| Potassium Dihydrogen Phosphate (KH2PO4, KDP) and Potassium Deuterium Phosphate (KD2PO4, DKDP) have high optical damage threshold and found wide applications in high power laser as EO Q-switch crystal. As a uniaxial anisotropic crystalline material, due to its easy hygroscopicity in air, the crystal processing and application must be carried out by using the specific procedures such as Pockels cell. DKDP crystal can be applied in wider wavelength region because of the infrared absorption edge red-shifting of the deuterated crystals.Ordinary DKDP EO Q-switch in the Pockels cell has a pair of electrodes, resulting in a non-uniform electric potential along the radial direction, so it is unavoidable that the decline of Q-switch performance. In this dissertation, the theoretical analysis and calculation show the radial non-uniform electric potential of DKDP crystals can be improved by adding a pair of auxiliary electrodes.In this dissertation, by using He-Ne laser as laser source and xenon flash lamp as the pump source, Nd:YAG crystal as the gain medium, DKDP crystal Pockels cell as Q-switch device, we have measured extinction ratio of DKDP Pockels cell and studied the performance of the Q-switched laser pulse, dynamic and static ratio, and peak power. And we have got the optimal parameters of the DKDP crystal. The main content of this dissertation includes:In Chapter 2, we set up an opportune theoretical model and coordinate system. Compared with experimental conclusions, we verify our model and coordinate system. And we have found that our conclusions consist with that had reported by predecessor. Under different circumstances, we try our best to find optimal crystal length L, electrodes width a, distance between two pairs of electrodes b, and ratio between two pairs of electrodes charge densities m.In Chapter 3, we do some researches in series that He-Ne laser beam passes L=26mm DKDP Pockels cell and Xenon-flash-pumped Nd:YAG dynamic laser beam Q-switches by DKDP Pockels cell. We have measured extinction ratio, net dynamic and static ratio, Q-swtiched pulse width, leakage power and peak power. All these data consist with theoretical rusults. At the end of the chapter, the way that auxiliary electrodes voltage is applied is given, and so Resistances are.In Chapter 4, according to formula we have obtained, we try to get an optimal combination through parameters changed. Given to L=24mm, we have to calculate proper electrodes width, proper distance between main and auxiliary electrodes and proper charge densities ratio and obtained the optimal resultsIn Chapter 5, conclusion which we obtain from experiment is given. And some experimental phenomena are analyzed and explained in this chapter. Also some shortages are pointed out at the end of this dissertation.The main innovations of this dissertation are as follows:ⅠWe first set up a theoretical model with the cylindrical coordinate and use multiple integral in order to solve. Potential differences at the end of DKDP crystal are first given by using the model that we have set up, too.ⅡWe first provide a methods to add a pair of auxiliary electrodes, researching DKDP crystal Pockels cell with auxiliary electrodes Q-switching pulse. We analyze the experimental and theoretical results, finding they are consistence.ⅢBy using the theoretical model we set up above, an optimal crystal length can first be calculated. Experiment has been done to verify the theory.ⅣA novel and practical DKDP Pockels cell is designed, and a patent has been given. |
PDF Full Text Request