The paper presents monolithic fiber-optic CPA systems - where the mode-locked oscillator, pulse stretcher, pulse shaper, pulse picker, and all amplifier stages are comprised of fusion spliced fiber devices - emitting up to 300 μJ compressed pulse output with duration <;500 fs (FWHM). This is a 6 times higher pulse energy than previously reported for monolithic fiber femtosecond lasers. Higher femtosecond pulse energy enables cutting and drilling through thicker materials, at faster rates, without imposing a heat affected zone (HAZ). Generating this femtosecond beam with a monolithic fiber-optic system provides the most compact and stable form factor, suitable for industrial work cell integration and global factory deployment.

We describe femtosecond laser systems optimized for high value applications in precision industrial micro-machining. Unprecedented system performance and reliability are enabled by novel fiber-optic architectures and integrated autonomous software control systems.

Single-frequency and narrow-linewidth pulse amplification is demonstrated in an erbium-doped higher-order mode fiber with effective area of 6000m2 and output long-period grating for re-conversion of the output beam back to the fundamental mode.

We demonstrate scaling of the effective area of higher-order mode, Er-doped fiber amplifiers. Two Er-doped higher-order mode fibers, one with 3800 μm(2) A(eff) in the LP(0,11) mode, and one with 6000 μm(2) effective area in the LP(0,14) mode, are demonstrated. Output beam profiles show clean higher order modes, and S(2) imaging measurements show low extraneous higher order mode content. CW and pulsed amplifier experiments are reported. Nanosecond pulses are amplified to 0.5 mJ pulse energy with 0.5 MW peak power.

Continuous wave and nanosecond pulse amplification in a higher-order-mode, Er-doped-fiber amplifier with 6000 μm2 effective area is demonstrated. Both 1480nm pump and 1560nm signal propagate in the LP0,14 mode.

We present for the first time a cascaded Raman fiber laser where the Yb-doped fiber laser and Raman fiber are combined into a single fiber. We achieve 42.6 % slope efficiency at 1236 nm with respect to launched pump power.

We perform detailed measurements of the higher-order-mode content of a low-loss, hollow-core, photonic-bandgap fiber. Mode content is characterized using Spatially and Spectrally resolved (S2) imaging, revealing a variety of phenomena. Discrete mode scattering to core-guided modes are measured at small relative group-delays. At large group delays a continuum of surface modes and core-guided modes can be observed. The LP11 mode is observed to split into four different group delays with different orientations, with the relative orientations preserved as the mode propagates through the fiber. Cutback measurements allow for quantification of the loss of different individual modes. The behavior of the modes in the low loss region of the fiber is compared to that in a high loss region of the fiber. Finally, a new measurement technique is introduced, the sliding-window Fourier transform of high-resolution transmission spectra of hollow-core fibers, which displays the dependence of HOM content on both wavelength and group delay. This measurement is used to illustrate the HOM content as function of coil diameter.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text J. W. Nicholson, C. Headley, J. Phillips, A. Desantolo, E. Gonzalos, S. Ghalmi, M. F. Yan, P. W. Wisk, D. Trevor, J. Fleming, E. Monberg, F. Dimarcello, R. S. Windeler, J. M. Fini, D. J. DiGiovanni, and S. Ramachandran, "Higher-Order-Mode Fiber Amplifiers," in Lasers, Sources and Related Photonic Devices, OSA Technical Digest Series (CD) (Optica Publishing Group, 2010), paper LSWD1. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Multiple higher-order-modes propagating simultaneously in large-mode-area optical fibers are measured and their relative power levels quantified using spatially and spectrally resolved imaging.

We demonstrate the first erbium-doped fiber amplifier operating in a single, large-mode area, higher-order mode. A high-power, fundamental-mode, Raman fiber laser operating at 1480 nm was used as a pump source. Using a UV-written, long-period grating, both pump and 1564 nm signal were converted to the LP(0,10) mode, which had an effective area of 2700 microm(2) at 1550 nm. A maximum output power of 5.8 W at 1564 nm with more than 20 dB of gain in a 2.68 m long amplifier was obtained. The mode profile was undistorted at the highest output power.

We demonstrate a Raman fiber laser with an operating wavelength of 1480 nm and record output power of 81 W. High-power operation is enabled by a long-period grating used to frustrate backward lasing at the Stokes wavelength in the Yb-doped fiber amplifier. A cascaded Raman fiber with a long-wavelength fundamental mode cutoff enables efficient multiple Stokes scattering from 1117 to 1480 nm while preventing further unwanted scattering to 1590 nm.

The nonlinear properties of a nanosecond pulse in a higher-order-mode, Er-doped-fiber amplifier with 2440 μm2 effective area are compared to a conventional 880 μm2 area fiber. Both 1480 nm pump and 1554 nm signal propagate in the LP09 mode.

Higher-order-modes of a 70-mu m core-diameter, Er-doped-fiber are characterized over a broad wavelength range using a supercontinuum with spatially and spectrally resolved imaging. Pumping the Er-doped-fiber with 1480-nm in the fundamental mode decreases the higher-order-mode content. (C) 2009 Optical Society of America

Amplified erbium-fiber-laser pulses compressed in large-mode-area fiber show significantly reduced nonlinearity compared to standard-single-mode fiber. Consequently, supercontinuum generated with the pulses compressed in large-mode-area fiber show a 10 dB increase in cross-coherence fringe visibility.

Visible supercontinuum in the fundamental mode is generated in a silica hybrid nonlinear fiber using a femtosecond, erbium-doped fiber laser pump. The nonlinear fiber consists of highly nonlinear, germano-silicate fiber (HNLF) fusion spliced to a photonic crystal fiber (PCF).

Femtosecond fiber lasers together with nonlinear fibers are compact, reliable, all-fiber supercontinuum sources. Maintaining an all-fiber configuration, however, necessitates pulse compression in an optical fiber, which can lead to nonlinearities for subhundred femtosecond, nanojoule pulses. In this work we show that using large-mode-area fibers for pulse compression mitigates the nonlinearity, resulting in compressed pulses with significantly reduced satellite pulses. Consequently, supercontinua generated with these pulses are shown to have as much as a 10 dB increase in coherence fringe contrast. By using a hybrid highly nonlinear fiber-photonic crystal fiber, the continuum can be extended to visible wavelengths while still maintaining high coherence.

Supercontinuum extending to visible wavelengths is generated in a hybrid silica nonlinear fiber pumped at 1560 nm by a femtosecond, erbium-doped fiber laser. The hybrid nonlinear fiber consists of a short length of highly nonlinear, germano-silicate fiber (HNLF) spliced to a length of photonic crystal fiber (PCF). A 2 cm length of HNLF provides an initial stage of continuum generation due to higher-order soliton compression and dispersive wave generation before launching into the PCF. The visible radiation is generated in the fundamental mode of the PCF.

We demonstrate the first all-solid (non-holey), silica-based fiber with anomalous-dispersion (+60ps/nm-km) at wavelengths (1080nm) where silica material dispersion is negative. We demonstrate its functionality as a critical enabler for an all-fiber, Yb-based, femtosecond ring laser.