Mid-IR femtosecond fiber laser has high-peak-power pulses

Aug. 6, 2015
A group in Canada has reported a mid-IR femtosecond fiber laser, a device emitting at a 2.8 μm wavelength.

A group at Centre d'Optique, Photonique et Laser (COPL), Université Laval (Québec, QC, Canada) has reported a mid-IR femtosecond fiber laser, a device emitting at a 2.8 μm wavelength. This extends the range of femtosecond fiber lasers into the molecular fingerprint region, making these lasers valuable for ultrafast science in this range. The laser is based on erbium-doped fluoride glass fiber.

A ring cavity is formed of 3 m of double-clad fiber fabricated by fluoride glass experts Le Verre Fluoré (Bruz, France), with bulk optics forming part of the cavity. The fiber itself has a 15-μm-diameter core, a numerical aperture (NA) of 0.12, and a cladding diameter of 260 μm. Surrounding the cladding is a polymer with a lower refractive index that allows cladding pumping. The fiber is pumped at 976 nm with a 7 W multimode laser diode, with the pump light coupled into one end of the fiber by a dichroic mirror and absorbed at the other end by a cladding mode stripper. Aspheric zinc selenide (ZnSe) lenses couple light into and out of both ends of the fiber. The result is a mode-locked train of pulses, with a full-width half-maximum (FWHM) duration of 207 fs, a repetition rate of 55.2 MHz, and a peak power of 3.5 kW. Because the fiber is operated in the anomalous dispersion regime, the pulses take the form of stable solitons whose near-ideal shape are seen by examining the second-harmonic light pulse generated by focusing the laser light through a beta barium borate (BBB) crystal. Reference: Simon Duval et al., Optica (2015); http://dx.doi.org/10.1364/optica.2.000623.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!