Nonlinear Dynamics Of Optical Parametric Process For The Generation Of Few-cycle Laser Pulses

Femtosecond laser is a powerful tool that has important implications for varieties of applications in physics,biology and chemistry research field.However,for many practical applications,there is a strong demand for laser pulses exhibiting short durations as well as broad frequency tunability.Optical parametric sources pumped by femtosecond fiber laser have been recognized as ideal platforms providing tunable ultrafast pulses with formidable performance,such as high repetition rate,high output power,broad wavelength coverage.Yet,due to intrinsic limitations,i.e.,the bandwidth limitation of the gain medium,the limited phase matching bandwidth,the pulse duration of such laser sources is restricted to be hundreds of femtoseconds.Advances in the development of few-cycle femtosecond laser sources over the last decades have opened the opportunity for the experimental study of phenomena in high-energy physics and light-matter interaction.The generation of few-cyle pulses has been attracting interest in recent years.The objective of this dissertation is to develop novel optical parametric sources for few-cyle laser pulse generation pumped by a femtosecond fiber laser.Besides,the new frontiers of the fiber laser pumped optical parametric oscillators(OPOs)is explored.The main findings of the thesis are summarized as follows:Initially the Forward Maxwell Equation is derived in detail to describe the optical phenomena in quadratic nonlinear media.We build a complete numerical model using this equation to simulate the pulse evolution process of femtosecond laser pumped optical parametric sources.Then,a complete numerical model is built to calculate the noise performance(relative intensity noise(RIN)and timing jitter)of the OPG output by solving the Forward Maxwell Equation(FME),with a quantum mechanical initiation mimicked by a noise field.Next,two novel self-compressed OPOs,including a 4.2-cycle mid infrared OPO and a sub-50 fs near infrared OPO,are developed using femtosecond fiber laser as the pump source.Detailed theoretical analysis and numerical simulation are performed to better understand the self-compression mechanism in femtosecond OPOs.The experiment results are in good agreement with numerical values.In the following,the RIN and the timing jitter spectral density of the OPG output pulses is studied in detail both experimentally and theoretically.The measured noise densities are in a fairly good agreement with numerical simulation.What’s more,a comparision of noise performance of OPA with three different seeds is studied experimentally.It is concluded that the narrowband continuous wave(cw)injection seeded OPA exhibits the best noise performance.Hence,a simple yet effective pulse synthesizer based on two cw injection-seeded high-repetition-rate optical parametric amplification systems is designed.In this way,a 3.9-cycle(19.2 fs)synthesized pulse with a central wavelength of 1470 nm is obtained.Finally,several cavity configurations towards new OPO frontiers are demonstrated:(a)the output wavelength of femtosecond fiber laser pumped OPO is extended to 330 nm by using a β-barium borate(BBO)crystal as the nonlinear gain medium for internal frequency doubling of the signal pulses.(b)the first dielectric-mirror-less optical parametric oscillator(OPO)based on Mg O:PPLN crystal is developed.(c)a practically compact 1-GHz repetition-rate femtosecond OPO based on miniaturized V-type cavity is studied,the near-infrared signal output pulses can cover the whole telecom band.(d)two structured beam femtosecond OPOs are proposed,in this way,tunable higher-order Poincaré(HOP)sphere and vortex signal beams are obtained.