Christophe A. Codemard

High Power Fiber Lasers: A Review

In this paper, we summarize the fundamental properties and review the latest developments in high power fiber lasers. The review is focused primarily on the most common fiber laser configurations and the associated cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancement observed in single-mode and multimode high power fiber lasers. The review includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, transverse modal instabilities and photodarkening. Finally, the paper summarizes the power evolution in continuous-wave and pulsed ytterbium-doped fiber lasers and their impact on industrial applications.

Single-frequency, single-mode, plane-polarized ytterbium-doped fiber master oscillator power amplifier source with 264 W of output power

We present a single-frequency, single-mode, plane-polarized ytterbium-doped all-fiber master oscillator power amplifier source at 1060 nm generating 264 W of continuous-wave output power. The final-stage amplifier operated with a high gain of 19 dB and a high conversion efficiency of 68%. There was no evidence of rollover from stimulated Brillouin scattering even at the highest output power, and the maximum output was limited only by the available pump power.

Picosecond fiber MOPA pumped supercontinuum source with 39 W output power

We report picosecond fiber MOPA pumped supercontinuum source with 39W output, spanning at least 0.4–1.75µm with high and relatively uniform spectral power density of ∼31.7mW/nm corresponding to peak power density of ∼12.5W/nm in 20ps pulse.

High-power tunable single-frequency single-mode erbium:ytterbium codoped large-core fiber master-oscillator power amplifier source

We present a cladding-pumped single-frequency, single-mode erbium:ytterbium codoped fiber master-oscillator power amplifier source generating up to 151 W of continuous-wave output power at 1563 nm with 33% slope efficiency and 20 dB gain. This source was also tunable and had a stable operation range of 1546 to 1566 nm at an output power level in excess of 125 W. The doped fiber exploited a large-core design for improved power handling and mitigation of stimulated Brillouin scattering. There was no sign of having stimulated Brillouin scattering even at the highest power. Despite a large core (V = 12), the output beam was nearly diffraction limited (M2 = 1.1). The source showed slight rollover at over 100 W of output power because of the onset of emission from ytterbium, centered at 1060 nm.

Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off

We demonstrate the suppression of stimulated Raman scattering in a high power, single-mode Yb-doped fiber amplifier using a W-type core structure. Raman-scattered light is not guided by the core. The amplifier consists of a master oscillator power amplifier (MOPA) system, seeded with 103 ps pulses at 32 MHz repetition rate in the final amplification stage. An average output power of 53 W, which corresponds to 13 kW of peak power, was achieved in the 23 m long W-type double-clad fiber without any significant loss of power due to transfer from the signal wavelength at 1060 nm to the Raman Stokes wavelength at 1114 nm and amplified spontaneous emission from Yb-ions at longer wavelengths (~1070 nm). The power conversion efficiency at 1060 nm was 80% with respect to the absorbed pump power.

High-energy in-fiber pulse amplification for coherent lidar applications

An Er:Yb codoped fiber amplifier chain for the generation of pulses for coherent lidar applications at a wavelength near 1.5 microm is reported. The final 1.8-m-long power amplification stage had a 50-microm core diameter and yielded a 23-dB energy gain, resulting in 0.29-mJ, 100-ns pulses at a repetition rate of 4 kHz with no Brillouin scattering and an M2 of 2.1.

Broadband third harmonic generation in tapered silica fibres

Optical microfibres have recently attracted much attention for nonlinear applications, due to their tight modal confinement. Here, we report broadband third harmonic generation based on the intermodal phase matching technique in silica microfibres of several centimetres. The third harmonic signal is predominantly generated from the taper transition regions (rather than the waist), wherein the range of diameters permits phase matching over a wide bandwidth. Microfibres up to 4.5 cm long were fabricated with waist diameters below 2.5 μm to allow a λ = 1.55 μm pump to phase match with several higher order third harmonic modes; conversion rates up to 3 × 10⁻⁴ were recorded when pumped with 4 ns pulses at a peak power of 1.25 kW. Analysis of the third harmonic frequencies generated from the nonlinearly broadened pump components indicate a 5 dB conversion bandwidth of at least 36 nm, with harmonic power detected over a 150 nm range.

A 980-nm Yb-doped fiber MOPA source and its frequency doubling

A continuous-wave (CW) master oscillator-power amplifier (MOPA) fiber source, tunable around 978 nm, was frequency-doubled to 488.7 nm. Both the laser and the amplifier were made with cladding-pumped jacketed air-clad Yb-doped fibers. The MOPA generated up to 2.7 W of power in an output beam with an M/sup 2/ value of 1.8. This was frequency-doubled in a periodically poled potassium titanyl phosphate crystal at room temperature, in a single-pass configuration. The generated blue light had a CW power of 18.1 mW, a nearly Gaussian spatial intensity profile, and an M/sup 2/ value of 1.7.

Multi-watts narrow-linewidth all fiber Yb-doped laser operating at 1179 nm.

An all-fiber, narrow-linewidth, high power Yb-doped silica fiber laser at 1179 nm has been demonstrated. More than 12 W output power has been obtained, corresponding to a slope efficiency of 43% with respect to launched pump power, by core-pumping at 1090 nm. In order to increase the pump absorption, the Yb-doped fiber was heated up to 125 degrees C. At the maximum output power, the suppression of amplified spontaneous emission was more than 50 dB. Furthermore, theoretical work confirms that the proposed laser architecture can be easily scaled to higher power.

High-power continuous-wave cladding-pumped Raman fiber laser

We demonstrate a high-power single-mode cladding-pumped Raman fiber laser. The Raman fiber laser consists of a 1.2 km long germanium-doped double-clad fiber in a linear cavity, which is spliced to a single-mode fiber. The laser is end pumped by a multimode erbium-ytterbium-doped fiber, which is coupled to the inner cladding of the Raman fiber. The embedded core was designed to be single mode at the Raman Stokes wavelength, and up to 10 W of power was obtained at 1660 nm from the single-mode fiber end. The laser has a slope efficiency of 67% and a threshold of 6.5 W.