Study Of THz Radiation Generated By Optically-Pumped D₂O Gas Molecules

The terahertz region of the electromagnetic spectrum spans the frequency range between the mid-infrared and the millimeter/microwave. Nowadays, THz technology has widely foreground and great potential of application in imaging, medicine diagnoses, environment science, information communication and basic physical study etc. From internal and overseas study in this region, it is indicated that the way to obtain THz radiation is one of the foreland and emphasis in the THz study area. This thesis focuses on THz radiation generated by Optically-Pumped D2O gas molecules, especially on its 385μm spectrum.The main content and key creation points of this dissertation are as follows:1. The mechanism and regularities of optically pumped D2O gas THz laser under complex laser process with different operating conditions were studied By solving the density matrix equation of three-level molecular system, the expression of THz signal gain coefficient(Gs)and the pumping signal absorption coefficient (Gp) were deduced and calculated by iteration method. The theoretical result was in good agreement with experiment and could guide to design this kind of THz laser.2. The relation function between the intensity of pumping laser and the output THz laser was founded, and the condition of frequency tuning was analyzed; The optimum operation parameters of the THz laser were calculated out; The effect of adding buffer gas was studied; According to these works, a high efficiency and optimal operation laser could be designed.3. A compact super-radiant optically pumped D2O gas Terahertz laser was developed, it consisted of pumping source, laser cavity, measurement and vacuum system, and the length of laser cavity could be changed in the range of 80-150cm.The output THz laser signal was 385μm in wavelength,100ns in pulse width and more than a hundred watts in peak power.4. A kind of automatic measurement system connected with a metal grid F-P interferometer was developed, it's controlled by computer and could be used to measure the spectral characteristics and intensity of output THz laser.