Researches On Spectral Characteristics Of Novel Yb-doped Laser Crystal And Mode-locked Lasers

The laser diode pumped solid-state laser is widely used in many field and has been a very important area of femtosecond laser research, owing to its compact size, low cost, good beam quality and high efficiency. The solid-state laser based on ytterbium-doped gain media has been a frontier of study, and so far dozens of ytterbium-doped crystals have achieved continuous wave or mode-locking operation.China has always been playing a leading role in at the study of laser gain media. In this thesis, systematic studies of the lasing characteristics have been carried out based on two types of novel laser crystals, including co-doped Yb, Y: Ca F2 crystal and Yb doped Ca F2-Sr F2 mixed crystal. A mode-locked Yb, Y: Ca F2 oscillator is demonstrated for the first time.The main contents of this thesis are listed as follows:1. The developments of the laser-diode-pumped solid state laser are presented. The characteristics, advantages and disadvantages of several laser crystals are discussed. We outlines several basic methods to achieve solid-state laser mode-locking operation,with the semiconductor saturable absorber mirror mode-locking mechanism as the focus. Three common dispersion compensation elements in mode-locked solid lasers are briefly introduced.2. Continuous wave operation for co-doped Yb, Y: Ca F2 crystals and Yb doped Ca F2-Sr F2 mixed crystals has been achieved in both plane-concave resonator and three-mirror-folded resonator using a laser diode as the pump source, and co-doped Yb, Y: Ca F2 crystals for the first time. The lasing characteristics, including absorption and fluorescence spectrum, absorption rate of the pump laser, output threshold, slope efficiency as well as lasing spectrum, have been investigated.3. Femtosecond mode-locked pulse operation from a laser-diode-pumped Yb, Y: Ca F2 crystal has been obtained for the first time. Mode-locked by a semiconductor saturable absorber mirror, the pulse duration variation with the change of the prism-pair separation has been experimentally studied. The minimum pulse width of 330 fs is achieved when the the separation of the prism-pair is 190 mm, with an average output power of 224 m W and a repetition rate of 82 MHz at a central wavelength of 1049 nm.