Study On Unit Technique Of Monocycle Pulses And Yb: YAG Thin Disk Laser

Monocycle pulses are not only the inevitable trend of the development of femtosecond pulses, but also the necessary method and stage for the generation of attosecond pulse and the advancement of attosecond technology. In this dissertation, the unit technique of monocycle pulses, including filamentation, gas-filled hollow fiber and SPIDER, and a 100-kHz Q-switched Yb: YAG thin disk laser was experimentally investigated. The main contents are summarized as follows:1. Using the techniques of filamentation and gas-filled hollow fiber, the characteristics of the broadened spectrum formed by filament with and without the hollow fiber restriction are experimentally studied respectively when intense femtosecond pulses are focused into an argon-filled tube. The influence of the input pulse energy and the gas pressure on the broaden spectrum without the hollow fiber restriction and that of input pulse energy, the position and the inner diameter of the hollow fiber on the broaden spectrum with the hollow fiber restriction are also analyzed in detail.2. The spectrum evolution along the filament formed by the femtosecond laser in argon gas is experimentally demonstrated through introducing a hollow fiber as a probe. Using the spectrum variation, the time domain variation of pulses in the range of filamentaion can be concluded. At a particular position of the filament, the width of the spectrum expands to its maximum value, which corresponds to the shortest pulse duration. The results indicate that the width of pulses present a non-uniform distribution in the range of the filament.3. SPIDER apparatus which is used to evaluate the time domain information of monocycle pulses are greatly improved in the technological operation. And a set of SPIDER apparatus with hardware and software have been produced successfully. This domestic experimental equipment can realize measuring the phase of femtosecond pulses reliably and practicably. In the hardware of the SPIDER apparatus, ultrathin beam splitters with ultrabroad bandwidth film coating and the ultrathin nonlinear crystal are applied to reduce the additional dispersion and enlarge the measurement bandwidth. In the software, the novel arithmetic is used to ensure the precise measurement results. In the manipulation, based on the VC program, the beautiful and friendly interface is designed to make the measurement more visual. 4. Using the Yb: YAG thin disk modular, the influencing factors on the intracavity loss in a Yb: YAG thin disk laser is experimentally studied. Adopting the technique of acousto-optic modulation, the influence of the output coupler transmission, the polarization and the repetition rate on the acoustic-optic Q-switched output power is discussed respectively. The stability of the acoustic-optic Q-switched pulse is also experimentally studied. Based on the Q-switched thin disk laser, second harmonic generation is obtained by introducing a frequency doubling crystal. By optimizing the polarization, the driver power and the gate width of the AO device, the stability of the Q-switched pulses can be improved greatly. At the repetition rate of 100 kHz, the average fundamental power of 50W with 205ns pulse duration and 2.0%rms pulse stability can be achieved and the average frequency doubling power of 20W with 195ns pulse duration and 1.5%rms pulse stability can be gained, which will be helpful to constructing a 100 kHz Ti: Sapphire amplifier.