The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

High power fiber lasers: current status and future perspectives [Invited]

Disclosed is an apparatus for use in wireless energy transfer, which includes a first resonator structure configured to transfer energy non-radiatively with a second resonator structure over a distance greater than a characteristic size of the second resonator structure. The non-radiative energy transfer is mediated by a coupling of a resonant field evanescent tail of the first resonator structure and a resonant field evanescent tail of the second resonator structure.

Wireless energy transfer

Self-similar propagation of ultrashort, parabolic pulses in a laser resonator is observed theoretically and experimentally. This constitutes a new type of pulse shaping in mode-locked lasers: in contrast to the well-known static (solitonlike) and breathing (dispersion-managed soliton) pulse evolutions, asymptotic solutions to the nonlinear wave equation that governs pulse propagation in most of the laser cavity are observed. Stable self-similar pulses exist with energies much greater than can be tolerated in solitonlike pulse shaping, and this has implications for practical lasers.

https://arxiv.org/pdf/physics/0402013.pdf

Self-similar evolution of parabolic pulses in a laser.

The electromagnetic energy transfer device includes a first resonator structure receiving energy from an external power supply. The first resonator structure has a first Q-factor. A second resonator structure is positioned distal from the first resonator structure, and supplies useful working power to an external load. The second resonator structure has a second Q-factor. The distance between the two resonators can be larger than the characteristic size of each resonator. Non-radiative energy transfer between the first resonator structure and the second resonator structure is mediated through coupling of their resonant-field evanescent tails.

Wireless non-radiative energy transfer

A modelocked fiber laser is designed to have strong pulse-shaping based on spectral filtering of a highly-chirped pulse in the laser cavity. The laser generates femtosecond pulses without a dispersive delay line or anomalous dispersion in the cavity.

All-normal-dispersion femtosecond fiber laser

Ultrashort pulse propagation in high gain optical fiber amplifiers with normal dispersion is studied by self-similarity analysis of the nonlinear Schrodinger equation with gain. An exact asymptotic solution is found, corresponding to a linearly chirped parabolic pulse which propagates self-similarly subject to simple scaling rules. The solution has been confirmed by numerical simulations and experiments studying propagation in a Yb-doped fiber amplifier. Additional experiments show that the pulses remain parabolic after propagation through standard single mode fiber with normal dispersion.

/pdf/self-similar-propagation-and-amplification-of-parabolic-421q833uss.pdf

Self-similar propagation and amplification of parabolic pulses in optical fibers.

The authors describe how the nonlinear process of two-photon absorption in a commercial laser diode may be used for all-optical demultiplexing in terabit per second optical time division multiplexing networks. Switching windows of 650 fs in duration have been observed, with corresponding switching energies of a few picojoules.

/pdf/ultrahigh-speed-all-optical-demultiplexing-based-on-two-3mikd6p5ah.pdf

Ultrahigh speed all-optical demultiplexing based on two-photon absorption in a laser diode

In this paper, we present an experimental and numerical study of semiconductor optical amplifier (SOA)-based noise suppression and its relevance to high-channel-density spectrum-sliced wavelength-division-multiplexed systems. We show that the improvement in signal quality is accompanied by spectral distortion, which renders it susceptible to deterioration in the presence of subsequent optical filtering. This phenomenon originates from the loss of intensity correlation between spectral components of the SOA output when the signal spectrum is altered. As a consequence, a design tradeoff is introduced between intensity noise and crosstalk in high-channel-density systems. These adverse effects can be overcome by optimized SOA design, resulting in a significant improvement in signal quality.

/pdf/noise-suppression-of-incoherent-light-using-a-gain-saturated-ufpbc0y6h9.pdf

Noise suppression of incoherent light using a gain-saturated SOA: implications for spectrum-sliced WDM systems

We demonstrate a pulsed ytterbium-doped fiber master-oscillator power amplifier source at 1060 nm producing over 300 W of average power in 20-ps pulses at 1-GHz repetition rate. The pulses generated by a gain-switched diode were compressed by a chirped fiber Bragg grating and amplified without any distortion with excellent spectral quality. This fiber master oscillator power amplifier system offers versatility and potential for further power scaling.

High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

Two-photon absorption in a commercial InGaAsP 1.3 /spl mu/m Fabry-Perot laser diode has been used for autocorrelation measurements of picosecond pulses at 1.5 /spl mu/m with average power peak-power products as low as 0.15/spl times/10/sup -3/ (mW)/sup 2/. The laser diode has also been observed to possess a sub-nanosecond electrical response suitable for optical thresholding applications.

B.C. Thomsen

Papers

Self-similar propagation and amplification of parabolic pulses in optical fibers.

Ultrahigh speed all-optical demultiplexing based on two-photon absorption in a laser diode

Noise suppression of incoherent light using a gain-saturated SOA: implications for spectrum-sliced WDM systems

High average power, high repetition rate, picosecond pulsed fiber master oscillator power amplifier source seeded by a gain-switched laser diode at 1060 nm

Autocorrelation and ultrafast optical thresholding at 1.5 [micro sign]m using a commercial InGaAsP 1.3 [micro sign]m laser diode