Tunable spatiotemporal mode-locked fiber laser at 1.55 μm.

We report the spatiotemporal mode-locked multimode fiber laser operating at 1.55 µm based on semiconductor saturable absorber mirrors with the mode-locking threshold as low as 104 mW. Benefiting from the multimode interference filtering effect introduced in the laser cavity not only the central wavelength can be continuously tuned from 1557 nm to 1567 nm, but also the number of the output pulses can be adjusted from 1 to 4 by simply adjusting the polarization controllers.

High-order mode suppression in double-clad optical fibers by adding absorbing inclusions.

We proposed and experimentally demonstrated a technique for the suppression of unwanted modes in double-clad fibers with a high core-to-clad diameter ratio by introducing high-index absorbing inclusions into the first cladding of the fibers. These inclusions disturb the shape of undesirable modes, and a noticeable part of the power becomes localized inside the inclusion, resulting in an increase in the propagation loss of these modes. Two fiber designs were studied and realized: one with cylindrical symmetry and an absorbing high-index ring as the inclusion and another with high-index absorbing rods inserted around the fiber core.

All-fiber polarization-maintaining mode-locked laser operated at 980 nm.

For the first time, to the best of our knowledge, we present an all-fiber polarization-maintaining passively mode-locked picosecond laser operated at 980 nm. The laser cavity had a ring configuration with a semiconductor saturable absorber mirror as a mode-locking element. As an active medium, we used a specially designed cladding-pumped Yb-doped fiber with reduced cladding-to-core diameter ratio.

Low-loss hybrid fiber with zero dispersion wavelength shifted to 1 µm.

We proposed and investigated a novel type of all-glass hybrid fiber where light is confined in the low-index core due to both total internal reflection and coherent Fresnel reflection (a photonic bandgap mechanism). The hybrid mode has an anomalous dispersion of 13 ps/(nm km) at 1064 nm and low loss (~6 dB/km), and it can be easily excited by splicing with a single-mode step-index fiber. The compression of positively chirped 8 ps pulses down to 330 fs was demonstrated with the fabricated hybrid fiber.

Very-large-mode-area photonic bandgap Bragg fiber polarizing in a wide spectral range.

A design of a polarizing all-glass Bragg fiber with a microstructure core has been proposed for the first time. This design provides suppression of high-order modes and of one of the polarization states of the fundamental mode. The polarizing fiber was fabricated by a new, simple method based on a combination of the modified chemical vapor deposition (MCVD) process and the rod-in-tube technique.