| Terahertz?THz?waves have important application prospects in penetration imaging,material identification,and high-rate communication.The terahertz wave parametric oscillator?TPO?based on the crystal parametric process can run wide-band continuous tunable THz waves with good time and spatial coherence at room temperature,which has wide application prospects,but the current output efficiency of THz parametric sources is relatively low.In this paper,the TPO test is carried out by using the two methods of Si-the TPO coupled with Si-prism?Si-TPO?and the TPO coupled with surface-emitted?SE-TPO?,and the experimental scheme for improving the output efficiency of THz wave is explored.Firstly,this paper firstly analyzes the basic theory of the stimulated polarition attering?SPS?to generate waves,and then obtains its dispersion and absorption characteristics from some parameters of lithium niobate crystal and when the pump light is 1064 nm.The phase matching relationship is then simulated on the Si-TPO to determine the basic parameters of the experiment.The SE-TPO experimental device was built,and the basic output characteristics were experimentally studied to obtain the angle tuning curve and the tunable output of the THz wave was realized.The frequency tuning range of the experimentally measured THz wave was 0.72.4 THz,THz.The wave frequency is around 1.2 THz,and the THz wave output is the largest.When the pump light energy is 14 mJ,the pump light power density is 255MW/cm2,the THz wave output is 474 nJ,and the energy conversion efficiency is3.36×10-5.When the pump light is cut and the pump light y is about 1 mm in the direction,the output efficiency of the THz wave is higher,and finally the spot is optimized,and the y-direction size limit of the pump spot diameter of 2 mm is limited.In 1 mm,the experiment was carried out.Compared with the 2 mm diameter spot,the tuning range was increased and the output energy was also improved.Compared with the 1 mm diameter spot,the output energy at 1.2 THz was increased by 1.9 times.The SE-TPO experimental device was built,and the basic output characteristics were experimentally studied to obtain the angle tuning curve and the tunable output of the THz wave was realized.The frequency tuning range of the experimentally measured THz wave was 1.472.37 THz,THz wave.The maximum output is obtained at a frequency of 1.8THz.When the pump light energy is 25 mJ,the pump optical power density is 114MW/cm2,the THz wave output energy is 23 nJ,and the energy conversion efficiency is0.91×10-6.Study the effects of different diameter spots and different pump power densities on the output THz wave.The spot diameter is 2.5 mm,the pump energy is 42mJ,the output of the THz wave is 66 nJ,and the two-point output SE-TPO is used to make the pump.The Puguang and Stokes light is totally reflected twice in the crystal.The THz wave can be output from two total reflection positions.The total output of the two THz waves is 109 nJ,and the output energy and efficiency are increased by 1.65 times relative to the trapezoidal crystal. |
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