ridge, NY, USA), with a 10-GHz photodetector (ET-5010F, EOT, Traverse City, MI, USA), an electrical spectrum analyzer (USB-SA124B, Signalhound, Battle Ground, WA, USA), and an autocorrelator (FR-103MN, Femtochrome Research, Berkeley, CA, We increased the pump power and the laser operated in continuous wave (CW) mode at a pump power of~58 mW.…”

Single-cycle all-fiber frequency comb

“…And finally, it is well-known that EDF can induce extra dispersion around its gain/absorption peak [77,78]. Currently, no resonant disper-sion from TDF was noticed -it is absent in both interferometry dispersion measurement [79] and MLL with heavily-doped TDF (300 dB/m pump absorption) [80]. However, our configuration is different, having 20× gain within 14 cm gain fiber.…”