Research On Laser Pumped Mid-infrared Up-conversion Detection Technology

It includes two important atmosphere windows of 3-5?m mid-infrared and 8-12?m long-wave infrared in mid-infrared band,which may have a promising future of widely application in various fields like remote sensing,environmental monitoring,communication and medical diagnosis.It is the coherent sources and detector with high performance that supports the development in the above field.As an efficient approach for realizing the generation of coherent mid-infrared,nonlinear optical frequency conversion technology has then been applied in the field of sensing,with nonlinear crystal as the key component for that kind of application.With a high transmissivity for waves above 5?m,non-oxide crystal is an important gain medium for middle and long-wave infrared source and up-conversion detection.This paper has concluded the current research status of mid-infrared coherent source and detecting based on non-oxide crystal,in a way to conduct theoretical and practical researches on middle infrared parametric oscillation(OPO)and mid-infrared up-conversion detecting technology based on new non-oxide BaGa4Se7 crystal.The main points of this paper are presented as follows:(1)It has concluded the current research status of the realization of generating mid-infrared coherence,by employing nonlinear frequency transformation moreover,it has made comprehensive comparison with several common nonlinear crystals,thus choosing the nonlinear medium used in this paper—new BaGa4Se7 crystal.(2)It has made introduction to the basic principles of nonlinear optical frequency transformation,which include:three-wave interactive coupling process,the energy conversion of different frequency,the threshold value of single resonant oscillator and its gain value properties,and so on.By doing this,it has lied theoretical foundation for later experiments.(3)By calculating factors like the phase matching conditions,threshold value and efficiency of BaGa4Se7 crystal used in mid-infrared OPO,and applying the laser pumping BaGa4Se7-OPO of nanosecond pulsed Nd:YAG laser with Electro-Optical Q-switch,it has concluded that with a wave length of 3.79?m,the tuned output range is 2.79-8.28?m and the maximum pulse energy value is 3.52mJ,with 6.5%of energy conversion efficiency value and 23.2%of photon conversion efficiency.(4)This paper has also conducted frequency up-conversion detecting researches on the mid-infrared generated by OPO,in a way to realize highly efficient frequency up-conversion form mid-infrared to near infrared and get the conclusion that the detecting sensitivity is higher than direct detecting approach(MCT Infrared Detectors)with three magnitudes.