Mechanism And Implementation Of Bidirectionally Pumped Femtosecond Optical Parametric Oscillator

With the use of photonic crystal fiber femtosecond laser amplification systems as pump sources,three types of bidirectionally pumped femtosecond optical parametric oscillators with single cavity and single crystal have been respectively designed and implemented by synchronizing signal pulses,colliding pump pulses and synchronizing pump pulses.The mechanism about the influences of synchronization and delay between the pump and signal pulses in bidirectionally pumped OPO on the transmission states of signal pulses in the resonant cavity has been proposed,and has been verified by the transformation of OPO output characteristics as a function of the delay between pulses.The main innovations of this thesis are summarized as follows:The theoretical analysis of the inter-pulse delay and synchronization process of bidirectionally pumped OPO has been carried out.Based on this,a signal pulse synchronous femtosecond bidirectionally pumped OPO with output power of 516 m W,wavelength turning range of 1410 nm ? 1606 nm,pulse duration of 226 fs has been realized.Unlike the conventional single-pumped OPO,the pump pulses are injected into the OPO cavity from the front and reverse directions,respectively,which can double the tolerable maximum pump power onto the nonlinear crystal.By means of synchronizing the two signals generated from the bidirectional pump pulses,distinct improvements for output characteristics have been demonstrated: In comparison with the singly pumped OPO,the average output power of this system is increased by 12 % ? 33 %,the opticalto-optical conversion efficiency is increased by up to 5.7 %,and the standard deviation of signal power fluctuations is reduced by 1.52 %.In view of the variation of system output signal parameters with the delay between two pump pulses,the influence of synchronization and delay between the pump and signal pulses on the transmission states of signal pulses in the resonant cavity has been analyzed and theoretically explained.Based on the above-mentioned theoretical explanation about synchronization and transmission states among the pulses in bidirectionally pumped OPO,a bidirectionally pumped OPO with pump pulses colliding has been designed and constructed.With the influence of collision process between the front and reverse pump pulses in the nonlinear crystal,a 50 % ? 90 % power boost over the singly pumped OPO has been achieved at lower pump power.In addition,a bidirectionally pumped OPO with synchronous pump pulses and adjustable delay has been designed and constructed,of which two pump pulses injecting the resonator in the same direction,realizing a direct observation of the pulse synchronization process in bidirectionally pumped OPO.Furthermore,the theoretical interpretation of pulse synchronization process has been verified.