Isolator-free unidirectionalthulium-doped fiber laser

We report the first demonstration of a unidirectional, isolator-free 2-mmthulium-doped fiber (TDF) laser, relying on the properties of the theta cavity (ring resonator with S-shaped feedback). The core pumped theta cavity TDF laser provides sub-Watt output power with a slope efficiency of 25%, a 2 dB flat tuning range of 1900–2050 nm, and a linewidth of 0.2 nm, and achieves the extinction ratio of 18– 25 dB (depending on the feedback value) between the favored and suppressed lasing directions. It is shown that these characteristics are competitive with, if not superior to, those of conventional ring cavities. The simulation results of the linear and Kerr-nonlinear theta cavities are also presented, explaining certain unexpected features of the laser behavior and establishing the importance of the doped fiber nonlinearity on the spectral shaping of the emitted signal

Large second harmonic generation enhancement in SiN waveguides by all-optically induced quasi phase matching

Integrated waveguides exhibiting efficient second-order nonlinearities are crucial to obtain compact and low power optical signal processing devices. Silicon nitride (SiN) has shown second harmonic generation (SHG) capabilities in resonant structures and single-pass devices leveraging intermodal phase matching, which is defined by waveguide design. Lithium niobate allows compensating for the phase mismatch using periodically poled waveguides, however the latter are not reconfigurable and remain difficult to integrate with SiN or silicon (Si) circuits. Here we show the all-optical enhancement of SHG in SiN waveguides by more than 30 dB. We demonstrate that a Watt-level laser causes a periodic modification of the waveguide second-order susceptibility. The resulting second order nonlinear grating has a periodicity allowing for quasi phase matching (QPM) between the pump and SH mode. Moreover, changing the pump wavelength or polarization updates the period, relaxing phase matching constraints imposed by the waveguide geometry. We show that the grating is long term inscribed in the waveguides, and we estimate a second order nonlinearity of the order of 0.3 pm/V, while a maximum conversion efficiency (CE) of 1.8x10-6 W-1 cm-2 is reached

Experimental and theoretical investigation of the operating principles of the Figure-9 laser, Advanced Photonics 2018 (BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF)

We present a theoretical vectorial model, validated by experimental measurements, describing the dependence of the Figure-9 laser output power, operating in continuous wave, on the coupling ratio of the directional coupler

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

A nonlinear coefficient of 3.6–4.1 W−1 km−1 and group velocity dispersion of −20 ps2∕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 Tm3 cations have been detected. These characteristics make these fibers attractive for pulsed fiber laser applications. A nonlinear polarization rotation mode-locked laser involving nonlinear polarization evolution directly in the doped fiber is demonstrated

All-fibered chalcogenide based continuous-wave parametric amplification in the mid-infrared

We demonstrate parametric amplification around 2 μm in a dispersion engineered tapered microstructured chalcogenide fiber. Almost 5 dB of signal amplification was achieved by 125 mW coupled power from a thulium-doped fiber pump laser

Fiber fuse in chalcogenide photonic crystal fibers

We observe fiber fuse in tapered GeAsSe photonic crystal fibers (PCF) at around 7 MW∕cm2 of intra-core intensity. Vertically cleaved facets from the un-tapered regions and the tapered regions were imaged. The images show shallow voids of different shapes confined to the fiber core. After longitudinally polishing a segment of the PCF, we imaged the PCF internal structure’s top view, revealing the fuse voids’ geometries and periodicity. In addition, fiber fuse was terminated in one PCF sample by a fast laser shutdown, hence saving a small segment from catastrophic damage. Four-wave-mixing was performed on this transmissive segment to estimate the dispersion. The results yielded an evident hole-pitch ratio change after fiber fuse. To our knowledge, this is the first report of fiber fuse on non-silica glass fibers and the first study of its aftermath on this un-destroyed segment of PCFs. © 2018 Optical Society of Americ

Data transmission in long-range dielectric-loaded surface plasmon polariton waveguides

In this paper we report successful transmission of 10 Gbit/s on-off-keying (OOK) modulated signal through the LR-DLSPPWs with almost negligible degradation of the data flow consistenc

Stable 2.1 μm near 100% polarized Ho-doped all-fiber laser based on a polarizer-free cavity scheme

A highly polarized Ho-doped truly all-fibre laser was demonstrated without in-cavity polarizer. Utilizing PM-FBG and loop mirror, maximum 0.5W output power with 30% slope efficiency, 70dB ASE suppression and 99.997% degree of polarization was recorded at 2.1μ

MIR supercontinuum in all-normal dispersion Chalcogenide photonic crystal fibers pumped with 2μm femtosecond laser

We demonstrate mid-infrared supercontinuum generation in an all-normal dispersion Chalcogenide PCF pumped by fiber laser. The -20dB bandwidth is 1.7~2.7μm dominated by self-phase modulation and optical wave breaking. Tapering is proposed to improve performance