Scalable fiber-based femtosecond laser systems and applications

Femtosecond Yb-fiber-based modelocked laser and amplifier systems are developed. Various approaches have been employed to increase the laser system's scalability in terms of repetition rate, wavelength and average power.; Passive harmonic modelocking, for the first time, is demonstrated in a modelocked Yb-doped fiber laser with up to 585 MHz scalable repetition rate. Timing jitter properties in passive harmonic modelocking are studied with optical cross-correlation technique and radio-frequency (RF) measurements. Semiconductor saturable absorbers are developed and characterized for laser modelocking. Using these devices in a novel colliding-pulse harmonic modelocking configuration, significant timing jitter suppression is achieved in passive harmonic modelocking.; Photonic crystal fibers (PCFs) have been incorporated into the laser system for wavelength scaling. Taking advantage of the unique nonlinearity and dispersion properties of the PCFs, three different approaches are implemented to increase the tunability of the fiber-based femtosecond laser system. Wavelength scaling in the ranges of 930∼1200-nm, 1100∼1300-nm and 450∼630-nm are achieved with the schemes of fiber-based optical parametric oscillator (FOPO), Raman soliton self-frequency shift and Cherenkov radiation (CR) in PCFs respectively.; The wavelength scaling capability is implemented in frequency metrology applications. The pump power dependence of the carrier-envelope-offset (CEO) frequency in modelocked Yb-fiber laser is measured. Furthermore, a fiber-based all-optical scheme for carrier-envelope phase stabilization is demonstrated for the first time.; The average power of the Yb-fiber based laser system is scaled to 350 mW with a core-pumped single-mode Yb-fiber amplifier. A cladding-pumped Yb-fiber amplifier is employed to further scale the power up to 5.5 W. Applications of these sources in femtosecond micromachining are investigated. Surface and sub-surface channels are fabricated by femtosecond-laser-assisted photochemical etching in silicon.