Anomalous laser-induced group velocity dispersion in fused silica.

We present 20fs(2) accuracy laser-induced group velocity dispersion (LI-GVD) measurements, resulting from propagation of a femtosecond laser pulse in 1mm of fused silica, as a function of peak intensity. For a 5.5 × 10(11) W/cm(2) peak intensity, LI-GVD values are found to vary from -3 to + 15 times the material GVD. Normal induced dispersion can be explained by the Kerr effect, but anomalous LI-GVD, found when the input pulses have negative pre-chirp, cannot. These findings have significant implications regarding self-compression and the design of femtosecond lasers.

Multimodal microscopy with sub-30 fs Yb fiber laser oscillator.

Nonlinear optical microscopy with sub-30 fs pulses from an Yb-fiber laser, approximately three times shorter than typical fiber laser pulses, leads to an order of magnitude brighter third harmonic generation imaging. Multiphoton fluorescence, second and third harmonic generation modalities are compared on stained microspheres and unstained biological tissues.

Generation of 42-fs and 10-nJ pulses from a fiber laser with self-similar evolution in the gain segment.

A double-clad Yb-doped all-normal-dispersion fiber laser with a narrow intra-cavity spectral filter is demonstrated to produce 22 nJ pulses at 42.5 MHz repetition rate. These pulses are characterized and compressed via mulitphoton intrapulse interference phase scan to as short as 42 fs and 10 nJ/pulse. Adaptive compression underlies the achievement of 250-kW peak power, which enables efficient second and third harmonic generation with spectra spanning 30 nm and 20 nm, respectively.