Comparison of amplification in large area fibers using cladding-pump and fundamental-mode core-pump schemes.

We compare the amplification of various modes in large mode area fibers when the pump is coupled into the fundamental core mode versus the standard cladding-pump scheme. Our simulations show that pumping in the LP(01) core mode results in differential gain for the fundamental signal mode which suppresses the higher order modes and amplified spontaneous emission compared to the cladding pump scheme. This differential gain effect is predicted to increase with core size and may provide a path to scale fiber mode area to several thousand square micron.

Diffraction limited amplification of picosecond pulses in 1170 microm2 effective area erbium fiber.

Robust fundamental mode propagation and amplification of picosecond pulses at 1.56 microm wavelength is demonstrated in a core-pumped Er fiber with 1170 microm2 effective area. Record peak power exceeding 120 kW, and 67 nJ pulse energy are achieved before the onset of pulse breakup. A small increase in input pulse energy results in a temporal collapse of the pulse center to 58 fs duration, with peak powers approaching 200 kW.

Picosecond pulse amplification in a core-pumped large-mode-area erbium fiber.

Amplification in a single-clad, large-mode-area erbium fiber as an alternative to double-clad Er-Yb amplifiers is presented. Both signal and pump are coupled through a mode-matched splice into the fundamental mode, which ensures preferential gain in the fundamental mode while minimizing the amplified spontaneous emission (ASE). The 875 microm(2) effective area of the Er fiber enables amplification of 6 ps pulses at 1.55 microm wavelength by approximately 33 dB in a single stage to >25 kW peak power with low nonlinear pulse distortion and a diffraction-limited output beam with M(2)<1.1.

Simultaneous direct amplification and compression of picosecond pulses to 65-kW peak power without pulse break-up in erbium fiber.

Picosecond pulses at 1.56 micro mm wavelength are directly amplified with a diffraction limited beam quality in a core-pumped Er fiber with an 875 micro m(2) effective area. The interplay between nonlinear spectral broadening and anomalous fiber dispersion compresses the input pulse duration during amplification so that 42 nJ energy pulses with approximately 65 kW peak power are achieved without pulse break-up.

Non-invasive characterization of microstructured optical fibers using Fourier domain optical coherence tomography.

Fourier domain optical coherence tomography (FDOCT) is used to non-invasively measure properties of the hole pattern in microstructured fibers. Features in the FDOCT data are interpreted and related to the hole diameter and spacing. Measurement examples are demonstrated for three different fibers with one hole, three holes at the vertices of an equilateral triangle, and a full triangular lattice. These studies provide the first path to real time monitoring of microstructured fibers during their draw.