Three-dimensional isotropic microfabrication in glass using spatiotemporal focusing of high-repetition-rate femtosecond laser pulses

To improve the processing efficiency and extend the tuning range of 3D isotropic fabrication,we apply the simultaneous spatiotemporal focusing(SSTF)technique to a high-repetition-rate femtosecond(fs)fiber laser system.In the SSTF scheme,we propose a pulse compensation scheme for the fiber laser with a narrow spectral bandwidth by building an extra-cavity pulse stretcher.We further demonstrate truly 3D isotropic microfabrication in photosensitive glass with a tunable resolution ranging from 8μm to 22μm using the SSTF of fs laser pulses.Moreover,we systematically investigate the influences of pulse energy,writing speed,processing depth,and spherical aberration on the fabrication resolution.As a proof-of-concept demonstration,the SSTF scheme was further employed for the fs laser-assisted etching of complicated glass microfluidic structures with 3D uniform sizes.The developed technique can be extended to many applications such as advanced photonics,3D biomimetic printing,micro-electromechanical systems,and lab-on-a-chips.

A compact Tirsapphire femtosecond pulse amplifier without stretcher at high repetition rate

We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.