Tampere University of Technology

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Frequency Conversion Using Ultrafast Fiber Lasers

Research output: Book/ReportDoctoral thesisCollection of Articles


Original languageEnglish
PublisherTampere University of Technology
Number of pages102
ISBN (Electronic)952-15-1716-6
ISBN (Print)952-15-1683-6
Publication statusPublished - 24 Nov 2006
Publication typeG5 Doctoral dissertation (article)

Publication series

NameTampere University of Technology. Publication
PublisherTampere University of Technology
ISSN (Print)1459-2045


This thesis investigates novel methods of generating ultrashort optical pulses in the visible and ultraviolet wavelength ranges by frequency conversion and supercontinuum generation using mode-locked fiber lasers. Optimization of mode-locked fiber lasers by intracavity dispersion compensation and repetition rate stabilization is described.

An Nd mode-locked fiber laser is introduced as a way to obtain picosecond pulses in the near infrared (~900 nm). The fiber gain medium allows for efficient pumping of the 900 nm transition of the Nd and suppression of the parasitic 1060 nm oscillation.

High quality picosecond pulse operation of an Yb-doped fiber laser is obtained by employing intracavity dispersion compensation in all-fiber format. The required negative dispersion is obtained from a single-mode fiber taper. Owing to the all-fiber format, the laser cavity is more compact than the traditional setups using bulk elements for dispersion compensation.

Temporal synchronization between two mode-locked fiber lasers is obtained by cross phase modulation in a single-mode optical fiber. Using a special cavity design, all-optical clocking of a mode-locked fiber laser has been obtained. The clock source is an inexpensive telecom-grade laser diode. Exploiting the dissimilar gain spectra of Er and Yb-doped active fibers, a two-color mode-locked source has been constructed. The source emits two trains of pulses at 1550 nm and 1060 nm, synchronized by cross-phase modulation.

Visible and ultraviolet light pulses are obtained from a high power Yb-doped fiber laser by frequency conversion in a waveguided KTP crystal. The mechanisms permitting simultaneous generation of second and third harmonic light are discussed.

An all-fiber laser source optimized for pumping periodically-poled crystals is proposed. The source relies on interplay between frequency chirp and nonlinearity to prevent spectral broadening of a laser pulse inside the fiber amplifier.

The intimate mechanisms of supercontinuum generation in photonic crystal fibers are investigated by spectrally-sensitive autocorrelations. Soliton fission is shown to play a key role in the early stages of spectral broadening.

Using a frequency-doubled Yb-doped fiber laser, all-visible supercontinuum radiation is generated in a fiber taper. This novel broadband source covers the entire visible spectrum and, unlike traditional supercontinuum generators, does not produce any residual infrared radiation.

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