Broadband thulium-doped fiber ASE source.

We report on a flat and broadband thulium-doped amplified spontaneous emission (ASE) fiber source working around 1.85 µm in the eye-safe spectral region. Core-pumped thulium fibers were prepared in-house using the modified chemical vapor deposition method. The amplified spontaneous emission source in a backward direction with respect to the pump and in a single-ended configuration produces stable, non-polarized radiation with an output power of up to 280 mW, corresponding to a slope efficiency of about 36% with respect to the pump power. To the best of our knowledge, the device reported herein is the broadest ASE source based on Tm-doped fiber without internal spectral filtering with an output power exceeding 90 mW and full width at half-maximum of the spectrum greater than 155 nm.

Broadly tunable laser based on novel metallic resonant leaky-mode diffraction grating.

We present a fibre laser broadly tunable in a wavelength range from 1058 nm to 1640 nm based on a new type of metallic resonant leaky-mode diffraction grating and three fibre-pigtailed semiconductor optical amplifiers. For TM polarization in Littrow configuration, the grating has experimentally measured diffraction efficiency into the -1st reflected order of more than 90 % over a spectral range of 1417 nm to 1700 nm. The laser covered a spectral range of 331 nm within a tuning band of 558 nm without any adjustment of optics and its tuning range was limited by amplification bands of available semiconductor optical amplifiers.

Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength self-sweeping: erratum.

This erratum presents a correction to the computed reflection spectra of transient fiber Bragg gratings that are spontaneously built-up in the ytterbium-doped fiber of the fiber laser with laser wavelength self-sweeping. The corrected spectra have high reflectivity reaching values up to 100%. Therefore, they still more support the conclusion drawn in the original paper that self-sweeping is an important mechanism for triggering the self-Q-switched regime with giant pulse generation.

Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength self-sweeping.

We present a method for the estimation of the reflection spectra of transient gratings in rare-earth doped fiber lasers having a self-sweeping of laser wavelength. We show that high reflectivities of several tens of percent can be achieved. An example of this is demonstrated through the use of an experimental Yb-doped Fabry-Perot fiber laser. The gratings' spectra are highly asymmetric due to the apodization of the refractive index modulation. The importance of the self-sweeping regime for triggering self-Q-switched laser instabilities is discussed.

Visible and near infra-red up-conversion in Tm3+/Yb3+ co-doped silica fibers under 980 nm excitation.

The spectroscopic properties of Tm(3+)/Yb(3+) co-doped silica fibers under excitation at 980 nm are reported. Three distinct up-conversion fluorescence bands were observed in the visible to near infra-red regions. The blue and red fluorescence bands at 475 and 650 nm, respectively, were found to originate from the (1)G(4) level of Tm(3+). A three step up-conversion process was established as the populating mechanism for these fluorescence bands. The fluorescence band at 800 nm was found to originate from two possible transitions in Tm(3+); one being the transition from the (3)H(4) to (3)H(6) manifold which was found to dominate at low pump powers; the other being the transition from the (1)G(4) to (3)H(6) level which dominates at higher pump powers. The fluorescence lifetime of the (3)H(4) and (3)F(4) levels of Tm(3+) and (2)F(5/2) level of Yb(3+) were studied as a function of Yb(3+) concentration, with no significant energy back transfer from Tm(3+) to Yb(3+) observed.

Modulational-instability sigma-resonator fiber laser.

A modulational-instability laser with a resonator in a sigma configuration has been developed. The importance of a suitable intracavity filter for removing the autocorrelation background of the output signal is shown. A pulse train with a repetition rate of 107 GHz determined by the Fabry-Perot etalon used in the resonator was obtained at 1.56mum .