Experimental Research On Four Optical Cycle Pulse Generation In Ti:sapphire Laser

In this letter, we systematically investigated the Ti:sapphire oscillator infemtosecond regime in order to generate optical pulse with several optical cycleduration. A set of compact oscillator generating 4 optical cycle pulse was establishedthrough precise design and systematical experiment. During the experiment,mechanism of compression of optical pulse was researched systematically, andsignificant experimental results were obtained. The main contents are as follows:1. Mechanism for generating femtosecond laser and principle for designingfemtosecond Ti:sapphire oscillator were introduced in detail. A set of Ti:sapphireoscillator was established outputting 4 optical cycle pulse.2. The temporal and spectral characteristic of ultra-broadband Ti:sapphire oscillatorwere systematically investigated in femtosecond regime for the first time.Experimental results showed pulse shortening mainly occurred not at its bottompart but at its central section while the spectrum broadened, and the relativeenergy at the bottom part increased at the same time.3. The time delay of interferometric auotcorrelation trace of femtosecond pulse wascalibrated in frequency domain. By virtue of the calibrated IAC,root-mean-square width and chirp parameter of femtosecond pulse to bemeasured were calculated. The measurement involved only a integration and afast Fourier transform. Consequently, real-time chirp diagnostic for Ti:sapphireoscillator was feasible.4. sluggish bistability of mode-locking was observed for the first time.