Research About Optical Parametric Chirped Pulse Amplification

Optical parametric chirped pulse amplification (OPCPA) is a primary technology for ultrashort pulse generation of high intensity, high peak power, high signal-noise ratio, high intensity contrast between pre-pulse and main pulse. In OPCPA process, the fine structure of pump pulse determines vastly the energy transformation efficiency from pump pulse to signal pulse, the bandwidth and signal-noise ratio of the amplified signal pulse. In order to obtain the ideal high power ultrashort pulse, pump pulse should be reshaped in OPCPA. The measurement of pump pulse fine structure is a way to judge the effect of shaping. Pump pulse is typically a narrowband nanosecond pulse, and current measurement methods, such as streak camera, are not adaptive for the fine structure measurement. A time-spectrum coding method for the fine structure measurement is proposed in this thesis. After sum-frequency between pre-measured pump pulse and stretched signal pulse, the spectra of sum-frequency and stretched signal pulse are measured. Then the sum-frequency pulse spectrum is divided by the stretched signal pulse spectrum, and the obtained normalized quotient profile is perfectly overlapped with the pending-measured pulse profile. The central wavelength of pump pulse in OPCPA is generally shorter than1μm and a seed source of central wavelength2μm should be prepared in order to obtain a2μm ultrashort, high power pulse. A continuous wavelength laser is made in this thesis. Tm:CYA crystal is used as gain medium, and pump pulse is an ordinal laser diode. The maximum output power is4.3W, and maximum slope efficiency is47.6%. The laser could be continuously tuned from1848nm to2033nm, giving a tuning range of185nm and a FWHM bandwidth of110nm. The broad tuning range shows the potential for a seed source of central wavelength2μm.The strong foundation for the generation of2μm ultrashort, high power pulse using OPCPA technology is made in this thesis.