Research Of Narrowband Pulsed Periodically Poled Optical Parametric Amplification Technology

Optical parametric down conversion technology based on second order nonlinear optics effect is an effective way to generate tunable coherent radiation and carry out frequency conversion process.Especially in recent years,the emergence of periodically poled crystals provided another opportunity of leap-step development for parametric sources.However,ordinary optical parametric oscillators(OPOs)are usually operating with multi-longitudinal modes due to the linewidth of the pump and the parametric gain bandwidth.The output linewidths couldn't satisfy some certain applications such as high resolution spectroscopy.Researchers developed injection seeded OPOs in order to squeeze the output spectrum.However,injection seeded OPOs usually need complicated feedback controlling systems,which leads to a high capitalized cost,inconvenience of integration and utilization.Under this circumstances,the possibility of obtaining narrowband pulsed outputs by means of optical parametric amplifiers based on periodically poled crystals was theoretically analyzed in this paper.The feasibility of this scheme was preliminarily demonstrated by the later experiments.Compared to injection seeded OPOs,although this scheme has a relatively high requirement for the pump,the whole setup which could maintain spectral narrowing effect well,is quite simplified without cavities and complicated controlling systems.It is a new direction for narrowband parametric sources development.Main work of this paper is shown as below:1.Previous work in this area was summarized and analyzed through literature research.Simulation of narrowband OPA was carried out based on normalized three-wave mixing coupled equations.It was proved that efficient narrowband outputs could be generated by single-pass structure according to theoretical calculation.Parameters necessary for experiments such as the peak power of the pump,the average power of the seed and the crystal length are obtained,which is the fundamental of next experiments.2.Frequency doubling LBO-Nd:YAG laser at 532 nm was first constructed as the pump in order to carry out near-infrared narrowband OPA experiment.Characteristics of the fiber coupled 820 nm seed laser were tested.It was finally experimentally demonstrated that the two-stage near-infrared OPA could work normally.A average power of 280 mW and pulse energy of 140 ?J were obtained,and the linewidth of the signal was 14.9 pm.Besides,the requirements for the pump in narrowband pulsed OPAs were also summarized.3.Based on the previous work in this paper,a commercial high performance 1064 nm micro-chip laser was adopted as the pump,and a single frequency Tm doped fiber laser was adopted as the seed laser.Efficient dual-wavelength narrowband outputs around 2 ?m were obtained by single-stage parametric amplification.The signal wave at 1971.13 nm had a pulse energy of 25 ?J and a linewidth less 82.7 pm.The idler wave at 2313.62 nm had a pulse energy of 17.8 ?J and a linewidth less 102.3 pm.The results reveal that this structure is a feasible way of obtaining near and mid-infrared pulsed laser and has potential for power scaling.