Ultrafast high power solid state lasers
Tan, Wei De
Date of Issue2011
School of Electrical and Electronic Engineering
Photonics Research Centre
Diode pumped ultrafast high power solid state lasers are capable of delivering high power picosecond or femtosecond pulses with excellent beam quality and as such have widespread scientific and technological applications. To that end, it necessary to develop and improve performances of existing systems though laser engineering or new materials. In this thesis, the CW and ultrafast laser performances of novel Yb: Sc2SiO5 (Yb: SSO) and Yb: CaYAlO4 (Yb: CYA) are investigated. Using a board stripe free space diode as the pump source, Yb: SSO and Yb: CYA generated maximum CW output powers of 2.7 W and 2.3 W respectively with slope efficiencies of 70 % and 92 %. When mode-locked in the negative dispersion regime, solitary mode-locking was achieved. In the case of Yb: SSO, the laser was operated near the zero vicinity of zero group velocity dispersion such that 93 fs pulses with an output power of 20 mW at 1043.4 nm. When mode-locked at 1077 nm in which the net negative dispersion was slightly larger than in the 1043.4 nm case, the laser generated 125 fs pulses with an output power of 100 mW. In the case of Yb: CYA, the laser was mode-locked with a large net negative dispersion such that the laser generated 156 fs pulses with an output power of 740 mW. When mode-locked in the positive dispersion regime, Yb: SSO and Yb: CYA both demonstrated mode-locked spectra with steep edges with spectral bandwidths capable of supporting femtosecond pulses. The pulses obtained were strongly chirped with time bandwidth products many times above the Transform limit. This provides strong evidence of dissipative solitons in these lasers. Particularly in the case of Yb: CYA, the laser emitted 1.5 W of output power that was compressible down to 380 fs. In addition, the mode-locking of Nd: GdVO4 was also demonstrated. By exploiting the birefringence and thermal lensing of the gain media, the laser was able to generate dual wavelength mode-locked emission with orthogonal polarizations using a V-shaped cavity. Such a device might find applications in laser interferometers.
DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics